import React, { useState, useEffect, useRef } from 'react';
import { Send, Plus, MessageSquare, Settings, Users, Download, Trash2, RefreshCw, Bot } from 'lucide-react';

const ChatFlowApp = () => {
  const [messages, setMessages] = useState([]);
  const [currentMessage, setCurrentMessage] = useState('');
  const [selectedModel, setSelectedModel] = useState('openai/gpt-3.5-turbo');
  const [isLoading, setIsLoading] = useState(false);
  const [sessions, setSessions] = useState([]);
  const [currentSessionId, setCurrentSessionId] = useState('default');
  const [onlineUsers, setOnlineUsers] = useState(1);
  const [apiStatus, setApiStatus] = useState('Connected');
  const [autoSave, setAutoSave] = useState(true);
  const messagesEndRef = useRef(null);
  const [userId] = useState('User-' + Math.random().toString(36).substr(2, 8));

  const models = [
    { name: "GPT-3.5 Turbo", id: "openai/gpt-3.5-turbo" },
    { name: "LLaMA 3.1 8B", id: "meta-llama/llama-3.1-8b-instruct" },
    { name: "LLaMA 3.1 70B", id: "meta-llama/llama-3.1-70b-instruct" },
    { name: "DeepSeek Chat v3", id: "deepseek/deepseek-chat-v3-0324:free" },
    { name: "DeepSeek R1", id: "deepseek/deepseek-r1-0528:free" },
    { name: "Qwen3 Coder", id: "qwen/qwen3-coder:free" },
    { name: "Microsoft MAI DS R1", id: "microsoft/mai-ds-r1:free" },
    { name: "Gemma 3 27B", id: "google/gemma-3-27b-it:free" },
    { name: "Gemma 3 4B", id: "google/gemma-3-4b-it:free" },
    { name: "Auto (Best Available)", id: "openrouter/auto" }
  ];

  const scrollToBottom = () => {
    messagesEndRef.current?.scrollIntoView({ behavior: "smooth" });
  };

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

  useEffect(() => {
    // Simulate online users update
    const interval = setInterval(() => {
      setOnlineUsers(Math.floor(Math.random() * 5) + 1);
    }, 10000);
    return () => clearInterval(interval);
  }, []);

  useEffect(() => {
    // Check API status on component mount
    const checkAPIStatus = async () => {
      try {
        const OPENROUTER_API_KEY = process.env.REACT_APP_OPENROUTER_API_KEY || 
                                   window.OPENROUTER_API_KEY || 
                                   process.env.OPENROUTER_API_KEY;
        
        if (!OPENROUTER_API_KEY) {
          setApiStatus('No API Key');
          return;
        }

        const response = await fetch("https://openrouter.ai/api/v1/models", {
          headers: { "Authorization": `Bearer ${OPENROUTER_API_KEY}` }
        });
        
        setApiStatus(response.ok ? 'Connected' : 'Error');
      } catch {
        setApiStatus('Error');
      }
    };
    
    checkAPIStatus();
  }, []);

  const generateChatTitle = (msgs) => {
    if (!msgs || msgs.length === 0) return "New Chat";
    const firstUserMessage = msgs.find(m => m.role === 'user');
    if (!firstUserMessage) return "New Chat";
    const content = firstUserMessage.content;
    return content.length > 30 ? content.substring(0, 30) + "..." : content;
  };

  const startNewChat = () => {
    if (messages.length > 0) {
      const newSession = {
        id: 'session-' + Date.now(),
        title: generateChatTitle(messages),
        messages: [...messages],
        createdAt: new Date().toISOString(),
        updatedAt: new Date().toISOString()
      };
      setSessions(prev => [newSession, ...prev]);
    }
    setMessages([]);
    setCurrentSessionId('session-' + Date.now());
  };

  const loadSession = (session) => {
    if (messages.length > 0) {
      const currentSession = {
        id: currentSessionId,
        title: generateChatTitle(messages),
        messages: [...messages],
        createdAt: new Date().toISOString(),
        updatedAt: new Date().toISOString()
      };
      setSessions(prev => {
        const filtered = prev.filter(s => s.id !== currentSessionId);
        return [currentSession, ...filtered];
      });
    }
    setMessages(session.messages);
    setCurrentSessionId(session.id);
  };

  const deleteSession = (sessionId) => {
    setSessions(prev => prev.filter(s => s.id !== sessionId));
    if (sessionId === currentSessionId) {
      startNewChat();
    }
  };

