//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// <string>

// basic_string<charT,traits,Allocator>&
//   erase(size_type pos = 0, size_type n = npos); // constexpr since C++20

#include <string>
#include <stdexcept>
#include <cassert>

#include "test_macros.h"
#include "min_allocator.h"

template <class S>
TEST_CONSTEXPR_CXX20 void
test(S s, typename S::size_type pos, typename S::size_type n, S expected)
{
    const typename S::size_type old_size = s.size();
    S s0 = s;
    if (pos <= old_size)
    {
        s.erase(pos, n);
        LIBCPP_ASSERT(s.__invariants());
        assert(s[s.size()] == typename S::value_type());
        assert(s == expected);
    }
#ifndef TEST_HAS_NO_EXCEPTIONS
    else if (!TEST_IS_CONSTANT_EVALUATED)
    {
        try
        {
            s.erase(pos, n);
            assert(false);
        }
        catch (std::out_of_range&)
        {
            assert(pos > old_size);
            assert(s == s0);
        }
    }
#endif
}

template <class S>
TEST_CONSTEXPR_CXX20 void
test(S s, typename S::size_type pos, S expected)
{
    const typename S::size_type old_size = s.size();
    S s0 = s;
    if (pos <= old_size)
    {
        s.erase(pos);
        LIBCPP_ASSERT(s.__invariants());
        assert(s[s.size()] == typename S::value_type());
        assert(s == expected);
    }
#ifndef TEST_HAS_NO_EXCEPTIONS
    else if (!TEST_IS_CONSTANT_EVALUATED)
    {
        try
        {
            s.erase(pos);
            assert(false);
        }
        catch (std::out_of_range&)
        {
            assert(pos > old_size);
            assert(s == s0);
        }
    }
#endif
}

template <class S>
TEST_CONSTEXPR_CXX20 void
test(S s, S expected)
{
    s.erase();
    LIBCPP_ASSERT(s.__invariants());
    assert(s[s.size()] == typename S::value_type());
    assert(s == expected);
}

