feat: Stream AI responses in real-time via Route Handler

app/(docs)/@chat/chat/[chatId]/chatArea.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { ChatAreaStateUpdater } from "@/(docs)/chatAreaState";
+import { useStreamingChatContext } from "@/(docs)/streamingChatContext";
 import { deleteChatAction } from "@/actions/deleteChat";
 import { ChatWithMessages } from "@/lib/chatHistory";
 import { LanguageEntry, MarkdownSection, PageEntry } from "@/lib/docs";
@@ -11,7 +12,10 @@ import Link from "next/link";
 import { useRouter } from "next/navigation";
 import { ReactNode } from "react";
 
-export function ChatAreaContainer(props: { chatId: string; children: ReactNode }) {
+export function ChatAreaContainer(props: {
+  chatId: string;
+  children: ReactNode;
+}) {
   return (
     <aside
       className={clsx(
@@ -75,6 +79,8 @@ export function ChatAreaContent(props: Props) {
   );
 
   const router = useRouter();
+  const streamingChatContext = useStreamingChatContext();
+  const isStreamingThis = streamingChatContext.chatId === chatId;
 
   return (
     <>
@@ -203,6 +209,12 @@ export function ChatAreaContent(props: Props) {
           </div>
         )
       )}
+      {isStreamingThis && (
+        <div className="">
+          <StyledMarkdown content={streamingChatContext.content} />
+          <span className="loading loading-dots loading-sm" />
+        </div>
+      )}
     </>
   );
 }

app/(docs)/@docs/[lang]/[pageId]/chatForm.tsx

@@ -9,9 +9,10 @@ import { useState, FormEvent, useEffect } from "react";
 // import { getLanguageName } from "../pagesList";
 import { DynamicMarkdownSection } from "./pageContent";
 import { useEmbedContext } from "@/terminal/embedContext";
-import { askAI } from "@/actions/chatActions";
 import { PagePath } from "@/lib/docs";
 import { useRouter } from "next/navigation";
+import { ChatStreamEvent } from "@/api/chat/route";
+import { useStreamingChatContext } from "@/(docs)/streamingChatContext";
 
 interface ChatFormProps {
   path: PagePath;
@@ -30,6 +31,7 @@ export function ChatForm({ path, sectionContent, close }: ChatFormProps) {
   const { files, replOutputs, execResults } = useEmbedContext();
 
   const router = useRouter();
+  const streamingChatContext = useStreamingChatContext();
 
   // const documentContentInView = sectionContent
   //   .filter((s) => s.inView)
@@ -64,39 +66,96 @@ export function ChatForm({ path, sectionContent, close }: ChatFormProps) {
   const handleSubmit = async (e: FormEvent<HTMLFormElement>) => {
     e.preventDefault();
     setIsLoading(true);
-    setErrorMessage(null); // Clear previous error message
+    setErrorMessage(null);
 
     const userQuestion = inputValue;
-    // if (!userQuestion && exampleData) {
-    //   // 質問が空欄なら、質問例を使用
-    //   userQuestion =
-    //     exampleData[Math.floor(exampleChoice * exampleData.length)];
-    //   setInputValue(userQuestion);
-    // }
-
-    const result = await askAI({
-      path,
-      userQuestion,
-      sectionContent,
-      replOutputs,
-      files,
-      execResults,
-    });
-
-    if (result.error !== null) {
-      setErrorMessage(result.error);
-      console.log(result.error);
-    } else {
-      document.getElementById(result.chat.sectionId)?.scrollIntoView({
-        behavior: "smooth",
+
+    let response: Response;
+    try {
+      response = await fetch("/api/chat", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          path,
+          userQuestion,
+          sectionContent,
+          replOutputs,
+          files,
+          execResults,
+        }),
       });
-      router.push(`/chat/${result.chat.chatId}`, { scroll: false });
-      router.refresh();
-      setInputValue("");
-      close();
+    } catch {
+      setErrorMessage("AIへの接続に失敗しました");
+      setIsLoading(false);
+      return;
+    }
+
+    if (!response.ok) {
+      setErrorMessage(`エラーが発生しました (${response.status})`);
+      setIsLoading(false);
+      return;
     }
 
