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


const _UUIDPattern = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;

export function isUUID(value: string): boolean {
	return _UUIDPattern.test(value);
}

// prep-work
const _data = new Uint8Array(16);
const _hex: string[] = [];
for (let i = 0; i < 256; i++) {
	_hex.push(i.toString(16).padStart(2, '0'));
}

// todo@jrieken
// 1. node nodejs use`crypto#randomBytes`, see: https://nodejs.org/docs/latest/api/crypto.html#crypto_crypto_randombytes_size_callback
let _fillRandomValues: (bucket: Uint8Array) => Uint8Array;

declare const crypto: undefined | { getRandomValues(data: Uint8Array): Uint8Array };

if (typeof crypto === 'object' && typeof crypto.getRandomValues === 'function') {
	// browser
	_fillRandomValues = crypto.getRandomValues.bind(crypto);

} else {
	_fillRandomValues = function (bucket: Uint8Array): Uint8Array {
		for (let i = 0; i < bucket.length; i++) {
			bucket[i] = Math.floor(Math.random() * 256);
		}
		return bucket;
	};
}

export function generateUuid(): string {
	// get data
	_fillRandomValues(_data);

	// set version bits
	_data[6] = (_data[6] & 0x0f) | 0x40;
	_data[8] = (_data[8] & 0x3f) | 0x80;

	// print as string
	let i = 0;
	let result = '';
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += '-';
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += '-';
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += '-';
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += '-';
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	result += _hex[_data[i++]];
	return result;
}