feat(chat): implement pull-to-refresh functionality and pagination for chat history

src/stores/chat/helper/history.ts

@@ -21,12 +21,88 @@ export function applyNetworkHistoryLoadedOutput(
   output: {
     messages: UiMessage[];
     localCount: number;
+    total: number;
+    limit: number;
   },
-): Pick<ChatState, "messages" | "historyLoaded"> {
+): Pick<
+  ChatState,
+  | "messages"
+  | "historyLoaded"
+  | "historyTotal"
+  | "historyLimit"
+  | "nextHistoryOffset"
+  | "isLoadingMoreHistory"
+> {
   const localSnapshotSize = output.localCount === 0 ? 1 : output.localCount;
   const optimisticTail = context.messages.slice(localSnapshotSize);
+  const historyLimit = normalizeHistoryLimit(output.limit);
   return {
     messages: [...output.messages, ...optimisticTail],
     historyLoaded: true,
+    historyTotal: Math.max(0, output.total),
+    historyLimit,
+    nextHistoryOffset: historyLimit,
+    isLoadingMoreHistory: false,
   };
 }
+
+export function applyOlderHistoryLoadedOutput(
+  context: ChatState,
+  output: {
+    messages: UiMessage[];
+    offset: number;
+    total: number;
+    limit: number;
+  },
+): Pick<
+  ChatState,
+  | "messages"
+  | "historyTotal"
+  | "historyLimit"
+  | "nextHistoryOffset"
+  | "isLoadingMoreHistory"
+> {
+  const historyLimit = normalizeHistoryLimit(
+    output.limit,
+    context.historyLimit,
+  );
+  return {
+    messages: prependUniqueHistoryMessages(context.messages, output.messages),
+    historyTotal: Math.max(0, output.total),
+    historyLimit,
+    nextHistoryOffset: output.offset + historyLimit,
+    isLoadingMoreHistory: false,
+  };
+}
+
+export function canLoadMoreHistory(context: ChatState): boolean {
+  return (
+    context.historyLoaded &&
+    !context.isLoadingMoreHistory &&
+    context.nextHistoryOffset < context.historyTotal
+  );
+}
+
+export function normalizeHistoryLimit(
+  limit: number,
+  fallback = CHAT_HISTORY_LIMIT,
+): number {
+  return Number.isFinite(limit) && limit > 0 ? Math.floor(limit) : fallback;
+}
+
+export function prependUniqueHistoryMessages(
+  currentMessages: readonly UiMessage[],
+  olderMessages: readonly UiMessage[],
+): UiMessage[] {
+  const existingIds = new Set(
+    currentMessages.flatMap((message) => (message.id ? [message.id] : [])),
+  );
+  const pageIds = new Set<string>();
+  const uniqueOlderMessages = olderMessages.filter((message) => {
+    if (!message.id) return true;
+    if (existingIds.has(message.id) || pageIds.has(message.id)) return false;
+    pageIds.add(message.id);
+    return true;
+  });
+  return [...uniqueOlderMessages, ...currentMessages];
+}