import { app, BrowserWindow, ipcMain, dialog, shell, nativeTheme, Notification } from 'electron';
import * as path from 'path';
import * as fs from 'fs';
import { spawn, ChildProcess, execSync, spawnSync } from 'child_process';
import axios from 'axios';
import { autoUpdater } from 'electron-updater';
import { compareUpdateVersions, isNewerUpdateVersion, normalizeUpdateVersion } from './update-version-utils';
import { CustomClip, MergeGroupItem, MergeGroup, QueueItem, DownloadProgress, DownloadResult } from './types';
import {
    setDebugLogFn, initToolDirs,
    getStreamlinkPath, getStreamlinkCommand, getFFmpegPath, getFFprobePath,
    refreshBundledToolPaths, ensureStreamlinkInstalled, ensureFfmpegInstalled,
    canExecute, canExecuteCommand,
    cacheVerifiedStreamlinkCommand, isVerifiedStreamlinkCommand,
    cacheVerifiedFfmpegCommands, isVerifiedFfmpegCommands,
    invalidateVerifiedToolCaches
} from './tools';

// ==========================================
// CONFIG & CONSTANTS
// ==========================================
const APP_VERSION = app.getVersion();
const UPDATE_CHECK_URL = 'http://24-music.de/version.json';
const GITEA_BASE_URL = (process.env.GITEA_BASE_URL || 'https://git.24-music.de').replace(/\/+$/, '');
const GITEA_REPO_OWNER = process.env.GITEA_REPO_OWNER || 'Administrator';
const GITEA_REPO_NAME = process.env.GITEA_REPO_NAME || 'Twitch-VOD-Manager';
const GITEA_RELEASES_API_LATEST_URL = `${GITEA_BASE_URL}/api/v1/repos/${GITEA_REPO_OWNER}/${GITEA_REPO_NAME}/releases/latest`;
const GITEA_RELEASES_DOWNLOAD_BASE_URL = `${GITEA_BASE_URL}/${GITEA_REPO_OWNER}/${GITEA_REPO_NAME}/releases/download`;

// Paths
const APPDATA_DIR = path.join(process.env.PROGRAMDATA || 'C:\\ProgramData', 'Twitch_VOD_Manager');
const CONFIG_FILE = path.join(APPDATA_DIR, 'config.json');
const QUEUE_FILE = path.join(APPDATA_DIR, 'download_queue.json');
const DEBUG_LOG_FILE = path.join(APPDATA_DIR, 'debug.log');
const TOOLS_DIR = path.join(APPDATA_DIR, 'tools');
const TOOLS_STREAMLINK_DIR = path.join(TOOLS_DIR, 'streamlink');
const TOOLS_FFMPEG_DIR = path.join(TOOLS_DIR, 'ffmpeg');
const DEFAULT_DOWNLOAD_PATH = path.join(app.getPath('desktop'), 'Twitch_VODs');
const DEFAULT_FILENAME_TEMPLATE_VOD = '{title}.mp4';
const DEFAULT_FILENAME_TEMPLATE_PARTS = '{date}_Part{part_padded}.mp4';
const DEFAULT_FILENAME_TEMPLATE_CLIP = '{date}_{part}.mp4';
const DEFAULT_METADATA_CACHE_MINUTES = 10;
const DEFAULT_PERFORMANCE_MODE: PerformanceMode = 'balanced';
const QUEUE_SAVE_DEBOUNCE_MS = 250;
const MIN_FREE_DISK_BYTES = 128 * 1024 * 1024;
const DEBUG_LOG_FLUSH_INTERVAL_MS = 1000;
const DEBUG_LOG_BUFFER_FLUSH_LINES = 48;
const DEBUG_LOG_READ_TAIL_BYTES = 512 * 1024;
const DEBUG_LOG_MAX_BYTES = 8 * 1024 * 1024;
const DEBUG_LOG_TRIM_TO_BYTES = 4 * 1024 * 1024;
const AUTO_UPDATE_CHECK_INTERVAL_MS = 10 * 60 * 1000;
const AUTO_UPDATE_STARTUP_CHECK_DELAY_MS = 5000;
const AUTO_UPDATE_MIN_CHECK_GAP_MS = 45 * 1000;
const AUTO_UPDATE_AUTO_DOWNLOAD = false;
const AUTO_UPDATE_CHECK_TIMEOUT_MS = 30 * 1000;
const CACHE_CLEANUP_INTERVAL_MS = 60 * 1000;
const MAX_LOGIN_TO_USER_ID_CACHE_ENTRIES = 4096;
const MAX_VOD_LIST_CACHE_ENTRIES = 512;
const MAX_CLIP_INFO_CACHE_ENTRIES = 4096;

// Timeouts
const API_TIMEOUT = 10000;
const DEFAULT_RETRY_DELAY_SECONDS = 5;
const MIN_FILE_BYTES = 256 * 1024;
const TWITCH_WEB_CLIENT_ID = 'kimne78kx3ncx6brgo4mv6wki5h1ko';

type PerformanceMode = 'stability' | 'balanced' | 'speed';
type RetryErrorClass = 'network' | 'rate_limit' | 'auth' | 'tooling' | 'integrity' | 'io' | 'validation' | 'unknown';
type UpdateCheckSource = 'startup' | 'interval' | 'manual';
type UpdateDownloadSource = 'auto' | 'manual';

function getMergeGroupPhaseText(phase: string): string {
    const isEnglish = config.language === 'en';
    switch (phase) {
        case 'downloading': return isEnglish ? 'Downloading VOD' : 'VOD wird heruntergeladen';
        case 'merging': return isEnglish ? 'Merging...' : 'Zusammenfugen...';
        case 'splitting': return isEnglish ? 'Splitting Part' : 'Part wird erstellt';
        case 'cleanup': return isEnglish ? 'Cleaning up...' : 'Aufraumen...';
        default: return phase;
    }
}

// ==========================================
// BACKEND I18N
// ==========================================
// User-visible messages produced in main.ts. Keep keys stable — the renderer
// no longer translates these (renderer.ts:downloadClip used to translate a
// hardcoded set, which was brittle as the strings drifted). Internal
// debug log messages stay English-only since they're developer-facing.
const BACKEND_MESSAGES = {
    de: {
        invalidVodUrl: 'Ungueltige VOD-URL',
        invalidClipUrl: 'Ungueltige Clip-URL',
        clipNotFound: 'Clip nicht gefunden',
        streamlinkAutoInstallFailed: 'Streamlink fehlt und konnte nicht automatisch installiert werden. Siehe debug.log.',
        streamlinkMissing: 'Streamlink fehlt.',
        streamlinkNotFound: 'Streamlink nicht gefunden. Installiere Streamlink oder Python+streamlink (py -3 -m pip install streamlink).',
        streamlinkExitCode: 'Streamlink Fehlercode {code}',
        ffmpegMissing: 'FFmpeg fehlt.',
        ffmpegMergeFailed: 'FFmpeg Merge fehlgeschlagen.',
        ffmpegSplitFailed: 'FFmpeg Split fehlgeschlagen.',
        fileTooSmall: 'Datei zu klein ({bytes} Bytes)',
        clipFileTooSmall: 'Clip-Datei zu klein ({bytes} Bytes) - Twitch hat den Stream evtl. nicht ausgeliefert.',
        integrityNoVideo: 'Integritaetspruefung fehlgeschlagen: Kein Videostream gefunden.',
        integrityTooShort: 'Integritaetspruefung fehlgeschlagen: Dauer zu kurz ({duration}s).',
        integrityDurationMismatch: 'Integritaetspruefung fehlgeschlagen: {actual}s statt erwarteter ~{expected}s.',
        integrityFailedGeneric: 'Integritaetspruefung fehlgeschlagen.',
        downloadCancelled: 'Download wurde abgebrochen.',
        downloadPaused: 'Download wurde pausiert.',
        downloadFailedExitCode: 'Download fehlgeschlagen (Exit-Code {code})',
        unknownDownloadError: 'Unbekannter Fehler beim Download',
        notAllClipPartsDownloaded: 'Nicht alle Clip-Teile konnten heruntergeladen werden.',
        notAllPartsDownloaded: 'Nicht alle Teile konnten heruntergeladen werden.',
        mergeGroupFileMissing: 'Heruntergeladene Datei {index} fehlt.',
        diskSpaceShortFor: 'Zu wenig Speicherplatz fur {context}: frei {free}, benoetigt ~{required}.',
        diskSpaceShortGeneric: 'Zu wenig Speicherplatz.',
        attemptFailed: 'Versuch {attempt}/{max} fehlgeschlagen ({errorClass}): {error}',
        retryingIn: 'Neuer Versuch in {seconds}s ({errorClass})...',
        statusCheckingTools: 'Prufe Download-Tools...',
        statusDownloadStarted: 'Download gestartet',
        statusBytesDownloaded: '{bytes} heruntergeladen',
        preflightNoInternet: 'Keine Internetverbindung erkannt.',
        preflightStreamlinkMissing: 'Streamlink fehlt oder ist nicht startbar.',
        preflightFfmpegMissing: 'FFmpeg fehlt oder ist nicht startbar.',
        preflightFfprobeMissing: 'FFprobe fehlt oder ist nicht startbar.',
        preflightDownloadPathNotWritable: 'Download-Ordner ist nicht beschreibbar.'
    },
    en: {
        invalidVodUrl: 'Invalid VOD URL',
        invalidClipUrl: 'Invalid clip URL',
        clipNotFound: 'Clip not found',
        streamlinkAutoInstallFailed: 'Streamlink is missing and could not be auto-installed. See debug.log.',
        streamlinkMissing: 'Streamlink is missing.',
        streamlinkNotFound: 'Streamlink not found. Install streamlink or Python+streamlink (py -3 -m pip install streamlink).',
        streamlinkExitCode: 'Streamlink exit code {code}',
        ffmpegMissing: 'FFmpeg is missing.',
        ffmpegMergeFailed: 'FFmpeg merge failed.',
        ffmpegSplitFailed: 'FFmpeg split failed.',
        fileTooSmall: 'File too small ({bytes} bytes)',
        clipFileTooSmall: 'Clip file too small ({bytes} bytes) - Twitch may not have served the stream.',
        integrityNoVideo: 'Integrity check failed: no video stream found.',
        integrityTooShort: 'Integrity check failed: duration too short ({duration}s).',
        integrityDurationMismatch: 'Integrity check failed: {actual}s instead of expected ~{expected}s.',
        integrityFailedGeneric: 'Integrity check failed.',
        downloadCancelled: 'Download was cancelled.',
        downloadPaused: 'Download was paused.',
        downloadFailedExitCode: 'Download failed (exit code {code})',
        unknownDownloadError: 'Unknown download error',
        notAllClipPartsDownloaded: 'Not all clip parts could be downloaded.',
        notAllPartsDownloaded: 'Not all parts could be downloaded.',
        mergeGroupFileMissing: 'Downloaded file {index} is missing.',
        diskSpaceShortFor: 'Not enough disk space for {context}: free {free}, need ~{required}.',
        diskSpaceShortGeneric: 'Not enough disk space.',
        attemptFailed: 'Attempt {attempt}/{max} failed ({errorClass}): {error}',
        retryingIn: 'Retrying in {seconds}s ({errorClass})...',
        statusCheckingTools: 'Checking download tools...',
        statusDownloadStarted: 'Download started',
        statusBytesDownloaded: '{bytes} downloaded',
        preflightNoInternet: 'No internet connection detected.',
        preflightStreamlinkMissing: 'Streamlink is missing or not runnable.',
        preflightFfmpegMissing: 'FFmpeg is missing or not runnable.',
        preflightFfprobeMissing: 'FFprobe is missing or not runnable.',
        preflightDownloadPathNotWritable: 'Download folder is not writable.'
    }
} as const;

type BackendMessageKey = keyof typeof BACKEND_MESSAGES.de;

function tBackend(key: BackendMessageKey, params?: Record<string, string | number>): string {
    const lang: 'de' | 'en' = config.language === 'en' ? 'en' : 'de';
    let template: string = BACKEND_MESSAGES[lang][key];
    if (params) {
        for (const [k, v] of Object.entries(params)) {
            template = template.replace(`{${k}}`, String(v));
        }
    }
    return template;
}

// Ensure directories exist
if (!fs.existsSync(APPDATA_DIR)) {
    fs.mkdirSync(APPDATA_DIR, { recursive: true });
}

// ==========================================
// INTERFACES
// ==========================================
interface Config {
    client_id: string;
    client_secret: string;
    download_path: string;
    streamers: string[];
    theme: string;
    download_mode: 'parts' | 'full';
    part_minutes: number;
    language: 'de' | 'en';
    filename_template_vod: string;
    filename_template_parts: string;
    filename_template_clip: string;
    smart_queue_scheduler: boolean;
    performance_mode: PerformanceMode;
    prevent_duplicate_downloads: boolean;
    persist_queue_on_restart: boolean;
    metadata_cache_minutes: number;
    parallel_downloads: number;
    auto_resume_queue_on_startup: boolean;
    downloaded_vod_ids: string[];
}

interface RuntimeMetrics {
    cacheHits: number;
    cacheMisses: number;
    duplicateSkips: number;
    retriesScheduled: number;
    retriesExhausted: number;
    integrityFailures: number;
    downloadsStarted: number;
    downloadsCompleted: number;
    downloadsFailed: number;
    downloadedBytesTotal: number;
    lastSpeedBytesPerSec: number;
    avgSpeedBytesPerSec: number;
    activeItemId: string | null;
    activeItemTitle: string | null;
    lastErrorClass: RetryErrorClass | null;
    lastRetryDelaySeconds: number;
}

interface RuntimeMetricsSnapshot extends RuntimeMetrics {
    timestamp: string;
    queue: {
        pending: number;
        downloading: number;
        paused: number;
        completed: number;
        error: number;
        total: number;
    };
    caches: {
        loginToUserId: number;
        vodList: number;
        clipInfo: number;
    };
    config: {
        performanceMode: PerformanceMode;
        smartScheduler: boolean;
        metadataCacheMinutes: number;
        duplicatePrevention: boolean;
    };
}

interface CacheEntry<T> {
    value: T;
    expiresAt: number;
}

interface VOD {
    id: string;
    title: string;
    created_at: string;
    duration: string;
    thumbnail_url: string;
    url: string;
    view_count: number;
    stream_id: string;
}

interface PreflightChecks {
    internet: boolean;
    streamlink: boolean;
    ffmpeg: boolean;
    ffprobe: boolean;
    downloadPathWritable: boolean;
}

interface PreflightResult {
    ok: boolean;
    autoFixApplied: boolean;
    checks: PreflightChecks;
    messages: string[];
    timestamp: string;
}

interface VideoInfo {
    duration: number;
    width: number;
    height: number;
    fps: number;
}

interface ReleaseUpdateInfo {
    tagName?: string;
    version?: string;
    releaseDate?: string;
    releaseName?: string;
    releaseNotes?: string;
}

// ==========================================
// CONFIG MANAGEMENT
// ==========================================
const defaultConfig: Config = {
    client_id: '',
    client_secret: '',
    download_path: DEFAULT_DOWNLOAD_PATH,
    streamers: [],
    theme: 'twitch',
    download_mode: 'full',
    part_minutes: 120,
    language: 'en',
    filename_template_vod: DEFAULT_FILENAME_TEMPLATE_VOD,
    filename_template_parts: DEFAULT_FILENAME_TEMPLATE_PARTS,
    filename_template_clip: DEFAULT_FILENAME_TEMPLATE_CLIP,
    smart_queue_scheduler: true,
    performance_mode: DEFAULT_PERFORMANCE_MODE,
    prevent_duplicate_downloads: true,
    persist_queue_on_restart: true,
    metadata_cache_minutes: DEFAULT_METADATA_CACHE_MINUTES,
    parallel_downloads: 1,
    auto_resume_queue_on_startup: false,
    downloaded_vod_ids: []
};

function normalizeFilenameTemplate(template: string | undefined, fallback: string): string {
    const value = (template || '').trim();
    return value || fallback;
}

function normalizeMetadataCacheMinutes(value: unknown): number {
    const parsed = Number(value);
    if (!Number.isFinite(parsed)) {
        return DEFAULT_METADATA_CACHE_MINUTES;
    }

    return Math.max(1, Math.min(120, Math.floor(parsed)));
}

function normalizePerformanceMode(mode: unknown): PerformanceMode {
    if (mode === 'stability' || mode === 'balanced' || mode === 'speed') {
        return mode;
    }

    return DEFAULT_PERFORMANCE_MODE;
}

function normalizeConfigTemplates(input: Config): Config {
    // downloaded_vod_ids is bounded so a long-running app doesn't accumulate
    // an unbounded list across years of downloads. Latest entries kept.
    const DOWNLOADED_IDS_MAX = 4096;
    const rawIds = Array.isArray(input.downloaded_vod_ids) ? input.downloaded_vod_ids : [];
    const cleanIds = rawIds.filter((id): id is string => typeof id === 'string' && id.length > 0);
    const trimmedIds = cleanIds.length > DOWNLOADED_IDS_MAX
        ? cleanIds.slice(cleanIds.length - DOWNLOADED_IDS_MAX)
        : cleanIds;

    return {
        ...input,
        filename_template_vod: normalizeFilenameTemplate(input.filename_template_vod, DEFAULT_FILENAME_TEMPLATE_VOD),
        filename_template_parts: normalizeFilenameTemplate(input.filename_template_parts, DEFAULT_FILENAME_TEMPLATE_PARTS),
        filename_template_clip: normalizeFilenameTemplate(input.filename_template_clip, DEFAULT_FILENAME_TEMPLATE_CLIP),
        smart_queue_scheduler: input.smart_queue_scheduler !== false,
        performance_mode: normalizePerformanceMode(input.performance_mode),
        prevent_duplicate_downloads: input.prevent_duplicate_downloads !== false,
        persist_queue_on_restart: input.persist_queue_on_restart !== false,
        metadata_cache_minutes: normalizeMetadataCacheMinutes(input.metadata_cache_minutes),
        auto_resume_queue_on_startup: input.auto_resume_queue_on_startup === true,
        downloaded_vod_ids: trimmedIds
    };
}

function recordDownloadedVodId(vodId: string): void {
    if (!vodId) return;
    if (!Array.isArray(config.downloaded_vod_ids)) config.downloaded_vod_ids = [];
    if (config.downloaded_vod_ids.includes(vodId)) return;
    config.downloaded_vod_ids.push(vodId);
    // Cap to keep config size bounded — drop oldest first.
    const DOWNLOADED_IDS_MAX = 4096;
    if (config.downloaded_vod_ids.length > DOWNLOADED_IDS_MAX) {
        config.downloaded_vod_ids = config.downloaded_vod_ids.slice(
            config.downloaded_vod_ids.length - DOWNLOADED_IDS_MAX
        );
    }
    saveConfig(config);
}

function isPlainObject(value: unknown): value is Record<string, unknown> {
    return typeof value === 'object' && value !== null && !Array.isArray(value);
}

function loadConfig(): Config {
    try {
        if (fs.existsSync(CONFIG_FILE)) {
            const data = fs.readFileSync(CONFIG_FILE, 'utf-8');
            const parsed = JSON.parse(data);
            if (!isPlainObject(parsed)) {
                console.error('Config file is not a JSON object — using defaults');
                return normalizeConfigTemplates(defaultConfig);
            }
            return normalizeConfigTemplates({ ...defaultConfig, ...parsed });
        }
    } catch (e) {
        console.error('Error loading config:', e);
    }
    return normalizeConfigTemplates(defaultConfig);
}

function writeFileAtomicSync(targetPath: string, payload: string | Buffer): void {
    const buffer = Buffer.isBuffer(payload) ? payload : Buffer.from(payload, 'utf-8');
    const tmpPath = targetPath + '.tmp';

    let fd: number | null = null;
    try {
        fd = fs.openSync(tmpPath, 'w');
        fs.writeSync(fd, buffer, 0, buffer.length, 0);
        try { fs.fsyncSync(fd); } catch { /* fsync may fail on some FS; rename is still safer than nothing */ }
    } finally {
        if (fd !== null) {
            try { fs.closeSync(fd); } catch { }
        }
    }

    try {
        fs.renameSync(tmpPath, targetPath);
    } catch {
        // On Windows, rename can fail if target exists or is locked. Fall back to copy.
        fs.copyFileSync(tmpPath, targetPath);
        try { fs.unlinkSync(tmpPath); } catch { }
    }
}

function saveConfig(config: Config): void {
    try {
        writeFileAtomicSync(CONFIG_FILE, JSON.stringify(config, null, 2));
    } catch (e) {
        console.error('Error saving config:', e);
    }
}

