import { useState, useRef, useEffect } from 'react';
import { useParams, useNavigate, Link } from 'react-router-dom';
import Layout from '../components/layout/Layout';
import { useAuth } from '../contexts/AuthContext';
import { Send, UserPlus, Loader2, LogOut, AlertTriangle, QrCode, Edit2, Filter, X } from 'lucide-react';
import { connectSocket, disconnectSocket, getSocket } from '../services/socket';
import { eventsAPI, heatsAPI, matchesAPI } from '../services/api';
import HeatsBanner from '../components/heats/HeatsBanner';
import Avatar from '../components/common/Avatar';
import ChatMessageList from '../components/chat/ChatMessageList';
import ChatInput from '../components/chat/ChatInput';
import ConfirmationModal from '../components/modals/ConfirmationModal';
import Modal from '../components/modals/Modal';
import useEventChat from '../hooks/useEventChat';
import ParticipantsSidebar from '../components/events/ParticipantsSidebar';

const EventChatPage = () => {
  const { slug } = useParams();
  const { user } = useAuth();
  const navigate = useNavigate();
  const [event, setEvent] = useState(null);
  const [isParticipant, setIsParticipant] = useState(false);
  const [loading, setLoading] = useState(true);
  const [checkedInUsers, setCheckedInUsers] = useState([]);
  const [showLeaveModal, setShowLeaveModal] = useState(false);
  const [isLeaving, setIsLeaving] = useState(false);
  const messagesEndRef = useRef(null);
  const messagesContainerRef = useRef(null);

  // Event Chat hook - manages messages, Socket.IO, and active users
  const {
    messages,
    newMessage,
    setNewMessage,
    activeUsers,
    isConnected,
    loadingOlder,
    hasMore,
    sendMessage: handleSendMessage,
    loadOlderMessages
  } = useEventChat(slug, user?.id, event, messagesContainerRef);

  // Heats state
  const [myHeats, setMyHeats] = useState([]);
  const [userHeats, setUserHeats] = useState(new Map());
  const [showHeatsBanner, setShowHeatsBanner] = useState(false);
  const [hideMyHeats, setHideMyHeats] = useState(false);
  const [showHeatsModal, setShowHeatsModal] = useState(false);

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

  // Fetch event data and check participation
  useEffect(() => {
    const fetchEvent = async () => {
      try {
        setLoading(true);

        // Get all events with participation info
        const allEvents = await eventsAPI.getAll();
        const eventData = allEvents.find(e => e.slug === slug);

        if (eventData) {
          setEvent(eventData);
          setIsParticipant(eventData.isJoined);
        } else {
          setEvent(null);
          setIsParticipant(false);
        }
      } catch (err) {
        console.error('Error loading event:', err);
        setEvent(null);
        setIsParticipant(false);
      } finally {
        setLoading(false);
      }
    };

    fetchEvent();
  }, [slug]);

  // Load heats data and checked-in users
  useEffect(() => {
    if (!event || !isParticipant) return;

    const loadData = async () => {
      try {
        // Load my heats
        const myHeatsData = await heatsAPI.getMyHeats(slug);
        setMyHeats(myHeatsData);
        setShowHeatsBanner(myHeatsData.length === 0);

        // Load all users' heats
        const allHeatsData = await heatsAPI.getAllHeats(slug);
        const heatsMap = new Map();
        allHeatsData.forEach((userHeat) => {
          heatsMap.set(userHeat.userId, userHeat.heats);
        });
        setUserHeats(heatsMap);

        // Load all checked-in users (participants)
        const eventDetails = await eventsAPI.getDetails(slug);
        if (eventDetails.data && eventDetails.data.participants) {
          const participants = eventDetails.data.participants
            .map(p => ({
              userId: p.userId,
              username: p.username,
              avatar: p.avatar || `https://api.dicebear.com/7.x/avataaars/svg?seed=${p.username}`,
              firstName: p.firstName,
              lastName: p.lastName,
            }))
            .filter(p => p.userId !== user.id); // Exclude current user
          setCheckedInUsers(participants);
        }
      } catch (error) {
        console.error('Failed to load data:', error);
      }
    };

    loadData();
  }, [event, isParticipant, slug, user.id]);

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

  // Heats updates listener (specific to EventChatPage)
  useEffect(() => {
    if (!event) return;

    const socket = getSocket();
    if (!socket) return;

    // Heats updated notification
    const handleHeatsUpdated = (data) => {
      const { userId, heats } = data;

      // Update userHeats map
      setUserHeats((prev) => {
        const newMap = new Map(prev);
        if (heats && heats.length > 0) {
          newMap.set(userId, heats);
        } else {
          newMap.delete(userId);
        }
        return newMap;
      });