-    setIsLoading(false);
+    const reader = response.body!.getReader();
+    const decoder = new TextDecoder();
+    let buffer = "";
+    let navigated = false;
+
+    // ストリームを非同期で読み続ける（ナビゲーション後もバックグラウンドで継続）
+    void (async () => {
+      try {
+        while (true) {
+          const result = await reader.read();
+          const { done, value } = result;
+          if (done) break;
+
+          buffer += decoder.decode(value, { stream: true });
+          const lines = buffer.split("\n");
+          buffer = lines.pop() ?? "";
+
+          for (const line of lines) {
+            if (!line.trim()) continue;
+            try {
+              const event = JSON.parse(line) as ChatStreamEvent;
+
+              if (event.type === "chat") {
+                streamingChatContext.startStreaming(event.chatId);
+                document.getElementById(event.sectionId)?.scrollIntoView({
+                  behavior: "smooth",
+                });
+                router.push(`/chat/${event.chatId}`, { scroll: false });
+                router.refresh();
+                navigated = true;
+                setIsLoading(false);
+                setInputValue("");
+                close();
+              } else if (event.type === "chunk") {
+                streamingChatContext.appendChunk(event.text);
+              } else if (event.type === "done") {
+                streamingChatContext.finishStreaming();
+                router.refresh();
+              } else if (event.type === "error") {
+                if (!navigated) {
+                  setErrorMessage(event.message);
+                  setIsLoading(false);
+                }
+                streamingChatContext.finishStreaming();
+              }
+            } catch {
+              // ignore JSON parse errors
+            }
+          }
+        }
+      } catch (err) {
+        console.error("Stream reading failed:", err);
+        // ナビゲーション後のエラーはストリーミングを終了してローディングを止める
+        if (!navigated) {
+          setErrorMessage(String(err));
+          setIsLoading(false);
+        }
+        streamingChatContext.finishStreaming();
+      }
+    })();
   };
 
   return (

app/(docs)/layout.tsx

@@ -1,5 +1,6 @@
 import { ReactNode } from "react";
 import { ChatAreaStateProvider } from "./chatAreaState";
+import { StreamingChatProvider } from "./streamingChatContext";
 
 // app/(workspace)/layout.tsx
 export default function WorkspaceLayout({
@@ -12,15 +13,17 @@ export default function WorkspaceLayout({
   chat: ReactNode;
 }) {
   return (
-    <ChatAreaStateProvider>
-      <div className="w-full flex flex-row">
-        {docs}
+    <StreamingChatProvider>
+      <ChatAreaStateProvider>
+        <div className="w-full flex flex-row">
+          {docs}
 
-        {chat}
+          {chat}
 
-        {/* children（page.tsx）は今回は使わないか、背景として利用 */}
-        {children}
-      </div>
-    </ChatAreaStateProvider>
+          {/* children（page.tsx）は今回は使わないか、背景として利用 */}
+          {children}
+        </div>
+      </ChatAreaStateProvider>
+    </StreamingChatProvider>
   );
 }

app/(docs)/streamingChatContext.tsx

@@ -0,0 +1,56 @@
+"use client";
+
+import {
+  createContext,
+  ReactNode,
+  useCallback,
+  useContext,
+  useState,
+} from "react";
+
+interface StreamingChatContextData {
+  chatId: string | null;
+  content: string;
+  startStreaming: (chatId: string) => void;
+  appendChunk: (chunk: string) => void;
+  finishStreaming: () => void;
+}
+
+const StreamingChatContext = createContext<StreamingChatContextData>(null!);
+
+export function useStreamingChatContext() {
+  return useContext(StreamingChatContext);
+}
+
+export function StreamingChatProvider({ children }: { children: ReactNode }) {
+  const [chatId, setChatId] = useState<string | null>(null);
+  const [content, setContent] = useState("");
+
+  const startStreaming = useCallback((chatId: string) => {
+    setContent("");
+    setChatId(chatId);
+  }, []);
+
+  const appendChunk = useCallback((chunk: string) => {
+    setContent((prev) => prev + chunk);
+  }, []);
+
+  const finishStreaming = useCallback(() => {
+    setChatId(null);
+    setContent("");
+  }, []);
+
+  return (
+    <StreamingChatContext.Provider
+      value={{
+        chatId,
+        content,
+        startStreaming,
+        appendChunk,
+        finishStreaming,
+      }}
+    >
+      {children}
+    </StreamingChatContext.Provider>
+  );
+}