Load complete chat history when reaching the top (#2481)

* fix(chat): load older timeline history consistently Pagination depended on scroll events, so short or compacted initial pages could never request older history. Reevaluate edge visibility as layout and history change, and standardize loading indicators on the canonical app spinner. * fix(chat): keep older history loading reliably Use authoritative timeline cursor progress so merged rows cannot stall pagination. Wait for bottom anchoring before evaluating the history edge, and re-arm retries on a fresh upward gesture without automatic failure loops.
2026-07-27 18:21:07 +08:00
parent 80c8a08393
commit b97d6d13f3
38 changed files with 609 additions and 177 deletions
@@ -0,0 +1,73 @@
+import { describe, expect, it } from "vitest";
+import {
+  createHistoryStartPaginationState,
+  evaluateHistoryStartPagination,
+  rearmHistoryStartPagination,
+} from "./history-start-pagination";
+
+const visibleHistoryStart = {
+  distanceFromHistoryStart: 0,
+  hasOlderHistory: true,
+  isLoadingOlderHistory: false,
+  isReady: true,
+  progressKey: "epoch-1:20",
+};
+
+describe("history start pagination", () => {
+  it("loads once for each authoritative history cursor", () => {
+    const initial = createHistoryStartPaginationState();
+    const first = evaluateHistoryStartPagination(initial, visibleHistoryStart);
+    const duplicate = evaluateHistoryStartPagination(first.state, visibleHistoryStart);
+    const nextPage = evaluateHistoryStartPagination(first.state, {
+      ...visibleHistoryStart,
+      progressKey: "epoch-1:10",
+    });
+
+    expect([first.shouldLoad, duplicate.shouldLoad, nextPage.shouldLoad]).toEqual([
+      true,
+      false,
+      true,
+    ]);
+  });
+
+  it("allows the same revision again after the user leaves the history edge", () => {
+    const first = evaluateHistoryStartPagination(
+      createHistoryStartPaginationState(),
+      visibleHistoryStart,
+    );
+    const away = evaluateHistoryStartPagination(first.state, {
+      ...visibleHistoryStart,
+      distanceFromHistoryStart: 200,
+    });
+    const returned = evaluateHistoryStartPagination(away.state, visibleHistoryStart);
+
+    expect([first.shouldLoad, away.shouldLoad, returned.shouldLoad]).toEqual([true, false, true]);
+  });
+
+  it("re-arms the same cursor when the user makes another upward edge gesture", () => {
+    const first = evaluateHistoryStartPagination(
+      createHistoryStartPaginationState(),
+      visibleHistoryStart,
+    );
+    const retried = evaluateHistoryStartPagination(
+      rearmHistoryStartPagination(first.state),
+      visibleHistoryStart,
+    );
+
+    expect([first.shouldLoad, retried.shouldLoad]).toEqual([true, true]);
+  });
+
+  it("waits while history loading is unavailable or already active", () => {
+    const state = createHistoryStartPaginationState();
+
+    expect([
+      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, isReady: false }).shouldLoad,
+      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, hasOlderHistory: false })
+        .shouldLoad,
+      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, isLoadingOlderHistory: true })
+        .shouldLoad,
+      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, progressKey: null })
+        .shouldLoad,
+    ]).toEqual([false, false, false, false]);
+  });
+});