      // If it's the current user, update myHeats
      if (userId === user.id) {
        setMyHeats(heats || []);
        setShowHeatsBanner(heats.length === 0);
      }
    };

    socket.on('heats_updated', handleHeatsUpdated);

    return () => {
      socket.off('heats_updated', handleHeatsUpdated);
    };
  }, [event, user.id]);

  const handleMatchWith = async (userId) => {
    try {
      const result = await matchesAPI.createMatch(userId, slug);

      // Show success message
      alert(`Match request sent successfully! The user will be notified.`);

      // Optional: Navigate to matches page or refresh matches list
      // For now, we just show a success message
    } catch (error) {
      console.error('Failed to send match request:', error);

      // Show appropriate error message
      if (error.status === 400 && error.message.includes('already exists')) {
        alert('You already have a match request with this user.');
      } else if (error.status === 403) {
        alert('You must be a participant of this event to send match requests.');
      } else if (error.status === 404) {
        alert('Event not found.');
      } else {
        alert('Failed to send match request. Please try again.');
      }
    }
  };

  const handleHeatsSave = () => {
    setShowHeatsBanner(false);
    setShowHeatsModal(false);
    // Heats will be updated via Socket.IO heats_updated event
  };

  const shouldHideUser = (userId) => {
    if (!hideMyHeats || myHeats.length === 0) return false;

    const targetUserHeats = userHeats.get(userId);
    if (!targetUserHeats || targetUserHeats.length === 0) return false;

    // Hide if ANY of their heats match ANY of my heats (same division + competition_type + heat_number)
    return targetUserHeats.some((targetHeat) =>
      myHeats.some(
        (myHeat) =>
          myHeat.divisionId === targetHeat.divisionId &&
          myHeat.competitionTypeId === targetHeat.competitionTypeId &&
          myHeat.heatNumber === targetHeat.heatNumber
      )
    );
  };

  // Combine checked-in users with online status
  const getAllDisplayUsers = () => {
    const activeUserIds = new Set(activeUsers.map(u => u.userId));

    // Merge checked-in users with online status
    const allUsers = checkedInUsers.map(user => ({
      ...user,
      isOnline: activeUserIds.has(user.userId),
    }));

    // Sort: online first, then offline
    return allUsers.sort((a, b) => {
      if (a.isOnline === b.isOnline) return 0;
      return a.isOnline ? -1 : 1;
    });
  };

  const handleLeaveEvent = async () => {
    try {
      setIsLeaving(true);
      await eventsAPI.leave(slug);

      // Disconnect socket
      const socket = getSocket();
      if (socket) {
        socket.emit('leave_event_room');
      }

      // Redirect to events page
      navigate('/events');
    } catch (error) {
      console.error('Failed to leave event:', error);
      alert('Failed to leave event. Please try again.');
    } finally {
      setIsLeaving(false);
      setShowLeaveModal(false);
    }
  };

  // Infinite scroll - detect scroll to top
  useEffect(() => {
    const container = messagesContainerRef.current;
    if (!container) return;

    const handleScroll = () => {
      if (container.scrollTop < 100 && !loadingOlder && hasMore) {
        loadOlderMessages();
      }
    };

    container.addEventListener('scroll', handleScroll);
    return () => container.removeEventListener('scroll', handleScroll);
  }, [loadingOlder, hasMore, messages]);

  if (loading) {
    return (
      <Layout>
        <div className="max-w-4xl mx-auto flex items-center justify-center min-h-[400px]">
          <div className="flex flex-col items-center gap-3">
            <Loader2 className="w-12 h-12 animate-spin text-primary-600" />
            <p className="text-gray-600">Loading event...</p>
          </div>
        </div>
      </Layout>
    );
  }

  if (!event) {
    return (
      <Layout>
        <div className="max-w-4xl mx-auto">
          <div className="bg-red-50 border border-red-200 rounded-md p-4 text-red-700">
            Event not found
          </div>
        </div>
      </Layout>
    );
  }

  // Check if user is participant
  if (!isParticipant) {
    return (
      <Layout>
        <div className="max-w-4xl mx-auto">
          <div className="bg-white rounded-lg shadow-md p-8">
            <div className="text-center">
              <div className="w-16 h-16 bg-amber-100 rounded-full flex items-center justify-center mx-auto mb-4">
                <QrCode className="w-8 h-8 text-amber-600" />
              </div>
              <h2 className="text-2xl font-bold text-gray-900 mb-2">
                Check-in Required
              </h2>
              <p className="text-gray-600 mb-6">
                You need to check in at the event venue by scanning the QR code to access this chat.
              </p>

              <div className="bg-amber-50 border border-amber-200 rounded-lg p-4 mb-6">
                <p className="text-sm text-amber-800 font-medium mb-1">
                  {event.name}
                </p>
                <p className="text-sm text-amber-700">
                  {event.location}
                </p>
              </div>

