import React, { useState, useRef, useEffect } from 'react';
import { motion, AnimatePresence } from 'framer-motion';
import { PaperAirplaneIcon, StopIcon } from '@heroicons/react/24/solid';
import MessageBubble from './MessageBubble';
import TypingIndicator from './TypingIndicator';
import FileUploader from './FileUploader';
import { sendMessage, sendMessageStream } from '../services/api';
import toast from 'react-hot-toast';

const ChatInterface = ({ conversationId, conversations, setConversations, darkMode }) => {
  const [message, setMessage] = useState('');
  const [isLoading, setIsLoading] = useState(false);
  const [showFileUploader, setShowFileUploader] = useState(false);
  const messagesEndRef = useRef(null);
  const textareaRef = useRef(null);

  const currentConversation = conversations.find(conv => conv.id === conversationId);
  const messages = currentConversation?.messages || [];

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

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

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

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

    // Add user message immediately
    setConversations(prev => prev.map(conv => 
      conv.id === conversationId 
        ? { 
            ...conv, 
            messages: [...conv.messages, userMessage],
            title: conv.messages.length === 0 ? message.slice(0, 50) + '...' : conv.title
          }
        : conv
    ));

    setMessage('');
    setIsLoading(true);
    const assistantMessageId = (Date.now() + 1).toString();

    try {
      let fullResponse = '';

      // Add a placeholder for the assistant's message
      setConversations(prev => prev.map(conv =>
        conv.id === conversationId
          ? { ...conv, messages: [...conv.messages, { id: assistantMessageId, role: 'assistant', content: '', timestamp: new Date() }] }
          : conv
      ));

      await sendMessageStream(message.trim(), (chunk) => {
        fullResponse += chunk;
        setConversations(prev => prev.map(conv =>
          conv.id === conversationId
            ? {
                ...conv,
                messages: conv.messages.map(msg =>
                  msg.id === assistantMessageId
                    ? { ...msg, content: fullResponse }
                    : msg
                ),
              }
            : conv
        ));
      });

    } catch (error) {
      toast.error('Failed to send message. Please try again.');
      console.error('Error sending message:', error);
      // Optional: remove placeholder on error
      setConversations(prev => prev.map(conv =>
        conv.id === conversationId
          ? { ...conv, messages: conv.messages.filter(msg => msg.id !== assistantMessageId) }
          : conv
      ));
    } finally {
      setIsLoading(false);
    }
  };

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

  const adjustTextareaHeight = () => {
    const textarea = textareaRef.current;
    if (textarea) {
      textarea.style.height = 'auto';
      textarea.style.height = Math.min(textarea.scrollHeight, 120) + 'px';
    }
  };

  useEffect(() => {
    adjustTextareaHeight();
  }, [message]);

  return (
    <div className="flex flex-col h-screen">
      {/* Messages Container */}
      <div className="flex-1 overflow-y-auto px-4 py-6">
        <div className="max-w-3xl mx-auto">
          {/* Empty State */}
          {messages.length === 0 && !isLoading && (
            <motion.div
              initial={{ opacity: 0, y: 20 }}
              animate={{ opacity: 1, y: 0 }}
              transition={{ duration: 0.6 }}
              className="flex flex-col items-center justify-center min-h-[60vh] text-center"
            >
              {/* CA Assistant Avatar */}
              <motion.div
                initial={{ scale: 0.8 }}
                animate={{ scale: 1 }}
                transition={{ duration: 0.5, delay: 0.2 }}
                className={`w-20 h-20 rounded-full flex items-center justify-center mb-6 ${
                  darkMode 
                    ? 'bg-gradient-to-br from-primary-600 to-purple-600' 
                    : 'bg-gradient-to-br from-primary-500 to-purple-500'
                } shadow-lg`}
              >
                <svg className="w-10 h-10 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} 
                    d="M12 6.253v13m0-13C10.832 5.477 9.246 5 7.5 5S4.168 5.477 3 6.253v13C4.168 18.477 5.754 18 7.5 18s3.332.477 4.5 1.253m0-13C13.168 5.477 14.754 5 16.5 5c1.746 0 3.332.477 4.5 1.253v13C19.832 18.477 18.246 18 16.5 18c-1.746 0-3.332.477-4.5 1.253" />
                </svg>
              </motion.div>