  // OpenRouter API integration
  const getAIResponse = async (userMessage) => {
    setIsLoading(true);
    
    try {
      // Get API key from environment variables (Hugging Face Spaces secrets)
      const OPENROUTER_API_KEY = process.env.REACT_APP_OPENROUTER_API_KEY || 
                                 window.OPENROUTER_API_KEY || 
                                 process.env.OPENROUTER_API_KEY;
      
      if (!OPENROUTER_API_KEY) {
        throw new Error("No API key found. Please add OPENROUTER_API_KEY to environment variables.");
      }

      const url = "https://openrouter.ai/api/v1/chat/completions";
      const headers = {
        "Content-Type": "application/json",
        "Authorization": `Bearer ${OPENROUTER_API_KEY}`,
        "HTTP-Referer": "https://huggingface.co/spaces",
        "X-Title": "Chat Flow AI Assistant"
      };

      // Prepare messages for API
      const apiMessages = [
        { role: "system", content: "You are a helpful AI assistant. Provide clear and helpful responses." },
        ...messages.map(msg => ({
          role: msg.role,
          content: msg.content.split('\n\n---\n*Response created by:')[0] // Remove attribution from content
        })),
        { role: "user", content: userMessage }
      ];

      const data = {
        model: selectedModel,
        messages: apiMessages,
        stream: false, // Set to false for simpler handling in React
        max_tokens: 2000,
        temperature: 0.7,
        top_p: 1,
        frequency_penalty: 0,
        presence_penalty: 0
      };

      const response = await fetch(url, {
        method: 'POST',
        headers: headers,
        body: JSON.stringify(data)
      });

      if (!response.ok) {
        let errorDetail = "";
        try {
          const errorData = await response.json();
          errorDetail = errorData.error?.message || `HTTP ${response.status}`;
        } catch {
          errorDetail = `HTTP ${response.status}: ${response.statusText}`;
        }
        throw new Error(`API Error: ${errorDetail}. Please try a different model or check your API key.`);
      }

      const result = await response.json();
      const aiResponse = result.choices[0].message.content;
      const selectedModelName = models.find(m => m.id === selectedModel)?.name || "AI";
      
      setIsLoading(false);
      return aiResponse + `\n\n---\n*Response created by: **${selectedModelName}***`;

    } catch (error) {
      setIsLoading(false);
      console.error('API Error:', error);
      
      if (error.message.includes('timeout')) {
        return "Request timed out. Please try again with a shorter message or different model.";
      } else if (error.message.includes('Connection')) {
        return "Connection error. Please check your internet connection and try again.";
      } else {
        return `Error: ${error.message}`;
      }
    }
  };

  const handleSendMessage = async (e) => {
    e.preventDefault();
    if (!currentMessage.trim() || isLoading) return;

    const userMessage = {
      role: 'user',
      content: currentMessage.trim(),
      timestamp: new Date().toISOString()
    };

    setMessages(prev => [...prev, userMessage]);
    const messageToSend = currentMessage.trim();
    setCurrentMessage('');

    try {
      const aiResponse = await getAIResponse(messageToSend);
      const assistantMessage = {
        role: 'assistant',
        content: aiResponse,
        timestamp: new Date().toISOString()
      };
      setMessages(prev => [...prev, assistantMessage]);
    } catch (error) {
      const errorMessage = {
        role: 'assistant',
        content: 'Sorry, I encountered an error. Please try again.',
        timestamp: new Date().toISOString()
      };
      setMessages(prev => [...prev, errorMessage]);
    }
  };

  const clearChat = () => {
    setMessages([]);
  };

  const downloadHistory = () => {
    const dataStr = JSON.stringify(messages, null, 2);
    const dataBlob = new Blob([dataStr], { type: 'application/json' });
    const url = URL.createObjectURL(dataBlob);
    const link = document.createElement('a');
    link.href = url;
    link.download = `chat_history_${new Date().toISOString().split('T')[0]}.json`;
    link.click();
    URL.revokeObjectURL(url);
  };

  const getSelectedModelName = () => {
    return models.find(m => m.id === selectedModel)?.name || "GPT-3.5 Turbo";
  };

