"use client";

// Core React and AI chat hooks
import { useState, useRef, useEffect } from "react";
import { useChat } from "ai/react";
// UI Icons for example prompts
import {
  AcademicCapIcon,
  ClockIcon,
  BookOpenIcon,
  LightBulbIcon,
  BriefcaseIcon,
} from "@heroicons/react/24/outline";

// Extends the basic message type to include streaming state
type MessageWithLoading = {
  content: string;
  role: string;
  isStreaming?: boolean;
};

// Predefined example prompts for users to quickly start conversations
const EXAMPLE_PROMPTS = [
  {
    title: "教案規劃", // Lesson Planning
    prompt: "我想規劃一堂關於數學的課程",
    icon: AcademicCapIcon,
  },
  {
    title: "英語對話",
    prompt: "我想練習英語對話",
    icon: ClockIcon,
  },
  {
    title: "作業批改",
    prompt: "我想批改學生的作文作業",
    icon: BookOpenIcon,
  },
  {
    title: "數學解題",
    prompt: "我想解數學題目",
    icon: LightBulbIcon,
  },
  {
    title: "我想學程式",
    prompt: "我想學習如何寫程式",
    icon: BriefcaseIcon,
  },
];

export default function LandingPageChatBot() {
  // Initialize chat functionality with error handling and streaming support
  const {
    messages: rawMessages,
    input,
    handleInputChange,
    handleSubmit,
    isLoading,
    append,
  } = useChat({
    api: "/api/landing_page_chat",
    streamProtocol: "data",
    onError: (error) => {
      console.error("Chat error:", error);
    },
    onFinish: (message) => {
      console.log("Chat finished:", message);
      // Reset streaming state when message is complete
      setMessages((prev) =>
        prev.map((msg) => ({ ...msg, isStreaming: false })),
      );
    },
    keepLastMessageOnError: true,
  });

  // Refs and state management
  const chatContainerRef = useRef<HTMLDivElement>(null);
  const [hasInteracted, setHasInteracted] = useState(false);
  const [messages, setMessages] = useState<MessageWithLoading[]>([]);

  // Update messages with streaming state when new messages arrive
  useEffect(() => {
    setMessages(
      rawMessages.map((msg, index) => ({
        ...msg,
        isStreaming:
          isLoading &&
          index === rawMessages.length - 1 &&
          msg.role === "assistant",
      })),
    );
  }, [rawMessages, isLoading]);

  // Auto-scroll chat to bottom when new messages arrive
  const scrollToBottom = () => {
    if (chatContainerRef.current) {
      const { scrollHeight, clientHeight } = chatContainerRef.current;
      chatContainerRef.current.scrollTop = scrollHeight - clientHeight;
    }
  };

  useEffect(() => {
    scrollToBottom();
  }, [messages]);

  // Message handling functions
  const sendMessage = async (text: string) => {
    setHasInteracted(true);
    await append({
      content: text,
      role: "user",
    });
  };

  const onSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
    setHasInteracted(true);
    handleSubmit(e);
  };

  return (
    <section className="w-full h-[1000px] bg-gradient-to-b from-background-secondary to-background-primary flex items-center justify-center px-4">
      <div className="w-full max-w-5xl mx-auto h-full flex items-center">
        {/* Initial landing view with example prompts */}
        {!hasInteracted && messages.length === 0 ? (
          <div className="text-center space-y-8 w-full">
            {/* Hero section with title and input */}
            <div className="space-y-4">
              <h2 className="text-5xl font-bold bg-gradient-to-r from-primary to-secondary bg-clip-text text-transparent">
                今天你想學什麼？
              </h2>
              <p className="text-text-secondary text-xl max-w-2xl mx-auto leading-relaxed">
                探索新主題、獲得教學協助，或發現學習資源
              </p>
            </div>

            {/* Message input form */}
            <form onSubmit={onSubmit} className="max-w-3xl mx-auto">
              <div className="relative flex items-center">
                <input
                  type="text"
                  value={input}
                  onChange={handleInputChange}
                  placeholder="請問任何關於學習的問題..."
                  className="w-full p-6 pr-36 rounded-2xl border border-border/50 bg-background-primary/50 
                           backdrop-blur-sm shadow-lg focus:outline-none focus:ring-2 focus:ring-primary/50 
                           text-lg transition-all duration-200 placeholder:text-text-secondary/50"
                />
                <button
                  type="submit"
                  disabled={isLoading}
                  className="absolute right-2 p-3 bg-primary text-white rounded-full
                           hover:bg-primary/90 transition-all duration-200
                           shadow-md hover:shadow-lg active:scale-95 disabled:opacity-50
                           disabled:hover:bg-primary disabled:cursor-not-allowed"
                >
                  <svg
                    xmlns="http://www.w3.org/2000/svg"
                    fill="none"
                    viewBox="0 0 24 24"
                    strokeWidth="1.5"
                    stroke="currentColor"
                    className={`size-6 ${isLoading ? "animate-pulse" : ""}`}
                  >
                    <path
                      strokeLinecap="round"
                      strokeLinejoin="round"
                      d="M6 12 3.269 3.125A59.769 59.769 0 0 1 21.485 12 59.768 59.768 0 0 1 3.27 20.875L5.999 12Zm0 0h7.5"
                    />
                  </svg>
                </button>
              </div>
            </form>

