import { dbPromise } from './database'

async function getPlaylist (id, order = 'ntry.indx', direction = 'ASC') {
  const db = await dbPromise
  const p = await db.get('SELECT * FROM Playlist WHERE id = ?', id)
  if (!p) throw new Error('No such playlist!')
  const q = await db.all(`SELECT ntry.id,ntry.trackId,ntry.playlistId,ntry.indx,ntry.userId,
    trck.title,trck.artist,trck.genre,trck.year,trck.duration,trck.track,trck.album
    FROM PlaylistEntry ntry INNER JOIN Track
    trck ON ntry.trackId = trck.id WHERE ntry.playlistId = ? ORDER BY ${order} ${direction}`, id)
  p.tracks = q || []
  return p
}

async function getPlaylists (userId) {
  const db = await dbPromise
  return db.all('SELECT * FROM Playlist WHERE userId = ? OR userId = NULL', userId)
}

async function createPlaylist (userId, title) {
  const db = await dbPromise
  const alreadyExists = await db.get('SELECT * FROM Playlist WHERE userId = ? AND title = ?', userId, title)
  if (alreadyExists) throw new Error('Playlist with the same name already exists!')
  await db.run('INSERT INTO Playlist (title,userId) VALUES (?,?)', title, userId)
  return db.get('SELECT id FROM Playlist WHERE title = ? AND userId = ?', title, userId)
}

async function deletePlaylist (userId, playlistId) {
  const db = await dbPromise
  const ply = await db.get('SELECT * FROM Playlist WHERE id = ?', playlistId)
  if (!ply) throw new Error('Could not find playlist specified.')
  if (ply.userId !== userId) throw new Error(ply.userId == null ? 'This public playlist cannot be deleted through the interface.' : 'Permission denied.')
  db.run('DELETE Playlist WHERE id = ?', playlistId)
  db.run('DELETE PlaylistEntry WHERE playlistId = ?', playlistId)
  return true
}

async function addTrack (userId, playlistId, trackId) {
  const db = await dbPromise
  const p = await getPlaylist(playlistId)
  if (!p) throw new Error('Invalid playlist.')
  if (p.userId != null && p.userId !== userId) throw new Error('Permission denied.')

  let alreadyExists = false
  for (const i in p.tracks) {
    const tr = p.tracks[i]
    if (tr.trackId === parseInt(trackId)) {
      alreadyExists = true
      break
    }
  }

  if (alreadyExists) throw new Error('This track is already in the playlist.')

  return db.run('INSERT INTO PlaylistEntry (playlistId,trackId,userId,indx) VALUES (?,?,?,?)', playlistId, trackId, userId, p.tracks.length)
}

async function removeTrack (userId, playlistId, trackId) {
  const db = await dbPromise
  const p = await getPlaylist(playlistId)
  if (!p) throw new Error('Invalid playlist.')
  if (p.userId != null && p.userId !== userId) throw new Error('Permission denied.')

  const trackEntry = await db.get('SELECT * FROM PlaylistEntry WHERE playlistId = ? AND trackId = ?', playlistId, trackId)
  if (!trackEntry) throw new Error('This track is not in the playlist.')

  return db.run('DELETE FROM PlaylistEntry WHERE id = ?', trackEntry.id)
}

async function moveTrack (userId, playlistId, trackId, position) {
  const db = await dbPromise
  const p = await getPlaylist(playlistId)
  if (!p) throw new Error('Invalid playlist.')
  if (p.userId != null && p.userId !== userId) throw new Error('Permission denied.')

  const trackEntry = await db.get('SELECT * FROM PlaylistEntry WHERE playlistId = ? AND trackId = ?', playlistId, trackId)
  if (!trackEntry) throw new Error('This track is not in the playlist.')

  const trcksNew = []
  for (const i in p.tracks) {
    const trck = p.tracks[i]
    if (trck.trackId === trackId) {
      trck.indx = position
      continue
    }
    if (trck.indx >= position) {
      trck.indx++
    }
    trcksNew.push(trck)
  }

  // Update indexes
  for (const i in trcksNew) {
    const trck = trcksNew[i]
    await db.run('UPDATE PlaylistEntry SET indx = ? WHERE trackId = ? AND playlistId = ?', trck.indx, trck.trackId, playlistId)
  }

  return true
}

export { getPlaylist, getPlaylists, createPlaylist, deletePlaylist, addTrack, removeTrack, moveTrack }