  return (
    <div className="flex h-screen bg-gray-900 text-white">
      {/* Sidebar */}
      <div className="w-80 bg-gray-800 border-r border-gray-700 flex flex-col">
        {/* Header */}
        <div className="p-4 border-b border-gray-700">
          <div className="flex items-center gap-3 mb-4">
            <div className="w-8 h-8 bg-blue-600 rounded-lg flex items-center justify-center">
              <Bot className="w-5 h-5" />
            </div>
            <h1 className="text-xl font-semibold">Chat Flow</h1>
          </div>
          <button
            onClick={startNewChat}
            className="w-full flex items-center gap-2 px-4 py-2 bg-blue-600 hover:bg-blue-700 rounded-lg transition-colors"
          >
            <Plus className="w-4 h-4" />
            New Chat
          </button>
        </div>

        {/* Chat History */}
        <div className="flex-1 overflow-y-auto p-4">
          <h3 className="text-sm font-medium text-gray-400 mb-3">💬 Chat History</h3>
          {sessions.length > 0 ? (
            <div className="space-y-2">
              {sessions.map((session) => (
                <div key={session.id} className="group flex items-center gap-2">
                  <button
                    onClick={() => loadSession(session)}
                    className={`flex-1 text-left px-3 py-2 rounded-lg transition-colors ${
                      session.id === currentSessionId
                        ? 'bg-blue-600 text-white'
                        : 'bg-gray-700 hover:bg-gray-600 text-gray-300'
                    }`}
                  >
                    <div className="text-sm font-medium truncate">{session.title}</div>
                    <div className="text-xs text-gray-400">
                      {new Date(session.updatedAt).toLocaleDateString()}
                    </div>
                  </button>
                  <button
                    onClick={() => deleteSession(session.id)}
                    className="opacity-0 group-hover:opacity-100 p-1 text-gray-400 hover:text-red-400 transition-all"
                  >
                    <Trash2 className="w-4 h-4" />
                  </button>
                </div>
              ))}
            </div>
          ) : (
            <p className="text-gray-500 text-sm">No previous chats yet</p>
          )}
        </div>

        {/* Settings */}
        <div className="p-4 border-t border-gray-700 space-y-4">
          {/* Online Users */}
          <div>
            <h3 className="text-sm font-medium text-gray-400 mb-2">👥 Who's Online</h3>
            <div className="flex items-center gap-2 text-sm">
              <div className="w-2 h-2 bg-green-500 rounded-full"></div>
              <span>{onlineUsers === 1 ? 'Just you online' : `${onlineUsers} people online`}</span>
            </div>
            <p className="text-xs text-gray-500 mt-1">You: {userId}</p>
          </div>

          {/* Model Selection */}
          <div>
            <label className="block text-sm font-medium text-gray-400 mb-2">AI Model</label>
            <select
              value={selectedModel}
              onChange={(e) => setSelectedModel(e.target.value)}
              className="w-full px-3 py-2 bg-gray-700 border border-gray-600 rounded-lg text-white focus:outline-none focus:ring-2 focus:ring-blue-500"
            >
              {models.map((model) => (
                <option key={model.id} value={model.id}>
                  {model.name}
                </option>
              ))}
            </select>
            <p className="text-xs text-green-400 mt-1 font-mono">{selectedModel}</p>
          </div>

          {/* API Status */}
          <div className="flex items-center gap-2 text-sm">
            <div className={`w-2 h-2 rounded-full ${apiStatus === 'Connected' ? 'bg-green-500' : 'bg-red-500'}`}></div>
            <span>{apiStatus === 'Connected' ? '🟢 API Connected' : '🔴 Connection Issue'}</span>
          </div>

          {/* Controls */}
          <div className="flex gap-2">
            <button
              onClick={downloadHistory}
              className="flex-1 flex items-center justify-center gap-1 px-3 py-2 bg-gray-700 hover:bg-gray-600 rounded-lg transition-colors text-sm"
              title="Download History"
            >
              <Download className="w-4 h-4" />
            </button>
            <button
              onClick={clearChat}
              className="flex-1 flex items-center justify-center gap-1 px-3 py-2 bg-gray-700 hover:bg-gray-600 rounded-lg transition-colors text-sm"
              title="Clear Chat"
            >
              <Trash2 className="w-4 h-4" />
            </button>
            <button
              onClick={() => window.location.reload()}
              className="flex-1 flex items-center justify-center gap-1 px-3 py-2 bg-gray-700 hover:bg-gray-600 rounded-lg transition-colors text-sm"
              title="Refresh"
            >
              <RefreshCw className="w-4 h-4" />
            </button>
          </div>
        </div>
      </div>

