import { useState, useEffect } from 'react';

const STORAGE_KEY = 'emberclone_favorites';
const FAVORITES_EVENT = 'emberclone_favorites_updated';

export const favoritesUtils = {
  getFavorites: (): Record<string, Set<string>> => {
    const data = localStorage.getItem(STORAGE_KEY);
    if (!data) return {};
    try {
      const parsed = JSON.parse(data);
      const result: Record<string, Set<string>> = {};
      for (const [type, ids] of Object.entries(parsed)) {
        result[type] = new Set(ids as string[]);
      }
      return result;
    } catch {
      return {};
    }
  },

  saveFavorites: (favorites: Record<string, Set<string>>) => {
    const data: Record<string, string[]> = {};
    for (const [type, ids] of Object.entries(favorites)) {
      data[type] = Array.from(ids);
    }
    localStorage.setItem(STORAGE_KEY, JSON.stringify(data));
    window.dispatchEvent(new CustomEvent(FAVORITES_EVENT));
  },

  isFavorite: (type: string, id: string): boolean => {
    const favs = favoritesUtils.getFavorites();
    return favs[type]?.has(id) ?? false;
  },

  toggleFavorite: (type: string, id: string) => {
    const favs = favoritesUtils.getFavorites();
    if (!favs[type]) {
      favs[type] = new Set();
    }

    if (favs[type].has(id)) {
      favs[type].delete(id);
    } else {
      favs[type].add(id);
    }

    favoritesUtils.saveFavorites(favs);
  },

  getAllFavorites: (type: string): string[] => {
    const favs = favoritesUtils.getFavorites();
    return Array.from(favs[type] || []);
  }
};

export function useFavorites() {
  const [favorites, setFavorites] = useState(() => favoritesUtils.getFavorites());

  useEffect(() => {
    const handleUpdate = () => {
      setFavorites(favoritesUtils.getFavorites());
    };

    window.addEventListener(FAVORITES_EVENT, handleUpdate);
    return () => window.removeEventListener(FAVORITES_EVENT, handleUpdate);
  }, []);

  const isFavorite = (type: string, id: string) => {
    return favorites[type]?.has(id) ?? false;
  };

  const toggle = (type: string, id: string) => {
    favoritesUtils.toggleFavorite(type, id);
  };

  const getAll = (type: string) => {
    return Array.from(favorites[type] || []);
  };

  return {
    isFavorite,
    toggle,
    getAll,
    favorites
  };
}