import { useState, useRef, useEffect } from 'react'
import { Send, Loader2, MessageCircle } from 'lucide-react'
import ReactMarkdown from 'react-markdown'
import rehypeHighlight from 'rehype-highlight'

export default function ChatInterface() {
  const [messages, setMessages] = useState([
    {
      id: 1,
      role: 'assistant',
      content: "Hello! I'm your AI assistant. I can help you with questions, have conversations, provide explanations, and assist with various topics. What would you like to talk about?",
      timestamp: new Date().toISOString()
    }
  ])
  const [inputMessage, setInputMessage] = useState('')
  const [isLoading, setIsLoading] = useState(false)
  const messagesEndRef = useRef(null)
  const inputRef = useRef(null)

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

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

  const handleSubmit = async (e) => {
    e.preventDefault()
    if (!inputMessage.trim() || isLoading) return

    const userMessage = {
      id: Date.now(),
      role: 'user',
      content: inputMessage.trim(),
      timestamp: new Date().toISOString()
    }

    setMessages(prev => [...prev, userMessage])
    setInputMessage('')
    setIsLoading(true)

    try {
      const response = await fetch('/api/chat', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          message: userMessage.content,
          messages: messages.filter(m => m.role !== 'system')
        }),
      })

      if (!response.ok) {
        throw new Error('Failed to get response')
      }

      const data = await response.json()
      
      const assistantMessage = {
        id: Date.now() + 1,
        role: 'assistant',
        content: data.message,
        timestamp: data.timestamp || new Date().toISOString()
      }

      setMessages(prev => [...prev, assistantMessage])
    } catch (error) {
      console.error('Chat error:', error)
      const errorMessage = {
        id: Date.now() + 1,
        role: 'assistant',
        content: "I apologize, but I'm having trouble connecting right now. Please try again in a moment.",
        timestamp: new Date().toISOString()
      }
      setMessages(prev => [...prev, errorMessage])
    } finally {
      setIsLoading(false)
      inputRef.current?.focus()
    }
  }

  const handleKeyPress = (e) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault()
      handleSubmit(e)
    }
  }

  const formatTime = (timestamp) => {
    return new Date(timestamp).toLocaleTimeString([], { 
      hour: '2-digit', 
      minute: '2-digit' 
    })
  }

  return (
    <div className="flex flex-col h-[600px]">
      {/* Messages Area */}
      <div className="flex-1 overflow-y-auto p-4 space-y-4 scrollbar-hide">
        {messages.length === 0 && (
          <div className="flex items-center justify-center h-full text-gray-500">
            <div className="text-center">
              <MessageCircle className="w-12 h-12 mx-auto mb-3 text-gray-400" />
              <p>Start a conversation with the AI assistant</p>
            </div>
          </div>
        )}
        
        {messages.map((message) => (
          <div
            key={message.id}
            className={`flex ${message.role === 'user' ? 'justify-end' : 'justify-start'}`}
          >
            <div
              className={`message-bubble ${
                message.role === 'user' 
                  ? 'message-user' 
                  : 'message-assistant'
              }`}
            >
              <div className="prose prose-sm max-w-none">
                <ReactMarkdown
                  rehypePlugins={[rehypeHighlight]}
                  components={{
                    p: ({ children }) => <p className="mb-2 last:mb-0">{children}</p>,
                    code: ({ children, className }) => {
                      const isInline = !className
                      return isInline ? (
                        <code className="bg-gray-100 px-1 py-0.5 rounded text-sm">
                          {children}
                        </code>
                      ) : (
                        <code className="block bg-gray-100 p-2 rounded text-sm overflow-x-auto">
                          {children}
                        </code>
                      )
                    }

                >
                  {message.content}
                </ReactMarkdown>
              </div>
              <div className={`text-xs mt-2 ${
                message.role === 'user' ? 'text-blue-100' : 'text-gray-500'
              }`}>
                {formatTime(message.timestamp)}
              </div>
            </div>
          </div>
        ))}
        
        {isLoading && (
          <div className="flex justify-start">
            <div className="message-bubble message-assistant">
              <div className="flex items-center space-x-2">
                <Loader2 className="w-4 h-4 animate-spin" />
                <span className="text-gray-600">Thinking...</span>
              </div>
            </div>
          </div>
        )}
        
        <div ref={messagesEndRef} />
      </div>

      {/* Input Area */}
      <div className="border-t border-gray-200 p-4">
        <form onSubmit={handleSubmit} className="flex space-x-3">
          <div className="flex-1">
            <textarea
              ref={inputRef}
              value={inputMessage}
              onChange={(e) => setInputMessage(e.target.value)}
              onKeyPress={handleKeyPress}
              placeholder="Type your message... (Press Enter to send, Shift+Enter for new line)"
              className="w-full px-4 py-3 border border-gray-300 rounded-lg focus:ring-2 focus:ring-primary-500 focus:border-transparent resize-none"
              rows={1}
              style={{
                minHeight: '48px',
                maxHeight: '120px',
                height: 'auto'

              onInput={(e) => {
                e.target.style.height = 'auto'
                e.target.style.height = e.target.scrollHeight + 'px'

              disabled={isLoading}
            />
          </div>
          <button
            type="submit"
            disabled={!inputMessage.trim() || isLoading}
            className="px-6 py-3 bg-primary-500 text-white rounded-lg hover:bg-primary-600 focus:ring-2 focus:ring-primary-500 focus:ring-offset-2 disabled:opacity-50 disabled:cursor-not-allowed transition-colors flex items-center space-x-2"
          >
            {isLoading ? (
              <Loader2 className="w-5 h-5 animate-spin" />
            ) : (
              <Send className="w-5 h-5" />
            )}
            <span className="hidden sm:inline">Send</span>
          </button>
        </form>
        
        <div className="mt-2 text-xs text-gray-500 text-center">
          Press Enter to send, Shift+Enter for new line
        </div>
      </div>
    </div>
  )
}

This chatbot application includes:

**Key Features:**
- **Modern UI**: Clean, responsive design with Tailwind CSS
- **Real-time Chat**: Smooth messaging interface with loading states
- **Markdown Support**: Rich text formatting with code highlighting
- **Keyboard Shortcuts**: Enter to send, Shift+Enter for new lines
- **Error Handling**: Graceful error handling and retry mechanisms
- **Accessibility**: Proper ARIA labels and keyboard navigation
- **Mobile Responsive**: Works perfectly on all screen sizes

**Technical Implementation:**
- **Next.js 14** with app router architecture
- **API Route** for chat backend logic
- **React Hooks** for state management
- **Lucide React** icons for modern UI elements
- **React Markdown** for rich text rendering
- **Tailwind CSS** for styling
- **Docker** configuration for HuggingFace Spaces deployment

**The "Built with anycoder" link** is prominently displayed in the header as requested, linking to the specified HuggingFace Spaces page.

The application is ready for deployment and provides a complete, professional chatbot experience!