feat(FN-4739): complete Step 5 — add useChatRooms clearRoom support

Fusion-Task-Id: FN-4739
Fusion-Task-Lineage: fc120dfa-d1b2-4065-9595-d0bc6304d2af

packages/dashboard/app/hooks/__tests__/useChatRooms.test.ts

@@ -12,6 +12,7 @@ vi.mock("../../api", () => ({
   fetchChatRoomMessages: vi.fn(),
   deleteChatRoom: vi.fn(),
   postChatRoomMessage: vi.fn(),
+  clearChatRoomMessages: vi.fn(),
 }));
 
 vi.mock("../../sse-bus", () => ({
@@ -30,6 +31,7 @@ const mockFetchChatRoomMembers = vi.mocked(apiModule.fetchChatRoomMembers);
 const mockFetchChatRoomMessages = vi.mocked(apiModule.fetchChatRoomMessages);
 const mockDeleteChatRoom = vi.mocked(apiModule.deleteChatRoom);
 const mockPostChatRoomMessage = vi.mocked(apiModule.postChatRoomMessage);
+const mockClearChatRoomMessages = vi.mocked(apiModule.clearChatRoomMessages);
 const mockSubscribeSse = vi.mocked(sseBusModule.subscribeSse);
 
 function room(id: string, name: string, updatedAt: string): ChatRoom {
@@ -82,6 +84,7 @@ describe("useChatRooms", () => {
     mockCreateChatRoom.mockResolvedValue({ room: room("room-new", "new", "2026-05-09T01:00:00.000Z") });
     mockDeleteChatRoom.mockResolvedValue({ success: true });
     mockPostChatRoomMessage.mockResolvedValue({ message: roomMessage("msg-posted", "room-new", "posted") });
+    mockClearChatRoomMessages.mockResolvedValue({ success: true, deletedCount: 1 });
   });
 
   it("loads rooms on mount", async () => {
@@ -312,6 +315,82 @@ describe("useChatRooms", () => {
     });
   });
 
+  it("clearRoom empties messages for active room", async () => {
+    const active = room("room-1", "one", "2026-05-09T01:00:00.000Z");
+    mockFetchChatRooms.mockResolvedValueOnce({ rooms: [active] });
+    const { result } = renderHook(() => useChatRooms("proj-1"));
+    await waitFor(() => expect(result.current.rooms.length).toBe(1));
+
+    mockFetchChatRoomMembers.mockResolvedValueOnce({ members: [] });
+    mockFetchChatRoomMessages.mockResolvedValueOnce({ messages: [roomMessage("msg-1", "room-1", "hello")] });
+    act(() => result.current.selectRoom("room-1"));
+    await waitFor(() => expect(result.current.messages).toHaveLength(1));
+
+    await act(async () => {
+      await result.current.clearRoom("room-1");
+    });
+
+    expect(mockClearChatRoomMessages).toHaveBeenCalledWith("room-1", "proj-1");
+    expect(result.current.messages).toEqual([]);
+  });
+
+  it("clearRoom does not mutate messages when another room is active", async () => {
+    const first = room("room-1", "one", "2026-05-09T01:00:00.000Z");
+    const second = room("room-2", "two", "2026-05-09T02:00:00.000Z");
+    mockFetchChatRooms.mockResolvedValueOnce({ rooms: [first, second] });
+    const { result } = renderHook(() => useChatRooms("proj-1"));
+    await waitFor(() => expect(result.current.rooms.length).toBe(2));
+
+    mockFetchChatRoomMembers.mockResolvedValueOnce({ members: [] });
+    mockFetchChatRoomMessages.mockResolvedValueOnce({ messages: [roomMessage("msg-2", "room-2", "hello")] });
+    act(() => result.current.selectRoom("room-2"));
+    await waitFor(() => expect(result.current.messages).toHaveLength(1));
+
+    await act(async () => {
+      await result.current.clearRoom("room-1");
+    });
+
+    expect(result.current.messages).toHaveLength(1);
+  });
+
+  it("SSE clear event empties messages for active room", async () => {
+    const active = room("room-1", "one", "2026-05-09T01:00:00.000Z");
+    mockFetchChatRooms.mockResolvedValueOnce({ rooms: [active] });
+    const { result } = renderHook(() => useChatRooms("proj-1"));
+    await waitFor(() => expect(result.current.rooms.length).toBe(1));
+
+    mockFetchChatRoomMembers.mockResolvedValueOnce({ members: [] });
+    mockFetchChatRoomMessages.mockResolvedValueOnce({ messages: [roomMessage("msg-1", "room-1", "hello")] });
+    act(() => result.current.selectRoom("room-1"));
+    await waitFor(() => expect(result.current.messages).toHaveLength(1));
+
+    act(() => {
+      capturedEvents["chat:room:messages:cleared"]?.({ data: JSON.stringify({ roomId: "room-1", deletedCount: 3 }) } as MessageEvent);
+    });
+
+    expect(result.current.messages).toEqual([]);
+  });
+
+  it("clearRoom rethrows API failure and preserves messages", async () => {
+    const active = room("room-1", "one", "2026-05-09T01:00:00.000Z");
+    mockFetchChatRooms.mockResolvedValueOnce({ rooms: [active] });
+    const { result } = renderHook(() => useChatRooms("proj-1"));
+    await waitFor(() => expect(result.current.rooms.length).toBe(1));
+
+    mockFetchChatRoomMembers.mockResolvedValueOnce({ members: [] });
+    mockFetchChatRoomMessages.mockResolvedValueOnce({ messages: [roomMessage("msg-1", "room-1", "hello")] });
+    act(() => result.current.selectRoom("room-1"));
+    await waitFor(() => expect(result.current.messages).toHaveLength(1));
+
+    mockClearChatRoomMessages.mockRejectedValueOnce(new Error("clear failed"));
+
+    await act(async () => {
+      await expect(result.current.clearRoom("room-1")).rejects.toThrow("clear failed");
+    });
+
+    expect(result.current.messages).toHaveLength(1);
+  });
+
   it("tears down sse subscription on unmount", async () => {
     const { unmount } = renderHook(() => useChatRooms("proj-1"));
     unmount();

