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

import java.lang.invoke.*;
import java.lang.reflect.*;
import java.util.*;
import java.util.function.*;

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

abstract class AbstractFunctionGenerator implements RandomGenerator {
	final Class functionalType;
	final RandomGenerator resultGenerator;
	final List>, Function, ? extends R>>> conditions;

	AbstractFunctionGenerator(
		Class functionalType,
		RandomGenerator resultGenerator,
		List>, Function, ? extends R>>> conditions
	) {
		this.functionalType = functionalType;
		this.resultGenerator = resultGenerator;
		this.conditions = conditions;
	}

	@SuppressWarnings("unchecked")
	F createFunctionProxy(InvocationHandler handler) {
		return (F) Proxy.newProxyInstance(functionalType.getClassLoader(), new Class[]{functionalType}, handler);
	}


	public Shrinkable createConstantFunction(Shrinkable shrinkableConstant) {
		return shrinkableConstant.map(this::constantFunction);
	}

	private F constantFunction(R constant) {
		InvocationHandler handler = (proxy, method, args) -> {
			if (JqwikReflectionSupport.isEqualsMethod(method)) {
				return handleEqualsMethod(proxy, args);
			}
			if (JqwikReflectionSupport.isToStringMethod(method)) {
				return handleToStringOfConstantMethod(constant);
			}
			if (JqwikReflectionSupport.isHashCodeMethod(method)) {
				return HashCodeSupport.hash(constant);
			}
			if (method.isDefault()) {
				return handleDefaultMethod(proxy, method, args);
			}

			return conditionalResult(args).orElse(new Object[]{constant})[0];
		};
		return createFunctionProxy(handler);
	}

	protected Object handleEqualsMethod(final Object proxy, Object[] args) {
		return proxy == args[0];
	}

	private Object handleToStringOfConstantMethod(final R constant) {
		return String.format(
			"Constant Function<%s>(%s)",
			functionalType.getSimpleName(),
			JqwikStringSupport.displayString(constant)
		);
	}

	// Returns result wrapped in array to allow null as result
	protected Optional conditionalResult(Object[] args) {
		Optional conditionalResult = Optional.empty();
		for (Tuple2>, Function, ? extends R>> condition : conditions) {
			List