frontend/src/App.tsx

import { useEffect, useRef, useState } from "react";
import { io, Socket } from "socket.io-client";
import ChatMessage from "./components/ChatMessage";

interface Message {
  role: "user" | "assistant";
  content: string;
}

const SOCKET_URL = `${window.location.protocol}//${window.location.hostname}:8000`;

export default function App() {
  const [messages, setMessages] = useState<Message[]>([]);
  const [input, setInput] = useState("");
  const [loading, setLoading] = useState(false);
  const [connected, setConnected] = useState(false);
  const socketRef = useRef<Socket | null>(null);
  const bottomRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const socket = io(SOCKET_URL);
    socketRef.current = socket;

    socket.on("connect", () => setConnected(true));
    socket.on("disconnect", () => setConnected(false));

    socket.on("answer", (data: { answer?: string; error?: string }) => {
      const content = data.answer ?? `Lỗi: ${data.error}`;
      setMessages((prev) => [...prev, { role: "assistant", content }]);
      setLoading(false);
    });

    return () => {
      socket.disconnect();
    };
  }, []);

  useEffect(() => {
    bottomRef.current?.scrollIntoView({ behavior: "smooth" });
  }, [messages, loading]);

  const handleSend = () => {
    const question = input.trim();
    if (!question || loading || !connected) return;

    setMessages((prev) => [...prev, { role: "user", content: question }]);
    setInput("");
    setLoading(true);
    socketRef.current?.emit("ask", { question });
  };

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === "Enter" && !e.shiftKey) {
      e.preventDefault();
      handleSend();
    }
  };

  return (
    <div className="flex flex-col h-screen bg-white">
      {/* Header */}
      <header className="bg-blue-700 text-white px-6 py-4 shadow-md">
        <h1 className="text-xl font-bold">Hỏi đáp Pháp luật Việt Nam</h1>
        <p className="text-blue-200 text-sm mt-0.5">
          RAG Agent - Tra cứu văn bản pháp luật
        </p>
      </header>

      {/* Messages */}
      <main className="flex-1 overflow-y-auto px-4 py-6 md:px-8">
        {messages.length === 0 && !loading && (
          <div className="text-center text-gray-400 mt-20">
            <p className="text-lg">Chào mừng bạn!</p>
            <p className="text-sm mt-1">
              Hãy đặt câu hỏi về pháp luật Việt Nam.
            </p>
          </div>
        )}
        {messages.map((msg, i) => (
          <ChatMessage key={i} role={msg.role} content={msg.content} />
        ))}
        {loading && (
          <div className="flex justify-start mb-4">
            <div className="bg-gray-100 rounded-2xl px-4 py-3 text-gray-500">
              <p className="text-sm font-medium mb-1 opacity-70">
                Trợ lý Pháp luật
              </p>
              <span className="inline-flex gap-1">
                <span className="w-2 h-2 bg-gray-400 rounded-full animate-bounce [animation-delay:0ms]" />
                <span className="w-2 h-2 bg-gray-400 rounded-full animate-bounce [animation-delay:150ms]" />
                <span className="w-2 h-2 bg-gray-400 rounded-full animate-bounce [animation-delay:300ms]" />
              </span>
            </div>
          </div>
        )}
        <div ref={bottomRef} />
      </main>

      {/* Input */}
      <footer className="border-t bg-white px-4 py-3 md:px-8">
        <div className="flex items-center gap-3 max-w-4xl mx-auto">
          <input
            type="text"
            className="flex-1 border border-gray-300 rounded-xl px-4 py-3 text-[15px] focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent disabled:bg-gray-50"
            placeholder={
              connected ? "Nhập câu hỏi..." : "Đang kết nối server..."
            }
            value={input}
            onChange={(e) => setInput(e.target.value)}
            onKeyDown={handleKeyDown}
            disabled={!connected || loading}
          />
          <button
            onClick={handleSend}
            disabled={!input.trim() || loading || !connected}
            className="bg-blue-600 text-white px-5 py-3 rounded-xl font-medium hover:bg-blue-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
          >
            Gửi
          </button>
        </div>
        {!connected && (
          <p className="text-center text-red-500 text-xs mt-2">
            Chưa kết nối được server. Hãy chắc chắn backend đang chạy tại{" "}
            {SOCKET_URL}
          </p>
        )}
      </footer>
    </div>
  );
}