// ==========================================
// QUEUE MANAGEMENT
// ==========================================
const VALID_QUEUE_STATUSES: ReadonlyArray<QueueItem['status']> = ['pending', 'downloading', 'paused', 'completed', 'error'];
const VALID_MERGE_PHASES: ReadonlyArray<MergeGroup['mergePhase']> = ['downloading', 'merging', 'splitting', 'cleanup', 'done'];

function isValidQueueStatus(status: unknown): status is QueueItem['status'] {
    return typeof status === 'string' && (VALID_QUEUE_STATUSES as readonly string[]).includes(status);
}

function sanitizeMergeGroup(raw: unknown): MergeGroup | undefined {
    if (!isPlainObject(raw)) return undefined;
    if (!Array.isArray(raw.items) || raw.items.length < 2) return undefined;

    const items: MergeGroupItem[] = [];
    for (const mi of raw.items) {
        if (!isPlainObject(mi)) continue;
        if (typeof mi.url !== 'string' || typeof mi.title !== 'string'
            || typeof mi.date !== 'string' || typeof mi.streamer !== 'string'
            || typeof mi.duration_str !== 'string') continue;
        items.push({ url: mi.url, title: mi.title, date: mi.date, streamer: mi.streamer, duration_str: mi.duration_str });
    }
    if (items.length < 2) return undefined;

    const phase: MergeGroup['mergePhase'] = (VALID_MERGE_PHASES as readonly string[]).includes(String(raw.mergePhase))
        ? raw.mergePhase as MergeGroup['mergePhase']
        : 'downloading';

    const downloadedFiles: Record<number, string> = {};
    if (isPlainObject(raw.downloadedFiles)) {
        for (const [k, v] of Object.entries(raw.downloadedFiles)) {
            const idx = Number(k);
            if (Number.isFinite(idx) && typeof v === 'string') downloadedFiles[idx] = v;
        }
    }

    return {
        items,
        mergePhase: phase,
        currentItemIndex: typeof raw.currentItemIndex === 'number' && Number.isFinite(raw.currentItemIndex) ? raw.currentItemIndex : 0,
        downloadedFiles,
        mergedFile: typeof raw.mergedFile === 'string' ? raw.mergedFile : undefined,
        splitFiles: Array.isArray(raw.splitFiles) ? raw.splitFiles.filter((f): f is string => typeof f === 'string') : undefined,
        totalDurationSec: typeof raw.totalDurationSec === 'number' && Number.isFinite(raw.totalDurationSec) ? raw.totalDurationSec : undefined
    };
}

function sanitizeCustomClip(raw: unknown): CustomClip | undefined {
    if (!isPlainObject(raw)) return undefined;
    const startSec = Number(raw.startSec);
    const durationSec = Number(raw.durationSec);
    const startPart = Number(raw.startPart);
    if (!Number.isFinite(startSec) || !Number.isFinite(durationSec) || durationSec <= 0 || !Number.isFinite(startPart)) return undefined;

    const filenameFormat = raw.filenameFormat;
    if (filenameFormat !== 'simple' && filenameFormat !== 'timestamp' && filenameFormat !== 'template' && filenameFormat !== 'parts') return undefined;

    return {
        startSec: Math.max(0, startSec),
        durationSec: Math.max(1, durationSec),
        startPart: Math.max(1, Math.floor(startPart)),
        filenameFormat,
        filenameTemplate: typeof raw.filenameTemplate === 'string' ? raw.filenameTemplate : undefined
    };
}

function sanitizeQueueItem(raw: unknown): QueueItem | null {
    if (!isPlainObject(raw)) return null;
    if (typeof raw.id !== 'string' || !raw.id) return null;
    if (typeof raw.url !== 'string' || !raw.url) return null;
    if (!isValidQueueStatus(raw.status)) return null;

    // 'downloading' on cold start is stale — no download is actually running
    // and the user expects to resume from start, so map it back to 'pending'
    const isStaleDownloading = raw.status === 'downloading';
    const finalStatus: QueueItem['status'] = isStaleDownloading ? 'pending' : raw.status;

    const progressNum = Number(raw.progress);
    const safeProgress = Number.isFinite(progressNum) ? Math.max(0, Math.min(100, progressNum)) : 0;

    const item: QueueItem = {
        id: raw.id,
        url: raw.url,
        title: typeof raw.title === 'string' ? raw.title : '',
        date: typeof raw.date === 'string' ? raw.date : '',
        streamer: typeof raw.streamer === 'string' ? raw.streamer : '',
        duration_str: typeof raw.duration_str === 'string' ? raw.duration_str : '0s',
        status: finalStatus,
        progress: isStaleDownloading ? 0 : safeProgress
    };

    if (typeof raw.currentPart === 'number' && Number.isFinite(raw.currentPart)) item.currentPart = raw.currentPart;
    if (typeof raw.totalParts === 'number' && Number.isFinite(raw.totalParts)) item.totalParts = raw.totalParts;
    if (typeof raw.speed === 'string') item.speed = raw.speed;
    if (typeof raw.eta === 'string') item.eta = raw.eta;
    if (typeof raw.last_error === 'string') item.last_error = raw.last_error;
    if (typeof raw.downloadedBytes === 'number' && Number.isFinite(raw.downloadedBytes)) item.downloadedBytes = raw.downloadedBytes;
    if (typeof raw.totalBytes === 'number' && Number.isFinite(raw.totalBytes)) item.totalBytes = raw.totalBytes;

    if (Array.isArray(raw.outputFiles)) {
        const files = raw.outputFiles.filter((f): f is string => typeof f === 'string' && f.length > 0);
        if (files.length > 0) item.outputFiles = files;
    }

    const customClip = sanitizeCustomClip(raw.customClip);
    if (customClip) item.customClip = customClip;

    const mergeGroup = sanitizeMergeGroup(raw.mergeGroup);
    if (mergeGroup) item.mergeGroup = mergeGroup;

    return item;
}

function loadQueue(): QueueItem[] {
    if (config.persist_queue_on_restart === false) {
        return [];
    }

    try {
        if (fs.existsSync(QUEUE_FILE)) {
            const data = fs.readFileSync(QUEUE_FILE, 'utf-8');
            const parsed = JSON.parse(data);
            if (!Array.isArray(parsed)) {
                console.error('Queue file is not a JSON array — ignoring');
                return [];
            }

            const items: QueueItem[] = [];
            let droppedCount = 0;
            for (const raw of parsed) {
                const sanitized = sanitizeQueueItem(raw);
                if (sanitized) items.push(sanitized);
                else droppedCount++;
            }
            if (droppedCount > 0) {
                console.error(`loadQueue: dropped ${droppedCount} invalid queue item(s)`);
            }
            return items;
        }
    } catch (e) {
        console.error('Error loading queue:', e);
    }
    return [];
}

let queueSaveTimer: NodeJS.Timeout | null = null;
let pendingQueueSnapshot: QueueItem[] | null = null;

function clearQueueFileFromDisk(): void {
    try {
        if (fs.existsSync(QUEUE_FILE)) {
            fs.unlinkSync(QUEUE_FILE);
        }
    } catch (e) {
        console.error('Error clearing queue file:', e);
    }
}

function writeQueueToDisk(queue: QueueItem[]): void {
    if (config.persist_queue_on_restart === false) {
        clearQueueFileFromDisk();
        return;
    }

    try {
        writeFileAtomicSync(QUEUE_FILE, JSON.stringify(queue, null, 2));
    } catch (e) {
        console.error('Error saving queue:', e);
    }
}

function saveQueue(queue: QueueItem[], force = false): void {
    if (config.persist_queue_on_restart === false) {
        pendingQueueSnapshot = null;
        if (queueSaveTimer) {
            clearTimeout(queueSaveTimer);
            queueSaveTimer = null;
        }
        clearQueueFileFromDisk();
        return;
    }

    pendingQueueSnapshot = queue;

    if (force) {
        if (queueSaveTimer) {
            clearTimeout(queueSaveTimer);
            queueSaveTimer = null;
        }

        writeQueueToDisk(pendingQueueSnapshot);
        pendingQueueSnapshot = null;
        return;
    }

    if (queueSaveTimer) {
        return;
    }

    queueSaveTimer = setTimeout(() => {
        queueSaveTimer = null;
        if (pendingQueueSnapshot) {
            writeQueueToDisk(pendingQueueSnapshot);
            pendingQueueSnapshot = null;
        }
    }, QUEUE_SAVE_DEBOUNCE_MS);
}

function flushQueueSave(): void {
    if (pendingQueueSnapshot) {
        saveQueue(pendingQueueSnapshot, true);
    } else {
        saveQueue(downloadQueue, true);
    }
}

// ==========================================
// GLOBAL STATE
// ==========================================
let mainWindow: BrowserWindow | null = null;
let config = loadConfig();
let accessToken: string | null = null;
let downloadQueue: QueueItem[] = loadQueue();
let queueIdCounter = 0;
let lastQueueBroadcastFingerprint = '';
let isDownloading = false;
// Process handle for the standalone video editor pipeline (cutter / merger /
// splitter). Queue downloads track their own children via activeDownloads,
// and clip downloads via activeClipProcesses. Keeping these separate
// prevents cancel-download from killing an unrelated cutter ffmpeg.
let currentEditorProcess: ChildProcess | null = null;
let currentDownloadCancelled = false;
let pauseRequested = false;
let activeQueueItemId: string | null = null;
let downloadStartTime = 0;
let downloadedBytes = 0;
// Per-item tracking for parallel downloads
const activeDownloads = new Map<string, { process: ChildProcess | null; cancelled: boolean; startTime: number; bytes: number }>();
const cancelledItemIds = new Set<string>();
const userIdLoginCache = new Map<string, string>();
const loginToUserIdCache = new Map<string, CacheEntry<string>>();
const vodListCache = new Map<string, CacheEntry<VOD[]>>();
const clipInfoCache = new Map<string, CacheEntry<any>>();
const inFlightUserIdRequests = new Map<string, Promise<string | null>>();
const inFlightVodRequests = new Map<string, Promise<VOD[]>>();
const inFlightClipRequests = new Map<string, Promise<any | null>>();
let cacheCleanupTimer: NodeJS.Timeout | null = null;
const runtimeMetrics: RuntimeMetrics = {
    cacheHits: 0,
    cacheMisses: 0,
    duplicateSkips: 0,
    retriesScheduled: 0,
    retriesExhausted: 0,
    integrityFailures: 0,
    downloadsStarted: 0,
    downloadsCompleted: 0,
    downloadsFailed: 0,
    downloadedBytesTotal: 0,
    lastSpeedBytesPerSec: 0,
    avgSpeedBytesPerSec: 0,
    activeItemId: null,
    activeItemTitle: null,
    lastErrorClass: null,
    lastRetryDelaySeconds: 0
};
let debugLogFlushTimer: NodeJS.Timeout | null = null;
let pendingDebugLogLines: string[] = [];
let autoUpdaterInitialized = false;
let autoUpdateCheckTimer: NodeJS.Timeout | null = null;
let autoUpdateStartupTimer: NodeJS.Timeout | null = null;
let autoUpdateCheckInProgress = false;
let autoUpdateReadyToInstall = false;
let autoUpdateDownloadInProgress = false;
let lastAutoUpdateCheckAt = 0;
let latestKnownUpdateVersion: string | null = null;
let downloadedUpdateVersion: string | null = null;
let latestReleaseUpdateInfo: ReleaseUpdateInfo | null = null;
let twitchLoginInFlight: Promise<boolean> | null = null;

function sleep(ms: number): Promise<void> {
    return new Promise((resolve) => setTimeout(resolve, ms));
}

function isDownloadPathWritable(targetPath: string): boolean {
    try {
        fs.mkdirSync(targetPath, { recursive: true });
        const probeFile = path.join(targetPath, `.write_test_${Date.now()}.tmp`);
        fs.writeFileSync(probeFile, 'ok');
        fs.unlinkSync(probeFile);
        return true;
    } catch {
        return false;
    }
}

async function hasInternetConnection(): Promise<boolean> {
    try {
        const res = await axios.get('https://id.twitch.tv/oauth2/validate', {
            timeout: 5000,
            validateStatus: () => true
        });
        return res.status > 0;
    } catch {
        return false;
    }
}

async function runPreflight(autoFix = false): Promise<PreflightResult> {
    appendDebugLog('preflight-start', { autoFix });

    refreshBundledToolPaths();

    const checks: PreflightChecks = {
        internet: await hasInternetConnection(),
        streamlink: false,
        ffmpeg: false,
        ffprobe: false,
        downloadPathWritable: isDownloadPathWritable(config.download_path)
    };

    if (autoFix) {
        await ensureStreamlinkInstalled();
        await ensureFfmpegInstalled();
        refreshBundledToolPaths(true);
    }

    const streamlinkCmd = getStreamlinkCommand();
    checks.streamlink = canExecuteCommand(streamlinkCmd.command, [...streamlinkCmd.prefixArgs, '--version']);
    if (checks.streamlink) {
        cacheVerifiedStreamlinkCommand(streamlinkCmd.command, [...streamlinkCmd.prefixArgs, '--version']);
    }

    const ffmpegPath = getFFmpegPath();
    const ffprobePath = getFFprobePath();
    checks.ffmpeg = canExecuteCommand(ffmpegPath, ['-version']);
    checks.ffprobe = canExecuteCommand(ffprobePath, ['-version']);
    if (checks.ffmpeg && checks.ffprobe) {
        cacheVerifiedFfmpegCommands(ffmpegPath, ffprobePath);
    }

    const messages: string[] = [];
    if (!checks.internet) messages.push(tBackend('preflightNoInternet'));
    if (!checks.streamlink) messages.push(tBackend('preflightStreamlinkMissing'));
    if (!checks.ffmpeg) messages.push(tBackend('preflightFfmpegMissing'));
    if (!checks.ffprobe) messages.push(tBackend('preflightFfprobeMissing'));
    if (!checks.downloadPathWritable) messages.push(tBackend('preflightDownloadPathNotWritable'));

    const result: PreflightResult = {
        ok: messages.length === 0,
        autoFixApplied: autoFix,
        checks,
        messages,
        timestamp: new Date().toISOString()
    };

    appendDebugLog('preflight-finished', result);
    return result;
}

function flushPendingDebugLogLines(): void {
    if (!pendingDebugLogLines.length) {
        return;
    }

    try {
        const payload = pendingDebugLogLines.join('');
        pendingDebugLogLines = [];
        fs.appendFileSync(DEBUG_LOG_FILE, payload);
        trimDebugLogFileIfNeeded();
    } catch {
        // ignore debug log errors
    }
}

function trimDebugLogFileIfNeeded(): void {
    try {
        if (!fs.existsSync(DEBUG_LOG_FILE)) {
            return;
        }

        const stats = fs.statSync(DEBUG_LOG_FILE);
        if (stats.size <= DEBUG_LOG_MAX_BYTES) {
            return;
        }

        const bytesToKeep = Math.min(DEBUG_LOG_TRIM_TO_BYTES, stats.size);
        const startOffset = Math.max(0, stats.size - bytesToKeep);
        const buffer = Buffer.allocUnsafe(bytesToKeep);

        let fileHandle: number | null = null;
        try {
            fileHandle = fs.openSync(DEBUG_LOG_FILE, 'r');
            fs.readSync(fileHandle, buffer, 0, bytesToKeep, startOffset);
        } finally {
            if (fileHandle !== null) {
                fs.closeSync(fileHandle);
            }
        }

        const firstLineBreak = buffer.indexOf(0x0a);
        const trimmed = firstLineBreak >= 0 && firstLineBreak + 1 < buffer.length
            ? buffer.subarray(firstLineBreak + 1)
            : buffer;

        fs.writeFileSync(DEBUG_LOG_FILE, trimmed);
    } catch {
        // ignore debug log errors
    }
}

function readDebugLogTailFromDisk(): string {
    const stats = fs.statSync(DEBUG_LOG_FILE);
    if (stats.size <= 0) {
        return '';
    }

    const bytesToRead = Math.min(stats.size, DEBUG_LOG_READ_TAIL_BYTES);
    if (bytesToRead === stats.size) {
        return fs.readFileSync(DEBUG_LOG_FILE, 'utf-8');
    }

    const buffer = Buffer.allocUnsafe(bytesToRead);
    let fileHandle: number | null = null;
    try {
        fileHandle = fs.openSync(DEBUG_LOG_FILE, 'r');
        fs.readSync(fileHandle, buffer, 0, bytesToRead, stats.size - bytesToRead);
    } finally {
        if (fileHandle !== null) {
            fs.closeSync(fileHandle);
        }
    }

    const firstLineBreak = buffer.indexOf(0x0a);
    const slice = firstLineBreak >= 0 && firstLineBreak + 1 < buffer.length
        ? buffer.subarray(firstLineBreak + 1)
        : buffer;

    return slice.toString('utf-8');
}

function startDebugLogFlushTimer(): void {
    if (debugLogFlushTimer) {
        return;
    }

    debugLogFlushTimer = setInterval(() => {
        flushPendingDebugLogLines();
    }, DEBUG_LOG_FLUSH_INTERVAL_MS);

    debugLogFlushTimer.unref?.();
}

function stopDebugLogFlushTimer(flush = true): void {
    if (debugLogFlushTimer) {
        clearInterval(debugLogFlushTimer);
        debugLogFlushTimer = null;
    }

    if (flush) {
        flushPendingDebugLogLines();
    }
}

function readDebugLog(lines = 200): string {
    try {
        flushPendingDebugLogLines();

        if (!fs.existsSync(DEBUG_LOG_FILE)) {
            return 'Debug-Log ist leer.';
        }

        const text = readDebugLogTailFromDisk();
        const rows = text.split(/\r?\n/).filter(Boolean);
        return rows.slice(-lines).join('\n') || 'Debug-Log ist leer.';
    } catch (e) {
        return `Debug-Log konnte nicht gelesen werden: ${String(e)}`;
    }
}

function appendDebugLog(message: string, details?: unknown): void {
    try {
        const ts = new Date().toISOString();
        const payload = details === undefined
            ? ''
            : ` | ${typeof details === 'string' ? details : JSON.stringify(details)}`;

        pendingDebugLogLines.push(`[${ts}] ${message}${payload}\n`);

        if (pendingDebugLogLines.length >= DEBUG_LOG_BUFFER_FLUSH_LINES) {
            flushPendingDebugLogLines();
        } else {
            startDebugLogFlushTimer();
        }
    } catch {
        // ignore debug log errors
    }
}