            {/* Example prompts grid */}
            <div className="mt-12">
              <div className="grid grid-cols-1 md:grid-cols-5 gap-4">
                {EXAMPLE_PROMPTS.map((prompt, index) => (
                  <button
                    key={index}
                    onClick={() => sendMessage(prompt.prompt)}
                    className="group p-4 rounded-2xl border border-border/50 bg-background-primary/30 
                             hover:bg-background-primary/50 backdrop-blur-sm transition-all duration-200
                             hover:border-primary/50 hover:shadow-lg text-left w-full"
                  >
                    <div className="flex items-center justify-between w-full">
                      <div className="flex items-center gap-3">
                        <prompt.icon className="w-8 h-8 text-primary" />
                        <h4 className="font-semibold text-text-primary text-md">
                          {prompt.title}
                        </h4>
                      </div>
                      <svg
                        className="w-6 h-6 text-primary opacity-0 group-hover:opacity-100 transition-opacity duration-200"
                        fill="none"
                        stroke="currentColor"
                        viewBox="0 0 24 24"
                        strokeWidth={2}
                      >
                        <path
                          strokeLinecap="round"
                          strokeLinejoin="round"
                          d="M9 5l7 7-7 7"
                        />
                      </svg>
                    </div>
                  </button>
                ))}
              </div>
            </div>
          </div>
        ) : (
          /* Chat interface after interaction */
          <div className="bg-background-primary/50 backdrop-blur-sm rounded-2xl shadow-lg border border-border/50 overflow-hidden w-full h-[700px] flex flex-col">
            {/* Chat header */}
            <div className="p-6 border-b border-border/50 bg-background-secondary/30">
              <h2 className="text-xl font-semibold text-text-primary">
                PlayGO 導覽員
              </h2>
            </div>

            {/* Messages container with auto-scroll */}
            <div
              ref={chatContainerRef}
              className="flex-1 overflow-y-auto p-6 space-y-6"
            >
              {/* Message bubbles with different styles for user/assistant */}
              {messages.map((message, index) => (
                <div
                  key={index}
                  className={`flex ${message.role === "user" ? "justify-end" : "justify-start"}`}
                >
                  <div
                    className={`max-w-[80%] p-4 rounded-2xl shadow-sm ${
                      message.role === "user"
                        ? "bg-primary text-white rounded-br-none"
                        : "bg-background-secondary/50 text-text-primary rounded-bl-none"
                    }`}
                  >
                    {message.content}
                    {message.isStreaming && (
                      <span className="inline-block w-2.5 h-2.5 ml-1.5 bg-primary rounded-full animate-pulse" />
                    )}
                  </div>
                </div>
              ))}
            </div>

            {/* Input form at bottom of chat */}
            <div className="p-6 border-t border-border/50 bg-background-secondary/30">
              <form onSubmit={onSubmit}>
                <div className="relative flex items-center">
                  <input
                    type="text"
                    value={input}
                    onChange={handleInputChange}
                    placeholder={
                      isLoading ? "AI is thinking..." : "Type your message..."
                    }
                    disabled={isLoading}
                    className="w-full p-4 pr-32 rounded-xl border border-border/50 bg-background-primary/50 
                             backdrop-blur-sm focus:outline-none focus:ring-2 focus:ring-primary/50
                             text-base transition-all duration-200 disabled:opacity-50"
                  />
                  <button
                    type="submit"
                    disabled={isLoading}
                    className="absolute right-2 p-2 bg-primary text-white rounded-full
                             hover:bg-primary/90 transition-all duration-200
                             shadow-md hover:shadow-lg active:scale-95 disabled:opacity-50
                             disabled:hover:bg-primary disabled:cursor-not-allowed"
                  >
                    <svg
                      xmlns="http://www.w3.org/2000/svg"
                      fill="none"
                      viewBox="0 0 24 24"
                      strokeWidth="1.5"
                      stroke="currentColor"
                      className={`size-5 ${isLoading ? "animate-pulse" : ""}`}
                    >
                      <path
                        strokeLinecap="round"
                        strokeLinejoin="round"
                        d="M6 12 3.269 3.125A59.769 59.769 0 0 1 21.485 12 59.768 59.768 0 0 1 3.27 20.875L5.999 12Zm0 0h7.5"
                      />
                    </svg>
                  </button>
                </div>
              </form>
            </div>
          </div>
        )}
      </div>
    </section>
  );
}