template <class S>
TEST_CONSTEXPR_CXX20 void test_string() {
  test(S(""), 0, 0, S(""));
  test(S(""), 0, 1, S(""));
  test(S(""), 1, 0, S("can't happen"));
  test(S("abcde"), 0, 0, S("abcde"));
  test(S("abcde"), 0, 1, S("bcde"));
  test(S("abcde"), 0, 2, S("cde"));
  test(S("abcde"), 0, 4, S("e"));
  test(S("abcde"), 0, 5, S(""));
  test(S("abcde"), 0, 6, S(""));
  test(S("abcde"), 1, 0, S("abcde"));
  test(S("abcde"), 1, 1, S("acde"));
  test(S("abcde"), 1, 2, S("ade"));
  test(S("abcde"), 1, 3, S("ae"));
  test(S("abcde"), 1, 4, S("a"));
  test(S("abcde"), 1, 5, S("a"));
  test(S("abcde"), 2, 0, S("abcde"));
  test(S("abcde"), 2, 1, S("abde"));
  test(S("abcde"), 2, 2, S("abe"));
  test(S("abcde"), 2, 3, S("ab"));
  test(S("abcde"), 2, 4, S("ab"));
  test(S("abcde"), 4, 0, S("abcde"));
  test(S("abcde"), 4, 1, S("abcd"));
  test(S("abcde"), 4, 2, S("abcd"));
  test(S("abcde"), 5, 0, S("abcde"));
  test(S("abcde"), 5, 1, S("abcde"));
  test(S("abcde"), 6, 0, S("can't happen"));
  test(S("abcdefghij"), 0, 0, S("abcdefghij"));
  test(S("abcdefghij"), 0, 1, S("bcdefghij"));
  test(S("abcdefghij"), 0, 5, S("fghij"));
  test(S("abcdefghij"), 0, 9, S("j"));
  test(S("abcdefghij"), 0, 10, S(""));
  test(S("abcdefghij"), 0, 11, S(""));
  test(S("abcdefghij"), 1, 0, S("abcdefghij"));
  test(S("abcdefghij"), 1, 1, S("acdefghij"));
  test(S("abcdefghij"), 1, 4, S("afghij"));
  test(S("abcdefghij"), 1, 8, S("aj"));
  test(S("abcdefghij"), 1, 9, S("a"));
  test(S("abcdefghij"), 1, 10, S("a"));
  test(S("abcdefghij"), 5, 0, S("abcdefghij"));
  test(S("abcdefghij"), 5, 1, S("abcdeghij"));
  test(S("abcdefghij"), 5, 2, S("abcdehij"));
  test(S("abcdefghij"), 5, 4, S("abcdej"));
  test(S("abcdefghij"), 5, 5, S("abcde"));
  test(S("abcdefghij"), 5, 6, S("abcde"));
  test(S("abcdefghij"), 9, 0, S("abcdefghij"));
  test(S("abcdefghij"), 9, 1, S("abcdefghi"));
  test(S("abcdefghij"), 9, 2, S("abcdefghi"));
  test(S("abcdefghij"), 10, 0, S("abcdefghij"));
  test(S("abcdefghij"), 10, 1, S("abcdefghij"));
  test(S("abcdefghij"), 11, 0, S("can't happen"));
  test(S("abcdefghijklmnopqrst"), 0, 0, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 0, 1, S("bcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 0, 10, S("klmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 0, 19, S("t"));
  test(S("abcdefghijklmnopqrst"), 0, 20, S(""));
  test(S("abcdefghijklmnopqrst"), 0, 21, S(""));
  test(S("abcdefghijklmnopqrst"), 1, 0, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 1, 1, S("acdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 1, 9, S("aklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 1, 18, S("at"));
  test(S("abcdefghijklmnopqrst"), 1, 19, S("a"));
  test(S("abcdefghijklmnopqrst"), 1, 20, S("a"));
  test(S("abcdefghijklmnopqrst"), 10, 0, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 10, 1, S("abcdefghijlmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 10, 5, S("abcdefghijpqrst"));
  test(S("abcdefghijklmnopqrst"), 10, 9, S("abcdefghijt"));
  test(S("abcdefghijklmnopqrst"), 10, 10, S("abcdefghij"));
  test(S("abcdefghijklmnopqrst"), 10, 11, S("abcdefghij"));
  test(S("abcdefghijklmnopqrst"), 19, 0, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 19, 1, S("abcdefghijklmnopqrs"));
  test(S("abcdefghijklmnopqrst"), 19, 2, S("abcdefghijklmnopqrs"));
  test(S("abcdefghijklmnopqrst"), 20, 0, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 20, 1, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 21, 0, S("can't happen"));

  test(S(""), 0, S(""));
  test(S(""), 1, S("can't happen"));
  test(S("abcde"), 0, S(""));
  test(S("abcde"), 1, S("a"));
  test(S("abcde"), 2, S("ab"));
  test(S("abcde"), 4, S("abcd"));
  test(S("abcde"), 5, S("abcde"));
  test(S("abcde"), 6, S("can't happen"));
  test(S("abcdefghij"), 0, S(""));
  test(S("abcdefghij"), 1, S("a"));
  test(S("abcdefghij"), 5, S("abcde"));
  test(S("abcdefghij"), 9, S("abcdefghi"));
  test(S("abcdefghij"), 10, S("abcdefghij"));
  test(S("abcdefghij"), 11, S("can't happen"));
  test(S("abcdefghijklmnopqrst"), 0, S(""));
  test(S("abcdefghijklmnopqrst"), 1, S("a"));
  test(S("abcdefghijklmnopqrst"), 10, S("abcdefghij"));
  test(S("abcdefghijklmnopqrst"), 19, S("abcdefghijklmnopqrs"));
  test(S("abcdefghijklmnopqrst"), 20, S("abcdefghijklmnopqrst"));
  test(S("abcdefghijklmnopqrst"), 21, S("can't happen"));

  test(S(""), S(""));
  test(S("abcde"), S(""));
  test(S("abcdefghij"), S(""));
  test(S("abcdefghijklmnopqrst"), S(""));
}

TEST_CONSTEXPR_CXX20 bool test() {
  test_string<std::string>();
#if TEST_STD_VER >= 11
  test_string<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>();
#endif

  return true;
}

int main(int, char**)
{
  test();
#if TEST_STD_VER > 17
  static_assert(test());
#endif

  return 0;
}