// Wire up tools module with debug logging and directory paths
setDebugLogFn(appendDebugLog);
initToolDirs(TOOLS_STREAMLINK_DIR, TOOLS_FFMPEG_DIR, () => app.getPath('temp'));

// ==========================================
// DURATION HELPERS
// ==========================================
function parseDuration(duration: string): number {
    let seconds = 0;
    const hours = duration.match(/(\d+)h/);
    const minutes = duration.match(/(\d+)m/);
    const secs = duration.match(/(\d+)s/);

    if (hours) seconds += parseInt(hours[1]) * 3600;
    if (minutes) seconds += parseInt(minutes[1]) * 60;
    if (secs) seconds += parseInt(secs[1]);

    return seconds;
}

function formatDuration(seconds: number): string {
    if (!isFinite(seconds) || seconds < 0) return '00:00:00';
    const h = Math.floor(seconds / 3600);
    const m = Math.floor((seconds % 3600) / 60);
    const s = Math.floor(seconds % 60);
    return `${h.toString().padStart(2, '0')}:${m.toString().padStart(2, '0')}:${s.toString().padStart(2, '0')}`;
}

function formatDurationDashed(seconds: number): string {
    if (!isFinite(seconds) || seconds < 0) return '00-00-00';
    const h = Math.floor(seconds / 3600);
    const m = Math.floor((seconds % 3600) / 60);
    const s = Math.floor(seconds % 60);
    return `${h.toString().padStart(2, '0')}-${m.toString().padStart(2, '0')}-${s.toString().padStart(2, '0')}`;
}

const claimedFilenames = new Set<string>();
const itemClaimedFilenames = new Map<string, Set<string>>();

function ensureUniqueFilename(filePath: string, itemId: string | null = null): string {
    const dir = path.dirname(filePath);
    const ext = path.extname(filePath);
    const base = path.basename(filePath, ext);
    let candidate = filePath;
    let counter = 0;
    while (fs.existsSync(candidate) || claimedFilenames.has(candidate)) {
        counter++;
        candidate = path.join(dir, `${base}_${counter}${ext}`);
    }
    claimedFilenames.add(candidate);
    if (itemId) {
        let perItem = itemClaimedFilenames.get(itemId);
        if (!perItem) {
            perItem = new Set();
            itemClaimedFilenames.set(itemId, perItem);
        }
        perItem.add(candidate);
    }
    return candidate;
}

function releaseClaimedFilenamesForItem(itemId: string): void {
    const perItem = itemClaimedFilenames.get(itemId);
    if (!perItem) return;
    for (const f of perItem) claimedFilenames.delete(f);
    itemClaimedFilenames.delete(itemId);
}

function sanitizeFilenamePart(input: string, fallback = 'unnamed'): string {
    const cleaned = (input || '')
        .replace(/[<>:"|?*\x00-\x1f]/g, '_')
        .replace(/[\\/]/g, '_')
        .trim();
    return cleaned || fallback;
}

function formatDateWithPattern(date: Date, pattern: string): string {
    const tokenMap: Record<string, string> = {
        yyyy: date.getFullYear().toString(),
        yy: date.getFullYear().toString().slice(-2),
        MM: (date.getMonth() + 1).toString().padStart(2, '0'),
        M: (date.getMonth() + 1).toString(),
        dd: date.getDate().toString().padStart(2, '0'),
        d: date.getDate().toString(),
        HH: date.getHours().toString().padStart(2, '0'),
        H: date.getHours().toString(),
        hh: date.getHours().toString().padStart(2, '0'),
        h: date.getHours().toString(),
        mm: date.getMinutes().toString().padStart(2, '0'),
        m: date.getMinutes().toString(),
        ss: date.getSeconds().toString().padStart(2, '0'),
        s: date.getSeconds().toString()
    };

    return pattern
        .replace(/yyyy|yy|MM|M|dd|d|HH|H|hh|h|mm|m|ss|s/g, (token) => tokenMap[token] ?? token)
        .replace(/\\(.)/g, '$1');
}

function formatSecondsWithPattern(totalSeconds: number, pattern: string): string {
    const safe = Math.max(0, Math.floor(totalSeconds));
    const hours = Math.floor(safe / 3600);
    const minutes = Math.floor((safe % 3600) / 60);
    const seconds = safe % 60;

    const tokenMap: Record<string, string> = {
        HH: hours.toString().padStart(2, '0'),
        H: hours.toString(),
        hh: hours.toString().padStart(2, '0'),
        h: hours.toString(),
        mm: minutes.toString().padStart(2, '0'),
        m: minutes.toString(),
        ss: seconds.toString().padStart(2, '0'),
        s: seconds.toString()
    };

    return pattern
        .replace(/HH|H|hh|h|mm|m|ss|s/g, (token) => tokenMap[token] ?? token)
        .replace(/\\(.)/g, '$1');
}

function parseVodId(url: string): string {
    const match = url.match(/videos\/(\d+)/i);
    return match?.[1] || '';
}

function isLikelyVodUrl(url: string): boolean {
    return /twitch\.tv\/videos\/\d+/i.test(url || '');
}

function parseFrameRate(rawFrameRate: string | undefined): number {
    const fallback = 30;
    const value = (rawFrameRate || '').trim();
    if (!value) return fallback;

    if (/^\d+(\.\d+)?$/.test(value)) {
        const numeric = Number(value);
        return Number.isFinite(numeric) && numeric > 0 ? numeric : fallback;
    }

    const ratio = value.match(/^(\d+(?:\.\d+)?)\/(\d+(?:\.\d+)?)$/);
    if (!ratio) return fallback;

    const numerator = Number(ratio[1]);
    const denominator = Number(ratio[2]);
    if (!Number.isFinite(numerator) || !Number.isFinite(denominator) || denominator <= 0) {
        return fallback;
    }

    const fps = numerator / denominator;
    return Number.isFinite(fps) && fps > 0 ? fps : fallback;
}

interface ClipTemplateContext {
    template: string;
    title: string;
    vodId: string;
    channel: string;
    date: Date;
    part: number;
    partPadded: string;
    trimStartSec: number;
    trimEndSec: number;
    trimLengthSec: number;
    fullLengthSec: number;
}

function renderClipFilenameTemplate(context: ClipTemplateContext): string {
    const baseDate = `${context.date.getDate().toString().padStart(2, '0')}.${(context.date.getMonth() + 1).toString().padStart(2, '0')}.${context.date.getFullYear()}`;
    let rendered = context.template
        .replace(/\{title\}/g, sanitizeFilenamePart(context.title, 'untitled'))
        .replace(/\{id\}/g, sanitizeFilenamePart(context.vodId, 'unknown'))
        .replace(/\{channel\}/g, sanitizeFilenamePart(context.channel, 'unknown'))
        .replace(/\{channel_id\}/g, '')
        .replace(/\{date\}/g, baseDate)
        .replace(/\{part\}/g, String(context.part))
        .replace(/\{part_padded\}/g, context.partPadded)
        .replace(/\{trim_start\}/g, formatDurationDashed(context.trimStartSec))
        .replace(/\{trim_end\}/g, formatDurationDashed(context.trimEndSec))
        .replace(/\{trim_length\}/g, formatDurationDashed(context.trimLengthSec))
        .replace(/\{length\}/g, formatDurationDashed(context.fullLengthSec))
        .replace(/\{ext\}/g, 'mp4')
        .replace(/\{random_string\}/g, Math.random().toString(36).slice(2, 10));

    rendered = rendered.replace(/\{date_custom="(.*?)"\}/g, (_, pattern: string) => {
        return sanitizeFilenamePart(formatDateWithPattern(context.date, pattern), 'date');
    });
    rendered = rendered.replace(/\{trim_start_custom="(.*?)"\}/g, (_, pattern: string) => {
        return sanitizeFilenamePart(formatSecondsWithPattern(context.trimStartSec, pattern), '00-00-00');
    });
    rendered = rendered.replace(/\{trim_end_custom="(.*?)"\}/g, (_, pattern: string) => {
        return sanitizeFilenamePart(formatSecondsWithPattern(context.trimEndSec, pattern), '00-00-00');
    });
    rendered = rendered.replace(/\{trim_length_custom="(.*?)"\}/g, (_, pattern: string) => {
        return sanitizeFilenamePart(formatSecondsWithPattern(context.trimLengthSec, pattern), '00-00-00');
    });
    rendered = rendered.replace(/\{length_custom="(.*?)"\}/g, (_, pattern: string) => {
        return sanitizeFilenamePart(formatSecondsWithPattern(context.fullLengthSec, pattern), '00-00-00');
    });

    const parts = rendered
        .split(/[\\/]+/)
        .map((segment) => sanitizeFilenamePart(segment, 'unnamed'))
        .filter((segment) => segment !== '.' && segment !== '..');

    if (parts.length === 0) {
        return 'clip.mp4';
    }

    const lastIdx = parts.length - 1;
    if (!/\.[A-Za-z0-9]{1,8}$/.test(parts[lastIdx])) {
        parts[lastIdx] = `${parts[lastIdx]}.mp4`;
    }

    return path.join(...parts);
}

function formatBytes(bytes: number): string {
    if (bytes < 1024) return bytes + ' B';
    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
    if (bytes < 1024 * 1024 * 1024) return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
    return (bytes / (1024 * 1024 * 1024)).toFixed(2) + ' GB';
}

function formatSpeed(bytesPerSec: number): string {
    if (bytesPerSec < 1024) return bytesPerSec.toFixed(0) + ' B/s';
    if (bytesPerSec < 1024 * 1024) return (bytesPerSec / 1024).toFixed(1) + ' KB/s';
    return (bytesPerSec / (1024 * 1024)).toFixed(1) + ' MB/s';
}

function formatETA(seconds: number): string {
    if (seconds < 60) return `${Math.floor(seconds)}s`;
    if (seconds < 3600) return `${Math.floor(seconds / 60)}m ${Math.floor(seconds % 60)}s`;
    const h = Math.floor(seconds / 3600);
    const m = Math.floor((seconds % 3600) / 60);
    return `${h}h ${m}m`;
}

function getFreeDiskBytes(targetPath: string): number | null {
    try {
        const statfsSync = (fs as unknown as { statfsSync?: (path: string) => { bsize?: number; frsize?: number; bavail?: number } }).statfsSync;
        if (!statfsSync) {
            return null;
        }

        const info = statfsSync(targetPath);
        const blockSize = Number(info?.bsize || info?.frsize || 0);
        const availableBlocks = Number(info?.bavail || 0);
        if (!Number.isFinite(blockSize) || !Number.isFinite(availableBlocks) || blockSize <= 0 || availableBlocks < 0) {
            return null;
        }

        return Math.floor(blockSize * availableBlocks);
    } catch {
        return null;
    }
}

function estimateRequiredDownloadBytes(item: QueueItem): number {
    const durationSeconds = Math.max(1, item.customClip?.durationSec || parseDuration(item.duration_str || '0s'));

    const bytesPerSecondByMode: Record<PerformanceMode, number> = {
        stability: 900 * 1024,
        balanced: 700 * 1024,
        speed: 550 * 1024
    };

    const mode = normalizePerformanceMode(config.performance_mode);
    const baseEstimate = durationSeconds * bytesPerSecondByMode[mode];
    const withHeadroom = Math.ceil(baseEstimate * (item.customClip ? 1.2 : 1.35));

    return Math.max(64 * 1024 * 1024, Math.min(withHeadroom, 40 * 1024 * 1024 * 1024));
}

function ensureDiskSpace(targetPath: string, requiredBytes: number, context: string): DownloadResult {
    const freeBytes = getFreeDiskBytes(targetPath);
    if (freeBytes === null) {
        appendDebugLog('disk-space-check-skipped', { targetPath, requiredBytes, context });
        return { success: true };
    }

    if (freeBytes < Math.max(requiredBytes, MIN_FREE_DISK_BYTES)) {
        const message = tBackend('diskSpaceShortFor', { context, free: formatBytes(freeBytes), required: formatBytes(requiredBytes) });
        appendDebugLog('disk-space-check-failed', {
            targetPath,
            requiredBytes,
            freeBytes,
            context
        });
        return { success: false, error: message };
    }

    return { success: true };
}

function getMetadataCacheTtlMs(): number {
    return normalizeMetadataCacheMinutes(config.metadata_cache_minutes) * 60 * 1000;
}

function getCachedValue<T>(cache: Map<string, CacheEntry<T>>, key: string): T | undefined {
    const cached = cache.get(key);
    if (!cached) {
        return undefined;
    }

    if (cached.expiresAt <= Date.now()) {
        cache.delete(key);
        return undefined;
    }

    cache.delete(key);
    cache.set(key, cached);
    return cached.value;
}

function pruneExpiredCacheEntries<T>(cache: Map<string, CacheEntry<T>>): number {
    const now = Date.now();
    let removed = 0;

    for (const [key, entry] of cache.entries()) {
        if (entry.expiresAt <= now) {
            cache.delete(key);
            removed += 1;
        }
    }

    return removed;
}

function enforceCacheEntryLimit<T>(cache: Map<string, CacheEntry<T>>, maxEntries: number): number {
    if (maxEntries <= 0) {
        const removed = cache.size;
        cache.clear();
        return removed;
    }

    let removed = 0;
    while (cache.size > maxEntries) {
        const oldest = cache.keys().next().value as string | undefined;
        if (!oldest) {
            break;
        }
        cache.delete(oldest);
        removed += 1;
    }

    return removed;
}

function setCachedValue<T>(
    cache: Map<string, CacheEntry<T>>,
    key: string,
    value: T,
    maxEntries: number
): void {
    cache.set(key, {
        value,
        expiresAt: Date.now() + getMetadataCacheTtlMs()
    });

    if (cache.size > maxEntries) {
        pruneExpiredCacheEntries(cache);
        enforceCacheEntryLimit(cache, maxEntries);
    }
}

function cleanupMetadataCaches(reason: 'interval' | 'manual' | 'shutdown'): void {
    const before = {
        loginToUserId: loginToUserIdCache.size,
        vodList: vodListCache.size,
        clipInfo: clipInfoCache.size
    };

    const expired = {
        loginToUserId: pruneExpiredCacheEntries(loginToUserIdCache),
        vodList: pruneExpiredCacheEntries(vodListCache),
        clipInfo: pruneExpiredCacheEntries(clipInfoCache)
    };

    const evicted = {
        loginToUserId: enforceCacheEntryLimit(loginToUserIdCache, MAX_LOGIN_TO_USER_ID_CACHE_ENTRIES),
        vodList: enforceCacheEntryLimit(vodListCache, MAX_VOD_LIST_CACHE_ENTRIES),
        clipInfo: enforceCacheEntryLimit(clipInfoCache, MAX_CLIP_INFO_CACHE_ENTRIES)
    };

    const removedTotal =
        expired.loginToUserId + expired.vodList + expired.clipInfo +
        evicted.loginToUserId + evicted.vodList + evicted.clipInfo;

    if (removedTotal > 0) {
        appendDebugLog('metadata-cache-cleanup', {
            reason,
            before,
            after: {
                loginToUserId: loginToUserIdCache.size,
                vodList: vodListCache.size,
                clipInfo: clipInfoCache.size
            },
            expired,
            evicted,
            removedTotal
        });
    }
}

function clearMetadataCaches(): void {
    loginToUserIdCache.clear();
    vodListCache.clear();
    clipInfoCache.clear();
}

function startMetadataCacheCleanup(): void {
    if (cacheCleanupTimer) {
        return;
    }

    cacheCleanupTimer = setInterval(() => {
        cleanupMetadataCaches('interval');
    }, CACHE_CLEANUP_INTERVAL_MS);

    cacheCleanupTimer.unref?.();
}

function stopMetadataCacheCleanup(): void {
    if (!cacheCleanupTimer) {
        return;
    }

    clearInterval(cacheCleanupTimer);
    cacheCleanupTimer = null;
}

function withInFlightDedup<T>(
    store: Map<string, Promise<T>>,
    key: string,
    factory: () => Promise<T>
): Promise<T> {
    const existing = store.get(key);
    if (existing) {
        return existing;
    }

    const requestPromise: Promise<T> = factory().finally(() => {
        if (store.get(key) === requestPromise) {
            store.delete(key);
        }
    });

    store.set(key, requestPromise);
    return requestPromise;
}

function getRetryAttemptLimit(): number {
    switch (normalizePerformanceMode(config.performance_mode)) {
        case 'stability':
            return 5;
        case 'speed':
            return 2;
        case 'balanced':
        default:
            return 3;
    }
}

function classifyDownloadError(errorMessage: string): RetryErrorClass {
    const text = (errorMessage || '').toLowerCase();
    if (!text) return 'unknown';

    if (text.includes('ungueltige vod-url') || text.includes('invalid vod url')) return 'validation';
    if (text.includes('429') || text.includes('rate limit') || text.includes('too many requests')) return 'rate_limit';
    if (text.includes('401') || text.includes('403') || text.includes('unauthorized') || text.includes('forbidden')) return 'auth';
    if (text.includes('timed out') || text.includes('timeout') || text.includes('network') || text.includes('connection') || text.includes('dns')) return 'network';
    if (text.includes('streamlink nicht gefunden') || text.includes('streamlink not found') || text.includes('streamlink is missing') || text.includes('ffmpeg') || text.includes('ffprobe') || text.includes('enoent')) return 'tooling';
    if (text.includes('integritaet') || text.includes('integrity') || text.includes('kein videostream') || text.includes('no video stream')) return 'integrity';
    if (text.includes('access denied') || text.includes('permission') || text.includes('disk') || text.includes('file') || text.includes('ordner') || text.includes('folder')) return 'io';

    return 'unknown';
}

function getRetryDelaySeconds(errorClass: RetryErrorClass, attempt: number): number {
    const jitter = Math.floor(Math.random() * 3);

    switch (errorClass) {
        case 'rate_limit':
            return Math.min(45, 10 + attempt * 6 + jitter);
        case 'network':
            return Math.min(30, 4 * attempt + jitter);
        case 'auth':
            return Math.min(40, 8 + attempt * 5 + jitter);
        case 'integrity':
            return Math.min(20, 3 + attempt * 2 + jitter);
        case 'io':
            return Math.min(25, 5 + attempt * 3 + jitter);
        case 'tooling':
            return DEFAULT_RETRY_DELAY_SECONDS;
        case 'validation':
            return 0;
        case 'unknown':
        default:
            return Math.min(25, DEFAULT_RETRY_DELAY_SECONDS + attempt * 2 + jitter);
    }
}

function getQueueCounts(queueData: QueueItem[] = downloadQueue): RuntimeMetricsSnapshot['queue'] {
    const counts = {
        pending: 0,
        downloading: 0,
        paused: 0,
        completed: 0,
        error: 0,
        total: queueData.length
    };

    for (const item of queueData) {
        if (item.status === 'pending') counts.pending += 1;
        else if (item.status === 'downloading') counts.downloading += 1;
        else if (item.status === 'paused') counts.paused += 1;
        else if (item.status === 'completed') counts.completed += 1;
        else if (item.status === 'error') counts.error += 1;
    }

