/*
    * License : The MIT License
    * Copyright(c) 2022 olyutorskii
    */
   
   package io.github.olyutorskii.aletojio.shrink;
   
   import io.github.olyutorskii.aletojio.rng.RndInt32;
   import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Objects;
  
  /**
   * Mixing entropy of N random number streams by XOR.
   *
   * <p>Random number output throughput decreases {@code 1/N}.
   */
  @SuppressWarnings("serial")
  public class XorMixer implements RndInt32 {
  
      private final Collection<RndInt32> rnds;
  
  
      /**
       * Constructor.
       *
       * @param rndColl random streams
       * @throws NullPointerException argument or stream is null
       * @throws IllegalArgumentException no stream
       */
      public XorMixer(Collection<RndInt32> rndColl)
              throws NullPointerException, IllegalArgumentException {
          super();
          Objects.requireNonNull(rndColl);
  
          if (rndColl.isEmpty()) {
              throw new IllegalArgumentException();
          }
  
          for (RndInt32 rnd : rndColl) {
              Objects.requireNonNull(rnd);
          }
  
          this.rnds = new ArrayList<>(rndColl);
  
          return;
      }
  
      /**
       * Constructor.
       *
       * @param rndVec random streams
       * @throws NullPointerException argument is null
       * @throws IllegalArgumentException no stream
       */
      public XorMixer(RndInt32... rndVec)
              throws NullPointerException, IllegalArgumentException {
          this(Arrays.asList(rndVec));
          return;
      }
  
      /**
       * {@inheritDoc}
       *
       * @return {@inheritDoc}
       */
      @Override
      public int nextInt32() {
          int result = 0x00;
  
          for (RndInt32 rnd : this.rnds) {
              result ^= rnd.nextInt32();
          }
  
          return result;
      }
  
  }