package net.bmahe.genetics4j.core.mutation;
   
   import java.util.Objects;
   import java.util.random.RandomGenerator;
   
   import org.apache.commons.lang3.Validate;
   
   import net.bmahe.genetics4j.core.Genotype;
   import net.bmahe.genetics4j.core.spec.mutation.RepeatedMutation;
  
  /**
   * Applies a child mutator repeatedly, passing each mutation result to the next invocation.
   */
  public class RepeatedMutator implements Mutator {
  
  	private final RandomGenerator randomGenerator;
  	private final RepeatedMutation repeatedMutation;
  	private final Mutator childMutator;
  
  	public RepeatedMutator(final RandomGenerator _randomGenerator,
  			final RepeatedMutation _repeatedMutation,
  			final Mutator _childMutator) {
  		this.randomGenerator = Objects.requireNonNull(_randomGenerator);
  		this.repeatedMutation = Objects.requireNonNull(_repeatedMutation);
  		this.childMutator = Objects.requireNonNull(_childMutator);
  	}
  
  	@Override
  	public Genotype mutate(final long generation, final Genotype original) {
  		Validate.isTrue(generation >= 0);
  		Objects.requireNonNull(original);
  
  		final int numRepetitions = numberOfRepetitions();
  		Genotype mutated = original;
  		for (int i = 0; i < numRepetitions; i++) {
  			mutated = childMutator.mutate(generation, mutated);
  		}
  
  		return mutated;
  	}
  
  	private int numberOfRepetitions() {
  		final int minRepetitions = repeatedMutation.minRepetitions();
  		final int maxRepetitions = repeatedMutation.maxRepetitions();
  		if (minRepetitions == maxRepetitions) {
  			return minRepetitions;
  		}
  
  		return (int) randomGenerator.nextLong(minRepetitions, (long) maxRepetitions + 1L);
  	}
  }