    return counts;
}

function generateQueueItemId(): string {
    queueIdCounter = (queueIdCounter + 1) % 1000;
    return `${Date.now()}-${queueIdCounter}`;
}

function getQueueBroadcastFingerprint(queueData: QueueItem[] = downloadQueue): string {
    return queueData.map((item) => [
        item.id,
        item.status,
        Math.round((Number(item.progress) || 0) * 10),
        item.currentPart || 0,
        item.totalParts || 0,
        item.speed || '',
        item.eta || '',
        item.last_error || ''
    ].join(':')).join('|');
}

function emitQueueUpdated(force = false): void {
    const nextFingerprint = getQueueBroadcastFingerprint(downloadQueue);
    if (!force && nextFingerprint === lastQueueBroadcastFingerprint) {
        return;
    }

    lastQueueBroadcastFingerprint = nextFingerprint;
    mainWindow?.webContents.send('queue-updated', downloadQueue);
}

function hasQueueItemId(id: string): boolean {
    return downloadQueue.some((item) => item.id === id);
}

function getRuntimeMetricsSnapshot(): RuntimeMetricsSnapshot {
    return {
        ...runtimeMetrics,
        timestamp: new Date().toISOString(),
        queue: getQueueCounts(downloadQueue),
        caches: {
            loginToUserId: loginToUserIdCache.size,
            vodList: vodListCache.size,
            clipInfo: clipInfoCache.size
        },
        config: {
            performanceMode: normalizePerformanceMode(config.performance_mode),
            smartScheduler: config.smart_queue_scheduler !== false,
            metadataCacheMinutes: normalizeMetadataCacheMinutes(config.metadata_cache_minutes),
            duplicatePrevention: config.prevent_duplicate_downloads !== false
        }
    };
}

function normalizeQueueUrlForFingerprint(url: string): string {
    return (url || '').trim().toLowerCase().replace(/^https?:\/\/(www\.)?/, '');
}

function getQueueItemFingerprint(item: Pick<QueueItem, 'url' | 'streamer' | 'date' | 'customClip'>): string {
    const clip = item.customClip;
    const clipFingerprint = clip
        ? [
            'clip',
            clip.startSec,
            clip.durationSec,
            clip.startPart,
            clip.filenameFormat,
            (clip.filenameTemplate || '').trim().toLowerCase()
        ].join(':')
        : 'vod';

    return [
        normalizeQueueUrlForFingerprint(item.url),
        (item.streamer || '').trim().toLowerCase(),
        (item.date || '').trim(),
        clipFingerprint
    ].join('|');
}

function isQueueItemActive(item: QueueItem): boolean {
    return item.status === 'pending' || item.status === 'downloading' || item.status === 'paused';
}

function hasActiveDuplicate(candidate: Pick<QueueItem, 'url' | 'streamer' | 'date' | 'customClip'>): boolean {
    const candidateFingerprint = getQueueItemFingerprint(candidate);

    return downloadQueue.some((existing) => {
        if (!isQueueItemActive(existing)) return false;
        return getQueueItemFingerprint(existing) === candidateFingerprint;
    });
}

function getQueuePriorityScore(item: QueueItem): number {
    const now = Date.now();
    const createdMs = Number(item.id) || now;
    const waitSeconds = Math.max(0, Math.floor((now - createdMs) / 1000));
    const durationSeconds = Math.max(0, parseDuration(item.duration_str || '0s'));
    const clipBoost = item.customClip ? 1500 : 0;
    const shortJobBoost = Math.max(0, 7200 - Math.min(7200, durationSeconds)) / 5;
    const ageBoost = Math.min(waitSeconds, 1800) / 2;

    return clipBoost + shortJobBoost + ageBoost;
}

function pickNextPendingQueueItem(): QueueItem | null {
    const pendingItems = downloadQueue.filter((item) => item.status === 'pending');
    if (!pendingItems.length) return null;

    if (!config.smart_queue_scheduler) {
        return pendingItems[0];
    }

    let best = pendingItems[0];
    let bestScore = getQueuePriorityScore(best);

    for (let i = 1; i < pendingItems.length; i += 1) {
        const candidate = pendingItems[i];
        const score = getQueuePriorityScore(candidate);
        if (score > bestScore) {
            best = candidate;
            bestScore = score;
        }
    }

    return best;
}

function parseClockDurationSeconds(duration: string | null): number | null {
    if (!duration) return null;
    const parts = duration.split(':').map((part) => Number(part));
    if (parts.length !== 3 || parts.some((part) => !Number.isFinite(part))) {
        return null;
    }

    return Math.max(0, Math.floor(parts[0] * 3600 + parts[1] * 60 + parts[2]));
}

function probeMediaFile(filePath: string): { durationSeconds: number; hasVideo: boolean } | null {
    try {
        const ffprobePath = getFFprobePath();
        if (!canExecuteCommand(ffprobePath, ['-version'])) {
            return null;
        }

        const res = spawnSync(ffprobePath, [
            '-v', 'error',
            '-print_format', 'json',
            '-show_format',
            '-show_streams',
            filePath
        ], {
            windowsHide: true,
            encoding: 'utf-8'
        });

        if (res.status !== 0 || !res.stdout) {
            return null;
        }

        const parsed = JSON.parse(res.stdout) as {
            format?: { duration?: string };
            streams?: Array<{ codec_type?: string }>;
        };

        const durationSeconds = Number(parsed?.format?.duration || 0);
        const hasVideo = Boolean(parsed?.streams?.some((stream) => stream.codec_type === 'video'));

        return {
            durationSeconds: Number.isFinite(durationSeconds) ? durationSeconds : 0,
            hasVideo
        };
    } catch {
        return null;
    }
}

function validateDownloadedFileIntegrity(filePath: string, expectedDurationSeconds: number | null): DownloadResult {
    const probed = probeMediaFile(filePath);
    if (!probed) {
        appendDebugLog('integrity-probe-skipped', { filePath });
        return { success: true };
    }

    if (!probed.hasVideo) {
        runtimeMetrics.integrityFailures += 1;
        return { success: false, error: tBackend('integrityNoVideo') };
    }

    if (probed.durationSeconds <= 1) {
        runtimeMetrics.integrityFailures += 1;
        return { success: false, error: tBackend('integrityTooShort', { duration: probed.durationSeconds.toFixed(2) }) };
    }

    if (expectedDurationSeconds && expectedDurationSeconds > 4) {
        const minExpected = Math.max(2, expectedDurationSeconds * 0.45);
        if (probed.durationSeconds < minExpected) {
            runtimeMetrics.integrityFailures += 1;
            return {
                success: false,
                error: tBackend('integrityDurationMismatch', { actual: probed.durationSeconds.toFixed(1), expected: String(expectedDurationSeconds) })
            };
        }
    }

    return { success: true };
}

// ==========================================
// TWITCH API
// ==========================================
async function twitchLogin(): Promise<boolean> {
    if (!config.client_id || !config.client_secret) {
        return false;
    }

    try {
        const response = await axios.post('https://id.twitch.tv/oauth2/token', null, {
            params: {
                client_id: config.client_id,
                client_secret: config.client_secret,
                grant_type: 'client_credentials'
            },
            timeout: API_TIMEOUT
        });
        accessToken = response.data.access_token;
        return true;
    } catch (e) {
        console.error('Login error:', e);
        return false;
    }
}

function requestTwitchLogin(): Promise<boolean> {
    if (twitchLoginInFlight) {
        return twitchLoginInFlight;
    }

    const loginPromise: Promise<boolean> = twitchLogin().finally(() => {
        if (twitchLoginInFlight === loginPromise) {
            twitchLoginInFlight = null;
        }
    });

    twitchLoginInFlight = loginPromise;
    return loginPromise;
}

async function ensureTwitchAuth(forceRefresh = false): Promise<boolean> {
    if (!config.client_id || !config.client_secret) {
        accessToken = null;
        return false;
    }

    if (!forceRefresh && accessToken) {
        return true;
    }

    return await requestTwitchLogin();
}

function normalizeLogin(input: string): string {
    return input.trim().replace(/^@+/, '').toLowerCase();
}

function formatTwitchDurationFromSeconds(totalSeconds: number): string {
    const seconds = Math.max(0, Math.floor(totalSeconds));
    const h = Math.floor(seconds / 3600);
    const m = Math.floor((seconds % 3600) / 60);
    const s = seconds % 60;

    if (h > 0) return `${h}h${m}m${s}s`;
    if (m > 0) return `${m}m${s}s`;
    return `${s}s`;
}

// Transient HTTP errors that warrant a retry (5xx, 408 timeout, 429 rate limit).
// 4xx (other than 408/429) are application errors and not retried.
function isTransientAxiosError(err: unknown): boolean {
    if (!axios.isAxiosError(err)) {
        // Non-axios errors thrown from axios.post are typically network-layer
        // failures (DNS, ECONNRESET, socket hangup) — retry those too.
        return true;
    }
    const status = err.response?.status;
    if (status === undefined) {
        // No response means the request never reached / never returned —
        // treat as transient (network blip, timeout).
        return true;
    }
    return status === 408 || status === 429 || (status >= 500 && status < 600);
}

const TWITCH_GQL_RETRY_ATTEMPTS = 3;
const TWITCH_GQL_RETRY_BASE_DELAY_MS = 400;

async function fetchPublicTwitchGql<T>(query: string, variables: Record<string, unknown>): Promise<T | null> {
    let lastError: unknown = null;

    for (let attempt = 1; attempt <= TWITCH_GQL_RETRY_ATTEMPTS; attempt++) {
        try {
            const response = await axios.post<{ data?: T; errors?: Array<{ message: string }> }>(
                'https://gql.twitch.tv/gql',
                { query, variables },
                {
                    headers: {
                        'Client-ID': TWITCH_WEB_CLIENT_ID,
                        'Content-Type': 'application/json'
                    },
                    timeout: API_TIMEOUT
                }
            );

            // GraphQL errors (in `errors[]`) are application-level and not
            // retried — the query itself is rejected.
            if (response.data.errors?.length) {
                const messages = response.data.errors.map((err) => err.message).join('; ');
                appendDebugLog('public-gql-errors', { messages, attempt });
                console.error('Public Twitch GQL errors:', messages);
                return null;
            }

            if (attempt > 1) {
                appendDebugLog('public-gql-recovered', { attempt });
            }
            return response.data.data || null;
        } catch (e) {
            lastError = e;
            const transient = isTransientAxiosError(e);
            const willRetry = transient && attempt < TWITCH_GQL_RETRY_ATTEMPTS;
            appendDebugLog('public-gql-failed', {
                attempt,
                maxAttempts: TWITCH_GQL_RETRY_ATTEMPTS,
                transient,
                willRetry,
                error: String(e)
            });
            if (!willRetry) {
                break;
            }
            // Exponential backoff with jitter
            const delay = TWITCH_GQL_RETRY_BASE_DELAY_MS * Math.pow(2, attempt - 1) + Math.floor(Math.random() * 250);
            await sleep(delay);
        }
    }

    console.error('Public Twitch GQL request failed:', lastError);
    return null;
}

async function getPublicUserId(username: string): Promise<string | null> {
    const login = normalizeLogin(username);
    if (!login) return null;

    const cachedUserId = getCachedValue(loginToUserIdCache, login);
    if (cachedUserId !== undefined) {
        runtimeMetrics.cacheHits += 1;
        return cachedUserId;
    }

    runtimeMetrics.cacheMisses += 1;

    type UserQueryResult = { user: { id: string; login: string } | null };
    const data = await fetchPublicTwitchGql<UserQueryResult>(
        'query($login:String!){ user(login:$login){ id login } }',
        { login }
    );

    const user = data?.user;
    if (!user?.id) return null;

    setCachedValue(loginToUserIdCache, login, user.id, MAX_LOGIN_TO_USER_ID_CACHE_ENTRIES);
    userIdLoginCache.set(user.id, user.login || login);
    return user.id;
}

async function getPublicVODsByLogin(loginName: string): Promise<VOD[]> {
    const login = normalizeLogin(loginName);
    if (!login) return [];

    type VideoNode = {
        id: string;
        title: string;
        publishedAt: string;
        lengthSeconds: number;
        viewCount: number;
        previewThumbnailURL: string;
    };

    type VodsQueryResult = {
        user: {
            videos: {
                edges: Array<{ node: VideoNode }>;
            };
        } | null;
    };

    const data = await fetchPublicTwitchGql<VodsQueryResult>(
        'query($login:String!,$first:Int!){ user(login:$login){ videos(first:$first, type:ARCHIVE, sort:TIME){ edges{ node{ id title publishedAt lengthSeconds viewCount previewThumbnailURL(width:320,height:180) } } } } }',
        { login, first: 100 }
    );

    const edges = data?.user?.videos?.edges || [];

    return edges
        .map(({ node }) => {
            const id = node?.id;
            if (!id) return null;

            return {
                id,
                title: node.title || 'Untitled VOD',
                created_at: node.publishedAt || new Date(0).toISOString(),
                duration: formatTwitchDurationFromSeconds(node.lengthSeconds || 0),
                thumbnail_url: node.previewThumbnailURL || '',
                url: `https://www.twitch.tv/videos/${id}`,
                view_count: node.viewCount || 0,
                stream_id: ''
            } as VOD;
        })
        .filter((vod): vod is VOD => Boolean(vod));
}

async function getUserId(username: string): Promise<string | null> {
    const login = normalizeLogin(username);
    if (!login) return null;

    const cachedUserId = getCachedValue(loginToUserIdCache, login);
    if (cachedUserId !== undefined) {
        runtimeMetrics.cacheHits += 1;
        return cachedUserId;
    }

    return await withInFlightDedup(inFlightUserIdRequests, login, async () => {
        const refreshedCachedUserId = getCachedValue(loginToUserIdCache, login);
        if (refreshedCachedUserId !== undefined) {
            runtimeMetrics.cacheHits += 1;
            return refreshedCachedUserId;
        }

        runtimeMetrics.cacheMisses += 1;

        const getUserViaPublicApi = async () => {
            return await getPublicUserId(login);
        };

        if (!(await ensureTwitchAuth())) return await getUserViaPublicApi();

        const fetchUser = async () => {
            return await axios.get('https://api.twitch.tv/helix/users', {
                params: { login },
                headers: {
                    'Client-ID': config.client_id,
                    'Authorization': `Bearer ${accessToken}`
                },
                timeout: API_TIMEOUT
            });
        };

        try {
            const response = await fetchUser();
            const user = response.data.data[0];
            if (!user?.id) return await getUserViaPublicApi();

            setCachedValue(loginToUserIdCache, login, user.id, MAX_LOGIN_TO_USER_ID_CACHE_ENTRIES);
            userIdLoginCache.set(user.id, user.login || login);
            return user.id;
        } catch (e) {
            if (axios.isAxiosError(e) && e.response?.status === 401 && (await ensureTwitchAuth(true))) {
                try {
                    const retryResponse = await fetchUser();
                    const user = retryResponse.data.data[0];
                    if (!user?.id) return await getUserViaPublicApi();

                    setCachedValue(loginToUserIdCache, login, user.id, MAX_LOGIN_TO_USER_ID_CACHE_ENTRIES);
                    userIdLoginCache.set(user.id, user.login || login);
                    return user.id;
                } catch (retryError) {
                    console.error('Error getting user after relogin:', retryError);
                    return await getUserViaPublicApi();
                }
            }

            console.error('Error getting user:', e);
            return await getUserViaPublicApi();
        }
    });
}

async function getVODs(userId: string, forceRefresh = false): Promise<VOD[]> {
    const cacheKey = `user:${userId}`;
    if (!forceRefresh) {
        const cachedVods = getCachedValue(vodListCache, cacheKey);
        if (cachedVods !== undefined) {
            runtimeMetrics.cacheHits += 1;
            return cachedVods;
        }
    }

    const requestKey = `${cacheKey}|${forceRefresh ? 'force' : 'default'}`;
    return await withInFlightDedup(inFlightVodRequests, requestKey, async () => {
        if (!forceRefresh) {
            const refreshedCachedVods = getCachedValue(vodListCache, cacheKey);
            if (refreshedCachedVods !== undefined) {
                runtimeMetrics.cacheHits += 1;
                return refreshedCachedVods;
            }
        }

        runtimeMetrics.cacheMisses += 1;

        const getVodsViaPublicApi = async () => {
            const login = userIdLoginCache.get(userId);
            if (!login) return [];

            const vods = await getPublicVODsByLogin(login);
            setCachedValue(vodListCache, cacheKey, vods, MAX_VOD_LIST_CACHE_ENTRIES);
            return vods;
        };

        if (!(await ensureTwitchAuth())) return await getVodsViaPublicApi();

        const MAX_VOD_PAGES = 50; // 50 pages x 100 per page = 5000 VODs max

        const fetchVodsPage = async (cursor?: string) => {
            const params: Record<string, string | number> = {
                user_id: userId,
                type: 'archive',
                first: 100
            };
            if (cursor) params.after = cursor;

            return await axios.get('https://api.twitch.tv/helix/videos', {
                params,
                headers: {
                    'Client-ID': config.client_id,
                    'Authorization': `Bearer ${accessToken}`
                },
                timeout: API_TIMEOUT
            });
        };

        const fetchAllVodPages = async (): Promise<VOD[]> => {
            const allVods: VOD[] = [];
            let cursor: string | undefined;
            let pageCount = 0;

            do {
                const response = await fetchVodsPage(cursor);
                const pageVods = response.data.data || [];
                allVods.push(...pageVods);

                if (pageCount === 0) {
                    const login = pageVods[0]?.user_login;
                    if (login) {
                        userIdLoginCache.set(userId, normalizeLogin(login));
                    }
                }

                cursor = response.data.pagination?.cursor;
                pageCount++;
            } while (cursor && pageCount < MAX_VOD_PAGES);

            return allVods;
        };

        try {
            const vods = await fetchAllVodPages();
            setCachedValue(vodListCache, cacheKey, vods, MAX_VOD_LIST_CACHE_ENTRIES);
            return vods;
        } catch (e) {
            if (axios.isAxiosError(e) && e.response?.status === 401 && (await ensureTwitchAuth(true))) {
                try {
                    const vods = await fetchAllVodPages();
                    setCachedValue(vodListCache, cacheKey, vods, MAX_VOD_LIST_CACHE_ENTRIES);
                    return vods;
                } catch (retryError) {
                    console.error('Error getting VODs after relogin:', retryError);
                    return await getVodsViaPublicApi();
                }
            }

            console.error('Error getting VODs:', e);
            return await getVodsViaPublicApi();
        }
    });
}

async function getClipInfo(clipId: string): Promise<any | null> {
    const cachedClip = getCachedValue(clipInfoCache, clipId);
    if (cachedClip !== undefined) {
        runtimeMetrics.cacheHits += 1;
        return cachedClip;
    }

    return await withInFlightDedup(inFlightClipRequests, clipId, async () => {
        const refreshedCachedClip = getCachedValue(clipInfoCache, clipId);
        if (refreshedCachedClip !== undefined) {
            runtimeMetrics.cacheHits += 1;
            return refreshedCachedClip;
        }

        runtimeMetrics.cacheMisses += 1;

        if (!(await ensureTwitchAuth())) return null;

        const fetchClip = async () => {
            return await axios.get('https://api.twitch.tv/helix/clips', {
                params: { id: clipId },
                headers: {
                    'Client-ID': config.client_id,
                    'Authorization': `Bearer ${accessToken}`
                },
                timeout: API_TIMEOUT
            });
        };

        try {
            const response = await fetchClip();
            const clip = response.data.data[0] || null;
            if (clip) {
                setCachedValue(clipInfoCache, clipId, clip, MAX_CLIP_INFO_CACHE_ENTRIES);
            }
            return clip;
        } catch (e) {
            if (axios.isAxiosError(e) && e.response?.status === 401 && (await ensureTwitchAuth(true))) {
                try {
                    const retryResponse = await fetchClip();
                    const clip = retryResponse.data.data[0] || null;
                    if (clip) {
                        setCachedValue(clipInfoCache, clipId, clip, MAX_CLIP_INFO_CACHE_ENTRIES);
                    }
                    return clip;
                } catch (retryError) {
                    console.error('Error getting clip after relogin:', retryError);
                    return null;
                }
            }

            console.error('Error getting clip:', e);
            return null;
        }
    });
}