              {/* Welcome Message */}
              <motion.h2 
                initial={{ opacity: 0 }}
                animate={{ opacity: 1 }}
                transition={{ delay: 0.4 }}
                className="text-2xl md:text-3xl font-bold mb-3 gradient-text"
              >
                Hello! I'm your CA Study Assistant
              </motion.h2>
              
              <motion.p 
                initial={{ opacity: 0 }}
                animate={{ opacity: 1 }}
                transition={{ delay: 0.5 }}
                className={`text-lg mb-8 ${darkMode ? 'text-gray-300' : 'text-gray-600'}`}
              >
                I'm here to help you with accounting, finance, taxation, and auditing concepts. 
                Ask me anything or upload your study materials!
              </motion.p>

              {/* Quick Start Suggestions */}
              <motion.div
                initial={{ opacity: 0, y: 20 }}
                animate={{ opacity: 1, y: 0 }}
                transition={{ delay: 0.6 }}
                className="w-full max-w-2xl"
              >
                <h3 className={`text-sm font-semibold mb-4 ${
                  darkMode ? 'text-gray-400' : 'text-gray-500'
                }`}>
                  Try asking me about:
                </h3>
                
                <div className="grid grid-cols-1 md:grid-cols-2 gap-3">
                  {[
                    { icon: "📊", text: "Financial statement analysis", query: "Explain financial statement analysis" },
                    { icon: "💰", text: "Depreciation methods", query: "What are different depreciation methods?" },
                    { icon: "🏦", text: "Working capital management", query: "Explain working capital management" },
                    { icon: "📈", text: "Ratio analysis", query: "How to perform ratio analysis?" },
                    { icon: "📋", text: "Auditing procedures", query: "What are key auditing procedures?" },
                    { icon: "💼", text: "Tax planning strategies", query: "Explain tax planning strategies" }
                  ].map((suggestion, index) => (
                    <motion.button
                      key={index}
                      initial={{ opacity: 0, x: -20 }}
                      animate={{ opacity: 1, x: 0 }}
                      transition={{ delay: 0.7 + index * 0.1 }}
                      whileHover={{ scale: 1.02, y: -2 }}
                      whileTap={{ scale: 0.98 }}
                      onClick={() => setMessage(suggestion.query)}
                      className={`flex items-center p-4 rounded-xl text-left transition-all ${
                        darkMode
                          ? 'bg-gray-800 hover:bg-gray-700 border-gray-700 text-gray-300'
                          : 'bg-gray-50 hover:bg-gray-100 border-gray-200 text-gray-700'
                      } border hover:border-primary-300 hover:shadow-md`}
                    >
                      <span className="text-2xl mr-3">{suggestion.icon}</span>
                      <span className="font-medium">{suggestion.text}</span>
                    </motion.button>
                  ))}
                </div>
              </motion.div>

              {/* Upload Reminder */}
              <motion.div
                initial={{ opacity: 0 }}
                animate={{ opacity: 1 }}
                transition={{ delay: 1.2 }}
                className={`mt-8 p-4 rounded-xl ${
                  darkMode 
                    ? 'bg-primary-900/20 border-primary-700/30' 
                    : 'bg-primary-50 border-primary-200'
                } border`}
              >
                <div className="flex items-center justify-center">
                  <svg className={`w-5 h-5 mr-2 ${
                    darkMode ? 'text-primary-400' : 'text-primary-600'
                  }`} fill="none" stroke="currentColor" viewBox="0 0 24 24">
                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} 
                      d="M9 12h6m-6 4h6m2 5H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z" />
                  </svg>
                  <span className={`text-sm ${
                    darkMode ? 'text-primary-300' : 'text-primary-700'
                  }`}>
                    💡 Upload your study materials for more specific and detailed answers
                  </span>
                </div>
              </motion.div>
            </motion.div>
          )}

