net.jqwik.engine.properties.arbitraries.randomized.RandomIntegralGenerators Maven / Gradle / Ivy

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package net.jqwik.engine.properties.arbitraries.randomized;

import java.math.*;

import net.jqwik.api.*;
import net.jqwik.api.RandomDistribution.*;
import net.jqwik.engine.properties.*;
import net.jqwik.engine.properties.shrinking.*;

public class RandomIntegralGenerators {

	public static RandomGenerator bigIntegers(
		int genSize,
		BigInteger min,
		BigInteger max,
		BigInteger shrinkingTarget,
		RandomDistribution distribution
	) {
		Range range = Range.of(min, max);

		checkTargetInRange(range, shrinkingTarget);

		if (range.isSingular()) {
			return ignored -> Shrinkable.unshrinkable(range.min);
		}

		RandomNumericGenerator numericGenerator =
			distribution.createGenerator(genSize, range.min, range.max, shrinkingTarget);

		return random -> {
			BigInteger value = numericGenerator.next(random);
			return new ShrinkableBigInteger(
				value,
				range,
				shrinkingTarget
			);
		};
	}

	private static void checkTargetInRange(Range range, BigInteger value) {
		if (!range.includes(value)) {
			String message = String.format("Shrinking target <%s> is outside allowed range %s", value, range);
			throw new JqwikException(message);
		}
	}

	public static BigInteger defaultShrinkingTarget(Range range) {
		if (range.includes(BigInteger.ZERO)) {
			return BigInteger.ZERO;
		}
		if (range.max.compareTo(BigInteger.ZERO) < 0) return range.max;
		if (range.min.compareTo(BigInteger.ZERO) > 0) return range.min;
		throw new RuntimeException("This should not be possible");
	}
}