/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { EventEmitter, Event, Disposable } from 'vscode';

export function filterEvent<T>(event: Event<T>, filter: (e: T) => boolean): Event<T> {
	return (listener, thisArgs = null, disposables?) => event(e => filter(e) && listener.call(thisArgs, e), null, disposables);
}

export function onceEvent<T>(event: Event<T>): Event<T> {
	return (listener, thisArgs = null, disposables?) => {
		const result = event(e => {
			result.dispose();
			return listener.call(thisArgs, e);
		}, null, disposables);

		return result;
	};
}


export interface PromiseAdapter<T, U> {
	(
		value: T,
		resolve:
			(value: U | PromiseLike<U>) => void,
		reject:
			(reason: any) => void
	): any;
}

const passthrough = (value: any, resolve: (value?: any) => void) => resolve(value);

/**
 * Return a promise that resolves with the next emitted event, or with some future
 * event as decided by an adapter.
 *
 * If specified, the adapter is a function that will be called with
 * `(event, resolve, reject)`. It will be called once per event until it resolves or
 * rejects.
 *
 * The default adapter is the passthrough function `(value, resolve) => resolve(value)`.
 *
 * @param event the event
 * @param adapter controls resolution of the returned promise
 * @returns a promise that resolves or rejects as specified by the adapter
 */
export function promiseFromEvent<T, U>(
	event: Event<T>,
	adapter: PromiseAdapter<T, U> = passthrough): { promise: Promise<U>, cancel: EventEmitter<void> } {
	let subscription: Disposable;
	let cancel = new EventEmitter<void>();
	return {
		promise: new Promise<U>((resolve, reject) => {
			cancel.event(_ => reject());
			subscription = event((value: T) => {
				try {
					Promise.resolve(adapter(value, resolve, reject))
						.catch(reject);
				} catch (error) {
					reject(error);
				}
			});
		}).then(
			(result: U) => {
				subscription.dispose();
				return result;
			},
			error => {
				subscription.dispose();
				throw error;
			}
		),
		cancel
	};
}

export function arrayEquals<T>(one: ReadonlyArray<T> | undefined, other: ReadonlyArray<T> | undefined, itemEquals: (a: T, b: T) => boolean = (a, b) => a === b): boolean {
	if (one === other) {
		return true;
	}

	if (!one || !other) {
		return false;
	}

	if (one.length !== other.length) {
		return false;
	}

	for (let i = 0, len = one.length; i < len; i++) {
		if (!itemEquals(one[i], other[i])) {
			return false;
		}
	}

	return true;
}