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// Copyright (c) 2026 Progmasoft.
// SPDX-License-Identifier: MPL-2.0 WITH AdditionRef-Progmasoft-Exception-2.0
#pragma once
#include <Progmasoft/Catch3/Detail/InvalidArgument.hpp>
#include <Progmasoft/Catch3/Random.hpp>
#include <functional>
#include <stdexcept>
#include <utility>
#include <vector>
namespace Progmasoft::Catch3
{
/// A value source paired with an ordered sequence of simpler candidates.
///
/// The property runner owns the shrinking policy; generators only describe
/// which candidates are valid and which order is most useful for
/// minimization.
template<typename ValueType>
class Generator final
{
public:
using GenerationFunction = std::function<ValueType(Random &)>;
using ShrinkingFunction
= std::function<std::vector<ValueType>(const ValueType &)>;
Generator(GenerationFunction generate, ShrinkingFunction shrink)
: generate_(std::move(generate))
, shrink_(std::move(shrink))
{
if (!generate_ || !shrink_)
{
Detail::RejectInvalidArgument(
"a generator requires both callbacks");
}
}
[[nodiscard]] ValueType
Generate(Random &random) const
{
return generate_(random);
}
[[nodiscard]] std::vector<ValueType>
Shrink(const ValueType &value) const
{
return shrink_(value);
}
private:
GenerationFunction generate_;
ShrinkingFunction shrink_;
};
/// Adapts user callables into a reusable generator.
template<typename ValueType,
typename GenerateFunction,
typename ShrinkFunction>
[[nodiscard]] Generator<ValueType>
MakeGenerator(GenerateFunction &&generate, ShrinkFunction &&shrink)
{
return Generator<ValueType>(
typename Generator<ValueType>::GenerationFunction(
std::forward<GenerateFunction>(generate)),
typename Generator<ValueType>::ShrinkingFunction(
std::forward<ShrinkFunction>(shrink)));
}
} // namespace Progmasoft::Catch3
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