/*
 * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
 * SPDX-License-Identifier: AGPL-3.0-only
 */

import { Injectable } from '@nestjs/common';
import { TimeService, Timer } from '@/core/TimeService.js';

/**
 * Fake implementation of TimeService that allows manual control of time.
 * When this service is used, the flow of time is fully stopped.
 *
 * Test cases can manually adjust the "now" parameter to move time forwards and backwards.
 * When moving forward, timers (interval and timeout) will automatically fire as appropriate.
 */
@Injectable()
export class GodOfTimeService extends TimeService<GodsOwnTimer> {
	private _now = 0;

	constructor() {
		super();
	}

	/**
	 * Get or set the current time, in milliseconds since the unix epoch.
	 */
	public get now() {
		return this._now;
	}
	public set now(value: number) {
		// Moving backwards is allowed, for now.
		if (value > this._now) {
			// Fire all expiring timers in chronological order.
			const expiringTimers = this.timers
				.values()
				.filter(t => t.expiresAt >= value)
				.toArray()
				.sort((a, b) => a.expiresAt - b.expiresAt);

			// Since we sorted the list, this will progressively increase "now" as we handle later and later events.
			for (const timer of expiringTimers) {
				// When the timer fires, "now" should equal the time that was originally waited for.
				this._now = timer.expiresAt;

				// Cleanup first in case timer throws an exception.
				this.timers.delete(timer.timerId);
				timer.callback();
			}
		}

		// Bump up to the final target value
		this._now = value;
	}

	/**
	 * Clears all timers and resets to time=0.
	 */
	public reset() {
		this.resetTo(0);
	}
	/**
	 * Clears all timers and resets to the real-world time.
	 */
	public resetToNow() {
		this.resetTo(Date.now());
	}

	/**
	 * Clears all timers and resets to a given time.
	 */
	public resetTo(to: number) {
		this.timers.clear();
		this.now = to;
	}

	protected startNativeTimer(timerId: symbol, repeating: boolean, callback: () => void, delay: number): GodsOwnTimer {
		const expiresAt = this.now + delay;
		return { timerId, repeating, delay, expiresAt, callback };
	}

	protected stopNativeTimer(): void {
		// no-op - fake timers have no side effects to clean up
	}
}

export interface GodsOwnTimer extends Timer {
	expiresAt: number;
}