// ==========================================
// VIDEO INFO (for cutter)
// ==========================================
async function getVideoInfo(filePath: string): Promise<VideoInfo | null> {
    const ffmpegReady = await ensureFfmpegInstalled();
    if (!ffmpegReady) {
        appendDebugLog('get-video-info-missing-ffmpeg');
        return null;
    }

    return new Promise((resolve) => {
        const ffprobe = getFFprobePath();
        const args = [
            '-v', 'quiet',
            '-print_format', 'json',
            '-show_format',
            '-show_streams',
            filePath
        ];

        const proc = spawn(ffprobe, args, { windowsHide: true });
        let output = '';

        proc.stdout?.on('data', (data) => {
            output += data.toString();
        });

        proc.on('close', (code) => {
            if (code !== 0) {
                resolve(null);
                return;
            }

            try {
                const info = JSON.parse(output);
                const videoStream = info.streams?.find((s: any) => s.codec_type === 'video');

                resolve({
                    duration: parseFloat(info.format?.duration || '0'),
                    width: videoStream?.width || 0,
                    height: videoStream?.height || 0,
                    fps: parseFrameRate(videoStream?.r_frame_rate)
                });
            } catch {
                resolve(null);
            }
        });

        proc.on('error', () => resolve(null));
    });
}

// ==========================================
// VIDEO CUTTER
// ==========================================
async function extractFrame(filePath: string, timeSeconds: number): Promise<string | null> {
    const ffmpegReady = await ensureFfmpegInstalled();
    if (!ffmpegReady) {
        appendDebugLog('extract-frame-missing-ffmpeg');
        return null;
    }

    return new Promise((resolve) => {
        const ffmpeg = getFFmpegPath();
        const tempFile = path.join(app.getPath('temp'), `frame_${Date.now()}.jpg`);

        const args = [
            '-ss', timeSeconds.toString(),
            '-i', filePath,
            '-vframes', '1',
            '-q:v', '2',
            '-y',
            tempFile
        ];

        const proc = spawn(ffmpeg, args, { windowsHide: true });

        proc.on('close', (code) => {
            if (code === 0 && fs.existsSync(tempFile)) {
                const imageData = fs.readFileSync(tempFile);
                const base64 = `data:image/jpeg;base64,${imageData.toString('base64')}`;
                fs.unlinkSync(tempFile);
                resolve(base64);
            } else {
                resolve(null);
            }
        });

        proc.on('error', () => resolve(null));
    });
}

async function cutVideo(
    inputFile: string,
    outputFile: string,
    startTime: number,
    endTime: number,
    onProgress: (percent: number) => void
): Promise<boolean> {
    const ffmpegReady = await ensureFfmpegInstalled();
    if (!ffmpegReady) {
        appendDebugLog('cut-video-missing-ffmpeg');
        return false;
    }

    const ffmpeg = getFFmpegPath();
    const duration = Math.max(0.1, endTime - startTime);

    let inputBytes = 0;
    try {
        inputBytes = fs.statSync(inputFile).size;
    } catch { }

    const cutRequiredBytes = Math.max(96 * 1024 * 1024, Math.ceil(inputBytes * 0.75));
    const cutDiskCheck = ensureDiskSpace(path.dirname(outputFile), cutRequiredBytes, 'Video-Cut');
    if (!cutDiskCheck.success) {
        appendDebugLog('cut-video-no-disk-space', {
            inputFile,
            outputFile,
            requiredBytes: cutRequiredBytes,
            error: cutDiskCheck.error
        });
        return false;
    }

    const runCutAttempt = async (copyMode: boolean): Promise<boolean> => {
        const args = [
            '-ss', formatDuration(startTime),
            '-i', inputFile,
            '-t', formatDuration(duration)
        ];

        if (copyMode) {
            args.push('-c', 'copy');
        } else {
            args.push(
                '-c:v', 'libx264',
                '-preset', 'veryfast',
                '-crf', '20',
                '-c:a', 'aac',
                '-b:a', '160k',
                '-movflags', '+faststart'
            );
        }

        args.push('-progress', 'pipe:1', '-y', outputFile);

        appendDebugLog('cut-video-attempt', { copyMode, args });

        return await new Promise((resolve) => {
            const proc = spawn(ffmpeg, args, { windowsHide: true });
            currentEditorProcess = proc;

            proc.stdout?.on('data', (data) => {
                const line = data.toString();
                const match = line.match(/out_time_us=(\d+)/);
                if (match) {
                    const currentUs = parseInt(match[1], 10);
                    const percent = Math.min(100, (currentUs / 1000000) / duration * 100);
                    onProgress(percent);
                }
            });

            proc.on('close', (code) => {
                currentEditorProcess = null;
                if (code === 0 && fs.existsSync(outputFile)) {
                    const stats = fs.statSync(outputFile);
                    if (stats.size <= 256) {
                        appendDebugLog('cut-video-empty-output', { outputFile, bytes: stats.size });
                        resolve(false);
                        return;
                    }
                    resolve(true);
                } else {
                    resolve(false);
                }
            });

            proc.on('error', () => {
                currentEditorProcess = null;
                resolve(false);
            });
        });
    };

    const copySuccess = await runCutAttempt(true);
    if (copySuccess) {
        return true;
    }

    appendDebugLog('cut-video-copy-failed-fallback-reencode', { inputFile, outputFile });
    try {
        if (fs.existsSync(outputFile)) fs.unlinkSync(outputFile);
    } catch { }

    return await runCutAttempt(false);
}

// ==========================================
// MERGE VIDEOS
// ==========================================
async function mergeVideos(
    inputFiles: string[],
    outputFile: string,
    onProgress: (percent: number) => void,
    totalDurationSec?: number
): Promise<boolean> {
    const ffmpegReady = await ensureFfmpegInstalled();
    if (!ffmpegReady) {
        appendDebugLog('merge-videos-missing-ffmpeg');
        return false;
    }

    const ffmpeg = getFFmpegPath();
    const concatFile = path.join(app.getPath('temp'), `concat_${Date.now()}.txt`);
    const concatContent = inputFiles.map((filePath) => {
        const normalized = filePath.replace(/\\/g, '/');
        return `file '${normalized.replace(/'/g, "'\\''")}'`;
    }).join('\n');
    fs.writeFileSync(concatFile, concatContent);

    let mergeInputBytes = 0;
    for (const filePath of inputFiles) {
        try {
            mergeInputBytes += fs.statSync(filePath).size;
        } catch {
            // ignore missing file in estimation
        }
    }

    const mergeRequiredBytes = Math.max(128 * 1024 * 1024, Math.ceil(mergeInputBytes * 1.1));
    const mergeDiskCheck = ensureDiskSpace(path.dirname(outputFile), mergeRequiredBytes, 'Video-Merge');
    if (!mergeDiskCheck.success) {
        appendDebugLog('merge-video-no-disk-space', {
            outputFile,
            files: inputFiles.length,
            requiredBytes: mergeRequiredBytes,
            error: mergeDiskCheck.error
        });
        try {
            fs.unlinkSync(concatFile);
        } catch { }
        return false;
    }

    // Determine total duration for accurate progress
    let mergeTotalDurationUs = 0;
    if (totalDurationSec && totalDurationSec > 0) {
        mergeTotalDurationUs = totalDurationSec * 1_000_000;
    } else {
        // Fallback: use ffprobe to get total duration of all input files
        const ffprobe = getFFprobePath();
        for (const filePath of inputFiles) {
            try {
                const result = execSync(
                    `"${ffprobe}" -v quiet -show_entries format=duration -of csv=p=0 "${filePath}"`,
                    { timeout: 10000, windowsHide: true }
                ).toString().trim();
                const dur = parseFloat(result);
                if (!isNaN(dur)) {
                    mergeTotalDurationUs += dur * 1_000_000;
                }
            } catch {
                // If ffprobe fails, fall back to old behavior
            }
        }
    }

    const runMergeAttempt = async (copyMode: boolean): Promise<boolean> => {
        const args = [
            '-f', 'concat',
            '-safe', '0',
            '-i', concatFile
        ];

        if (copyMode) {
            args.push('-c', 'copy');
        } else {
            args.push(
                '-c:v', 'libx264',
                '-preset', 'veryfast',
                '-crf', '20',
                '-c:a', 'aac',
                '-b:a', '160k',
                '-movflags', '+faststart'
            );
        }

        args.push('-progress', 'pipe:1', '-y', outputFile);
        appendDebugLog('merge-video-attempt', { copyMode, argsCount: args.length });

        return await new Promise((resolve) => {
            const proc = spawn(ffmpeg, args, { windowsHide: true });
            currentEditorProcess = proc;

            proc.stdout?.on('data', (data) => {
                const line = data.toString();
                const match = line.match(/out_time_us=(\d+)/);
                if (match) {
                    const currentUs = parseInt(match[1], 10);
                    if (mergeTotalDurationUs > 0) {
                        onProgress(Math.min(99, (currentUs / mergeTotalDurationUs) * 100));
                    } else {
                        onProgress(Math.min(99, currentUs / 10000000));
                    }
                }
            });

            proc.on('close', (code) => {
                currentEditorProcess = null;
                const success = code === 0 && fs.existsSync(outputFile);
                if (success) {
                    onProgress(100);
                }
                resolve(success);
            });

            proc.on('error', () => {
                currentEditorProcess = null;
                resolve(false);
            });
        });
    };

    try {
        const copySuccess = await runMergeAttempt(true);
        if (copySuccess) {
            return true;
        }

        appendDebugLog('merge-video-copy-failed-fallback-reencode', { outputFile, files: inputFiles.length });
        try {
            if (fs.existsSync(outputFile)) fs.unlinkSync(outputFile);
        } catch { }

        return await runMergeAttempt(false);
    } finally {
        try {
            fs.unlinkSync(concatFile);
        } catch { }
    }
}

// ==========================================
// SPLIT MERGED FILE
// ==========================================
async function splitMergedFile(
    inputFile: string,
    outputFolder: string,
    partDurationSec: number,
    totalDurationSec: number,
    filenameGenerator: (partNum: number) => string,
    onProgress: (currentPart: number, totalParts: number) => void,
    itemId: string | null = null
): Promise<{ success: boolean; files: string[] }> {
    const ffmpegReady = await ensureFfmpegInstalled();
    if (!ffmpegReady) {
        appendDebugLog('split-merged-missing-ffmpeg');
        return { success: false, files: [] };
    }

    const ffmpeg = getFFmpegPath();
    const numParts = Math.ceil(totalDurationSec / partDurationSec);
    const splitFiles: string[] = [];

    for (let i = 0; i < numParts; i++) {
        if (currentDownloadCancelled) {
            return { success: false, files: splitFiles };
        }

        const startSec = i * partDurationSec;
        const thisDuration = Math.min(partDurationSec, totalDurationSec - startSec);
        const outputFile = ensureUniqueFilename(path.join(outputFolder, filenameGenerator(i + 1)), itemId);

        onProgress(i + 1, numParts);

        const args = [
            '-ss', formatDuration(startSec),
            '-i', inputFile,
            '-t', formatDuration(thisDuration),
            '-c', 'copy',
            '-y', outputFile
        ];

        appendDebugLog('split-merged-part', { part: i + 1, total: numParts, startSec, duration: thisDuration });

        const success = await new Promise<boolean>((resolve) => {
            const proc = spawn(ffmpeg, args, { windowsHide: true });
            currentEditorProcess = proc;

            proc.on('close', (code) => {
                currentEditorProcess = null;
                resolve(code === 0 && fs.existsSync(outputFile));
            });

            proc.on('error', () => {
                currentEditorProcess = null;
                resolve(false);
            });
        });

        if (!success) {
            appendDebugLog('split-merged-part-failed', { part: i + 1, outputFile });
            return { success: false, files: splitFiles };
        }

        splitFiles.push(outputFile);
    }

    return { success: true, files: splitFiles };
}

// ==========================================
// DOWNLOAD FUNCTIONS
// ==========================================
function downloadVODPart(
    url: string,
    filename: string,
    startTime: string | null,
    endTime: string | null,
    onProgress: (progress: DownloadProgress) => void,
    itemId: string,
    partNum: number,
    totalParts: number
): Promise<DownloadResult> {
    return new Promise((resolve) => {
        const streamlinkCmd = getStreamlinkCommand();
        const args = [...streamlinkCmd.prefixArgs, url, 'best', '-o', filename, '--force'];
        let lastErrorLine = '';
        const expectedDurationSeconds = parseClockDurationSeconds(endTime);
        let lastStreamlinkPercent = 0;

        if (startTime) {
            args.push('--hls-start-offset', startTime);
        }
        if (endTime) {
            args.push('--hls-duration', endTime);
        }

        console.log('Starting download:', streamlinkCmd.command, args);
        appendDebugLog('download-part-start', { itemId, command: streamlinkCmd.command, filename, args });

        const proc = spawn(streamlinkCmd.command, args, { windowsHide: true });

        // Register in per-item tracking map for parallel downloads
        // (no longer mirrored on a global — currentEditorProcess is editor-only)
        const itemTracking = { process: proc, cancelled: false, startTime: Date.now(), bytes: 0 };
        activeDownloads.set(itemId, itemTracking);

        downloadStartTime = itemTracking.startTime;
        downloadedBytes = 0;
        let lastBytes = 0;
        let lastTime = Date.now();

        // Monitor file size for progress
        const progressInterval = setInterval(() => {
            if (fs.existsSync(filename)) {
                try {
                    const stats = fs.statSync(filename);
                    downloadedBytes = stats.size;
                    itemTracking.bytes = stats.size;

                    const now = Date.now();
                    const timeDiff = (now - lastTime) / 1000;
                    const bytesDiff = downloadedBytes - lastBytes;
                    const speed = timeDiff > 0 ? bytesDiff / timeDiff : 0;

                    runtimeMetrics.lastSpeedBytesPerSec = speed;
                    if (speed > 0) {
                        runtimeMetrics.avgSpeedBytesPerSec = runtimeMetrics.avgSpeedBytesPerSec <= 0
                            ? speed
                            : (runtimeMetrics.avgSpeedBytesPerSec * 0.8) + (speed * 0.2);
                    }

                    lastBytes = downloadedBytes;
                    lastTime = now;

                    let etaStr = '';
                    if (downloadedBytes > 0) {
                        const elapsedSec = (Date.now() - (itemTracking?.startTime || Date.now())) / 1000;
                        if (elapsedSec > 5 && lastStreamlinkPercent > 1) {
                            // Use streamlink's reported progress for accurate ETA
                            const remainingSec = (elapsedSec / lastStreamlinkPercent) * (100 - lastStreamlinkPercent);
                            if (remainingSec > 0 && remainingSec < 86400) {
                                etaStr = formatETA(remainingSec);
                            }
                        }
                    }

                    onProgress({
                        id: itemId,
                        progress: -1, // Unknown total
                        speed: formatSpeed(speed),
                        eta: etaStr,
                        status: tBackend('statusBytesDownloaded', { bytes: formatBytes(downloadedBytes) }),
                        currentPart: partNum,
                        totalParts: totalParts,
                        downloadedBytes: downloadedBytes,
                        speedBytesPerSec: speed
                    });
                } catch { }
            }
        }, 1000);

        proc.stdout?.on('data', (data: Buffer) => {
            const line = data.toString();
            console.log('Streamlink:', line);

            // Parse progress
            const match = line.match(/(\d+\.\d+)%/);
            if (match) {
                const percent = parseFloat(match[1]);
                lastStreamlinkPercent = percent;
                onProgress({
                    id: itemId,
                    progress: percent,
                    speed: '',
                    eta: '',
                    status: `${percent.toFixed(1)}%`,
                    currentPart: partNum,
                    totalParts: totalParts
                });
            }
        });

        proc.stderr?.on('data', (data: Buffer) => {
            const message = data.toString().trim();
            if (message) {
                lastErrorLine = message.split('\n').pop() || message;
                appendDebugLog('download-part-stderr', { itemId, message: lastErrorLine });
                console.error('Streamlink error:', message);
            }
        });

        proc.on('close', async (code) => {
            clearInterval(progressInterval);
            activeDownloads.delete(itemId);

            if (currentDownloadCancelled || cancelledItemIds.has(itemId)) {
                cancelledItemIds.delete(itemId);
                appendDebugLog('download-part-cancelled', { itemId, filename });
                resolve({ success: false, error: tBackend('downloadCancelled') });
                return;
            }

            if (code === 0 && fs.existsSync(filename)) {
                const stats = fs.statSync(filename);
                if (stats.size <= MIN_FILE_BYTES) {
                    const tooSmall = tBackend('fileTooSmall', { bytes: String(stats.size) });
                    appendDebugLog('download-part-failed-small-file', { itemId, filename, bytes: stats.size });
                    resolve({ success: false, error: tooSmall });
                    return;
                }

                const integrityResult = validateDownloadedFileIntegrity(filename, expectedDurationSeconds);
                if (!integrityResult.success) {
                    appendDebugLog('download-part-failed-integrity', {
                        itemId,
                        filename,
                        bytes: stats.size,
                        error: integrityResult.error
                    });
                    resolve(integrityResult);
                    return;
                }

                runtimeMetrics.downloadedBytesTotal += stats.size;
                appendDebugLog('download-part-success', { itemId, filename, bytes: stats.size });
                resolve({ success: true });
                return;
            }

            const genericError = lastErrorLine || tBackend('streamlinkExitCode', { code: String(code ?? -1) });
            appendDebugLog('download-part-failed', { itemId, filename, code, error: genericError });
            resolve({ success: false, error: genericError });
        });

        proc.on('error', (err) => {
            clearInterval(progressInterval);
            console.error('Process error:', err);
            activeDownloads.delete(itemId);
            const rawError = String(err);
            const errorMessage = rawError.includes('ENOENT')
                ? tBackend('streamlinkNotFound')
                : rawError;
            appendDebugLog('download-part-process-error', { itemId, error: errorMessage, rawError });
            resolve({ success: false, error: errorMessage });
        });
    });
}

async function downloadVOD(
    item: QueueItem,
    onProgress: (progress: DownloadProgress) => void
): Promise<DownloadResult> {
    const vodId = parseVodId(item.url);
    if (!isLikelyVodUrl(item.url) || !vodId) {
        return {
            success: false,
            error: tBackend('invalidVodUrl')
        };
    }

    const streamlinkCmd = getStreamlinkCommand();
    const streamlinkVersionArgs = [...streamlinkCmd.prefixArgs, '--version'];
    const streamlinkAlreadyVerified = isVerifiedStreamlinkCommand(streamlinkCmd.command, streamlinkVersionArgs);

    if (!streamlinkAlreadyVerified) {
        onProgress({
            id: item.id,
            progress: -1,
            speed: '',
            eta: '',
            status: tBackend('statusCheckingTools'),
            currentPart: 0,
            totalParts: 0
        });
    }

    const streamlinkReady = await ensureStreamlinkInstalled();
    if (!streamlinkReady) {
        return {
            success: false,
            error: tBackend('streamlinkAutoInstallFailed')
        };
    }

    onProgress({
        id: item.id,
        progress: -1,
        speed: '',
        eta: '',
        status: tBackend('statusDownloadStarted'),
        currentPart: 0,
        totalParts: 0
    });

    const streamer = item.streamer.replace(/[^a-zA-Z0-9_-]/g, '');
    const date = new Date(item.date);
    const dateStr = `${date.getDate().toString().padStart(2, '0')}.${(date.getMonth() + 1).toString().padStart(2, '0')}.${date.getFullYear()}`;

    const folder = path.join(config.download_path, streamer, dateStr);
    fs.mkdirSync(folder, { recursive: true });

    const totalDuration = parseDuration(item.duration_str);

    const requiredBytesEstimate = estimateRequiredDownloadBytes(item);
    const diskSpaceCheck = ensureDiskSpace(folder, requiredBytesEstimate, 'Download');
    if (!diskSpaceCheck.success) {
        return diskSpaceCheck;
    }

    const makeTemplateFilename = (
        template: string,
        templateFallback: string,
        partNum: number,
        trimStartSec: number,
        trimLengthSec: number
    ): string => {
        const relativeName = renderClipFilenameTemplate({
            template: normalizeFilenameTemplate(template, templateFallback),
            title: item.title,
            vodId,
            channel: item.streamer,
            date,
            part: partNum,
            partPadded: partNum.toString().padStart(2, '0'),
            trimStartSec,
            trimEndSec: trimStartSec + trimLengthSec,
            trimLengthSec,
            fullLengthSec: totalDuration
        });

        return path.join(folder, relativeName);
    };

