import React, { useState, useEffect, useRef } from 'react'
import { chatAPI, API_BASE_URL } from '../api'
import '../styles/chat.css'

export default function Chat({ conversationId, onNotificationsUpdate }) {
  const [conversations, setConversations] = useState([])
  const [selectedConversation, setSelectedConversation] = useState(conversationId || null)
  const [messages, setMessages] = useState([])
  const [newMessage, setNewMessage] = useState('')
  const [isLoading, setIsLoading] = useState(true)
  const [error, setError] = useState('')
  const [isSending, setIsSending] = useState(false)
  const messageInputRef = useRef(null)

  const currentUserId = localStorage.getItem('user_id')

  useEffect(() => {
    loadConversations()
  }, [])

  useEffect(() => {
    if (selectedConversation) {
      loadMessages()
      // Poll for new messages every 2 seconds
      const interval = setInterval(loadMessages, 2000)
      return () => clearInterval(interval)
    }
  }, [selectedConversation])

  const loadConversations = async () => {
    try {
      setIsLoading(true)
      const response = await chatAPI.getConversations()
      setConversations(response.data || [])
      // Notify parent about notifications update
      if (onNotificationsUpdate) {
        onNotificationsUpdate()
      }
    } catch (err) {
      setError('Failed to load conversations')
    } finally {
      setIsLoading(false)
    }
  }

  const loadMessages = async () => {
    if (!selectedConversation) return

    try {
      const response = await chatAPI.getMessages(selectedConversation)
      setMessages(response.data || [])
      
      // Mark messages as read
      await chatAPI.markAsRead(selectedConversation)
      
      // Update unread_count to 0 for this conversation immediately
      setConversations(prev =>
        prev.map(conv =>
          conv.id === selectedConversation
            ? { ...conv, unread_count: 0 }
            : conv
        )
      )
      
      // Update parent notifications
      if (onNotificationsUpdate) {
        onNotificationsUpdate()
      }
    } catch (err) {
      setError('Failed to load messages')
    }
  }

  const handleSendMessage = async (e) => {
    e.preventDefault()
    if (!newMessage.trim() || !selectedConversation) return

    setIsSending(true)
    try {
      const response = await chatAPI.sendMessage(selectedConversation, newMessage)
      setMessages((prev) => [...prev, response.data])
      setNewMessage('')
      // Auto-focus back to input field after sending
      setTimeout(() => messageInputRef.current?.focus(), 0)
    } catch (err) {
      setError('Failed to send message')
    } finally {
      setIsSending(false)
    }
  }

  if (isLoading) {
    return <div className="chat">Loading conversations...</div>
  }

  if (conversations.length === 0) {
    return (
      <div className="chat">
        <div className="empty-state">
          <h2>No conversations yet</h2>
          <p>Match with someone to start chatting!</p>
          <a href="/discover">Discover</a>
        </div>
      </div>
    )
  }

  return (
    <div className="chat">
      <div className="chat-container">
        <div className="conversations-list">
          <h2>Conversations</h2>
          {conversations.map((conv) => (
            <div
              key={conv.id}
              className={`conversation-item ${selectedConversation === conv.id ? 'active' : ''}`}
              onClick={() => setSelectedConversation(conv.id)}
            >
              <div className="conversation-header">
                {conv.other_user_photo ? (
                  <img 
                    src={`${API_BASE_URL}/media/${conv.other_user_photo}`} 
                    alt={conv.other_user_display_name}
                    className="conversation-avatar"
                  />
                ) : (
                  <div className="conversation-avatar-placeholder">
                    {conv.other_user_display_name.charAt(0).toUpperCase()}
                  </div>
                )}
                <div className="conversation-info">
                  <h4>{conv.other_user_display_name}</h4>
                  <p className="latest-msg">{conv.latest_message || 'No messages yet'}</p>
                </div>
                {conv.unread_count > 0 && (
                  <span className="unread-badge">{conv.unread_count}</span>
                )}
              </div>
            </div>
          ))}
        </div>

        <div className="messages-pane">
          {selectedConversation ? (
            <>
              <div className="messages-header">
                <h3>
                  {conversations.find((c) => c.id === selectedConversation)?.other_user_display_name}
                </h3>
              </div>

              <div className="messages-list">
                {messages.map((msg) => (
                  <div
                    key={msg.id}
                    className={`message ${msg.sender_id == currentUserId ? 'sent' : 'received'}`}
                  >
                    <p>{msg.content}</p>
                    <span className="timestamp">
                      {new Date(msg.created_at).toLocaleTimeString()}
                    </span>
                  </div>
                ))}
              </div>

              <form onSubmit={handleSendMessage} className="message-form">
                <input
                  ref={messageInputRef}
                  type="text"
                  value={newMessage}
                  onChange={(e) => setNewMessage(e.target.value)}
                  placeholder="Type a message..."
                  disabled={isSending}
                  autoFocus
                />
                <button type="submit" disabled={isSending || !newMessage.trim()}>
                  Send
                </button>
              </form>
            </>
          ) : (
            <div className="no-conversation">Select a conversation to start messaging</div>
          )}
        </div>
      </div>
    </div>
  )
}