feat(web): per-chat message drafts

- store unsent draft text per chat in zustand
- restore draft when switching chats
- clear draft after successful send

web/src/components/MessageComposer.tsx

@@ -7,6 +7,9 @@ import { buildWsUrl } from "../utils/ws";
 export function MessageComposer() {
   const activeChatId = useChatStore((s) => s.activeChatId);
   const me = useAuthStore((s) => s.me);
+  const draftsByChat = useChatStore((s) => s.draftsByChat);
+  const setDraft = useChatStore((s) => s.setDraft);
+  const clearDraft = useChatStore((s) => s.clearDraft);
   const addOptimisticMessage = useChatStore((s) => s.addOptimisticMessage);
   const confirmMessageByClientId = useChatStore((s) => s.confirmMessageByClientId);
   const removeOptimisticMessage = useChatStore((s) => s.removeOptimisticMessage);
@@ -25,6 +28,19 @@ export function MessageComposer() {
   const [previewUrl, setPreviewUrl] = useState<string | null>(null);
   const [isRecording, setIsRecording] = useState(false);
 
+  useEffect(() => {
+    if (!activeChatId) {
+      if (text !== "") {
+        setText("");
+      }
+      return;
+    }
+    const draft = draftsByChat[activeChatId] ?? "";
+    if (draft !== text) {
+      setText(draft);
+    }
+  }, [activeChatId, draftsByChat, text]);
+
   useEffect(() => {
     return () => {
       if (previewUrl) {
@@ -64,6 +80,7 @@ export function MessageComposer() {
       const message = await sendMessageWithClientId(activeChatId, textValue, "text", clientMessageId, replyToMessageId);
       confirmMessageByClientId(activeChatId, clientMessageId, message);
       setText("");
+      clearDraft(activeChatId);
       setReplyToMessage(activeChatId, null);
       const ws = getWs();
       ws?.send(JSON.stringify({ event: "typing_stop", payload: { chat_id: activeChatId } }));
@@ -284,7 +301,11 @@ export function MessageComposer() {
           placeholder="Write a message..."
           value={text}
           onChange={(e) => {
-            setText(e.target.value);
+            const next = e.target.value;
+            setText(next);
+            if (activeChatId) {
+              setDraft(activeChatId, next);
+            }
             if (activeChatId) {
               const ws = getWs();
               ws?.send(JSON.stringify({ event: "typing_start", payload: { chat_id: activeChatId } }));

web/src/store/chatStore.ts

@@ -6,6 +6,7 @@ interface ChatState {
   chats: Chat[];
   activeChatId: number | null;
   messagesByChat: Record<number, Message[]>;
+  draftsByChat: Record<number, string>;
   typingByChat: Record<number, number[]>;
   replyToByChat: Record<number, Message | null>;
   unreadBoundaryByChat: Record<number, number>;
@@ -38,12 +39,15 @@ interface ChatState {
   setReplyToMessage: (chatId: number, message: Message | null) => void;
   updateChatPinnedMessage: (chatId: number, pinnedMessageId: number | null) => void;
   applyPresenceEvent: (chatId: number, userId: number, isOnline: boolean, lastSeenAt?: string) => void;
+  setDraft: (chatId: number, text: string) => void;
+  clearDraft: (chatId: number) => void;
 }
 
 export const useChatStore = create<ChatState>((set, get) => ({
   chats: [],
   activeChatId: null,
   messagesByChat: {},
+  draftsByChat: {},
   typingByChat: {},
   replyToByChat: {},
   unreadBoundaryByChat: {},
@@ -272,5 +276,21 @@ export const useChatStore = create<ChatState>((set, get) => ({
         }
         return chat;
       })
-    }))
+    })),
+  setDraft: (chatId, text) =>
+    set((state) => ({
+      draftsByChat: {
+        ...state.draftsByChat,
+        [chatId]: text
+      }
+    })),
+  clearDraft: (chatId) =>
+    set((state) => {
+      if (!(chatId in state.draftsByChat)) {
+        return state;
+      }
+      const next = { ...state.draftsByChat };
+      delete next[chatId];
+      return { draftsByChat: next };
+    })
 }));