stack-chan

import AudioIn from 'pins/audioin'
import Timer from 'timer'

export default class Microphone {
  recording: boolean

  constructor() {
    this.recording = false
  }

  async record(durationMilliSec = 3000): Promise<ArrayBuffer> {
    if (this.recording) {
      throw new Error('already recording')
    }
    this.recording = true
    const audio = new AudioIn()
    const { sampleRate, numChannels, bitsPerSample } = audio
    const byteRate = sampleRate * numChannels * (bitsPerSample >> 3)
    const contentLength = (durationMilliSec / 1000) * byteRate
    const buffer = new ArrayBuffer(44 + contentLength)
    const view = new DataView(buffer)
    try {
      // set header
      view.setUint8(0, 'R'.charCodeAt(0))
      view.setUint8(1, 'I'.charCodeAt(0))
      view.setUint8(2, 'F'.charCodeAt(0))
      view.setUint8(3, 'F'.charCodeAt(0))
      view.setUint32(4, 36 + contentLength, true)
      view.setUint8(8, 'W'.charCodeAt(0))
      view.setUint8(9, 'A'.charCodeAt(0))
      view.setUint8(10, 'V'.charCodeAt(0))
      view.setUint8(11, 'E'.charCodeAt(0))
      view.setUint8(12, 'f'.charCodeAt(0))
      view.setUint8(13, 'm'.charCodeAt(0))
      view.setUint8(14, 't'.charCodeAt(0))
      view.setUint8(15, ' '.charCodeAt(0))
      view.setUint32(16, 16, true)
      view.setUint16(20, 1, true)
      view.setUint16(22, numChannels, true)
      view.setUint32(24, sampleRate, true)
      view.setUint32(28, byteRate, true)
      view.setUint16(32, (1 * bitsPerSample) >> 3, true)
      view.setUint16(34, bitsPerSample, true)
      view.setUint8(36, 'd'.charCodeAt(0))
      view.setUint8(37, 'a'.charCodeAt(0))
      view.setUint8(38, 't'.charCodeAt(0))
      view.setUint8(39, 'a'.charCodeAt(0))
      view.setUint32(40, contentLength, true)

      const recordSamples = async (durationMilliSec): Promise<void> => {
        const readingsPerSecond = 8
        const sampleCount = Math.floor(audio.sampleRate / readingsPerSecond)
        let samplesRemaining = (durationMilliSec / 1000) * audio.sampleRate

        return new Promise((resolve) => {
          let offset = 44
          Timer.repeat((id) => {
            //@ts-ignore
            audio.read(sampleCount, buffer, offset)
            offset += sampleCount * (bitsPerSample / 8)

            samplesRemaining -= sampleCount
            trace(`${samplesRemaining}\n`)
            if (samplesRemaining <= 0) {
              Timer.clear(id)
              resolve()
            }
          }, 1000 / readingsPerSecond)
        })
      }

      await recordSamples(durationMilliSec)
    } finally {
      this.recording = false
      audio.close()
    }
    return view.buffer
  }
}