subtracks/app/storage/music.ts

import { DownloadedSong } from '@app/models/music'
import { getItem, multiGet, multiSet } from '@app/storage/asyncstorage'

const key = {
  downloadedSongKeys: '@downloadedSongKeys',
  downloadedAlbumKeys: '@downloadedAlbumKeys',
  downloadedArtistKeys: '@downloadedArtistKeys',
  downloadedPlaylistKeys: '@downloadedPlaylistKeys',
}

export async function getDownloadedSongs(): Promise<DownloadedSong[]> {
  const keysItem = await getItem(key.downloadedSongKeys)
  const keys: string[] = keysItem ? JSON.parse(keysItem) : []

  const items = await multiGet(keys)
  return items.map(x => {
    const parsed = JSON.parse(x[1] as string)
    return {
      id: x[0],
      type: 'song',
      ...parsed,
    }
  })
}

export async function setDownloadedSongs(items: DownloadedSong[]): Promise<void> {
  await multiSet([
    [key.downloadedSongKeys, JSON.stringify(items.map(x => x.id))],
    ...items.map(x => [
      x.id,
      JSON.stringify({
        name: x.name,
        album: x.album,
        artist: x.artist,
      }),
    ]),
  ])
}