index.js

require('dotenv').config()

const fs = require('fs')
const AWS = require('aws-sdk')
const s3 = new AWS.S3()
const mm = require('musicmetadata')
const async = require('async')
const request = require('request')

exports.handler = function(e, ctx, cb) {
  const record = e.Records[0]

  /**
	 * Types (extensions) that we supported - for now
	 * @type {Array}
	 */
  const supportTypes = ['mp3', 'm4a', 'ogg', 'flac']

  const bucket = record.s3.bucket.name
  const key = decodeURIComponent(record.s3.object.key.replace(/\+/g, ' '))

  // Check the media type.
  const typeMatch = key.match(/\.([^.]*)$/)
  if (!typeMatch) {
    cb('Could not determine the media type.')
    return
  }

  const type = typeMatch[1]
  if (supportTypes.indexOf(type) === -1) {
    cb(`Unsupported media type: ${type}`)
    return
  }

  if (
    record.eventName === 'ObjectCreated:Put' ||
    record.eventName === 'ObjectCreated:CompleteMultipartUpload'
  ) {
    return handlePut(bucket, key, cb)
  } else if (
    record.eventName === 'ObjectRemoved:Delete' ||
    record.eventName === 'ObjectRemoved:DeleteMarkerCreated'
  ) {
    return handleDelete(bucket, key, cb)
  }

  cb(`Unsupported event type: ${record.eventName}`)
}

/**
 * Download the new/modified file from S3, read its tags, and post to Koel.
 * @param  {string}   bucket The bucket name
 * @param  {string}   key    The object key
 * @param  {Function} cb
 * @return {[type]}          [description]
 */
function handlePut(bucket, key, cb) {
  'use strict'

  let tags = {}
  let lyrics = '' // Lyrics is handled differently

  async.waterfall(
    [
      function fetch(next) {
        s3.getObject(
          {
            Bucket: bucket,
            Key: key
          },
          (err, data) => {
            if (err) {
              return cb(`Failed to fetch object from S3: ${err}`)
            }

            // In order to get the duration properly, we must write the buffer to a file.
            const fileName = `/tmp/${Math.random().toString(36)}`
            fs.writeFileSync(fileName, data.Body)
            const parser = mm(
              fs.createReadStream(fileName),
              { duration: true },
              (err, rawTags) => {
                if (err) {
                  console.error(`Error reading tags: ${err}.`)
                  return
                }

                tags = rawTags
                next()
              }
            )

            parser.on('ULT', result => {
              lyrics = result.text
            })
          }
        )
      },

      /**
		 * Format the tags into something Koel can handle.
		 * @param  {Function} next
		 */
      function formatTags(next) {
        tags.lyrics = lyrics
        tags.artist = tags.artist.length ? tags.artist[0] : ''
        tags.albumartist = tags.albumartist.length ? tags.albumartist[0] : ''
        tags.track = tags.track.no

        if (tags.picture.length) {
          tags.cover = {
            extension: tags.picture[0].format,
            data: tags.picture[0].data.toString('base64')
          }
        }
        delete tags.picture

        next()
      },

      function postToKoel() {
        request.post(
          {
            url: `${process.env.KOEL_HOST}/api/os/s3/song`,
            form: {
              bucket,
              key,
              tags,
              appKey: process.env.KOEL_APP_KEY
            }
          },
          err => {
            if (err) {
              console.log(`Error posting to Koel: ${err}.`)
            }
          }
        )
      }
    ],
    function(err) {
      if (err) {
        console.error(`Error: ${err}.`)
      } else {
        console.log(`Successfully sync ${key}`)
      }

      cb(null, 'Successful.')
    }
  )
}

/**
 * Delete a song from Koel.
 * @param  {string}   bucket The bucket name
 * @param  {string}   key    The object key
 * @param  {Function} cb
 */
function handleDelete(bucket, key, cb) {
  request.delete(
    {
      url: `${process.env.KOEL_HOST}/api/os/s3/song`,
      form: {
        bucket,
        key,
        appKey: process.env.KOEL_APP_KEY
      }
    },
    err => {
      if (err) {
        console.log(`Error deleting song from Koel: ${err}.`)
      } else {
        cb(null, 'Successful.')
      }
    }
  )
}