save bandcamp album tracks to a pls playlist

bandcamp-pls.js

// save bandcamp album tracks to a pls playlist;
// mp3 file urls are protected by a token, so these playlist
// will "expire", but at least one can use a native player;
// still, please do read http://bandcamp.com/help/audio_basics#steal
// and http://bandcamp.com/terms_of_use
//
// ```
// mkdir bandcamp-pls && \
// cd bandcamp-pls && \
// npm init --yes && \
// npm i -SE node-fetch safe-eval filenamify object-get open && \
// mkdir playlists
// ```
const fetch = require('node-fetch')
const safeEval = require('safe-eval')
const filenamify = require('filenamify')
const objectGet = require('object-get')
const open = require('open')
const fs = require('fs')
const path = require('path')
const { promisify } = require('util')
const writeFileAsync = promisify(fs.writeFile)
const targetUrl = process.argv.slice(2).filter(param => param.startsWith('http'))[0] || ''
const openPlaylist = process.argv.includes('--open')

async function main() {
  if (!targetUrl || !targetUrl.includes('bandcamp.com')) {
    throw new Error('usage: node bandcamp-pls (--open) [url]')
  }

  // fetch will use a custom user-agent, which I'm not going to override
  const page = await fetch(targetUrl)
  const text = await page.text()
  const lines = text.split(/\n/)

  let jsonString = []
  let inRange = false
  let successful = false
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i]
    const trimmed = lines[i].trim()
    // search for track and album data global variable
    if (trimmed.startsWith('var TralbumData = {')) {
      jsonString.push('{')
      inRange = true
    }
    if (inRange && /^ {4}[a-z_]*?:/.test(line) && !trimmed.startsWith('//')) {
      jsonString.push(trimmed.replace(/\s+\/\/\s+.*$/gi, ''))
    }
    if (inRange && trimmed === '};') {
      jsonString.push('}')
      jsonString = jsonString.join('')
      successful = true
      break
    }
  }

  if (!successful || !jsonString) {
    throw new Error('!album data not found')
  }

  const albumData = safeEval(jsonString) || {}
  const title = (objectGet(albumData, 'current.title') || 'unknown').trim()
  const description = objectGet(albumData, 'current.credits') || ''
  const defaultPrice = objectGet(albumData, 'current.defaultPrice')
  const setPrice = objectGet(albumData, 'current.set_price')
  const price = defaultPrice || setPrice || 0

  console.info('\n# ' + title)
  if (description) {
    console.info('\n' + description)
  }
  if (price) {
    console.info(`\n_If you like this album, you can have it for $${price}_`)
  }

  const trackInfo = objectGet(albumData, 'trackinfo') || []
  if (!trackInfo.length) {
    throw new Error('!no trackinfo found')
  }
  const output = trackInfo.reduce(
    (playlist, track, i) => {
      const n = i + 1
      const len = Math.round(track.duration * 60)
      const file = track.file['mp3-128']
      const title = track.title
      playlist.push(`File${n}=${file}`)
      playlist.push(`Title${n}=${title}`)
      playlist.push(`Length${n}=${len}`)
      return playlist
    },
    ['[playlist]']
  )
  output.push(`NumberOfEntries=${trackInfo.length}`)
  output.push('Version=2')

  const fileName = filenamify(title.toLocaleLowerCase()) + '.pls'
  const fileNameWithPath = path.resolve(__dirname, './playlists/' + fileName)
  await writeFileAsync(fileNameWithPath, output.join('\n'), 'utf-8')
  console.info(`\n"${fileName}" saved`)

  if (openPlaylist) {
    await open(fileNameWithPath)
  }
}

main().catch((error) => {
  if (error.message.startsWith('!')) {
    console.error(error.message.replace(/^!/, ''))
  } else {
    console.error(error)
  }
})