    // Custom Clip - download specific time range
    if (item.customClip) {
        const clip = item.customClip;
        const partDuration = config.part_minutes * 60;

        // Helper to generate filename based on format
        const makeClipFilename = (partNum: number, startOffset: number, clipLengthSec: number): string => {
            if (clip.filenameFormat === 'template') {
                return makeTemplateFilename(
                    clip.filenameTemplate || config.filename_template_clip,
                    DEFAULT_FILENAME_TEMPLATE_CLIP,
                    partNum,
                    startOffset,
                    clipLengthSec
                );
            }

            if (clip.filenameFormat === 'timestamp') {
                const h = Math.floor(startOffset / 3600);
                const m = Math.floor((startOffset % 3600) / 60);
                const s = Math.floor(startOffset % 60);
                const timeStr = `${h.toString().padStart(2, '0')}-${m.toString().padStart(2, '0')}-${s.toString().padStart(2, '0')}`;
                return path.join(folder, `${dateStr}_CLIP_${timeStr}_${partNum}.mp4`);
            }

            if (clip.filenameFormat === 'parts') {
                // Mirrors the global filename_template_parts default:
                // `{date}_Part{part_padded}.mp4` -> e.g. 08.05.2026_Part07.mp4
                return path.join(folder, `${dateStr}_Part${partNum.toString().padStart(2, '0')}.mp4`);
            }

            return path.join(folder, `${dateStr}_${partNum}.mp4`);
        };

        // If clip is longer than part duration, split into parts
        if (clip.durationSec > partDuration) {
            const numParts = Math.ceil(clip.durationSec / partDuration);
            const downloadedFiles: string[] = [];

            for (let i = 0; i < numParts; i++) {
                if (currentDownloadCancelled || cancelledItemIds.has(item.id)) break;

                const partNum = clip.startPart + i;
                const startOffset = clip.startSec + (i * partDuration);
                const remainingDuration = clip.durationSec - (i * partDuration);
                const thisDuration = Math.min(partDuration, remainingDuration);

                const partFilename = ensureUniqueFilename(makeClipFilename(partNum, startOffset, thisDuration), item.id);

                const result = await downloadVODPart(
                    item.url,
                    partFilename,
                    formatDuration(startOffset),
                    formatDuration(thisDuration),
                    onProgress,
                    item.id,
                    i + 1,
                    numParts
                );

                if (!result.success) return result;
                downloadedFiles.push(partFilename);
            }

            return {
                success: downloadedFiles.length === numParts,
                error: downloadedFiles.length === numParts ? undefined : tBackend('notAllClipPartsDownloaded'),
                outputFiles: downloadedFiles.length === numParts ? [...downloadedFiles] : undefined
            };
        } else {
            // Single clip file
            const filename = ensureUniqueFilename(makeClipFilename(clip.startPart, clip.startSec, clip.durationSec), item.id);
            const result = await downloadVODPart(
                item.url,
                filename,
                formatDuration(clip.startSec),
                formatDuration(clip.durationSec),
                onProgress,
                item.id,
                1,
                1
            );
            return result.success ? { ...result, outputFiles: [filename] } : result;
        }
    }

    // Check download mode
    if (config.download_mode === 'full' || totalDuration <= config.part_minutes * 60) {
        // Full download
        const filename = ensureUniqueFilename(makeTemplateFilename(
            config.filename_template_vod,
            DEFAULT_FILENAME_TEMPLATE_VOD,
            1,
            0,
            totalDuration
        ), item.id);
        const result = await downloadVODPart(item.url, filename, null, null, onProgress, item.id, 1, 1);
        return result.success ? { ...result, outputFiles: [filename] } : result;
    } else {
        // Part-based download
        const partDuration = config.part_minutes * 60;
        const numParts = Math.ceil(totalDuration / partDuration);
        const downloadedFiles: string[] = [];

        for (let i = 0; i < numParts; i++) {
            if (currentDownloadCancelled || cancelledItemIds.has(item.id)) break;

            const startSec = i * partDuration;
            const endSec = Math.min((i + 1) * partDuration, totalDuration);
            const duration = endSec - startSec;

            const partFilename = ensureUniqueFilename(makeTemplateFilename(
                config.filename_template_parts,
                DEFAULT_FILENAME_TEMPLATE_PARTS,
                i + 1,
                startSec,
                duration
            ), item.id);

            const result = await downloadVODPart(
                item.url,
                partFilename,
                formatDuration(startSec),
                formatDuration(duration),
                onProgress,
                item.id,
                i + 1,
                numParts
            );

            if (!result.success) {
                return result;
            }

            downloadedFiles.push(partFilename);
        }

        return {
            success: downloadedFiles.length === numParts,
            error: downloadedFiles.length === numParts ? undefined : tBackend('notAllPartsDownloaded'),
            outputFiles: downloadedFiles.length === numParts ? [...downloadedFiles] : undefined
        };
    }
}

// ==========================================
// MERGE GROUP DOWNLOAD PIPELINE
// ==========================================
async function processDownloadMergeGroup(
    item: QueueItem,
    onProgress: (progress: DownloadProgress) => void
): Promise<DownloadResult> {
    const mg = item.mergeGroup!;
    const totalDurationSec = mg.totalDurationSec || mg.items.reduce((sum, i) => sum + parseDuration(i.duration_str), 0);
    mg.totalDurationSec = totalDurationSec;

    // ---- PHASE 1: DOWNLOADING ----
    if (mg.mergePhase === 'downloading') {
        const streamlinkReady = await ensureStreamlinkInstalled();
        if (!streamlinkReady) {
            return { success: false, error: tBackend('streamlinkMissing') };
        }

        const ffmpegReady = await ensureFfmpegInstalled();
        if (!ffmpegReady) {
            return { success: false, error: tBackend('ffmpegMissing') };
        }

        const streamer = mg.items[0].streamer.replace(/[^a-zA-Z0-9_-]/g, '');
        const date = new Date(mg.items[0].date);
        const dateStr = `${date.getDate().toString().padStart(2, '0')}.${(date.getMonth() + 1).toString().padStart(2, '0')}.${date.getFullYear()}`;
        const folder = path.join(config.download_path, streamer, dateStr);
        fs.mkdirSync(folder, { recursive: true });

        // Disk space pre-check: 3x total estimated size
        const estimatedBytes = mg.items.reduce((sum, i) => {
            const dur = parseDuration(i.duration_str);
            return sum + Math.ceil(dur * 500_000); // ~500KB/s estimate
        }, 0);
        const requiredBytes = Math.max(256 * 1024 * 1024, estimatedBytes * 3);
        const diskCheck = ensureDiskSpace(folder, requiredBytes, 'Merge-Group-Download');
        if (!diskCheck.success) {
            return diskCheck;
        }

        for (let i = 0; i < mg.items.length; i++) {
            if (currentDownloadCancelled || cancelledItemIds.has(item.id)) {
                return { success: false, error: tBackend('downloadCancelled') };
            }

            // Skip already downloaded files (retry recovery)
            if (mg.downloadedFiles[i] && fs.existsSync(mg.downloadedFiles[i])) {
                appendDebugLog('merge-group-skip-existing', { index: i, file: mg.downloadedFiles[i] });
                continue;
            }

            // Reset stale per-item cancel state (global cancel already checked above)
            cancelledItemIds.delete(item.id);
            mg.currentItemIndex = i;
            mg.mergePhase = 'downloading';
            saveQueue(downloadQueue);

            const vodItem = mg.items[i];
            const tmpFilename = ensureUniqueFilename(path.join(folder, `merge_tmp_${i}_${Date.now()}.mp4`), item.id);

            // Calculate progress weighting per VOD
            const vodDuration = parseDuration(vodItem.duration_str);
            const vodWeight = vodDuration / totalDurationSec;
            const priorWeight = mg.items.slice(0, i).reduce((s, v) => s + parseDuration(v.duration_str), 0) / totalDurationSec;

            const result = await downloadVODPart(
                vodItem.url,
                tmpFilename,
                null,   // startTime: null = full VOD
                null,   // endTime: null = full VOD
                (progress) => {
                    // Weighted progress: download phase = 0-70%
                    const vodProgress = progress.progress > 0 ? progress.progress : 0;
                    const overallProgress = (priorWeight + vodWeight * (vodProgress / 100)) * 70;
                    onProgress({
                        ...progress,
                        id: item.id,
                        progress: overallProgress,
                        status: `${getMergeGroupPhaseText('downloading')} ${i + 1}/${mg.items.length} — ${progress.status}`,
                        currentPart: i + 1,
                        totalParts: mg.items.length
                    });
                },
                item.id,
                i + 1,
                mg.items.length
            );

            if (!result.success) {
                return result;
            }

            mg.downloadedFiles[i] = tmpFilename;
            saveQueue(downloadQueue);
        }
    }

    // ---- PHASE 2: MERGING ----
    mg.mergePhase = 'merging';
    saveQueue(downloadQueue);
    emitQueueUpdated();

    // Check all downloaded files exist (retry recovery)
    for (let i = 0; i < mg.items.length; i++) {
        if (!mg.downloadedFiles[i] || !fs.existsSync(mg.downloadedFiles[i])) {
            mg.mergePhase = 'downloading';
            return { success: false, error: tBackend('mergeGroupFileMissing', { index: i + 1 }) };
        }
    }

    if (!mg.mergedFile || !fs.existsSync(mg.mergedFile)) {
        const streamer = mg.items[0].streamer.replace(/[^a-zA-Z0-9_-]/g, '');
        const date = new Date(mg.items[0].date);
        const dateStr = `${date.getDate().toString().padStart(2, '0')}.${(date.getMonth() + 1).toString().padStart(2, '0')}.${date.getFullYear()}`;
        const folder = path.join(config.download_path, streamer, dateStr);
        const mergedFilePath = path.join(folder, `merged_${Date.now()}.mp4`);

        // Get files in correct order (explicit sort by index — do NOT rely on Object.values ordering)
        const sortedFiles = Object.keys(mg.downloadedFiles)
            .sort((a, b) => Number(a) - Number(b))
            .map(k => mg.downloadedFiles[Number(k)]);

        const mergeSuccess = await mergeVideos(
            sortedFiles,
            mergedFilePath,
            (percent) => {
                const overallProgress = 70 + (percent / 100) * 20; // merge = 70-90%
                onProgress({
                    id: item.id,
                    progress: overallProgress,
                    speed: '',
                    eta: '',
                    status: getMergeGroupPhaseText('merging'),
                    currentPart: 0,
                    totalParts: 0
                });
            },
            totalDurationSec
        );

        if (!mergeSuccess) {
            return { success: false, error: tBackend('ffmpegMergeFailed') };
        }

        mg.mergedFile = mergedFilePath;
        saveQueue(downloadQueue);
    }

    // ---- PHASE 3: SPLITTING ----
    mg.mergePhase = 'splitting';
    saveQueue(downloadQueue);
    emitQueueUpdated();

    if (currentDownloadCancelled || cancelledItemIds.has(item.id)) {
        return { success: false, error: tBackend('downloadCancelled') };
    }

    const partDuration = config.part_minutes * 60;
    const streamer = mg.items[0].streamer.replace(/[^a-zA-Z0-9_-]/g, '');
    const date = new Date(mg.items[0].date);
    const dateStr = `${date.getDate().toString().padStart(2, '0')}.${(date.getMonth() + 1).toString().padStart(2, '0')}.${date.getFullYear()}`;
    const folder = path.join(config.download_path, streamer, dateStr);
    const vodId = parseVodId(mg.items[0].url) || 'merged';

    const splitResult = await splitMergedFile(
        mg.mergedFile!,
        folder,
        partDuration,
        totalDurationSec,
        (partNum: number) => {
            const startSec = (partNum - 1) * partDuration;
            const thisDuration = Math.min(partDuration, totalDurationSec - startSec);
            return renderClipFilenameTemplate({
                template: normalizeFilenameTemplate(config.filename_template_parts, DEFAULT_FILENAME_TEMPLATE_PARTS),
                title: mg.items[0].title,
                vodId,
                channel: mg.items[0].streamer,
                date,
                part: partNum,
                partPadded: partNum.toString().padStart(2, '0'),
                trimStartSec: startSec,
                trimEndSec: startSec + thisDuration,
                trimLengthSec: thisDuration,
                fullLengthSec: totalDurationSec
            });
        },
        (currentPart, totalParts) => {
            const overallProgress = 90 + ((currentPart - 1) / totalParts) * 10; // split = 90-100%
            onProgress({
                id: item.id,
                progress: overallProgress,
                speed: '',
                eta: '',
                status: `${getMergeGroupPhaseText('splitting')} ${currentPart}/${totalParts}...`,
                currentPart,
                totalParts
            });
        },
        item.id
    );

    if (!splitResult.success) {
        // Clean up any partial split files
        for (const partFile of splitResult.files) {
            try { if (fs.existsSync(partFile)) fs.unlinkSync(partFile); } catch { }
        }
        return { success: false, error: tBackend('ffmpegSplitFailed') };
    }

    mg.splitFiles = splitResult.files;

    // ---- PHASE 4: CLEANUP ----
    mg.mergePhase = 'cleanup';
    saveQueue(downloadQueue);

    // Delete individual downloads
    for (const key of Object.keys(mg.downloadedFiles)) {
        const filePath = mg.downloadedFiles[Number(key)];
        try {
            if (fs.existsSync(filePath)) fs.unlinkSync(filePath);
        } catch { }
    }

    // Delete merged file
    if (mg.mergedFile) {
        try {
            if (fs.existsSync(mg.mergedFile)) fs.unlinkSync(mg.mergedFile);
        } catch { }
    }

    mg.mergePhase = 'done';
    appendDebugLog('merge-group-complete', {
        itemId: item.id,
        parts: splitResult.files.length,
        totalDurationSec
    });

    return { success: true, outputFiles: [...splitResult.files] };
}

async function processOneQueueItem(item: QueueItem): Promise<void> {
    appendDebugLog('queue-item-start', {
        itemId: item.id,
        title: item.title,
        url: item.url,
        smartScore: config.smart_queue_scheduler ? getQueuePriorityScore(item) : 0
    });

    runtimeMetrics.downloadsStarted += 1;
    runtimeMetrics.activeItemId = item.id;
    runtimeMetrics.activeItemTitle = item.title;
    activeQueueItemId = item.id;

    cancelledItemIds.delete(item.id);
    item.status = 'downloading';
    saveQueue(downloadQueue);
    emitQueueUpdated();

    item.last_error = '';

    try {
        let finalResult: DownloadResult = { success: false, error: tBackend('unknownDownloadError') };
        const maxAttempts = getRetryAttemptLimit();

        for (let attempt = 1; attempt <= maxAttempts; attempt++) {
            appendDebugLog('queue-item-attempt', { itemId: item.id, attempt, max: maxAttempts });

            const result = item.mergeGroup
                ? await processDownloadMergeGroup(item, (progress) => {
                    mainWindow?.webContents.send('download-progress', progress);
                })
                : await downloadVOD(item, (progress) => {
                    mainWindow?.webContents.send('download-progress', progress);
                });

            if (result.success) {
                finalResult = result;
                break;
            }

            finalResult = result;

            if (!isDownloading || currentDownloadCancelled || cancelledItemIds.has(item.id) || pauseRequested) {
                finalResult = { success: false, error: pauseRequested ? tBackend('downloadPaused') : tBackend('downloadCancelled') };
                break;
            }

            const errorClass = classifyDownloadError(result.error || '');
            runtimeMetrics.lastErrorClass = errorClass;

            if (errorClass === 'tooling' || errorClass === 'validation') {
                appendDebugLog('queue-item-no-retry', {
                    itemId: item.id,
                    errorClass,
                    error: result.error || 'unknown'
                });
                break;
            }

            if (attempt < maxAttempts) {
                const retryDelaySeconds = getRetryDelaySeconds(errorClass, attempt);
                runtimeMetrics.retriesScheduled += 1;
                runtimeMetrics.lastRetryDelaySeconds = retryDelaySeconds;

                item.last_error = tBackend('attemptFailed', { attempt, max: maxAttempts, errorClass, error: result.error || tBackend('unknownDownloadError') });
                mainWindow?.webContents.send('download-progress', {
                    id: item.id,
                    progress: -1,
                    speed: '',
                    eta: '',
                    status: tBackend('retryingIn', { seconds: retryDelaySeconds, errorClass }),
                    currentPart: item.currentPart,
                    totalParts: item.totalParts
                } as DownloadProgress);
                saveQueue(downloadQueue);
                emitQueueUpdated();
                await sleep(retryDelaySeconds * 1000);
            } else {
                runtimeMetrics.retriesExhausted += 1;
            }
        }

        if (!hasQueueItemId(item.id)) {
            appendDebugLog('queue-item-finished-removed', { itemId: item.id });
            return;
        }

        const wasPaused = pauseRequested || (finalResult.error || '').includes('pausiert');
        item.status = finalResult.success ? 'completed' : (wasPaused ? 'paused' : 'error');
        item.progress = finalResult.success ? 100 : item.progress;
        item.last_error = finalResult.success || wasPaused ? '' : (finalResult.error || tBackend('unknownDownloadError'));

        if (finalResult.success && Array.isArray(finalResult.outputFiles) && finalResult.outputFiles.length > 0) {
            // Attach the produced file paths so the renderer can offer
            // "Open file" / "Show in folder" actions on completed items,
            // surviving a queue persistence round-trip.
            item.outputFiles = [...finalResult.outputFiles];
        }

        if (finalResult.success) {
            // Record the VOD ID so the renderer can mark this VOD as
            // already-downloaded the next time the user browses the
            // streamer's archive. Merge groups don't have a single VOD
            // ID — record each component instead.
            if (item.mergeGroup?.items?.length) {
                for (const m of item.mergeGroup.items) {
                    const id = parseVodId(m.url);
                    if (id) recordDownloadedVodId(id);
                }
            } else {
                const id = parseVodId(item.url);
                if (id) recordDownloadedVodId(id);
            }
        }

        if (finalResult.success) {
            runtimeMetrics.downloadsCompleted += 1;
        } else if (!wasPaused) {
            runtimeMetrics.downloadsFailed += 1;
        }

        appendDebugLog('queue-item-finished', {
            itemId: item.id,
            status: item.status,
            error: item.last_error
        });

        saveQueue(downloadQueue);
        emitQueueUpdated();
    } finally {
        activeDownloads.delete(item.id);
        cancelledItemIds.delete(item.id);
        // Release only THIS item's claimed filenames (other parallel downloads keep their claims)
        releaseClaimedFilenamesForItem(item.id);
    }
}

async function processQueue(): Promise<void> {
    if (isDownloading || !downloadQueue.some((item) => item.status === 'pending')) return;

    appendDebugLog('queue-start', {
        items: downloadQueue.length,
        smartScheduler: config.smart_queue_scheduler,
        performanceMode: config.performance_mode,
        parallelDownloads: config.parallel_downloads || 1
    });

    isDownloading = true;
    pauseRequested = false;
    currentDownloadCancelled = false;
    cancelledItemIds.clear();
    mainWindow?.webContents.send('download-started');
    emitQueueUpdated();

    const maxSlots = Math.min(Math.max(1, config.parallel_downloads || 1), 2);
    const activePromises = new Map<string, Promise<void>>();

    while (isDownloading && !pauseRequested) {
        // Clean up finished promises
        for (const [id] of activePromises) {
            const queueItem = downloadQueue.find(i => i.id === id);
            if (!queueItem || queueItem.status !== 'downloading') {
                activePromises.delete(id);
            }
        }

