fix(web): summarize session titles, sort by activity, and paginate history (BUG-553)

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/session-groups.ts

@@ -0,0 +1,90 @@
+import type { ChatSession } from "@/lib/home-types";
+
+export const SESSION_RECENCY_LABELS = {
+  today: "今天",
+  yesterday: "昨天",
+  week: "最近 7 天",
+  month: "最近 30 天",
+  older: "更早",
+} as const;
+
+export type SessionRecencyKey = keyof typeof SESSION_RECENCY_LABELS;
+
+export type SessionRecencyGroup<T extends { updatedAt: number } = ChatSession> = {
+  readonly key: SessionRecencyKey;
+  readonly label: string;
+  readonly sessions: readonly T[];
+};
+
+function startOfLocalDay(now: Date): number {
+  return new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime();
+}
+
+export function sortSessions<T extends { pinned: boolean; updatedAt: number }>(sessions: readonly T[]): T[] {
+  return sessions
+    .map((session, index) => ({ session, index }))
+    .sort((left, right) => {
+      const pinned = Number(right.session.pinned) - Number(left.session.pinned);
+      if (pinned !== 0) return pinned;
+      const time = right.session.updatedAt - left.session.updatedAt;
+      if (time !== 0) return time;
+      return left.index - right.index;
+    })
+    .map((item) => item.session);
+}
+
+export function recencyKeyFor(updatedAt: number, now = Date.now()): SessionRecencyKey {
+  const todayStart = startOfLocalDay(new Date(now));
+  const dayMs = 24 * 60 * 60 * 1000;
+  if (updatedAt >= todayStart) return "today";
+  if (updatedAt >= todayStart - dayMs) return "yesterday";
+  if (updatedAt >= todayStart - 6 * dayMs) return "week";
+  if (updatedAt >= todayStart - 29 * dayMs) return "month";
+  return "older";
+}
+
+export function groupSessionsByRecency<T extends { updatedAt: number }>(
+  sessions: readonly T[],
+  now = Date.now(),
+): SessionRecencyGroup<T>[] {
+  const buckets: Record<SessionRecencyKey, T[]> = {
+    today: [],
+    yesterday: [],
+    week: [],
+    month: [],
+    older: [],
+  };
+  for (const session of sessions) {
+    buckets[recencyKeyFor(session.updatedAt, now)].push(session);
+  }
+  const order: SessionRecencyKey[] = ["today", "yesterday", "week", "month", "older"];
+  return order.flatMap((key) => {
+    const group = buckets[key];
+    if (group.length === 0) return [];
+    return [{ key, label: SESSION_RECENCY_LABELS[key], sessions: group }];
+  });
+}
+
+export function mergeSessionPage<T extends { id: string; updatedAt: number }>(
+  existing: readonly T[],
+  incoming: readonly T[],
+): T[] {
+  const seen = new Map(existing.map((session) => [session.id, session]));
+  const next = [...existing];
+  for (const row of incoming) {
+    const current = seen.get(row.id);
+    if (current) continue;
+    seen.set(row.id, row);
+    next.push(row);
+  }
+  return next;
+}
+
+export function beginSessionPageLoad(
+  inFlight: { current: boolean },
+  cursor: string | null,
+): boolean {
+  if (inFlight.current || !cursor) return false;
+  inFlight.current = true;
+  return true;
+}