Add Next.js chat frontend

frontend/.env.example

@@ -0,0 +1 @@
+NEXT_PUBLIC_API_URL=http://localhost:8000

frontend/src/app/page.tsx

@@ -1,103 +1,5 @@
-import Image from "next/image";
+import ChatApp from "../components/ChatApp";
 
 export default function Home() {
-  return (
-    <div className="grid grid-rows-[20px_1fr_20px] items-center justify-items-center min-h-screen p-8 pb-20 gap-16 sm:p-20 font-[family-name:var(--font-geist-sans)]">
-      <main className="flex flex-col gap-[32px] row-start-2 items-center sm:items-start">
-        <Image
-          className="dark:invert"
-          src="/next.svg"
-          alt="Next.js logo"
-          width={180}
-          height={38}
-          priority
-        />
-        <ol className="list-inside list-decimal text-sm/6 text-center sm:text-left font-[family-name:var(--font-geist-mono)]">
-          <li className="mb-2 tracking-[-.01em]">
-            Get started by editing{" "}
-            <code className="bg-black/[.05] dark:bg-white/[.06] px-1 py-0.5 rounded font-[family-name:var(--font-geist-mono)] font-semibold">
-              src/app/page.tsx
-            </code>
-            .
-          </li>
-          <li className="tracking-[-.01em]">
-            Save and see your changes instantly.
-          </li>
-        </ol>
-
-        <div className="flex gap-4 items-center flex-col sm:flex-row">
-          <a
-            className="rounded-full border border-solid border-transparent transition-colors flex items-center justify-center bg-foreground text-background gap-2 hover:bg-[#383838] dark:hover:bg-[#ccc] font-medium text-sm sm:text-base h-10 sm:h-12 px-4 sm:px-5 sm:w-auto"
-            href="https://vercel.com/new?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            <Image
-              className="dark:invert"
-              src="/vercel.svg"
-              alt="Vercel logomark"
-              width={20}
-              height={20}
-            />
-            Deploy now
-          </a>
-          <a
-            className="rounded-full border border-solid border-black/[.08] dark:border-white/[.145] transition-colors flex items-center justify-center hover:bg-[#f2f2f2] dark:hover:bg-[#1a1a1a] hover:border-transparent font-medium text-sm sm:text-base h-10 sm:h-12 px-4 sm:px-5 w-full sm:w-auto md:w-[158px]"
-            href="https://nextjs.org/docs?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            Read our docs
-          </a>
-        </div>
-      </main>
-      <footer className="row-start-3 flex gap-[24px] flex-wrap items-center justify-center">
-        <a
-          className="flex items-center gap-2 hover:underline hover:underline-offset-4"
-          href="https://nextjs.org/learn?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <Image
-            aria-hidden
-            src="/file.svg"
-            alt="File icon"
-            width={16}
-            height={16}
-          />
-          Learn
-        </a>
-        <a
-          className="flex items-center gap-2 hover:underline hover:underline-offset-4"
-          href="https://vercel.com/templates?framework=next.js&utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <Image
-            aria-hidden
-            src="/window.svg"
-            alt="Window icon"
-            width={16}
-            height={16}
-          />
-          Examples
-        </a>
-        <a
-          className="flex items-center gap-2 hover:underline hover:underline-offset-4"
-          href="https://nextjs.org?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-          target="_blank"
-          rel="noopener noreferrer"
-        >
-          <Image
-            aria-hidden
-            src="/globe.svg"
-            alt="Globe icon"
-            width={16}
-            height={16}
-          />
-          Go to nextjs.org →
-        </a>
-      </footer>
-    </div>
-  );
+  return <ChatApp />;
 }

frontend/src/components/ChatApp.tsx

@@ -0,0 +1,92 @@
+'use client';
+
+import { useState, useRef } from 'react';
+import { streamChat, ChatRequest } from '../utils/api';
+
+interface Message {
+  role: 'user' | 'assistant';
+  content: string;
+}
+
+export default function ChatApp() {
+  const [messages, setMessages] = useState<Message[]>([]);
+  const [input, setInput] = useState('');
+  const [loading, setLoading] = useState(false);
+  const endRef = useRef<HTMLDivElement>(null);
+
+  const scrollToEnd = () => {
+    endRef.current?.scrollIntoView({ behavior: 'smooth' });
+  };
+
+  const sendMessage = async () => {
+    if (!input.trim() || loading) return;
+
+    const prompt = input;
+    setInput('');
+    setMessages((prev) => [...prev, { role: 'user', content: prompt }, { role: 'assistant', content: '' }]);
+    setLoading(true);
+    try {
+      const req: ChatRequest = { user: 'demo', session: 'default', prompt };
+      for await (const chunk of streamChat(req)) {
+        setMessages((prev) => {
+          const msgs = [...prev];
+          msgs[msgs.length - 1] = {
+            role: 'assistant',
+            content: msgs[msgs.length - 1].content + chunk,
+          };
+          return msgs;
+        });
+        scrollToEnd();
+      }
+    } catch (err) {
+      console.error(err);
+      setMessages((prev) => {
+        const msgs = [...prev];
+        msgs[msgs.length - 1] = {
+          role: 'assistant',
+          content: 'Error retrieving response',
+        };
+        return msgs;
+      });
+    } finally {
+      setLoading(false);
+      scrollToEnd();
+    }
+  };
+
+  const onSubmit = (e: React.FormEvent) => {
+    e.preventDefault();
+    void sendMessage();
+  };
+
+  return (
+    <div className="flex flex-col max-w-2xl mx-auto h-screen p-4">
+      <div className="flex-1 overflow-y-auto space-y-4">
+        {messages.map((msg, idx) => (
+          <div key={idx} className={msg.role === 'user' ? 'text-right' : 'text-left'}>
+            <span className="px-3 py-2 inline-block rounded bg-gray-200 dark:bg-gray-700">
+              {msg.content}
+            </span>
+          </div>
+        ))}
+        <div ref={endRef} />
+      </div>
+      <form onSubmit={onSubmit} className="mt-4 flex gap-2">
+        <input
+          type="text"
+          className="flex-1 border rounded px-3 py-2 text-black"
+          value={input}
+          onChange={(e) => setInput(e.target.value)}
+          placeholder="Type your message..."
+        />
+        <button
+          type="submit"
+          className="bg-blue-600 text-white px-4 py-2 rounded disabled:opacity-50"
+          disabled={loading}
+        >
+          Send
+        </button>
+      </form>
+    </div>
+  );
+}

frontend/src/utils/api.ts

@@ -0,0 +1,31 @@
+export interface ChatRequest {
+  user: string;
+  session: string;
+  prompt: string;
+}
+
+export async function* streamChat(
+  req: ChatRequest
+): AsyncGenerator<string> {
+  const url = `${process.env.NEXT_PUBLIC_API_URL}/chat/stream`;
+  const res = await fetch(url, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+    },
+    body: JSON.stringify(req),
+  });
+
+  if (!res.ok || !res.body) {
+    throw new Error('API request failed');
+  }
+
+  const reader = res.body.getReader();
+  const decoder = new TextDecoder();
+
+  while (true) {
+    const { value, done } = await reader.read();
+    if (done) break;
+    yield decoder.decode(value);
+  }
+}