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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/TypeTraits.hpp>
#include <Progmasoft/Catch3/Generator.hpp>
#include <algorithm>
#include <limits>
#include <type_traits>
namespace Progmasoft::Catch3
{
namespace Detail
{
template<typename IntegerType, Detail::EnableIfInteger<IntegerType> = 0>
[[nodiscard]] std::vector<IntegerType>
ShrinkInteger(IntegerType value,
IntegerType minimum,
IntegerType maximum)
{
std::vector<IntegerType> candidates;
const auto addCandidate = [&](IntegerType candidate) {
if (candidate < minimum || candidate > maximum
|| candidate == value
|| std::find(candidates.begin(),
candidates.end(),
candidate)
!= candidates.end())
{
return;
}
candidates.push_back(candidate);
};
if (value == 0)
{
return candidates;
}
// First try the conventional simplest value, then halve toward it.
// The adjacent value at the end lets the runner find boundary
// counterexamples (for example, the first failing integer in a
// threshold property).
if (minimum <= 0 && maximum >= 0)
{
addCandidate(0);
}
IntegerType smaller = value;
while (smaller != 0)
{
smaller = static_cast<IntegerType>(smaller / 2);
if (smaller == 0)
{
break;
}
addCandidate(smaller);
}
if (value > 0)
{
if (value > minimum)
{
addCandidate(static_cast<IntegerType>(value - 1));
}
if (minimum > 0)
{
addCandidate(minimum);
}
}
else
{
if (value < maximum)
{
addCandidate(static_cast<IntegerType>(value + 1));
}
if (maximum < 0)
{
addCandidate(maximum);
}
}
return candidates;
}
} // namespace Detail
/// Generates integers over the inclusive range and shrinks toward simple
/// values.
template<typename IntegerType, Detail::EnableIfInteger<IntegerType> = 0>
[[nodiscard]] Generator<IntegerType>
Integer(IntegerType minimum = std::numeric_limits<IntegerType>::lowest(),
IntegerType maximum = std::numeric_limits<IntegerType>::max())
{
if (minimum > maximum)
{
Detail::RejectInvalidArgument(
"Integer requires minimum <= maximum");
}
return MakeGenerator<IntegerType>(
[minimum, maximum](Random &random) {
return random.Between(minimum, maximum);
},
[minimum, maximum](const IntegerType &value) {
return Detail::ShrinkInteger(value, minimum, maximum);
});
}
} // namespace Progmasoft::Catch3
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