/*
 * Copyright Terracotta, Inc.
 *
 * 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
 *
 *     http://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.
 */
package org.terracotta.dynamic_config.api.model;

import java.util.Base64;
import java.util.UUID;

/**
 * @author Mathieu Carbou
 */
class Uuid {

  static String generateShortUuid() {
    UUID uuid = UUID.randomUUID();
    byte[] data = new byte[16];
    long msb = uuid.getMostSignificantBits();
    long lsb = uuid.getLeastSignificantBits();
    for (int i = 0; i < 8; i++) {
      data[i] = (byte) (msb & 0xff);
      msb >>>= 8;
    }
    for (int i = 8; i < 16; i++) {
      data[i] = (byte) (lsb & 0xff);
      lsb >>>= 8;
    }
    return Base64.getEncoder().encodeToString(data)
        // java-8 and other - compatible B64 url decoder use - and _ instead of + and /
        // padding can be ignored to shorten the UUID
        .replace('+', '-')
        .replace('/', '_')
        .replace("=", "");
  }

}