/*
 * Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.services.dynamodbv2.datamodeling.internal;

import java.io.IOException;
import java.security.SecureRandom;
import java.util.Properties;

public class Utils {
  private static final ThreadLocal<SecureRandom> RND =
      new ThreadLocal<SecureRandom>() {
        @Override
        protected SecureRandom initialValue() {
          final SecureRandom result = new SecureRandom();
          result.nextBoolean(); // Force seeding
          return result;
        }
      };

  private Utils() {
    // Prevent instantiation
  }

  public static SecureRandom getRng() {
    return RND.get();
  }

  public static byte[] getRandom(int len) {
    final byte[] result = new byte[len];
    getRng().nextBytes(result);
    return result;
  }

  public static <V> V checkNotNull(final V ref, final String errMsg) {
    if (ref == null) {
      throw new NullPointerException(errMsg);
    } else {
      return ref;
    }
  }

  /*
   * Loads the version of the library
   */
  public static String loadVersion() {
    try {
      final Properties properties = new Properties();
      final ClassLoader loader = Utils.class.getClassLoader();
      properties.load(loader.getResourceAsStream("project.properties"));
      return properties.getProperty("version");
    } catch (final IOException ex) {
      return "unknown";
    }
  }
}