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

import * as path from 'path';
import * as crypto from 'crypto';
import * as os from 'os';

export function ensure(target: object, key: string): any {
	if (target[key] === void 0) {
		target[key] = {} as any;
	}
	return target[key];
}

export function generateUserId(): Promise<string> {
	return new Promise<string>(resolve => {
		try {
			let interfaces = os.networkInterfaces();
			let mac;
			for (let key of Object.keys(interfaces)) {
				let item = interfaces[key][0];
				if (!item.internal) {
					mac = item.mac;
					break;
				}
			}
			if (mac) {
				resolve(crypto.createHash('sha256').update(mac + os.homedir(), 'utf8').digest('hex'));
			} else {
				resolve(generateGuid());
			}
		} catch (err) {
			resolve(generateGuid()); // fallback
		}
	});
}

export function generateGuid(): string {
	let hexValues: string[] = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'];
	// c.f. rfc4122 (UUID version 4 = xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx)
	let oct: string = '';
	let tmp: number;
	/* tslint:disable:no-bitwise */
	for (let a: number = 0; a < 4; a++) {
		tmp = (4294967296 * Math.random()) | 0;
		oct += hexValues[tmp & 0xF] +
			hexValues[tmp >> 4 & 0xF] +
			hexValues[tmp >> 8 & 0xF] +
			hexValues[tmp >> 12 & 0xF] +
			hexValues[tmp >> 16 & 0xF] +
			hexValues[tmp >> 20 & 0xF] +
			hexValues[tmp >> 24 & 0xF] +
			hexValues[tmp >> 28 & 0xF];
	}

	// 'Set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to zero and one, respectively'
	let clockSequenceHi: string = hexValues[8 + (Math.random() * 4) | 0];
	return oct.substr(0, 8) + '-' + oct.substr(9, 4) + '-4' + oct.substr(13, 3) + '-' + clockSequenceHi + oct.substr(16, 3) + '-' + oct.substr(19, 12);
	/* tslint:enable:no-bitwise */
}
