import { writable } from 'svelte/store';
import { get, set } from 'idb-keyval';
import type { VideoThumbnail } from '$lib/api/youtube';

export interface Subscription {
  channelId: string;
  channelName: string;
  thumbnail: string;
}

const STORAGE_KEY = 'actualyt-subscriptions';

function createSubscriptionStore() {
  const { subscribe, set: setStore, update } = writable<Subscription[]>([]);
  let initialized = false;

  async function init() {
    if (initialized) return;
    try {
      const stored = await get<Subscription[]>(STORAGE_KEY);
      if (stored) {
        setStore(stored);
      }
      initialized = true;
    } catch (e) {
      console.error('Failed to load subscriptions:', e);
    }
  }

  async function persist(subs: Subscription[]) {
    try {
      await set(STORAGE_KEY, subs);
    } catch (e) {
      console.error('Failed to save subscriptions:', e);
    }
  }

  return {
    subscribe,
    init,
    add: async (channelId: string, channelName: string, thumbnails: VideoThumbnail[]) => {
      update(subs => {
        if (subs.some(s => s.channelId === channelId)) {
          return subs;
        }
        const thumbnail = thumbnails[0]?.url || '';
        const newSubs = [...subs, { channelId, channelName, thumbnail }];
        persist(newSubs);
        return newSubs;
      });
    },
    remove: async (channelId: string) => {
      update(subs => {
        const newSubs = subs.filter(s => s.channelId !== channelId);
        persist(newSubs);
        return newSubs;
      });
    },
    isSubscribed: (subs: Subscription[], channelId: string): boolean => {
      return subs.some(s => s.channelId === channelId);
    }
  };
}

export const subscriptions = createSubscriptionStore();