        // Fill available slots
        while (activePromises.size < maxSlots && !pauseRequested) {
            const item = pickNextPendingQueueItem();
            if (!item) break;

            const itemPromise = processOneQueueItem(item);
            activePromises.set(item.id, itemPromise);
        }

        if (activePromises.size === 0) break;

        // Wait for any one download to finish before re-checking
        await Promise.race([...activePromises.values()]);
    }

    // Wait for all remaining active downloads to complete
    if (activePromises.size > 0) {
        await Promise.allSettled([...activePromises.values()]);
    }

    isDownloading = false;
    pauseRequested = false;
    runtimeMetrics.activeItemId = null;
    runtimeMetrics.activeItemTitle = null;
    activeQueueItemId = null;
    activeDownloads.clear();
    cancelledItemIds.clear();

    saveQueue(downloadQueue);
    emitQueueUpdated();
    mainWindow?.webContents.send('download-finished');
    try {
        if (Notification.isSupported()) {
            const completed = downloadQueue.filter(i => i.status === 'completed').length;
            const failed = downloadQueue.filter(i => i.status === 'error').length;
            const notification = new Notification({
                title: 'Twitch VOD Manager',
                body: failed > 0
                    ? `${completed} Downloads fertig, ${failed} fehlgeschlagen`
                    : `${completed} Downloads abgeschlossen`
            });
            // Click brings the app to the foreground AND opens the download
            // folder so the user can immediately see the output files.
            notification.on('click', () => {
                try {
                    if (mainWindow) {
                        if (mainWindow.isMinimized()) mainWindow.restore();
                        mainWindow.focus();
                    }
                    if (config.download_path && fs.existsSync(config.download_path)) {
                        void shell.openPath(config.download_path);
                    }
                } catch (e) {
                    appendDebugLog('notification-click-failed', String(e));
                }
            });
            notification.show();
        }
    } catch { }
    appendDebugLog('queue-finished', { items: downloadQueue.length });
}

// ==========================================
// WINDOW CREATION
// ==========================================
function createWindow(): void {
    nativeTheme.themeSource = config.theme === 'light' ? 'light' : 'dark';

    mainWindow = new BrowserWindow({
        width: 1400,
        height: 900,
        minWidth: 1200,
        minHeight: 700,
        title: `Twitch VOD Manager [v${APP_VERSION}]`,
        backgroundColor: '#0e0e10',
        autoHideMenuBar: true,
        webPreferences: {
            nodeIntegration: false,
            contextIsolation: true,
            preload: path.join(__dirname, 'preload.js')
        }
    });

    if (process.platform !== 'darwin') {
        mainWindow.removeMenu();
    }

    mainWindow.loadFile(path.join(__dirname, '../src/index.html'));

    mainWindow.webContents.on('did-finish-load', () => {
        emitQueueUpdated(true);
        if (isDownloading) {
            mainWindow?.webContents.send('download-started');
        }

        if (autoUpdateReadyToInstall && downloadedUpdateVersion) {
            mainWindow?.webContents.send('update-downloaded', buildUpdateInfoPayload(downloadedUpdateVersion));
        }

        // Auto-resume: if the user opted in AND the persisted queue has
        // pending entries, kick off processing after a short delay so the
        // UI has time to render and the user can still pause if they want.
        if (config.auto_resume_queue_on_startup && !isDownloading) {
            const hasPending = downloadQueue.some((it) => it.status === 'pending');
            if (hasPending) {
                appendDebugLog('auto-resume-queue-scheduled', { pending: downloadQueue.filter((it) => it.status === 'pending').length });
                setTimeout(() => {
                    if (config.auto_resume_queue_on_startup && !isDownloading
                        && downloadQueue.some((it) => it.status === 'pending')) {
                        void processQueue();
                    }
                }, 5000);
            }
        }
    });

    mainWindow.on('closed', () => {
        mainWindow = null;
    });

    // Setup auto-updater after window is ready
    setTimeout(() => {
        setupAutoUpdater();
    }, 3000);
}

// ==========================================
// AUTO-UPDATER (electron-updater)
// ==========================================
function hasNewerKnownUpdateThanDownloaded(): boolean {
    if (!latestKnownUpdateVersion || !downloadedUpdateVersion) {
        return false;
    }

    return isNewerUpdateVersion(latestKnownUpdateVersion, downloadedUpdateVersion);
}

function normalizeReleaseVersionCandidate(value: unknown): string | undefined {
    if (typeof value !== 'string') {
        return undefined;
    }

    const trimmed = value.trim();
    if (!trimmed) {
        return undefined;
    }

    return normalizeUpdateVersion(trimmed) || trimmed.replace(/^v/i, '');
}

function cacheLatestReleaseUpdateInfo(releaseData: any): void {
    if (!releaseData || typeof releaseData !== 'object') {
        return;
    }

    const tagName = typeof releaseData.tag_name === 'string' ? releaseData.tag_name.trim() : '';
    const version = normalizeReleaseVersionCandidate(tagName)
        || normalizeReleaseVersionCandidate(releaseData.name);
    const releaseName = typeof releaseData.name === 'string' ? releaseData.name.trim() : '';
    const releaseNotes = typeof releaseData.body === 'string' ? releaseData.body : '';
    const releaseDate = typeof releaseData.published_at === 'string'
        ? releaseData.published_at
        : (typeof releaseData.created_at === 'string' ? releaseData.created_at : undefined);

    latestReleaseUpdateInfo = {
        tagName: tagName || undefined,
        version,
        releaseDate,
        releaseName: releaseName || undefined,
        releaseNotes: releaseNotes.trim() ? releaseNotes : undefined
    };
}

function buildUpdateInfoPayload(version: string, releaseDate?: string): {
    version: string;
    releaseDate?: string;
    releaseName?: string;
    releaseNotes?: string;
} {
    const normalizedVersion = normalizeReleaseVersionCandidate(version) || version;
    const cachedVersion = latestReleaseUpdateInfo?.version
        ? (normalizeReleaseVersionCandidate(latestReleaseUpdateInfo.version) || latestReleaseUpdateInfo.version)
        : undefined;
    const hasMatchingReleaseInfo = !cachedVersion || cachedVersion === normalizedVersion;

    return {
        version: normalizedVersion,
        releaseDate: releaseDate || (hasMatchingReleaseInfo ? latestReleaseUpdateInfo?.releaseDate : undefined),
        releaseName: hasMatchingReleaseInfo ? latestReleaseUpdateInfo?.releaseName : undefined,
        releaseNotes: hasMatchingReleaseInfo ? latestReleaseUpdateInfo?.releaseNotes : undefined
    };
}

async function requestUpdateCheck(source: UpdateCheckSource, force = false): Promise<{ started: boolean; reason?: string }> {
    if (autoUpdateCheckInProgress) {
        return { started: false, reason: 'in-progress' };
    }

    const now = Date.now();
    if (!force && lastAutoUpdateCheckAt > 0 && (now - lastAutoUpdateCheckAt) < AUTO_UPDATE_MIN_CHECK_GAP_MS) {
        return { started: false, reason: 'throttled' };
    }

    autoUpdateCheckInProgress = true;
    lastAutoUpdateCheckAt = now;
    appendDebugLog('update-check-start', { source });

    try {
        try {
            const giteaRes = await axios.get(GITEA_RELEASES_API_LATEST_URL, {
                timeout: 5000,
                headers: {
                    'Accept': 'application/json',
                    'User-Agent': 'Twitch-VOD-Manager'
                }
            });
            cacheLatestReleaseUpdateInfo(giteaRes.data);
            const tagName = latestReleaseUpdateInfo?.tagName || giteaRes.data?.tag_name;
            if (tagName) {
                autoUpdater.setFeedURL({
                    provider: 'generic',
                    url: `${GITEA_RELEASES_DOWNLOAD_BASE_URL}/${tagName}`
                });
                appendDebugLog('gitea-feed-url-set', { tagName, owner: GITEA_REPO_OWNER, repo: GITEA_REPO_NAME });
            }
        } catch (apiErr) {
            appendDebugLog('gitea-api-failed', String(apiErr));
        }

        let timeoutHandle: NodeJS.Timeout | null = null;
        try {
            await Promise.race([
                autoUpdater.checkForUpdates(),
                new Promise<never>((_, reject) => {
                    timeoutHandle = setTimeout(() => {
                        reject(new Error(`Update check timed out after ${AUTO_UPDATE_CHECK_TIMEOUT_MS}ms`));
                    }, AUTO_UPDATE_CHECK_TIMEOUT_MS);
                })
            ]);
        } finally {
            if (timeoutHandle) {
                clearTimeout(timeoutHandle);
                timeoutHandle = null;
            }
        }

        return { started: true };
    } catch (err) {
        appendDebugLog('update-check-failed', { source, error: String(err) });
        console.error('Update check failed:', err);
        return { started: false, reason: 'error' };
    } finally {
        autoUpdateCheckInProgress = false;
    }
}

async function requestUpdateDownload(source: UpdateDownloadSource): Promise<{ started: boolean; reason?: string }> {
    if (autoUpdateReadyToInstall && !hasNewerKnownUpdateThanDownloaded()) {
        return { started: false, reason: 'ready-to-install' };
    }

    if (autoUpdateDownloadInProgress) {
        return { started: false, reason: 'in-progress' };
    }

    autoUpdateDownloadInProgress = true;
    appendDebugLog('update-download-start', { source });

    try {
        await autoUpdater.downloadUpdate();
        return { started: true };
    } catch (err) {
        appendDebugLog('update-download-failed', { source, error: String(err) });
        console.error('Download failed:', err);
        return { started: false, reason: 'error' };
    } finally {
        autoUpdateDownloadInProgress = false;
    }
}

function stopAutoUpdatePolling(): void {
    if (autoUpdateCheckTimer) {
        clearInterval(autoUpdateCheckTimer);
        autoUpdateCheckTimer = null;
    }

    if (autoUpdateStartupTimer) {
        clearTimeout(autoUpdateStartupTimer);
        autoUpdateStartupTimer = null;
    }
}

function startAutoUpdatePolling(): void {
    if (!autoUpdateCheckTimer) {
        autoUpdateCheckTimer = setInterval(() => {
            void requestUpdateCheck('interval');
        }, AUTO_UPDATE_CHECK_INTERVAL_MS);

        autoUpdateCheckTimer.unref?.();
    }

    if (autoUpdateStartupTimer) {
        clearTimeout(autoUpdateStartupTimer);
        autoUpdateStartupTimer = null;
    }

    autoUpdateStartupTimer = setTimeout(() => {
        autoUpdateStartupTimer = null;
        void requestUpdateCheck('startup', true);
    }, AUTO_UPDATE_STARTUP_CHECK_DELAY_MS);
}

function setupAutoUpdater() {
    if (autoUpdaterInitialized) {
        startAutoUpdatePolling();
        return;
    }

    autoUpdaterInitialized = true;
    autoUpdater.autoDownload = false;
    autoUpdater.autoInstallOnAppQuit = true;
    autoUpdater.autoRunAppAfterInstall = true;

    autoUpdater.on('checking-for-update', () => {
        console.log('Checking for updates...');
        mainWindow?.webContents.send('update-checking');
    });

    autoUpdater.on('update-available', (info) => {
        const incomingVersion = normalizeUpdateVersion(info.version);
        const displayVersion = incomingVersion || info.version;

        if (latestKnownUpdateVersion && compareUpdateVersions(incomingVersion, latestKnownUpdateVersion) < 0) {
            appendDebugLog('update-available-ignored-older', {
                incomingVersion: displayVersion,
                knownVersion: latestKnownUpdateVersion
            });
            return;
        }

        latestKnownUpdateVersion = incomingVersion || latestKnownUpdateVersion;

        const hasAlreadyDownloadedThisVersion = Boolean(
            autoUpdateReadyToInstall &&
            downloadedUpdateVersion &&
            compareUpdateVersions(downloadedUpdateVersion, incomingVersion) === 0
        );

        console.log('Update available:', displayVersion);
        if (!hasAlreadyDownloadedThisVersion) {
            autoUpdateReadyToInstall = false;
        }

        autoUpdateDownloadInProgress = false;

        if (hasAlreadyDownloadedThisVersion) {
            if (mainWindow) {
                mainWindow.webContents.send('update-downloaded', buildUpdateInfoPayload(displayVersion, info.releaseDate));
            }
            return;
        }

        if (mainWindow) {
            mainWindow.webContents.send('update-available', buildUpdateInfoPayload(displayVersion, info.releaseDate));
        }

        if (AUTO_UPDATE_AUTO_DOWNLOAD) {
            void requestUpdateDownload('auto');
        }
    });

    autoUpdater.on('update-not-available', () => {
        console.log('No updates available');
        mainWindow?.webContents.send('update-not-available');
    });

    autoUpdater.on('download-progress', (progress) => {
        console.log(`Download progress: ${progress.percent.toFixed(1)}%`);
        if (mainWindow) {
            mainWindow.webContents.send('update-download-progress', {
                percent: progress.percent,
                bytesPerSecond: progress.bytesPerSecond,
                transferred: progress.transferred,
                total: progress.total
            });
        }
    });

    autoUpdater.on('update-downloaded', (info) => {
        const downloadedVersion = normalizeUpdateVersion(info.version) || info.version;
        console.log('Update downloaded:', downloadedVersion);
        autoUpdateReadyToInstall = true;
        autoUpdateDownloadInProgress = false;
        downloadedUpdateVersion = downloadedVersion;
        if (!latestKnownUpdateVersion || compareUpdateVersions(downloadedVersion, latestKnownUpdateVersion) > 0) {
            latestKnownUpdateVersion = downloadedVersion;
        }
        if (mainWindow) {
            mainWindow.webContents.send('update-downloaded', buildUpdateInfoPayload(downloadedVersion, info.releaseDate));
        }
    });

    autoUpdater.on('error', (err) => {
        autoUpdateCheckInProgress = false;
        autoUpdateDownloadInProgress = false;
        const message = String(err);
        appendDebugLog('auto-updater-error', message);
        mainWindow?.webContents.send('update-error', { message });
        console.error('Auto-updater error:', err);
    });

    startAutoUpdatePolling();
}

// ==========================================
// IPC HANDLERS
// ==========================================
ipcMain.handle('get-config', () => config);

ipcMain.handle('save-config', (_, newConfig: Partial<Config>) => {
    const previousClientId = config.client_id;
    const previousClientSecret = config.client_secret;
    const previousCacheMinutes = config.metadata_cache_minutes;
    const previousPersistQueueOnRestart = config.persist_queue_on_restart;
    const previousTheme = config.theme;

    config = normalizeConfigTemplates({ ...config, ...newConfig });

    if (config.client_id !== previousClientId || config.client_secret !== previousClientSecret) {
        accessToken = null;
        twitchLoginInFlight = null;
    }

    if (config.metadata_cache_minutes !== previousCacheMinutes) {
        clearMetadataCaches();
    }

    if (config.theme !== previousTheme) {
        nativeTheme.themeSource = config.theme === 'light' ? 'light' : 'dark';
    }

    saveConfig(config);

    if (config.persist_queue_on_restart === false) {
        pendingQueueSnapshot = null;
        if (queueSaveTimer) {
            clearTimeout(queueSaveTimer);
            queueSaveTimer = null;
        }
        clearQueueFileFromDisk();
    } else if (previousPersistQueueOnRestart === false) {
        saveQueue(downloadQueue, true);
    }

    return config;
});

ipcMain.handle('login', async () => {
    return await twitchLogin();
});

ipcMain.handle('get-user-id', async (_, username: string) => {
    return await getUserId(username);
});

ipcMain.handle('get-vods', async (_, userId: string, forceRefresh: boolean = false) => {
    return await getVODs(userId, forceRefresh);
});

ipcMain.handle('get-queue', () => downloadQueue);

ipcMain.handle('add-to-queue', (_, item: Omit<QueueItem, 'id' | 'status' | 'progress'>) => {
    if (config.prevent_duplicate_downloads && hasActiveDuplicate(item)) {
        runtimeMetrics.duplicateSkips += 1;
        mainWindow?.webContents.send('queue-duplicate-skipped', {
            title: item.title,
            streamer: item.streamer,
            url: item.url
        });
        appendDebugLog('queue-item-duplicate-skipped', {
            title: item.title,
            url: item.url,
            streamer: item.streamer
        });
        return downloadQueue;
    }

    const queueItem: QueueItem = {
        ...item,
        id: generateQueueItemId(),
        status: 'pending',
        progress: 0
    };
    downloadQueue.push(queueItem);
    saveQueue(downloadQueue);
    emitQueueUpdated();
    return downloadQueue;
});

ipcMain.handle('remove-from-queue', (_, id: string) => {
    const wasActiveItem = activeQueueItemId === id || activeDownloads.has(id);

    if (wasActiveItem) {
        cancelledItemIds.add(id);
        const tracking = activeDownloads.get(id);
        if (tracking?.process) {
            tracking.process.kill();
        }
        currentDownloadCancelled = true;
        activeDownloads.delete(id);
        activeQueueItemId = null;
        runtimeMetrics.activeItemId = null;
        runtimeMetrics.activeItemTitle = null;
        appendDebugLog('queue-item-removed-active-cancelled', { id });
    }

