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package net.jqwik.engine.properties.shrinking;

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

import net.jqwik.api.*;
import net.jqwik.api.lifecycle.*;
import net.jqwik.engine.support.*;

class PairwiseParameterShrinker extends AbstractSampleShrinker {

	public PairwiseParameterShrinker(Map, TryExecutionResult> falsificationCache) {
		super(falsificationCache);
	}

	@Override
	public FalsifiedSample shrink(
		Falsifier> falsifier,
		FalsifiedSample sample,
		Consumer sampleShrunkConsumer,
		Consumer shrinkAttemptConsumer
	) {
		FalsifiedSample current = sample;
		List> allPairs =
			Combinatorics.distinctPairs(sample.shrinkables().size()).collect(Collectors.toList());
		for (Tuple.Tuple2 pair : allPairs) {
			current = shrinkPair(falsifier, current, sampleShrunkConsumer, shrinkAttemptConsumer, pair.get1(), pair.get2());
		}
		return current;
	}

	private FalsifiedSample shrinkPair(
		Falsifier> falsifier,
		FalsifiedSample sample,
		Consumer sampleShrunkConsumer,
		Consumer shrinkAttemptConsumer,
		int index1,
		int index2
	) {
		Function>, Stream>>> shrinker =
			shrinkables -> {
				Stream> shrink1 = shrinkables.get(index1).shrink();
				Stream> shrink2 = shrinkables.get(index2).shrink();

				return JqwikStreamSupport.zip(shrink1, shrink2, (shrinkable1, shrinkable2) -> {
					ArrayList> newShrinkables = new ArrayList<>(sample.shrinkables());
					newShrinkables.set(index1, shrinkable1);
					newShrinkables.set(index2, shrinkable2);
					return newShrinkables;
				});
			};

		return shrink(
			falsifier,
			sample,
			sampleShrunkConsumer,
			shrinkAttemptConsumer,
			shrinker
		);
	}

}