class DemoWasmProcessor extends AudioWorkletProcessor {
  constructor(options) {
    super(options)

    // Instantiate the WebAssembly module loaded in the main js code.
    const wasmData = options.processorOptions.wasmData
    WebAssembly.instantiate(wasmData).then(wasm => {
      this.onWasmInstantiated(wasm.instance)
    }).catch((error) => {
      console.error(error)
    })

    this.port.onmessage = e => {
      switch (e.data.type) {
        case "toggleTone": {
          if (this.wasm) {
            this.wasm.exports.toggle_tone()
          }
          break
        }
      }
    }
  }

  onWasmInstantiated(wasm) {
    this.wasm = wasm

    // Audio worklets seem to use a fixed buffer size of 128
    const bufferSize = 128

    // Allocate sample buffers that can be passed to the wasm code
    this.inBufferPointer = this.wasm.exports.allocate_f32_array(bufferSize)
    this.outBufferPointer = this.wasm.exports.allocate_f32_array(bufferSize)
    this.inBuffer = new Float32Array(
      this.wasm.exports.memory.buffer,
      this.inBufferPointer,
      bufferSize
    )
    this.outBuffer = new Float32Array(
      this.wasm.exports.memory.buffer,
      this.outBufferPointer,
      bufferSize
    )

    const toneGeneratorFrequency = 600;
    this.wasm.exports.init(sampleRate, toneGeneratorFrequency)
  }

  process(inputs, outputs, parameters) {
    if (!this.wasm) {
      return true
    }

    if (inputs.length > 0) {
      const inputChannels = inputs[0]
      if (inputChannels.length > 0) {
        // Copy input samples to the wasm input buffer
        this.inBuffer.set(inputChannels[0])
        // Do processing on the input buffer
        const maxLevel = this.wasm.exports.buffer_max_level(this.inBufferPointer, this.inBuffer.length)
        this.port.postMessage({ type: "maxLevel", value: maxLevel })
      }
    }

    // Render output into the wasm output buffer
    this.wasm.exports.render(this.outBufferPointer, this.outBuffer.length)
    // Copy rendered samples to each channel
    const outputChannels = outputs[0]
    for (let channel = 0; channel < outputChannels.length; ++channel) {
      outputChannels[channel].set(this.outBuffer)
    }

    return true
  }
}

registerProcessor('demo-wasm-processor', DemoWasmProcessor)