    // Clean up merge-group temp files (must run for any merge group, not just active)
    const removedItem = downloadQueue.find(item => item.id === id);
    if (removedItem?.mergeGroup) {
        const mg = removedItem.mergeGroup;
        for (const key of Object.keys(mg.downloadedFiles)) {
            try { if (fs.existsSync(mg.downloadedFiles[Number(key)])) fs.unlinkSync(mg.downloadedFiles[Number(key)]); } catch { }
        }
        if (mg.mergedFile) {
            try { if (fs.existsSync(mg.mergedFile)) fs.unlinkSync(mg.mergedFile); } catch { }
        }
    }

    downloadQueue = downloadQueue.filter(item => item.id !== id);
    saveQueue(downloadQueue);
    emitQueueUpdated();
    return downloadQueue;
});

ipcMain.handle('clear-completed', () => {
    downloadQueue = downloadQueue.filter(item => item.status !== 'completed');
    saveQueue(downloadQueue);
    emitQueueUpdated();
    return downloadQueue;
});

ipcMain.handle('reorder-queue', (_, orderIds: string[]) => {
    const order = new Map(orderIds.map((id, idx) => [id, idx]));
    const withOrder = [...downloadQueue].sort((a, b) => {
        const ai = order.has(a.id) ? (order.get(a.id) as number) : Number.MAX_SAFE_INTEGER;
        const bi = order.has(b.id) ? (order.get(b.id) as number) : Number.MAX_SAFE_INTEGER;
        return ai - bi;
    });

    downloadQueue = withOrder;
    saveQueue(downloadQueue);
    emitQueueUpdated();
    return downloadQueue;
});

ipcMain.handle('retry-failed-downloads', () => {
    downloadQueue = downloadQueue.map((item) => {
        if (item.status !== 'error') return item;

        return {
            ...item,
            status: 'pending',
            progress: 0,
            last_error: ''
        };
    });

    saveQueue(downloadQueue);
    emitQueueUpdated();

    if (!isDownloading) {
        void processQueue();
    }

    return downloadQueue;
});

ipcMain.handle('retry-queue-item', (_, id: string) => {
    if (typeof id !== 'string' || !id) return downloadQueue;
    const idx = downloadQueue.findIndex((it) => it.id === id);
    if (idx < 0) return downloadQueue;
    const item = downloadQueue[idx];
    if (item.status !== 'error') return downloadQueue;

    downloadQueue[idx] = {
        ...item,
        status: 'pending',
        progress: 0,
        last_error: ''
    };

    saveQueue(downloadQueue);
    emitQueueUpdated();
    appendDebugLog('queue-item-retry-single', { id, title: item.title });

    if (!isDownloading) {
        void processQueue();
    }

    return downloadQueue;
});

ipcMain.handle('create-merge-group', (_, itemIds: string[]) => {
    const selectedItems = downloadQueue.filter(item => itemIds.includes(item.id));

    if (selectedItems.length < 2) {
        return downloadQueue;
    }

    // Validate all are pending
    if (selectedItems.some(item => item.status !== 'pending')) {
        return downloadQueue;
    }

    // Preserve user-defined order from renderer (itemIds array order)
    const sorted = itemIds
        .map(id => selectedItems.find(item => item.id === id))
        .filter((item): item is QueueItem => item !== undefined);

    // Calculate total duration
    const totalDurationSec = sorted.reduce((sum, item) => sum + parseDuration(item.duration_str), 0);
    const totalDurationStr = (() => {
        const h = Math.floor(totalDurationSec / 3600);
        const m = Math.floor((totalDurationSec % 3600) / 60);
        const s = totalDurationSec % 60;
        const parts: string[] = [];
        if (h > 0) parts.push(`${h}h`);
        if (m > 0) parts.push(`${m}m`);
        if (s > 0 || parts.length === 0) parts.push(`${s}s`);
        return parts.join('');
    })();

    // Generate title (language-aware)
    const first = sorted[0];
    const isEnglish = config.language === 'en';
    const title = sorted.length === 2
        ? `Merge: ${first.title} + ${sorted[1].title}`
        : `Merge: ${first.title} + ${sorted.length - 1} ${isEnglish ? 'more' : 'weitere'}`;

    // Build merge group
    const mergeGroup: MergeGroup = {
        items: sorted.map(item => ({
            url: item.url,
            title: item.title,
            date: item.date,
            streamer: item.streamer,
            duration_str: item.duration_str
        })),
        mergePhase: 'downloading',
        currentItemIndex: 0,
        downloadedFiles: {},
        totalDurationSec
    };

    // Create merged queue item
    const mergedItem: QueueItem = {
        id: generateQueueItemId(),
        title,
        url: first.url,
        date: first.date,
        streamer: first.streamer,
        duration_str: totalDurationStr,
        status: 'pending',
        progress: 0,
        mergeGroup
    };

    // Find position of first selected item
    const firstIndex = downloadQueue.findIndex(item => itemIds.includes(item.id));

    // Remove selected items and insert merged item at first position
    downloadQueue = downloadQueue.filter(item => !itemIds.includes(item.id));
    downloadQueue.splice(firstIndex >= 0 ? Math.min(firstIndex, downloadQueue.length) : downloadQueue.length, 0, mergedItem);

    saveQueue(downloadQueue);
    emitQueueUpdated();
    return downloadQueue;
});

ipcMain.handle('start-download', async () => {
    downloadQueue = downloadQueue.map((item) => item.status === 'paused' ? { ...item, status: 'pending' } : item);

    const hasPendingItems = downloadQueue.some(item => item.status === 'pending');
    if (!hasPendingItems) {
        emitQueueUpdated();
        return false;
    }

    saveQueue(downloadQueue);
    emitQueueUpdated();

    if (!isDownloading) {
        void processQueue();
    }
    return true;
});

ipcMain.handle('pause-download', () => {
    if (!isDownloading) return false;

    pauseRequested = true;
    currentDownloadCancelled = true;
    // Kill queue downloads only — cutter/merger/splitter use currentEditorProcess
    // and aren't affected by pause-download.
    for (const [id, tracking] of activeDownloads) {
        cancelledItemIds.add(id);
        if (tracking.process) {
            tracking.process.kill();
        }
    }
    return true;
});

ipcMain.handle('cancel-download', () => {
    isDownloading = false;
    pauseRequested = false;
    currentDownloadCancelled = true;
    // Kill queue downloads only — see pause-download note above.
    for (const [id, tracking] of activeDownloads) {
        cancelledItemIds.add(id);
        if (tracking.process) {
            tracking.process.kill();
        }
    }
    return true;
});

ipcMain.handle('select-folder', async () => {
    const result = await dialog.showOpenDialog(mainWindow!, {
        properties: ['openDirectory']
    });
    return result.filePaths[0] || null;
});

ipcMain.handle('select-video-file', async () => {
    const result = await dialog.showOpenDialog(mainWindow!, {
        properties: ['openFile'],
        filters: [
            { name: 'Video Files', extensions: ['mp4', 'mkv', 'ts', 'mov', 'avi'] }
        ]
    });
    return result.filePaths[0] || null;
});

ipcMain.handle('open-folder', (_, folderPath: string) => {
    if (fs.existsSync(folderPath)) {
        shell.openPath(folderPath);
    }
});

ipcMain.handle('open-file', async (_, filePath: string): Promise<boolean> => {
    if (typeof filePath !== 'string' || !filePath) return false;
    if (!fs.existsSync(filePath)) return false;
    const result = await shell.openPath(filePath);
    // shell.openPath returns '' on success, an error string on failure.
    return result === '';
});

ipcMain.handle('show-in-folder', (_, filePath: string): boolean => {
    if (typeof filePath !== 'string' || !filePath) return false;
    if (!fs.existsSync(filePath)) return false;
    shell.showItemInFolder(filePath);
    return true;
});

ipcMain.handle('get-version', () => APP_VERSION);

ipcMain.handle('check-update', async () => {
    try {
        setupAutoUpdater();
        const result = await requestUpdateCheck('manual', true);
        if (result.reason === 'error') {
            return { error: true };
        }

        return result.started
            ? { checking: true }
            : { checking: true, skipped: result.reason };
    } catch (err) {
        console.error('Update check failed:', err);
        return { error: true };
    }
});

ipcMain.handle('download-update', async () => {
    try {
        setupAutoUpdater();
        const result = await requestUpdateDownload('manual');
        if (result.reason === 'error') {
            return { error: true };
        }

        return result.started
            ? { downloading: true }
            : { downloading: true, skipped: result.reason };
    } catch (err) {
        console.error('Download failed:', err);
        return { error: true };
    }
});

ipcMain.handle('install-update', () => {
    autoUpdater.quitAndInstall(true, true);
});

ipcMain.handle('open-external', async (_, url: string) => {
    await shell.openExternal(url);
});

// Tracks active standalone clip downloads so cancel-download / window-all-closed
// can kill them. Separate from activeDownloads (queue) because clip downloads
// don't go through the queue scheduler.
const activeClipProcesses = new Map<string, ChildProcess>();

ipcMain.handle('download-clip', async (_, clipUrl: string) => {
    let clipId = '';
    const match1 = clipUrl.match(/clips\.twitch\.tv\/([A-Za-z0-9_-]+)/);
    const match2 = clipUrl.match(/twitch\.tv\/[^/]+\/clip\/([A-Za-z0-9_-]+)/);

    if (match1) clipId = match1[1];
    else if (match2) clipId = match2[1];
    else return { success: false, error: tBackend('invalidClipUrl') };

    const clipInfo = await getClipInfo(clipId);
    if (!clipInfo) return { success: false, error: tBackend('clipNotFound') };

    // Sanitize broadcaster_name for path safety — Twitch returns the display
    // name which can contain unicode, spaces, or punctuation that breaks
    // path joining on some Windows configurations.
    const safeBroadcaster = sanitizeFilenamePart(
        typeof clipInfo.broadcaster_name === 'string' ? clipInfo.broadcaster_name : '',
        'unknown'
    );
    const folder = path.join(config.download_path, 'Clips', safeBroadcaster);
    fs.mkdirSync(folder, { recursive: true });

    const clipDiskCheck = ensureDiskSpace(folder, 128 * 1024 * 1024, 'Clip-Download');
    if (!clipDiskCheck.success) {
        return { success: false, error: clipDiskCheck.error || tBackend('diskSpaceShortGeneric') };
    }

    const rawTitle = typeof clipInfo.title === 'string' ? clipInfo.title : '';
    const safeTitle = (rawTitle.replace(/[^a-zA-Z0-9_\- ]/g, '').trim().substring(0, 50)) || 'clip';
    // Use ensureUniqueFilename so retrying a clip with the same title doesn't
    // overwrite the previous download. itemId is the clipId — if the user
    // cancels via cancel-download, that's the handle.
    const filename = ensureUniqueFilename(path.join(folder, `${safeTitle}.mp4`), clipId);

    return new Promise<{ success: boolean; error?: string; filename?: string }>((resolve) => {
        const streamlinkCmd = getStreamlinkCommand();
        const proc = spawn(streamlinkCmd.command, [
            ...streamlinkCmd.prefixArgs,
            `https://clips.twitch.tv/${clipId}`,
            'best',
            '-o', filename,
            '--force'
        ], { windowsHide: true });

        activeClipProcesses.set(clipId, proc);
        appendDebugLog('clip-download-start', { clipId, broadcaster: safeBroadcaster, filename });

        proc.on('close', (code) => {
            activeClipProcesses.delete(clipId);
            releaseClaimedFilenamesForItem(clipId);

            if (code !== 0 || !fs.existsSync(filename)) {
                appendDebugLog('clip-download-failed', { clipId, code });
                resolve({ success: false, error: tBackend('downloadFailedExitCode', { code: String(code ?? -1) }) });
                return;
            }

            // Integrity: clips are short but should still be at least a few KB
            // and parse as a video stream via ffprobe. Empty/zero-byte files
            // were previously reported as "success" because exit code was 0.
            const stats = fs.statSync(filename);
            if (stats.size < 16 * 1024) {
                try { fs.unlinkSync(filename); } catch { }
                appendDebugLog('clip-download-too-small', { clipId, bytes: stats.size });
                resolve({ success: false, error: tBackend('clipFileTooSmall', { bytes: String(stats.size) }) });
                return;
            }

            const integrity = validateDownloadedFileIntegrity(filename, null);
            if (!integrity.success) {
                try { fs.unlinkSync(filename); } catch { }
                appendDebugLog('clip-download-integrity-failed', { clipId, error: integrity.error });
                resolve({ success: false, error: integrity.error || tBackend('integrityFailedGeneric') });
                return;
            }

            appendDebugLog('clip-download-success', { clipId, bytes: stats.size, filename });
            resolve({ success: true, filename });
        });

        proc.on('error', () => {
            activeClipProcesses.delete(clipId);
            releaseClaimedFilenamesForItem(clipId);
            resolve({ success: false, error: tBackend('streamlinkNotFound') });
        });
    });
});

ipcMain.handle('run-preflight', async (_, autoFix: boolean = false) => {
    return await runPreflight(autoFix);
});

ipcMain.handle('get-debug-log', async (_, lines: number = 200) => {
    // Cap so a misbehaving renderer (or future feature) cannot ask the
    // main process to slice millions of lines from a multi-MB log.
    const safeLines = Number.isFinite(lines) ? Math.max(1, Math.min(5000, Math.floor(lines))) : 200;
    return readDebugLog(safeLines);
});

ipcMain.handle('open-debug-log-file', (): boolean => {
    if (!fs.existsSync(DEBUG_LOG_FILE)) return false;
    shell.showItemInFolder(DEBUG_LOG_FILE);
    return true;
});

ipcMain.handle('is-downloading', () => isDownloading);

ipcMain.handle('get-runtime-metrics', () => getRuntimeMetricsSnapshot());

ipcMain.handle('export-runtime-metrics', async () => {
    try {
        const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
        const defaultName = `runtime-metrics-${timestamp}.json`;
        const preferredDir = fs.existsSync(config.download_path) ? config.download_path : app.getPath('desktop');

        const dialogResult = await dialog.showSaveDialog(mainWindow!, {
            defaultPath: path.join(preferredDir, defaultName),
            filters: [{ name: 'JSON', extensions: ['json'] }]
        });

        if (dialogResult.canceled || !dialogResult.filePath) {
            return { success: false, cancelled: true };
        }

        const snapshot = getRuntimeMetricsSnapshot();
        // Atomic write: same fsync+rename pattern used for config/queue
        // (cycle 1) so a power loss mid-export can't leave a half-written
        // metrics file at the user's chosen path.
        writeFileAtomicSync(dialogResult.filePath, JSON.stringify(snapshot, null, 2));
        return { success: true, filePath: dialogResult.filePath };
    } catch (e) {
        appendDebugLog('runtime-metrics-export-failed', String(e));
        return { success: false, error: String(e) };
    }
});

// Video Cutter IPC
ipcMain.handle('get-video-info', async (_, filePath: string) => {
    return await getVideoInfo(filePath);
});

ipcMain.handle('extract-frame', async (_, filePath: string, timeSeconds: number) => {
    return await extractFrame(filePath, timeSeconds);
});

ipcMain.handle('cut-video', async (_, inputFile: string, startTime: number, endTime: number) => {
    const dir = path.dirname(inputFile);
    const baseName = path.basename(inputFile, path.extname(inputFile));
    const timestamp = new Date().toISOString().replace(/[:.]/g, '-').substring(11, 19);
    const outputFile = path.join(dir, `${baseName}_cut_${timestamp}.mp4`);

    let lastProgress = 0;
    const success = await cutVideo(inputFile, outputFile, startTime, endTime, (percent) => {
        lastProgress = percent;
        mainWindow?.webContents.send('cut-progress', percent);
    });

    return { success, outputFile: success ? outputFile : null };
});

// Merge IPC
ipcMain.handle('merge-videos', async (_, inputFiles: string[], outputFile: string) => {
    const success = await mergeVideos(inputFiles, outputFile, (percent) => {
        mainWindow?.webContents.send('merge-progress', percent);
    });

    return { success, outputFile: success ? outputFile : null };
});

ipcMain.handle('select-multiple-videos', async () => {
    const result = await dialog.showOpenDialog(mainWindow!, {
        properties: ['openFile', 'multiSelections'],
        filters: [
            { name: 'Video Files', extensions: ['mp4', 'mkv', 'ts', 'mov', 'avi'] }
        ]
    });
    return result.filePaths;
});

ipcMain.handle('save-video-dialog', async (_, defaultName: string) => {
    const result = await dialog.showSaveDialog(mainWindow!, {
        defaultPath: defaultName,
        filters: [
            { name: 'MP4 Video', extensions: ['mp4'] }
        ]
    });
    return result.filePath || null;
});

// ==========================================
// APP LIFECYCLE
// ==========================================
app.whenReady().then(() => {
    app.setAppUserModelId('com.twitch.vodmanager');
    refreshBundledToolPaths(true);
    startMetadataCacheCleanup();
    startDebugLogFlushTimer();
    createWindow();
    appendDebugLog('startup-tools-check-skipped', 'Deferred to first use');

    app.on('activate', () => {
        if (BrowserWindow.getAllWindows().length === 0) {
            createWindow();
        }
    });
});

// Both window-all-closed and before-quit ran nearly identical cleanup blocks
// before, with slight drift (only window-all-closed killed children, only
// window-all-closed did anything platform-specific). Consolidating them into
// a single idempotent helper means any future tweak (e.g. flushing a new
// debug stream) lands once and applies on every quit path.
let shutdownCleanupDone = false;

function shutdownCleanup(reason: 'window-all-closed' | 'before-quit'): void {
    if (shutdownCleanupDone) return;
    shutdownCleanupDone = true;

    appendDebugLog('shutdown-cleanup', { reason });

    stopMetadataCacheCleanup();
    cleanupMetadataCaches('shutdown');
    stopAutoUpdatePolling();

    // Kill all active children: queue downloads, standalone clip downloads,
    // and any in-flight cutter/merger/splitter ffmpeg. before-quit used to
    // skip this entirely; window-all-closed did it but only via direct
    // kill() (no try/catch around the queue process kill).
    for (const [, tracking] of activeDownloads) {
        if (tracking.process) {
            try { tracking.process.kill(); } catch { /* already exited */ }
        }
    }
    activeDownloads.clear();

    for (const [, proc] of activeClipProcesses) {
        try { proc.kill(); } catch { /* already exited */ }
    }
    activeClipProcesses.clear();

    if (currentEditorProcess) {
        try { currentEditorProcess.kill(); } catch { /* already exited */ }
        currentEditorProcess = null;
    }

    saveConfig(config);
    flushQueueSave();

    // Flush debug log AFTER persisting state so any errors saving config /
    // queue land in the log before the timer is gone.
    stopDebugLogFlushTimer(true);
}

app.on('window-all-closed', () => {
    shutdownCleanup('window-all-closed');
    if (process.platform !== 'darwin') {
        app.quit();
    }
});

app.on('before-quit', () => {
    shutdownCleanup('before-quit');
});