///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
///////////////////////////////////////////////////////////////////////////////

#include <UnitTest++/UnitTest++.h>
#include <gsl/multi_span>

#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <string>
#include <vector>

using namespace std;
using namespace gsl;

namespace
{
struct BaseClass
{
};
struct DerivedClass : BaseClass
{
};
}

SUITE(multi_span_tests)
{

    TEST(default_constructor)
    {
        {
            multi_span<int> s;
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int> cs;
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
            multi_span<int, 0> s;
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int, 0> cs;
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 1> s;
            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
#endif
        }

        {
            multi_span<int> s{};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int> cs{};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }
    }

    TEST(from_nullptr_constructor)
    {
        {
            multi_span<int> s = nullptr;
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int> cs = nullptr;
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
            multi_span<int, 0> s = nullptr;
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int, 0> cs = nullptr;
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 1> s = nullptr;
            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
#endif
        }

        {
            multi_span<int> s{nullptr};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int> cs{nullptr};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
            multi_span<int*> s{nullptr};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int*> cs{nullptr};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }
    }

    TEST(from_nullptr_length_constructor)
    {
        {
            multi_span<int> s{nullptr, 0};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int> cs{nullptr, 0};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
            multi_span<int, 0> s{nullptr, 0};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int, 0> cs{nullptr, 0};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 1> s{nullptr, 0};
            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
#endif
        }

        {
            auto workaround_macro = []() { multi_span<int> s{nullptr, 1}; };
            CHECK_THROW(workaround_macro(), fail_fast);

            auto const_workaround_macro = []() { multi_span<const int> cs{nullptr, 1}; };
            CHECK_THROW(const_workaround_macro(), fail_fast);
        }

        {
            auto workaround_macro = []() { multi_span<int, 0> s{nullptr, 1}; };
            CHECK_THROW(workaround_macro(), fail_fast);

            auto const_workaround_macro = []() { multi_span<const int, 0> s{nullptr, 1}; };
            CHECK_THROW(const_workaround_macro(), fail_fast);
        }

        {
            multi_span<int*> s{nullptr, 0};
            CHECK(s.length() == 0 && s.data() == nullptr);

            multi_span<const int*> cs{nullptr, 0};
            CHECK(cs.length() == 0 && cs.data() == nullptr);
        }
    }

    TEST(from_element_constructor)
    {
        int i = 5;

        {
            multi_span<int> s = i;
            CHECK(s.length() == 1 && s.data() == &i);
            CHECK(s[0] == 5);

            multi_span<const int> cs = i;
            CHECK(cs.length() == 1 && cs.data() == &i);
            CHECK(cs[0] == 5);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            const j = 1;
            multi_span<int, 0> s = j;
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 0> s = i;
            CHECK(s.length() == 0 && s.data() == &i);
#endif
        }

        {
            multi_span<int, 1> s = i;
            CHECK(s.length() == 1 && s.data() == &i);
            CHECK(s[0] == 5);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 2> s = i;
            CHECK(s.length() == 2 && s.data() == &i);
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_a_temp = []() -> int { return 4; };
            auto use_a_span = [](multi_span<int> s) { (void) s; };
            use_a_span(get_a_temp());
#endif
        }
    }

    TEST(from_pointer_length_constructor)
    {
        int arr[4] = {1, 2, 3, 4};

        {
            multi_span<int> s{&arr[0], 2};
            CHECK(s.length() == 2 && s.data() == &arr[0]);
            CHECK(s[0] == 1 && s[1] == 2);
        }

        {
            multi_span<int, 2> s{&arr[0], 2};
            CHECK(s.length() == 2 && s.data() == &arr[0]);
            CHECK(s[0] == 1 && s[1] == 2);
        }

        {
            int* p = nullptr;
            multi_span<int> s{p, 0};
            CHECK(s.length() == 0 && s.data() == nullptr);
        }

        {
            int* p = nullptr;
            auto workaround_macro = [=]() { multi_span<int> s{p, 2}; };
            CHECK_THROW(workaround_macro(), fail_fast);
        }
    }

    TEST(from_pointer_pointer_constructor)
    {
        int arr[4] = {1, 2, 3, 4};

        {
            multi_span<int> s{&arr[0], &arr[2]};
            CHECK(s.length() == 2 && s.data() == &arr[0]);
            CHECK(s[0] == 1 && s[1] == 2);
        }

        {
            multi_span<int, 2> s{&arr[0], &arr[2]};
            CHECK(s.length() == 2 && s.data() == &arr[0]);
            CHECK(s[0] == 1 && s[1] == 2);
        }

