"use strict";

// Dedicated audio output thread
class AudioThread extends AudioWorkletProcessor {

    ///////////////////////// Initialization Methods //////////////////////////

    constructor() {
        super();

        // Configure instance fields
        this.buffers = []; // Input sample buffer queue
        this.offset  = 0;  // Offset into oldest buffer

        // Wait for initializer message from parent thread
        this.port.onmessage = m=>this.init(m.data);
    }

    async init(main) {

        // Configure message ports
        this.core           = this.port;
        this.core.onmessage = m=>this.onCore(m.data);
        this.main           = main;
        this.main.onmessage = m=>this.onMain(m.data);

        // Notify main thread
        this.port.postMessage(0);
    }



    ///////////////////////////// Public Methods //////////////////////////////

    // Produce output samples (called by the user agent)
    process(inputs, outputs, parameters) {
        let output = outputs[0];
        let length = output [0].length;
        let empty  = null;

        // Process all samples
        for (let x = 0; x < length;) {

            // No bufferfed samples are available
            if (this.buffers.length == 0) {
                for (; x < length; x++)
                    output[0] = output[1] = 0;
                break;
            }

            // Transfer samples from the oldest buffer
            let y, buffer = this.buffers[0];
            for (y = this.offset; x < length && y < buffer.length; x++, y+=2) {
                output[0][x] = buffer[y    ];
                output[1][x] = buffer[y + 1];
            }

            // Advance to the next buffer
            if ((this.offset = y) == buffer.length) {
                if (empty == null)
                    empty = [];
                empty.push(this.buffers.shift());
                this.offset = 0;
            }

        }

        // Return emptied sample buffers to the core thread
        if (empty != null)
            this.core.postMessage(empty, empty.map(e=>e.buffer));

        return true;
    }



    ///////////////////////////// Message Methods /////////////////////////////

    // Message received from core thread
    onCore(msg) {
    }

    // Message received from main thread
    onMain(msg) {
    }

}
registerProcessor("AudioThread", AudioThread);