/**
 *  Copyright 2026 Angus.Fenying <fenying@litert.org>
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *    https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

import { uuidToString } from './Utils.js';

/**
 * The class for generating UUID in version 4.
 */
export class Uuid4Generator {

    /**
     * Generate a UUIDv4 string.
     *
     * @returns A UUIDv4 string.
     */
    public generate(): string {

        return uuidToString(this.generateAsBuffer());
    }

    /**
     * Generate a UUIDv4 as a 16-byte buffer.
     *
     * @returns A 16-byte buffer representing the UUIDv4.
     */
    public generateAsBuffer(): Buffer {

        const buffer = Buffer.allocUnsafe(16);

        for (let i = 0; i < 4; i++) {
            buffer.writeUInt32BE(Math.floor(Math.random() * 0x100000000), i * 4);
        }

        buffer[6] = (buffer[6] & 0x0F) | 0x40; // Set version to 4
        buffer[8] = (buffer[8] & 0x3F) | 0x80; // Set variant to 10

        return buffer;
    }
}