//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// <algorithm>

// template<InputIterator InIter, RandomAccessIterator RAIter>
//   requires ShuffleIterator<RAIter>
//         && OutputIterator<RAIter, InIter::reference>
//         && HasLess<InIter::value_type, RAIter::value_type>
//         && LessThanComparable<RAIter::value_type>
//   RAIter
//   partial_sort_copy(InIter first, InIter last, RAIter result_first, RAIter result_last);

#include <algorithm>
#include <random>
#include <cassert>

#include "test_macros.h"
#include "test_iterators.h"

std::mt19937 randomness;

template <class Iter>
void
test_larger_sorts(int N, int M)
{
    int* input = new int[N];
    int* output = new int[M];
    for (int i = 0; i < N; ++i)
        input[i] = i;
    std::shuffle(input, input+N, randomness);
    int* r = std::partial_sort_copy(Iter(input), Iter(input+N), output, output+M);
    int* e = output + std::min(N, M);
    assert(r == e);
    int i = 0;
    for (int* x = output; x < e; ++x, ++i)
        assert(*x == i);
    delete [] output;
    delete [] input;
}

template <class Iter>
void
test_larger_sorts(int N)
{
    test_larger_sorts<Iter>(N, 0);
    test_larger_sorts<Iter>(N, 1);
    test_larger_sorts<Iter>(N, 2);
    test_larger_sorts<Iter>(N, 3);
    test_larger_sorts<Iter>(N, N/2-1);
    test_larger_sorts<Iter>(N, N/2);
    test_larger_sorts<Iter>(N, N/2+1);
    test_larger_sorts<Iter>(N, N-2);
    test_larger_sorts<Iter>(N, N-1);
    test_larger_sorts<Iter>(N, N);
    test_larger_sorts<Iter>(N, N+1000);
}

template <class Iter>
void
test()
{
    test_larger_sorts<Iter>(0, 100);
    test_larger_sorts<Iter>(10);
    test_larger_sorts<Iter>(256);
    test_larger_sorts<Iter>(257);
    test_larger_sorts<Iter>(499);
    test_larger_sorts<Iter>(500);
    test_larger_sorts<Iter>(997);
    test_larger_sorts<Iter>(1000);
    test_larger_sorts<Iter>(1009);
}

int main(int, char**)
{
    int i = 0;
    std::partial_sort_copy(&i, &i, &i, &i+5);
    assert(i == 0);
    test<cpp17_input_iterator<const int*> >();
    test<forward_iterator<const int*> >();
    test<bidirectional_iterator<const int*> >();
    test<random_access_iterator<const int*> >();
    test<const int*>();

  return 0;
}
