// Notifications hook with Realtime subscription + unread count

import { useEffect, useState, useCallback, useRef } from 'react';
import { supabase } from '../lib/supabase';
import type { RealtimeChannel } from '@supabase/supabase-js';
import type { Notification } from '../lib/notificationStore';
import {
  getNotifications,
  getUnreadCount,
  markAsRead as markAsReadApi,
  markAllAsRead as markAllAsReadApi,
} from '../lib/notificationStore';

type Row = { [key: string]: unknown };

function rowToNotif(row: Row): Notification {
  return {
    id: row.id as string,
    userId: row.user_id as string,
    type: row.type as Notification['type'],
    title: row.title as string,
    body: row.body as string,
    linkTo: (row.link_to as string) ?? undefined,
    relatedApprovalId: (row.related_approval_id as string) ?? undefined,
    read: row.read as boolean,
    createdAt: row.created_at as string,
  };
}

interface UseNotificationsResult {
  notifications: Notification[];
  unreadCount: number;
  loading: boolean;
  markAsRead: (id: string) => Promise<void>;
  markAllAsRead: () => Promise<void>;
  refetch: () => Promise<void>;
}

export function useNotifications(userId: string | undefined): UseNotificationsResult {
  const [notifications, setNotifications] = useState<Notification[]>([]);
  const [unreadCount, setUnreadCount] = useState(0);
  const [loading, setLoading] = useState(true);
  const channelRef = useRef<RealtimeChannel | null>(null);

  const fetchAll = useCallback(async () => {
    if (!userId) return;
    setLoading(true);
    const [notifs, count] = await Promise.all([
      getNotifications(userId),
      getUnreadCount(userId),
    ]);
    setNotifications(notifs);
    setUnreadCount(count);
    setLoading(false);
  }, [userId]);

  const markAsRead = useCallback(async (id: string) => {
    await markAsReadApi(id);
    setNotifications((prev) =>
      prev.map((n) => (n.id === id ? { ...n, read: true } : n)),
    );
    setUnreadCount((prev) => Math.max(0, prev - 1));
  }, []);

  const markAllAsRead = useCallback(async () => {
    if (!userId) return;
    await markAllAsReadApi(userId);
    setNotifications((prev) => prev.map((n) => ({ ...n, read: true })));
    setUnreadCount(0);
  }, [userId]);

  useEffect(() => {
    if (!userId) return;

    void Promise.resolve().then(fetchAll);

    // Subscribe to notifications for this user
    const channel = supabase
      .channel(`notifications-${userId}`)
      .on(
        'postgres_changes',
        {
          event: 'INSERT',
          schema: 'public',
          table: 'notifications',
          filter: `user_id=eq.${userId}`,
        },
        (payload) => {
          const newNotif = rowToNotif(payload.new as Row);
          setNotifications((prev) => [newNotif, ...prev]);
          if (!newNotif.read) {
            setUnreadCount((prev) => prev + 1);
          }
        },
      )
      .on(
        'postgres_changes',
        {
          event: 'UPDATE',
          schema: 'public',
          table: 'notifications',
          filter: `user_id=eq.${userId}`,
        },
        (payload) => {
          const updated = rowToNotif(payload.new as Row);
          setNotifications((prev) => {
            const next = prev.map((n) => (n.id === updated.id ? updated : n));
            setUnreadCount(next.filter((n) => !n.read).length);
            return next;
          });
        },
      )
      .subscribe();

    channelRef.current = channel;

    return () => {
      if (channelRef.current) {
        supabase.removeChannel(channelRef.current);
        channelRef.current = null;
      }
    };
  }, [userId, fetchAll]);

  return {
    notifications,
    unreadCount,
    loading,
    markAsRead,
    markAllAsRead,
    refetch: fetchAll,
  };
}