Tone.js/Tone/core/util/StateTimeline.ts

// import "../type/Type";
import { Timeline, TimelineEvent } from "./Timeline";

export type PlaybackState = "started" | "stopped" | "paused";

export interface StateTimelineEvent extends TimelineEvent {
	state: PlaybackState;
	duration?: Seconds;
	offset?: Seconds;
	/**
	 * Either the buffer is explicitly scheduled to end using the stop method,
	 * or it's implicitly ended when the buffer is over.
	 */
	implicitEnd?: boolean;
}

/**
 *  A Timeline State. Provides the methods: `setStateAtTime("state", time)` and `getValueAtTime(time)`
 *  @param initial The initial state of the StateTimeline.  Defaults to `undefined`
 */
export class StateTimeline extends Timeline<StateTimelineEvent> {

	/**
	 *  The initial state
	 */
	private _initial: PlaybackState;

	constructor(initial: PlaybackState = "stopped") {
		super();
		this._initial = initial;
	}

	/**
	 *  Returns the scheduled state scheduled before or at
	 *  the given time.
	 *  @param  time  The time to query.
	 *  @return  The name of the state input in setStateAtTime.
	 */
	getValueAtTime(time: Seconds): PlaybackState {
		const event = this.get(time);
		if (event !== null) {
			return event.state;
		} else {
			return this._initial;
		}
	}

	/**
	 *  Add a state to the timeline.
	 *  @param  state The name of the state to set.
	 *  @param  time  The time to query.
	 */
	setStateAtTime(state: PlaybackState, time: Seconds): this {
		// all state changes need to be >= the previous state time
		// TODO throw error if time < the previous event time
		this.add({
			state,
			time,
		});
		return this;
	}

	/**
	 *  Return the event before the time with the given state
	 *  @param  state The state to look for
	 *  @param  time  When to check before
	 *  @return  The event with the given state before the time
	 */
	getLastState(state: PlaybackState, time: number): StateTimelineEvent | undefined {
		// time = this.toSeconds(time);
		const index = this._search(time);
		for (let i = index; i >= 0; i--) {
			const event = this._timeline[i];
			if (event.state === state) {
				return event;
			}
		}
	}

	/**
	 *  Return the event after the time with the given state
	 *  @param  state The state to look for
	 *  @param  time  When to check from
	 *  @return  The event with the given state after the time
	 */
	getNextState(state: PlaybackState, time: number): StateTimelineEvent | undefined {
		// time = this.toSeconds(time);
		const index = this._search(time);
		if (index !== -1) {
			for (let i = index; i < this._timeline.length; i++) {
				const event = this._timeline[i];
				if (event.state === state) {
					return event;
				}
			}
		}
	}
}