52 lines
1.9 KiB
JavaScript
52 lines
1.9 KiB
JavaScript
// Time-windowed memoization. Reuses a previously-computed value if the
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// signature + input identity match AND the cached entry is younger than
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// `refreshMs`. Used by the renderer's dynamic-key sort throttle (every
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// progress tick re-sorts a 5000-row queue → reuse for 200 ms, the user
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// can't perceive sub-200 ms reorder lag).
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//
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// Loaded both as a CommonJS module (Node tests) and as a browser global
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// (renderer/app.js via index.html script tag) — same single implementation
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// across runtime and tests.
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(function (root) {
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'use strict';
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/**
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* Build a throttled cache. The clock is injected so tests don't have to
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* sleep — pass `() => fakeClock.value` from tests.
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*
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* @param {number} refreshMs cache TTL in milliseconds
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* @param {() => number} [now] clock source, defaults to Date.now
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*/
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function makeThrottledCache(refreshMs, now) {
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if (!Number.isFinite(refreshMs) || refreshMs < 0) {
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throw new TypeError('refreshMs must be a non-negative finite number');
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}
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const clock = typeof now === 'function' ? now : () => Date.now();
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let entry = null;
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return {
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get(sig, input) {
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if (!entry) return undefined;
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if (entry.sig !== sig) return undefined;
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if (entry.input !== input) return undefined;
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if (clock() - entry.ts >= refreshMs) return undefined;
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return entry.value;
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},
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set(sig, input, value) {
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entry = { sig, input, value, ts: clock() };
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return value;
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},
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clear() { entry = null; },
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// Introspection (mainly for tests/debug). Returns null when empty.
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peek() {
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if (!entry) return null;
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return { sig: entry.sig, ts: entry.ts, age: clock() - entry.ts };
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}
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};
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}
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const api = { makeThrottledCache };
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if (typeof module !== 'undefined' && module.exports) module.exports = api;
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else if (root) root.ThrottledCache = api;
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})(typeof window !== 'undefined' ? window : this);
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