packages/dashboard/app/hooks/useChatRooms.ts

@@ -1,6 +1,7 @@
 import { useCallback, useEffect, useRef, useState } from "react";
 import type { ChatAttachment, ChatRoom, ChatRoomMember, ChatRoomMessage } from "@fusion/core";
 import {
+  clearChatRoomMessages,
   createChatRoom,
   deleteChatRoom,
   fetchChatRoomMembers,
@@ -25,6 +26,7 @@ export interface UseChatRoomsResult {
   createRoom: (input: { name: string; memberAgentIds: string[] }) => Promise<ChatRoom>;
   deleteRoom: (roomId: string) => Promise<void>;
   sendRoomMessage: (content: string, opts?: { attachments?: ChatAttachment[] }) => Promise<void>;
+  clearRoom: (roomId: string) => Promise<void>;
   refreshRooms: () => Promise<void>;
 }
 
@@ -228,6 +230,17 @@ export function useChatRooms(
     }
   }, [projectId]);
 
+  const clearRoom = useCallback(async (roomId: string) => {
+    if (!roomId || !roomsRef.current.some((room) => room.id === roomId)) {
+      return;
+    }
+
+    await clearChatRoomMessages(roomId, projectId);
+    if (activeRoomRef.current?.id === roomId) {
+      setMessages([]);
+    }
+  }, [projectId]);
+
   useEffect(() => {
     void refreshRooms();
   }, [refreshRooms]);
@@ -329,6 +342,21 @@ export function useChatRooms(
           if (!payload?.id) return;
           setMessages((previous) => previous.filter((message) => message.id !== payload.id));
         },
+        "chat:room:messages:cleared": (event) => {
+          if (projectContextVersionRef.current !== contextVersionAtStart) return;
+          const payload = parseSsePayload<{ roomId: string; deletedCount: number }>(event);
+          if (!payload?.roomId) return;
+
+          if (activeRoomRef.current?.id === payload.roomId) {
+            setMessages([]);
+          }
+
+          setRooms((previous) => {
+            const room = previous.find((candidate) => candidate.id === payload.roomId);
+            if (!room) return previous;
+            return upsertRoom(previous, { ...room, updatedAt: new Date().toISOString() });
+          });
+        },
       },
     });
   }, [projectId, refreshRooms]);
@@ -355,6 +383,7 @@ export function useChatRooms(
     createRoom: createRoomLocal,
     deleteRoom: deleteRoomLocal,
     sendRoomMessage,
+    clearRoom,
     refreshRooms,
   };
 }