feat: add custom hook useAIChat for managing AI chat interactions

- Implemented useAIChat hook to handle chat messages, input state, and streaming responses.
- Added types for ChatMessage and ChatContext to ensure type safety.
- Integrated TRPC mutation for sending messages and handling responses.
- Included functionality for clearing messages and managing streaming content.

src/renderer/hooks/useAIChat.ts

@@ -0,0 +1,130 @@
+import { useState, useCallback, useRef } from 'react';
+import { trpc } from '@/lib/trpc';
+
+export interface ChatMessage {
+  id: string;
+  role: 'user' | 'assistant';
+  content: string;
+  error?: boolean;
+}
+
+export interface ChatContext {
+  type: 'global' | 'project';
+  projectId?: string;
+  uiContext?: string;
+}
+
+export interface UseAIChatReturn {
+  messages: ChatMessage[];
+  input: string;
+  setInput: (v: string) => void;
+  isStreaming: boolean;
+  streamingContent: string;
+  handleSend: (overrideMessage?: string, overrideContext?: ChatContext) => void;
+  clearMessages: () => void;
+}
+
+export function useAIChat(defaultContext: ChatContext): UseAIChatReturn {
+  const [messages, setMessages] = useState<ChatMessage[]>([]);
+  const [input, setInput] = useState('');
+  const [isStreaming, setIsStreaming] = useState(false);
+  const [streamingContent, setStreamingContent] = useState('');
+
+  const streamingContentRef = useRef('');
+  const chatMutation = trpc.ai.chat.useMutation();
+
+  const clearMessages = useCallback(() => {
+    setMessages([]);
+    setStreamingContent('');
+    streamingContentRef.current = '';
+  }, []);
+
+  const handleSend = useCallback(
+    (overrideMessage?: string, overrideContext?: ChatContext) => {
+      const trimmed = (overrideMessage ?? input).trim();
+      if (!trimmed || isStreaming) return;
+
+      const userMsg: ChatMessage = {
+        id: crypto.randomUUID(),
+        role: 'user',
+        content: trimmed,
+      };
+
+      setMessages((prev) => [...prev, userMsg]);
+      if (!overrideMessage) setInput('');
+      setIsStreaming(true);
+      setStreamingContent('');
+      streamingContentRef.current = '';
+
+      const unsubscribe = window.electronAI.onStreamChunk(({ token, done }) => {
+        if (done) {
+          const finalContent = streamingContentRef.current;
+          setMessages((prev) => [
+            ...prev,
+            { id: crypto.randomUUID(), role: 'assistant', content: finalContent },
+          ]);
+          setStreamingContent('');
+          streamingContentRef.current = '';
+          setIsStreaming(false);
+          unsubscribe();
+          return;
+        }
+        streamingContentRef.current += token;
+        setStreamingContent(streamingContentRef.current);
+      });
+
+      const ctx = overrideContext ?? defaultContext;
+
+      chatMutation.mutate(
+        {
+          message: trimmed,
+          context: {
+            type: ctx.type,
+            ...(ctx.type === 'project' && ctx.projectId ? { projectId: ctx.projectId } : {}),
+            ...(ctx.uiContext ? { uiContext: ctx.uiContext } : {}),
+          },
+        },
+        {
+          onSuccess: (data) => {
+            if (data.error) {
+              unsubscribe();
+              setMessages((prev) => [
+                ...prev,
+                { id: crypto.randomUUID(), role: 'assistant', content: data.error!, error: true },
+              ]);
+              setStreamingContent('');
+              streamingContentRef.current = '';
+              setIsStreaming(false);
+            }
+          },
+          onError: (err) => {
+            unsubscribe();
+            setMessages((prev) => [
+              ...prev,
+              {
+                id: crypto.randomUUID(),
+                role: 'assistant',
+                content: err.message || 'An unexpected error occurred.',
+                error: true,
+              },
+            ]);
+            setStreamingContent('');
+            streamingContentRef.current = '';
+            setIsStreaming(false);
+          },
+        },
+      );
+    },
+    [input, isStreaming, defaultContext, chatMutation],
+  );
+
+  return {
+    messages,
+    input,
+    setInput,
+    isStreaming,
+    streamingContent,
+    handleSend,
+    clearMessages,
+  };
+}