Tone.js/Tone/event/Loop.ts

import { ToneEvent } from "./ToneEvent";
import { NormalRange, Positive, Seconds, Time, TransportTime } from "../core/type/Units";
import { ToneWithContext, ToneWithContextOptions } from "../core/context/ToneWithContext";
import { optionsFromArguments } from "../core/util/Defaults";
import { noOp } from "../core/util/Interface";
import { BasicPlaybackState } from "../core/util/StateTimeline";

export interface LoopOptions extends ToneWithContextOptions {
	callback: (time: Seconds) => void;
	interval: Time;
	playbackRate: Positive;
	iterations: number;
	probability: NormalRange;
	mute: boolean;
	humanize: boolean | Time;
}

/**
 * Loop creates a looped callback at the 
 * specified interval. The callback can be 
 * started, stopped and scheduled along
 * the Transport's timeline. 
 * @example
 * import { Loop, Transport } from "tone";
 * const loop = new Loop((time) => {
 * 	// triggered every eighth note. 
 * 	console.log(time);
 * }, "8n").start(0);
 * Transport.start();
 * @category Event
 */
export class Loop extends ToneWithContext<LoopOptions> {

	readonly name: string = "Loop";

	/**
	 * The event which produces the callbacks
	 */
	private _event: ToneEvent;

	/**
	 * The callback to invoke with the next event in the pattern
	 */
	callback: (time: Seconds) => void

	/**
	 * @param callback The callback to invoke at the time.
	 * @param interval The time between successive callback calls. 
	 */
	constructor(callback?: (time: Seconds) => void, interval?: Time);
	constructor(options?: Partial<LoopOptions>);
	constructor() {
		super(optionsFromArguments(Loop.getDefaults(), arguments, ["callback", "interval"]));
		const options = optionsFromArguments(Loop.getDefaults(), arguments, ["callback", "interval"]);

		this._event = new ToneEvent({
			context: this.context,
			callback: this._tick.bind(this),
			loop: true,
			loopEnd: options.interval,
			playbackRate: options.playbackRate,
			probability: options.probability
		});

		this.callback = options.callback;
		// set the iterations
		this.iterations = options.iterations;
	}

	static getDefaults(): LoopOptions {
		return Object.assign(ToneWithContext.getDefaults(), {
			interval: "4n",
			callback: noOp,
			playbackRate: 1,
			iterations: Infinity,
			probability: 1,
			mute: false,
			humanize: false
		});
	}

	/**
	 * Start the loop at the specified time along the Transport's timeline.
	 * @param  time  When to start the Loop.
	 */
	start(time?: TransportTime): this {
		this._event.start(time);
		return this;
	}

	/**
	 * Stop the loop at the given time.
	 * @param  time  When to stop the Loop.
	 */
	stop(time?: TransportTime): this{
		this._event.stop(time);
		return this;
	}

	/**
	 * Cancel all scheduled events greater than or equal to the given time
	 * @param  time  The time after which events will be cancel.
	 */
	cancel(time?: TransportTime): this{
		this._event.cancel(time);
		return this;
	}

	/**
	 * Internal function called when the notes should be called
	 * @param time  The time the event occurs
	 */
	private _tick(time: Seconds) {
		this.callback(time);
	}

	/**
	 * The state of the Loop, either started or stopped.
	 */
	get state(): BasicPlaybackState {
		return this._event.state;
	}

	/**
	 * The progress of the loop as a value between 0-1. 0, when the loop is stopped or done iterating. 
	 */
	get progress(): NormalRange {
		return this._event.progress;
	}

	/**
	 * The time between successive callbacks. 
	 * @example
	 * import { Loop, Transport } from "tone";
	 * const loop = new Loop();
	 * loop.interval = "8n"; // loop every 8n
	 */
	get interval(): Time {
		return this._event.loopEnd;
	}
	set interval(interval) {
		this._event.loopEnd = interval;
	}

	/**
	 * The playback rate of the loop. The normal playback rate is 1 (no change). 
	 * A `playbackRate` of 2 would be twice as fast. 
	 */
	get playbackRate(): Positive {
		return this._event.playbackRate;
	}
	set playbackRate(rate) {
		this._event.playbackRate = rate;
	}

	/**
	 * Random variation +/-0.01s to the scheduled time. 
	 * Or give it a time value which it will randomize by.
	 */
	get humanize(): boolean | Time {
		return this._event.humanize;
	}
	set humanize(variation) {
		this._event.humanize = variation;
	}

	/**
	 * The probably of the callback being invoked.
	 */
	get probability(): NormalRange {
		return this._event.probability;
	}

	set probability(prob) {
		this._event.probability = prob;
	}

	/**
	 * Muting the Loop means that no callbacks are invoked.
	 */
	get mute(): boolean {
		return this._event.mute;
	}

	set mute(mute) {
		this._event.mute = mute;
	}

	/**
	 * The number of iterations of the loop. The default value is `Infinity` (loop forever).
	 */
	get iterations(): number {
		if (this._event.loop === true) {
			return Infinity;
		} else {
			return this._event.loop as number;
		}
	}
	set iterations(iters) {
		if (iters === Infinity) {
			this._event.loop = true;
		} else {
			this._event.loop = iters;
		}
	}

	dispose(): this{
		super.dispose();
		this._event.dispose();
		return this;
	}
}