              <div className="flex gap-3 justify-center">
                <Link
                  to="/events"
                  className="px-6 py-2 border border-gray-300 rounded-lg hover:bg-gray-50 transition-colors"
                >
                  Back to Events
                </Link>
                {import.meta.env.DEV && (
                  <Link
                    to={`/events/${slug}/details`}
                    className="px-6 py-2 bg-primary-600 text-white rounded-lg hover:bg-primary-700 transition-colors"
                  >
                    View QR Code (dev)
                  </Link>
                )}
              </div>
            </div>
          </div>
        </div>
      </Layout>
    );
  }

  return (
    <Layout>
      <div className="max-w-6xl mx-auto">
        <div className="bg-white rounded-lg shadow-md overflow-hidden">
          {/* Header */}
          <div className="bg-primary-600 text-white p-4">
            <div className="flex items-start justify-between">
              <div className="flex-1">
                <h2 className="text-2xl font-bold">{event.name}</h2>
                <p className="text-primary-100 text-sm">{event.location}</p>
                <div className="mt-2 flex items-center gap-3">
                  <span className={`text-xs px-2 py-1 rounded ${isConnected ? 'bg-green-500' : 'bg-red-500'}`}>
                    {isConnected ? '● Connected' : '● Disconnected'}
                  </span>

                  {/* My Heats Display */}
                  {myHeats.length > 0 && (
                    <div className="flex items-center gap-2">
                      <span className="text-xs text-primary-100">Your heats:</span>
                      <div className="flex flex-wrap gap-1">
                        {myHeats.map((heat, idx) => (
                          <span
                            key={idx}
                            className="text-xs px-2 py-0.5 bg-primary-700 text-white rounded font-mono"
                          >
                            {formatHeat(heat)}
                          </span>
                        ))}
                      </div>
                    </div>
                  )}
                </div>
              </div>
              {myHeats.length > 0 && (
                <button
                  onClick={() => setShowHeatsModal(true)}
                  className="flex items-center gap-2 px-3 py-2 bg-primary-700 hover:bg-primary-800 rounded-md transition-colors text-sm"
                >
                  <Edit2 className="w-4 h-4" />
                  Edit Heats
                </button>
              )}
            </div>
          </div>

          {/* Heats Banner */}
          {showHeatsBanner && (
            <HeatsBanner
              slug={slug}
              onSave={handleHeatsSave}
              onDismiss={() => setShowHeatsBanner(false)}
            />
          )}

          <div className="flex h-[calc(100vh-280px)]">
            <ParticipantsSidebar
              users={getAllDisplayUsers().filter(u => !shouldHideUser(u.userId))}
              activeUsers={activeUsers}
              userHeats={userHeats}
              myHeats={myHeats}
              hideMyHeats={hideMyHeats}
              onHideMyHeatsChange={setHideMyHeats}
              onMatchWith={handleMatchWith}
            />

            {/* Chat Area */}
            <div className="flex-1 flex flex-col">
              <ChatMessageList
                messages={messages}
                currentUserId={user.id}
                messagesEndRef={messagesEndRef}
                messagesContainerRef={messagesContainerRef}
                loadingOlder={loadingOlder}
                hasMore={hasMore}
              />

              {/* Message Input */}
              <div className="border-t p-4">
                <ChatInput
                  value={newMessage}
                  onChange={(e) => setNewMessage(e.target.value)}
                  onSubmit={handleSendMessage}
                  disabled={!isConnected}
                  placeholder="Write a message..."
                />
              </div>
            </div>
          </div>

          {/* Leave Event Button */}
          <div className="mt-4 flex justify-center">
            <button
              onClick={() => setShowLeaveModal(true)}
              className="flex items-center gap-2 px-4 py-2 bg-red-600 text-white rounded-lg hover:bg-red-700 transition-colors font-medium"
            >
              <LogOut size={16} />
              Leave Event
            </button>
          </div>
        </div>

        <ConfirmationModal
          isOpen={showLeaveModal}
          onClose={() => setShowLeaveModal(false)}
          onConfirm={handleLeaveEvent}
          title="Leave Event?"
          description="This action cannot be undone"
          message={`Are you sure you want to leave ${event?.name || 'this event'}? You will need to scan the QR code again to rejoin.`}
          confirmText="Leave Event"
          isLoading={isLeaving}
          loadingText="Leaving..."
          icon={AlertTriangle}
        />

        <Modal
          isOpen={showHeatsModal}
          onClose={() => setShowHeatsModal(false)}
          title="Edit Your Competition Heats"
        >
          <HeatsBanner
            slug={slug}
            onSave={handleHeatsSave}
            onDismiss={() => setShowHeatsModal(false)}
            existingHeats={myHeats}
          />
        </Modal>
      </div>
    </Layout>
  );
};

export default EventChatPage;