btrtracks/src/lastfm.js

import path from 'path'
import asn from './common/async'
import dl from './common/download'
import crypto from 'crypto'

const fs = require('fs').promises
const values = require(path.join(process.cwd(), 'values.json'))
const memexpire = 1800

let externalTracks = {}
let downloadQueue = []
let downloading = false
let dbPromise

function createHash (data) {
  return crypto
    .createHash('sha1')
    .update(data.artist + data.name)
    .digest('hex')
    .substr(0, 8)
}

async function downloadLocally (id) {
  let info = await getTrackMetaReal(id)
  if (!info) throw new Error('No track with this ID in external list.')
  let file = await dl.fetchVideo(info)
  let filename = info.artist + ' - ' + info.title + '.mp3'
  info.file = path.join(values.directory, filename)
  await asn.promiseExec(`ffmpeg -i "${file.source}" -metadata artist="${info.artist}" -metadata title="${info.title}" -codec copy "${info.file}"`)
  await fs.unlink(file.source)
  let db = await dbPromise
  let ins = await asn.insertDB(db, info)
  if (!ins) {
    throw new Error('A track of this description already exists in the database.')
  }
}

async function getTrackMetaReal (id) {
  if (!id || !externalTracks[id]) return null
  let trdata = externalTracks[id]

  // Check for expiry
  if (trdata.file && trdata.expires > Date.now()) {
    return Object.assign({}, trdata)
  }

  let trsrch = 'ytsearch3:' + trdata.artist + ' - ' + trdata.title
  let dldata = await dl.getVideoInfo(trsrch)

  let bestMatch
  if (dldata.length === 1) bestMatch = dldata[0]

  let candidates = []
  for (let i in dldata) {
    let obj = dldata[i]
    let title = obj.title.toLowerCase()

    // Skip any video with 'video' in it, but keep lyric videos
    if (title.indexOf('video') !== -1 && title.indexOf('lyric') === -1) continue

    // If the title has 'audio' in it, it might be the best match
    if (title.indexOf('audio') !== -1) {
      bestMatch = obj
      break
    }

    candidates.push(obj)
  }

  if (candidates.length && !bestMatch) {
    // Sort candidates by view count
    candidates = candidates.sort(function (a, b) {
      return b.view_count - a.view_count
    })

    // Select the one with the most views
    bestMatch = candidates[0]
  }

  // If there were no suitable candidates, just take the first response
  if (!candidates.length && !bestMatch) bestMatch = dldata[0]

  externalTracks[id] = {
    id: trdata.id,
    title: trdata.title,
    artist: trdata.artist,
    file: bestMatch.url,
    duration: bestMatch.duration,
    expires: Date.now() + memexpire * 1000,
    external: true
  }

  return Object.assign({}, externalTracks[id])
}

async function search (track, limit = 30) {
  if (!values.lastfm) return []

  let data
  try {
    data = await asn.GET(`http://ws.audioscrobbler.com/2.0/?method=track.search&track=${track}&api_key=${values.lastfm}&format=json&limit=${limit}`)
    data = JSON.parse(data)

    if (!data.results || !data.results.trackmatches || !data.results.trackmatches.track) {
      throw new Error('No results')
    }
  } catch (e) {
    return []
  }

  let final = []
  for (let i in data.results.trackmatches.track) {
    let res = data.results.trackmatches.track[i]
    let clean = {
      id: createHash(res),
      artist: res.artist,
      title: res.name,
      external: true,
      mbid: res.mbid
    }

    if (externalTracks[clean.id]) {
      // Copy object
      clean = Object.assign({}, externalTracks[clean.id])
    } else {
      // Save in cache
      externalTracks[clean.id] = clean
    }

    final.push(clean)
  }

  return final
}

// Download thread
let dltd = null
function invokeDownload (add) {
  if (add) downloadQueue.push(add)
  if (dltd) return
  dltd = setTimeout(function (argument) {
    dltd = null
    if (downloading) return invokeDownload()
    if (!downloadQueue.length) return
    downloading = true
    downloadLocally(downloadQueue.shift()).then(() => {
      downloading = false
      if (downloadQueue.length) invokeDownload()
    }).catch((e) => {
      console.error(e)
      downloading = false
      if (downloadQueue.length) invokeDownload()
    })
  }, 2 * 1000)
}

export default function (db) {
  dbPromise = db
  return { search, getTrackMetaReal, invokeDownload }
}