import { useState, useEffect, useCallback, useRef } from 'react';
import { useSession } from 'next-auth/react';
import { Notification, NotificationCount } from '@/lib/types/notification';
import { useUnifiedRefresh } from './use-unified-refresh';
import { REFRESH_INTERVALS } from '@/lib/constants/refresh-intervals';
import { requestDeduplicator } from '@/lib/utils/request-deduplication';

// Default empty notification count
const defaultNotificationCount: NotificationCount = {
  total: 0,
  unread: 0,
  sources: {}
};

export function useNotifications() {
  const { data: session, status } = useSession();
  const [notifications, setNotifications] = useState<Notification[]>([]);
  const [notificationCount, setNotificationCount] = useState<NotificationCount>(defaultNotificationCount);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const isMountedRef = useRef<boolean>(false);

  // Fetch notification count with request deduplication
  const fetchNotificationCount = useCallback(async (force = false) => {
    if (!session?.user || !isMountedRef.current) return;
    
    try {
      setError(null);
      
      console.log('[useNotifications] Fetching notification count', { force });
      
      // Use request deduplication to prevent duplicate calls
      const requestKey = `notifications-count-${session.user.id}`;
      const url = force 
        ? `/api/notifications/count?force=true&_t=${Date.now()}`
        : '/api/notifications/count';
      
      const data = await requestDeduplicator.execute(
        requestKey,
        async () => {
          const response = await fetch(url, {
            credentials: 'include',
            cache: force ? 'no-store' : 'default',
          });
          
          if (!response.ok) {
            const errorText = await response.text();
            console.error('Failed to fetch notification count:', {
              status: response.status,
              body: errorText
            });
            throw new Error(errorText || 'Failed to fetch notification count');
          }
          
          return response.json();
        },
        2000 // 2 second deduplication window
      );
      
      if (isMountedRef.current) {
        console.log('[useNotifications] Received notification count:', data);
        setNotificationCount(data);
      }
    } catch (err: any) {
      console.error('Error fetching notification count:', err);
      if (isMountedRef.current) {
        setError(err.message || 'Failed to fetch notification count');
      }
    }
  }, [session?.user]);

  // Mark all notifications as read (when dropdown is opened)
  const markAllAsRead = useCallback(async () => {
    if (!session?.user || !isMountedRef.current) return false;
    
    try {
      const response = await fetch('/api/notifications/mark-all-read', {
        method: 'POST',
        credentials: 'include',
      });
      
      if (!response.ok) {
        throw new Error('Failed to mark all notifications as read');
      }
      
      // Update local state - reset count to 0
      setNotificationCount({
        total: 0,
        unread: 0,
        sources: {
          email: { total: 0, unread: 0 },
          rocketchat: { total: 0, unread: 0 },
          leantime: { total: 0, unread: 0 },
          calendar: { total: 0, unread: 0 },
        },
      });
      
      return true;
    } catch (err: any) {
      console.error('Error marking all notifications as read:', err);
      setError(err.message || 'Failed to mark all notifications as read');
      return false;
    }
  }, [session?.user]);

  // Mark notification as read
  const markAsRead = useCallback(async (notificationId: string) => {
    if (!session?.user || !isMountedRef.current) return false;
    
    try {
      const response = await fetch(`/api/notifications/${notificationId}/read`, {
        method: 'POST',
        credentials: 'include',
      });
      
      if (!response.ok) {
        throw new Error('Failed to mark notification as read');
      }
      
      // Update local state - remove from list and update count
      setNotifications(prev => prev.filter(n => n.id !== notificationId));
      setNotificationCount(prev => ({
        ...prev,
        unread: Math.max(0, prev.unread - 1),
      }));
      
      return true;
    } catch (err: any) {
      console.error('Error marking notification as read:', err);
      setError(err.message || 'Failed to mark notification as read');
      return false;
    }
  }, [session?.user]);

  // Fetch notifications with request deduplication
  const fetchNotifications = useCallback(async (page = 1, limit = 20, source?: string) => {
    if (!session?.user || !isMountedRef.current) return;
    
    setLoading(true);
    setError(null);
    
    try {
      console.log('[useNotifications] Fetching notifications', { page, limit, source });
      
      // Use request deduplication to prevent duplicate calls
      const requestKey = `notifications-${session.user.id}-${page}-${limit}-${source || 'all'}`;
      const url = `/api/notifications?limit=${limit}${source ? `&source=${source}` : ''}`;
      
      const data = await requestDeduplicator.execute(
        requestKey,
        async () => {
          const response = await fetch(url, {
            credentials: 'include',
            cache: 'no-store',
          });
          
          if (!response.ok) {
            const errorText = await response.text();
            console.error('Failed to fetch notifications:', {
              status: response.status,
              body: errorText
            });
            throw new Error(errorText || 'Failed to fetch notifications');
          }
          
          return response.json();
        },
        2000 // 2 second deduplication window
      );
      
      if (isMountedRef.current) {
        // Filter by source if specified
        let filtered = data.notifications || [];
        if (source) {
          filtered = filtered.filter((n: Notification) => n.source === source);
        }
        setNotifications(filtered);
      }
    } catch (err: any) {
      console.error('Error fetching notifications:', err);
      if (isMountedRef.current) {
        setError(err.message || 'Failed to fetch notifications');
      }
    } finally {
      if (isMountedRef.current) {
        setLoading(false);
      }
    }
  }, [session?.user]);

  // Use unified refresh system for notification count
  // Note: Widgets update the count via /api/notifications/update
  // This polling is a fallback to ensure count is refreshed periodically
  const { refresh: refreshCount } = useUnifiedRefresh({
    resource: 'notifications-count',
    interval: REFRESH_INTERVALS.NOTIFICATIONS_COUNT,
    enabled: status === 'authenticated',
    onRefresh: async () => {
      await fetchNotificationCount(false);  // Use cache, widgets update it
    },
    priority: 'high',
  });

  // Listen for custom events to trigger immediate refresh
  useEffect(() => {
    if (status !== 'authenticated') return;

    const handleNotificationUpdate = (event: CustomEvent) => {
      console.log('[useNotifications] Received notification update event', event.detail);
      // Refresh count immediately when widget updates
      // Use a small delay to ensure the registry has been updated
      setTimeout(() => {
        fetchNotificationCount(false); // Use cache, widget already updated it
      }, 100);
    };

    // Listen for custom event from widgets
    window.addEventListener('notification-updated', handleNotificationUpdate as EventListener);

    return () => {
      window.removeEventListener('notification-updated', handleNotificationUpdate as EventListener);
    };
  }, [status, fetchNotificationCount]);

  // Initialize fetching on component mount and cleanup on unmount
  useEffect(() => {
    isMountedRef.current = true;
    
    if (status === 'authenticated' && session?.user) {
      // Initial fetches - use cache, widgets will update it
      fetchNotificationCount(false);
      fetchNotifications();
    }
    
    return () => {
      isMountedRef.current = false;
    };
  }, [status, session?.user, fetchNotificationCount, fetchNotifications]);

  return {
    notifications,
    notificationCount,
    loading,
    error,
    fetchNotifications,
    fetchNotificationCount: () => fetchNotificationCount(true),
    markAsRead,
    markAllAsRead,
  };
}