async begin()

in 9-realtime/openai-realtime-console-example/src/lib/wavtools/lib/wav_recorder.js [301:381]
77 lines of code
12 McCabe index (conditional complexity)

  async begin(deviceId) {
    if (this.processor) {
      throw new Error(
        `Already connected: please call .end() to start a new session`,
      );
    }

    if (
      !navigator.mediaDevices ||
      !('getUserMedia' in navigator.mediaDevices)
    ) {
      throw new Error('Could not request user media');
    }
    try {
      const config = { audio: true };
      if (deviceId) {
        config.audio = { deviceId: { exact: deviceId } };
      }
      this.stream = await navigator.mediaDevices.getUserMedia(config);
    } catch (err) {
      throw new Error('Could not start media stream');
    }

    const context = new AudioContext({ sampleRate: this.sampleRate });
    const source = context.createMediaStreamSource(this.stream);
    // Load and execute the module script.
    try {
      await context.audioWorklet.addModule(this.scriptSrc);
    } catch (e) {
      console.error(e);
      throw new Error(`Could not add audioWorklet module: ${this.scriptSrc}`);
    }
    const processor = new AudioWorkletNode(context, 'audio_processor');
    processor.port.onmessage = (e) => {
      const { event, id, data } = e.data;
      if (event === 'receipt') {
        this.eventReceipts[id] = data;
      } else if (event === 'chunk') {
        if (this._chunkProcessorSize) {
          const buffer = this._chunkProcessorBuffer;
          this._chunkProcessorBuffer = {
            raw: WavPacker.mergeBuffers(buffer.raw, data.raw),
            mono: WavPacker.mergeBuffers(buffer.mono, data.mono),
          };
          if (
            this._chunkProcessorBuffer.mono.byteLength >=
            this._chunkProcessorSize
          ) {
            this._chunkProcessor(this._chunkProcessorBuffer);
            this._chunkProcessorBuffer = {
              raw: new ArrayBuffer(0),
              mono: new ArrayBuffer(0),
            };
          }
        } else {
          this._chunkProcessor(data);
        }
      }
    };

    const node = source.connect(processor);
    const analyser = context.createAnalyser();
    analyser.fftSize = 8192;
    analyser.smoothingTimeConstant = 0.1;
    node.connect(analyser);
    if (this.outputToSpeakers) {
      // eslint-disable-next-line no-console
      console.warn(
        'Warning: Output to speakers may affect sound quality,\n' +
          'especially due to system audio feedback preventative measures.\n' +
          'use only for debugging',
      );
      analyser.connect(context.destination);
    }

    this.source = source;
    this.node = node;
    this.analyser = analyser;
    this.processor = processor;
    return true;
  }