          {/* Messages */}
          <AnimatePresence>
            {messages.map((msg, index) => (
              <MessageBubble
                key={msg.id}
                message={msg}
                darkMode={darkMode}
                isLast={index === messages.length - 1}
              />
            ))}
          </AnimatePresence>

          {isLoading && <TypingIndicator darkMode={darkMode} />}
          
          <div ref={messagesEndRef} />
        </div>
      </div>

      {/* File Uploader Modal */}
      <AnimatePresence>
        {showFileUploader && (
          <motion.div
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            exit={{ opacity: 0 }}
            className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50 p-4"
            onClick={() => setShowFileUploader(false)}
          >
            <motion.div
              initial={{ scale: 0.9, opacity: 0 }}
              animate={{ scale: 1, opacity: 1 }}
              exit={{ scale: 0.9, opacity: 0 }}
              onClick={(e) => e.stopPropagation()}
              className={`max-w-md w-full p-6 rounded-2xl ${
                darkMode ? 'bg-gray-800' : 'bg-white'
              } shadow-2xl`}
            >
              <h3 className="text-lg font-semibold mb-4">Upload Document</h3>
              <FileUploader darkMode={darkMode} onClose={() => setShowFileUploader(false)} />
            </motion.div>
          </motion.div>
        )}
      </AnimatePresence>

      {/* Input Area */}
      <div className={`border-t ${
        darkMode ? 'border-gray-700/50 bg-gray-900/95' : 'border-gray-200/50 bg-white/95'
      } backdrop-blur-sm p-6`}>
        <div className="max-w-3xl mx-auto">
          <form onSubmit={handleSubmit} className="relative">
            {/* Enhanced Input Container */}
            <div className={`relative overflow-hidden rounded-2xl border-2 transition-all duration-300 ${
              darkMode 
                ? 'bg-gradient-to-br from-gray-800 to-gray-900 border-gray-600 focus-within:border-primary-500 focus-within:from-gray-700 focus-within:to-gray-800' 
                : 'bg-gradient-to-br from-white to-gray-50 border-gray-300 focus-within:border-primary-500 focus-within:from-blue-50 focus-within:to-white'
            } focus-within:ring-4 focus-within:ring-primary-500/20 shadow-xl hover:shadow-2xl focus-within:shadow-2xl`}>
              
              {/* Subtle Inner Glow */}
              <div className={`absolute inset-0 opacity-0 focus-within:opacity-100 transition-opacity duration-300 ${
                darkMode 
                  ? 'bg-gradient-to-br from-primary-900/20 to-purple-900/20' 
                  : 'bg-gradient-to-br from-primary-50/50 to-purple-50/50'
              }`} />
              
              {/* Input Content */}
              <div className="relative flex items-end space-x-4 p-4">
                {/* File Upload Button */}
                <motion.button
                  type="button"
                  whileHover={{ scale: 1.05 }}
                  whileTap={{ scale: 0.95 }}
                  onClick={() => setShowFileUploader(true)}
                  className={`flex-shrink-0 p-3 rounded-xl transition-all duration-200 ${
                    darkMode
                      ? 'hover:bg-gray-700/70 text-gray-400 hover:text-primary-400 hover:shadow-lg'
                      : 'hover:bg-gray-100/70 text-gray-500 hover:text-primary-600 hover:shadow-md'
                  } relative group backdrop-blur-sm`}
                  title="Upload document"
                >
                  <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} 
                      d="M15.172 7l-6.586 6.586a2 2 0 102.828 2.828l6.414-6.586a4 4 0 00-5.656-5.656l-6.415 6.585a6 6 0 108.486 8.486L20.5 13" />
                  </svg>
                  
