@doc.e.dub/csound-browser/src/mains/messages.main.js

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// exec log-event: msg => cb(msg)
export const messageEventHandler = (worker) => (event) => {
  if (event.data.log) {
    if (worker && worker.publicEvents && worker.publicEvents.triggerMessage) {
      worker.publicEvents.triggerMessage(event.data.log);
    } else {
      // in case of errors, this can happen
      // in which case, it's good to see the log
      console.log(event.data.log);
    }
  } else if (event.data.sabWorker && worker && worker.hasSharedArrayBuffer) {
    if (event.data.sabWorker === "unlocked" && typeof worker.startPromiz === "function") {
      worker.startPromiz();
    }
  } else if (event.data.playStateChange && worker && worker.onPlayStateChange) {
    worker.onPlayStateChange(event.data.playStateChange);
  }
};

const iterableMessageChannel = () => {
  const { port1, port2 } = new MessageChannel();
  return [port1, port2];
};

const safelyClosePorts = ([p1, p2]) => {
  if (typeof p1.close !== "undefined") {
    try {
      p1.close();
      // eslint-disable unicorn/prefer-optional-catch-binding
    } catch (_) {}
  }
  if (typeof p2.close !== "undefined") {
    try {
      p2.close();
      // eslint-disable unicorn/prefer-optional-catch-binding
    } catch (_) {}
  }
};

export class IPCMessagePorts {
  constructor() {
    const { port1: mainMessagePort, port2: workerMessagePort } = new MessageChannel();
    this.mainMessagePort = mainMessagePort;
    this.workerMessagePort = workerMessagePort;
    const { port1: mainMessagePortAudio, port2: workerMessagePortAudio } = new MessageChannel();
    this.mainMessagePortAudio = mainMessagePortAudio;
    this.workerMessagePortAudio = workerMessagePortAudio;
    const {
      port1: csoundWorkerFrameRequestPort,
      port2: audioWorkerFrameRequestPort,
    } = new MessageChannel();
    this.csoundWorkerFrameRequestPort = csoundWorkerFrameRequestPort;
    this.audioWorkerFrameRequestPort = audioWorkerFrameRequestPort;
    const {
      port1: csoundWorkerAudioInputPort,
      port2: audioWorkerAudioInputPort,
    } = new MessageChannel();
    this.csoundWorkerAudioInputPort = csoundWorkerAudioInputPort;
    this.audioWorkerAudioInputPort = audioWorkerAudioInputPort;
    const { port1: csoundWorkerRtMidiPort, port2: csoundMainRtMidiPort } = new MessageChannel();
    this.csoundWorkerRtMidiPort = csoundWorkerRtMidiPort;
    this.csoundMainRtMidiPort = csoundMainRtMidiPort;

    const { port1: sabWorkerCallbackReply, port2: sabMainCallbackReply } = new MessageChannel();
    this.sabWorkerCallbackReply = sabWorkerCallbackReply;
    this.sabMainCallbackReply = sabMainCallbackReply;

    const { port1: mainFilesystemPort, port2: workerFilesystemPort } = new MessageChannel();
    this.mainFilesystemPort = mainFilesystemPort;
    this.workerFilesystemPort = workerFilesystemPort;

    this.restartAudioWorkerPorts = this.restartAudioWorkerPorts.bind(this);
  }

  restartAudioWorkerPorts() {
    safelyClosePorts([this.csoundWorkerAudioInputPort, this.audioWorkerAudioInputPort]);
    [this.csoundWorkerAudioInputPort, this.audioWorkerAudioInputPort] = iterableMessageChannel();

    safelyClosePorts([this.mainMessagePortAudio, this.workerMessagePortAudio]);
    [this.mainMessagePortAudio, this.workerMessagePortAudio] = iterableMessageChannel();

    safelyClosePorts([this.csoundWorkerFrameRequestPort, this.audioWorkerFrameRequestPort]);
    [
      this.csoundWorkerFrameRequestPort,
      this.audioWorkerFrameRequestPort,
    ] = iterableMessageChannel();
  }
}