Prevent stale live snapshots from flickering sorted packages

tests/package-order-state.test.ts

@@ -0,0 +1,69 @@
+import { describe, expect, it } from "vitest";
+import { createPackageOrderState } from "../src/renderer/package-order-state";
+
+describe("pending package order", () => {
+  it("keeps the chosen order through stale updates until the command and snapshot agree", () => {
+    const state = createPackageOrderState();
+    state.accept(["a", "b", "c"]);
+    const request = state.begin(["c", "b", "a"]);
+    expect(state.accept(["a", "b", "c"])).toEqual(["c", "b", "a"]);
+    state.confirm(request);
+    expect(state.accept(["a", "b", "c"])).toEqual(["c", "b", "a"]);
+    expect(state.accept(["c", "b", "a"])).toEqual(["c", "b", "a"]);
+    expect(state.accept(["b", "a", "c"])).toEqual(["b", "a", "c"]);
+  });
+
+  it("does not mistake the old order for confirmation when the user reverses quickly", () => {
+    const state = createPackageOrderState();
+    state.accept(["a", "b"]);
+    const first = state.begin(["b", "a"]);
+    const second = state.begin(["a", "b"]);
+    expect(state.accept(["a", "b"])).toEqual(["a", "b"]);
+    state.confirm(first);
+    expect(state.accept(["b", "a"])).toEqual(["a", "b"]);
+    state.confirm(second);
+    expect(state.accept(["b", "a"])).toEqual(["a", "b"]);
+    state.accept(["a", "b"]);
+    expect(state.accept(["b", "a"])).toEqual(["b", "a"]);
+  });
+
+  it("retains newly added packages and never resurrects removed packages", () => {
+    const state = createPackageOrderState();
+    state.accept(["a", "b", "c"]);
+    const request = state.begin(["c", "b", "a"]);
+    expect(state.accept(["a", "c", "new"])).toEqual(["c", "a", "new"]);
+    state.confirm(request);
+    state.accept(["c", "a", "new"]);
+    expect(state.accept(["new", "a", "c"])).toEqual(["new", "a", "c"]);
+  });
+
+  it("ignores rejected obsolete requests and rolls back the current request to the latest server order", () => {
+    const state = createPackageOrderState();
+    state.accept(["a", "b"]);
+    const first = state.begin(["b", "a"]);
+    const second = state.begin(["a", "b"]);
+    expect(state.reject(first)).toBeNull();
+    state.accept(["b", "a", "new"]);
+    expect(state.reject(second)).toEqual(["b", "a", "new"]);
+    expect(state.accept(["new", "b", "a"])).toEqual(["new", "b", "a"]);
+  });
+
+  it("can receive the matching snapshot before the command promise resolves", () => {
+    const state = createPackageOrderState();
+    state.accept(["a", "b"]);
+    const request = state.begin(["b", "a"]);
+    state.accept(["b", "a"]);
+    state.confirm(request);
+    const incoming = ["b", "a"];
+    expect(state.accept(incoming)).toBe(incoming);
+    expect(state.accept(["a", "b"])).toEqual(["a", "b"]);
+  });
+
+  it("preserves an empty authoritative queue", () => {
+    const state = createPackageOrderState();
+    const request = state.begin(["b", "a"]);
+    state.confirm(request);
+    expect(state.accept([])).toEqual([]);
+    expect(state.accept(["new"])).toEqual(["new"]);
+  });
+});