const AV = require('leanengine')

const ffmpeg = require('fluent-ffmpeg')

const fs = require('fs')

const os = require('os')

const path = require('path')

const request = require('request')

/*

* 使用 ffmpeg 将 amr 音频转码为 mp3

*

* 安装依赖：

*

* npm install fluent-ffmpeg request

*

* 在 `leanengine.yaml` 中添加：

*

* systemDependencies:

* - ffmpeg

*

*/

/*

* 参数的 file 字段接受一个 AV.File（amr 音频）

* 返回一个新的 AV.File（mp3 音频）

*/

AV.Cloud.define('amrToMp3', async request => {

const amrPath = await downloadFile(request.params.file)

const mp3Path = path.join(path.dirname(amrPath), path.basename('.amr') + '.mp3')

await new Promise( (resolve, reject) => {

ffmpeg(amrPath)

.format('mp3')

.on('end', () => resolve() )

.on('error', err => reject(err) )

.save(mp3Path)

})

const newFileName = path.basename(request.params.file.get('name'), '.amr') + '.mp3'

const mp3File = await new AV.File(newFileName, fs.createReadStream(mp3Path)).save()

await fs.promises.unlink(amrPath)

await fs.promises.unlink(mp3Path)

return mp3File

})

function downloadFile(file) {

return new Promise( (resolve, reject) => {

const filepath = `${os.tmpdir()}${file.id}.amr`

request(file.get('url')).pipe(fs.createWriteStream(filepath))

.on('close', () => resolve(filepath) )

.on('error', err => reject(err) )

})

}