      {/* Main Chat Area */}
      <div className="flex-1 flex flex-col">
        {/* Chat Messages */}
        <div className="flex-1 overflow-y-auto">
          {messages.length === 0 ? (
            <div className="h-full flex items-center justify-center">
              <div className="text-center max-w-md mx-auto px-4">
                <div className="w-16 h-16 bg-gray-700 rounded-full flex items-center justify-center mx-auto mb-6">
                  <Bot className="w-8 h-8 text-blue-400" />
                </div>
                <h2 className="text-2xl font-semibold mb-4 text-gray-100">Your personal assistant</h2>
                <p className="text-gray-400 leading-relaxed">
                  A personal assistant streamlines your life by managing tasks, schedules, 
                  and communications efficiently.
                </p>
              </div>
            </div>
          ) : (
            <div className="p-6 space-y-6 max-w-4xl mx-auto">
              {messages.map((message, index) => (
                <div key={index} className="flex gap-4">
                  <div className="w-8 h-8 rounded-full bg-gray-700 flex items-center justify-center flex-shrink-0">
                    {message.role === 'user' ? (
                      <div className="w-6 h-6 bg-blue-600 rounded-full"></div>
                    ) : (
                      <Bot className="w-5 h-5 text-blue-400" />
                    )}
                  </div>
                  <div className="flex-1 min-w-0">
                    <div className="prose prose-invert max-w-none">
                      {message.role === 'assistant' && message.content.includes('---\n*Response created by:') ? (
                        <>
                          <div className="whitespace-pre-wrap text-gray-100">
                            {message.content.split('\n\n---\n*Response created by:')[0]}
                          </div>
                          <div className="text-xs text-gray-500 mt-2 italic">
                            Response created by: <strong>{message.content.split('**')[1]}</strong>
                          </div>
                        </>
                      ) : (
                        <div className="whitespace-pre-wrap text-gray-100">{message.content}</div>
                      )}
                    </div>
                  </div>
                </div>
              ))}
              {isLoading && (
                <div className="flex gap-4">
                  <div className="w-8 h-8 rounded-full bg-gray-700 flex items-center justify-center flex-shrink-0">
                    <Bot className="w-5 h-5 text-blue-400" />
                  </div>
                  <div className="flex-1">
                    <div className="flex items-center gap-2 text-gray-400">
                      <div className="w-2 h-2 bg-gray-400 rounded-full animate-bounce"></div>
                      <div className="w-2 h-2 bg-gray-400 rounded-full animate-bounce" style={{animationDelay: '0.1s'}}></div>
                      <div className="w-2 h-2 bg-gray-400 rounded-full animate-bounce" style={{animationDelay: '0.2s'}}></div>
                    </div>
                  </div>
                </div>
              )}
              <div ref={messagesEndRef} />
            </div>
          )}
        </div>

        {/* Message Input */}
        <div className="border-t border-gray-700 p-4">
          <div className="max-w-4xl mx-auto">
            <div className="flex gap-3">
              <div className="flex-1 relative">
                <input
                  type="text"
                  value={currentMessage}
                  onChange={(e) => setCurrentMessage(e.target.value)}
                  onKeyDown={(e) => {
                    if (e.key === 'Enter' && !e.shiftKey) {
                      e.preventDefault();
                      handleSendMessage(e);
                    }
                  }}
                  placeholder="Chat Smarter. Chat many Brains"
                  className="w-full px-4 py-3 bg-gray-800 border border-gray-600 rounded-lg text-white placeholder-gray-400 focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent"
                  disabled={isLoading}
                />
              </div>
              <button
                onClick={handleSendMessage}
                disabled={!currentMessage.trim() || isLoading}
                className="px-6 py-3 bg-blue-600 hover:bg-blue-700 disabled:bg-gray-600 disabled:cursor-not-allowed rounded-lg transition-colors flex items-center gap-2"
              >
                <Send className="w-4 h-4" />
                Send
              </button>
            </div>
            <div className="mt-2 text-center">
              <span className="text-xs text-gray-500">Currently using: <strong>{getSelectedModelName()}</strong></span>
            </div>
          </div>
        </div>
      </div>
    </div>
  );
};

export default ChatFlowApp;