import React, { useState, useEffect, useCallback } from 'react';
import { Bell, CheckCheck, Loader2 } from 'lucide-react';
import { backendApi, NotificationItem } from '../services/apiClient';

function formatNotificationDate(iso: string): string {
  const d = new Date(iso);
  const now = new Date();
  const diff = now.getTime() - d.getTime();
  if (diff < 60000) return 'только что';
  if (diff < 3600000) return `${Math.floor(diff / 60000)} мин. назад`;
  if (diff < 86400000) return d.toLocaleTimeString('ru-RU', { hour: '2-digit', minute: '2-digit' });
  return d.toLocaleDateString('ru-RU', { day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit' });
}

interface NotificationPanelProps {
  isOpen: boolean;
  onClose: () => void;
  unreadCount: number;
  onUnreadCountChange: (count: number) => void;
  onNavigate: (entityType: string, entityId: string) => void;
}

export const NotificationPanel: React.FC<NotificationPanelProps> = ({
  isOpen,
  onClose,
  unreadCount,
  onUnreadCountChange,
  onNavigate,
}) => {
  const [list, setList] = useState<NotificationItem[]>([]);
  const [loading, setLoading] = useState(false);
  const [readAllLoading, setReadAllLoading] = useState(false);

  const fetchList = useCallback(async () => {
    setLoading(true);
    try {
      const data = await backendApi.getNotifications({ limit: 50 });
      setList(Array.isArray(data) ? data : []);
    } catch {
      setList([]);
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => {
    if (isOpen) {
      fetchList();
    }
  }, [isOpen, fetchList]);

  const handleMarkRead = useCallback(
    async (id: number) => {
      try {
        await backendApi.markNotificationRead(id);
        setList((prev) => prev.map((n) => (n.id === id ? { ...n, readAt: new Date().toISOString() } : n)));
        onUnreadCountChange(Math.max(0, unreadCount - 1));
      } catch {
        // ignore
      }
    },
    [unreadCount, onUnreadCountChange]
  );

  const handleReadAll = useCallback(async () => {
    setReadAllLoading(true);
    try {
      await backendApi.markAllNotificationsRead();
      setList((prev) => prev.map((n) => ({ ...n, readAt: n.readAt || new Date().toISOString() })));
      onUnreadCountChange(0);
    } catch {
      // ignore
    } finally {
      setReadAllLoading(false);
    }
  }, [onUnreadCountChange]);

  const handleItemClick = useCallback(
    (item: NotificationItem) => {
      if (item.entityType && item.entityId) {
        onNavigate(item.entityType, item.entityId);
        onClose();
        if (!item.readAt) {
          handleMarkRead(item.id);
        }
      }
    },
    [onNavigate, onClose, handleMarkRead]
  );

  if (!isOpen) return null;

  return (
    <>
      <div className="fixed inset-0 z-40" onClick={onClose} aria-hidden="true" />
      <div
        className="absolute right-0 top-full mt-2 w-80 max-w-[calc(100vw-2rem)] bg-white rounded-xl shadow-2xl border border-slate-200 z-50 animate-fade-in max-h-[70vh] flex flex-col"
        onClick={(e) => e.stopPropagation()}
      >
        <div className="sticky top-0 bg-white rounded-t-xl px-4 py-3 border-b border-slate-100 flex items-center justify-between">
          <h3 className="text-sm font-bold text-slate-800">Уведомления</h3>
          {unreadCount > 0 && (
            <button
              type="button"
              onClick={handleReadAll}
              disabled={readAllLoading}
              className="flex items-center gap-1.5 text-xs font-medium text-primary-600 hover:text-primary-700 disabled:opacity-50"
            >
              {readAllLoading ? <Loader2 className="w-3.5 h-3.5 animate-spin" /> : <CheckCheck className="w-3.5 h-3.5" />}
              Прочитать всё
            </button>
          )}
        </div>
        <div className="overflow-y-auto flex-1 p-2">
          {loading ? (
            <div className="flex items-center justify-center py-8">
              <Loader2 className="w-8 h-8 text-primary-400 animate-spin" />
            </div>
          ) : list.length === 0 ? (
            <div className="py-8 text-center text-slate-500 text-sm">Нет уведомлений</div>
          ) : (
            <ul className="space-y-1">
              {list.map((item) => (
                <li key={item.id}>
                  <button
                    type="button"
                    onClick={() => handleItemClick(item)}
                    className={`w-full text-left px-3 py-2.5 rounded-lg transition-colors ${
                      item.readAt ? 'text-slate-600 hover:bg-slate-50' : 'bg-primary-50/50 text-slate-800 hover:bg-primary-50'
                    }`}
                  >
                    <p className="text-xs font-bold text-slate-900 truncate">{item.title}</p>
                    {item.body && <p className="text-[11px] text-slate-500 mt-0.5 line-clamp-2">{item.body}</p>}
                    <p className="text-[10px] text-slate-400 mt-1">{formatNotificationDate(item.createdAt)}</p>
                  </button>
                </li>
              ))}
            </ul>
          )}
        </div>
      </div>
    </>
  );
};