                  {/* Enhanced Tooltip */}
                  <div className={`absolute -top-14 left-1/2 transform -translate-x-1/2 px-3 py-2 rounded-lg text-xs whitespace-nowrap opacity-0 group-hover:opacity-100 transition-all duration-200 ${
                    darkMode ? 'bg-gray-800 text-white shadow-xl border border-gray-700' : 'bg-gray-900 text-white shadow-xl'
                  }`}>
                    Upload documents
                    <div className={`absolute top-full left-1/2 transform -translate-x-1/2 w-0 h-0 border-l-4 border-r-4 border-t-4 border-transparent ${
                      darkMode ? 'border-t-gray-800' : 'border-t-gray-900'
                    }`} />
                  </div>
                </motion.button>

                {/* Enhanced Text Input */}
                <div className="flex-1 relative">
                  <textarea
                    ref={textareaRef}
                    value={message}
                    onChange={(e) => setMessage(e.target.value)}
                    onKeyDown={handleKeyDown}
                    placeholder={messages.length === 0 ? "Hi! Ask me about accounting, finance, taxation, or upload your study materials..." : "Ask a follow-up question..."}
                    className={`w-full resize-none border-none outline-none bg-transparent py-3 px-2 text-base leading-relaxed ${
                      darkMode ? 'text-white placeholder-gray-400' : 'text-gray-900 placeholder-gray-500'
                    } placeholder:text-sm placeholder:leading-relaxed`}
                    rows={1}
                    disabled={isLoading}
                    style={{ 
                      minHeight: '24px',
                      maxHeight: '120px',
                      lineHeight: '1.5'
                    }}
                  />
                  
                  {/* Input Focus Indicator */}
                  <div className={`absolute left-0 bottom-0 h-0.5 w-0 bg-gradient-to-r from-primary-500 to-purple-500 transition-all duration-300 ${
                    message.trim() ? 'w-full' : 'group-focus-within:w-full'
                  }`} />
                </div>

                {/* Enhanced Send Button */}
                <motion.button
                  type="submit"
                  disabled={!message.trim() || isLoading}
                  whileHover={message.trim() && !isLoading ? { scale: 1.05 } : {}}
                  whileTap={message.trim() && !isLoading ? { scale: 0.95 } : {}}
                  className={`flex-shrink-0 p-3 rounded-xl transition-all duration-200 relative group ${
                    message.trim() && !isLoading
                      ? 'bg-gradient-to-r from-primary-600 to-primary-700 hover:from-primary-700 hover:to-primary-800 text-white shadow-lg hover:shadow-xl'
                      : darkMode
                        ? 'bg-gray-600/50 text-gray-400 hover:bg-gray-600/70'
                        : 'bg-gray-300/50 text-gray-500 hover:bg-gray-300/70'
                  } disabled:cursor-not-allowed`}
                  title={isLoading ? "Stop generation" : "Send message"}
                >
                  {isLoading ? (
                    <div className="relative">
                      <StopIcon className="w-5 h-5" />
                      <div className="absolute inset-0 border-2 border-white border-t-transparent rounded-full animate-spin opacity-50"></div>
                    </div>
                  ) : (
                    <PaperAirplaneIcon className="w-5 h-5" />
                  )}
                  
                  {/* Enhanced Send Button Glow Effect */}
                  {message.trim() && !isLoading && (
                    <div className="absolute inset-0 rounded-xl bg-gradient-to-r from-primary-600 to-primary-700 opacity-0 group-hover:opacity-30 transition-opacity duration-200 blur-lg -z-10"></div>
                  )}
                </motion.button>
              </div>
              
              {/* Bottom Border Accent */}
              <div className={`absolute bottom-0 left-0 right-0 h-0.5 bg-gradient-to-r from-transparent via-primary-500 to-transparent opacity-0 focus-within:opacity-100 transition-opacity duration-300`} />
            </div>
          </form>

          {/* Footer Text */}
          <motion.p 
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            transition={{ delay: 0.3 }}
            className={`text-xs text-center mt-3 ${
              darkMode ? 'text-gray-500' : 'text-gray-400'
            }`}
          >
            ⚡ Powered by AI • CA Study Assistant can make mistakes. Consider checking important information.
          </motion.p>
        </div>
      </div>
    </div>
  );
};

export default ChatInterface;