refactor(chat): extract render item helpers

src/app/chat/chat-render-items.ts

@@ -0,0 +1,45 @@
+import type { UiMessage } from "@/data/dto/chat";
+
+export type ChatMessageKeyResolver = (message: UiMessage) => string;
+
+export type ChatRenderItem =
+  | { type: "date"; date: string; key: string }
+  | { type: "msg"; message: UiMessage; key: string };
+
+export function createChatMessageKeyResolver(): ChatMessageKeyResolver {
+  const localMessageKeys = new WeakMap<UiMessage, string>();
+  let nextLocalMessageKey = 0;
+
+  return (message) => {
+    if (message.id && message.id.length > 0) return `msg-${message.id}`;
+
+    const existing = localMessageKeys.get(message);
+    if (existing) return existing;
+
+    nextLocalMessageKey += 1;
+    const next = `local-msg-${nextLocalMessageKey}`;
+    localMessageKeys.set(message, next);
+    return next;
+  };
+}
+
+export function buildChatRenderItems(
+  messages: readonly UiMessage[],
+  getMessageKey: ChatMessageKeyResolver,
+): ChatRenderItem[] {
+  const items: ChatRenderItem[] = [];
+
+  messages.forEach((message, index) => {
+    const messageKey = getMessageKey(message);
+    if (index === 0 || message.date !== messages[index - 1].date) {
+      items.push({
+        type: "date",
+        date: message.date,
+        key: `date-${message.date}-${messageKey}`,
+      });
+    }
+    items.push({ type: "msg", message, key: messageKey });
+  });
+
+  return items;
+}