        {
            multi_span<int> s{&arr[0], &arr[0]};
            CHECK(s.length() == 0 && s.data() == &arr[0]);
        }

        {
            multi_span<int, 0> s{&arr[0], &arr[0]};
            CHECK(s.length() == 0 && s.data() == &arr[0]);
        }

        {
            auto workaround_macro = [&]() { multi_span<int> s{&arr[1], &arr[0]}; };
            CHECK_THROW(workaround_macro(), fail_fast);
        }

        {
            int* p = nullptr;
            auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
            CHECK_THROW(workaround_macro(), fail_fast);
        }

        {
            int* p = nullptr;
            auto workaround_macro = [&]() { multi_span<int> s{p, p}; };
            CHECK_THROW(workaround_macro(), fail_fast);
        }

        {
            int* p = nullptr;
            auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
            CHECK_THROW(workaround_macro(), fail_fast);
        }
    }

    TEST(from_array_constructor)
    {
        int arr[5] = {1, 2, 3, 4, 5};

        {
            multi_span<int> s{arr};
            CHECK(s.length() == 5 && s.data() == &arr[0]);
        }

        {
            multi_span<int, 5> s{arr};
            CHECK(s.length() == 5 && s.data() == &arr[0]);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 6> s{arr};
#endif
        }

        {
            multi_span<int, 0> s{arr};
            CHECK(s.length() == 0 && s.data() == &arr[0]);
        }

        int arr2d[2][3] = {1, 2, 3, 4, 5, 6};

        {
            multi_span<int> s{arr2d};
            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
            CHECK(s[0] == 1 && s[5] == 6);
        }

        {
            multi_span<int, 0> s{arr2d};
            CHECK(s.length() == 0 && s.data() == &arr2d[0][0]);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 5> s{arr2d};
#endif
        }

        {
            multi_span<int, 6> s{arr2d};
            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
            CHECK(s[0] == 1 && s[5] == 6);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 7> s{arr2d};
#endif
        }

        {
            multi_span<int[3]> s{arr2d[0]};
            CHECK(s.length() == 1 && s.data() == &arr2d[0]);
        }

        {
            multi_span<int, 2, 3> s{arr2d};
            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
            auto workaround_macro = [&]() { return s[{1, 2}] == 6; };
            CHECK(workaround_macro());
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 3, 3> s{arr2d};
#endif
        }

        int arr3d[2][3][2] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};

        {
            multi_span<int> s{arr3d};
            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
            CHECK(s[0] == 1 && s[11] == 12);
        }

        {
            multi_span<int, 0> s{arr3d};
            CHECK(s.length() == 0 && s.data() == &arr3d[0][0][0]);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 11> s{arr3d};
#endif
        }

        {
            multi_span<int, 12> s{arr3d};
            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
            CHECK(s[0] == 1 && s[5] == 6);
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 13> s{arr3d};
#endif
        }

        {
            multi_span<int[3][2]> s{arr3d[0]};
            CHECK(s.length() == 1 && s.data() == &arr3d[0]);
        }

        {
            multi_span<int, 3, 2, 2> s{arr3d};
            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
            auto workaround_macro = [&]() { return s[{2, 1, 0}] == 11; };
            CHECK(workaround_macro());
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 3, 3, 3> s{arr3d};
#endif
        }
    }

    TEST(from_dynamic_array_constructor)
    {
        double(*arr)[3][4] = new double[100][3][4];

        {
            multi_span<double, dynamic_range, 3, 4> s(arr, 10);
            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
            CHECK_THROW(s[10][3][4], fail_fast);
        }

        {
            multi_span<double, dynamic_range, 4, 3> s(arr, 10);
            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
        }

        {
            multi_span<double> s(arr, 10);
            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
        }

        {
            multi_span<double, dynamic_range, 3, 4> s(arr, 0);
            CHECK(s.length() == 0 && s.data() == &arr[0][0][0]);
        }

        delete[] arr;
    }

    TEST(from_std_array_constructor)
    {
        std::array<int, 4> arr = {1, 2, 3, 4};

        {
            multi_span<int> s{arr};
            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());

            multi_span<const int> cs{arr};
            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
        }

        {
            multi_span<int, 4> s{arr};
            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());

            multi_span<const int, 4> cs{arr};
            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
        }

        {
            multi_span<int, 2> s{arr};
            CHECK(s.size() == 2 && s.data() == arr.data());

            multi_span<const int, 2> cs{arr};
            CHECK(cs.size() == 2 && cs.data() == arr.data());
        }

        {
            multi_span<int, 0> s{arr};
            CHECK(s.size() == 0 && s.data() == arr.data());

            multi_span<const int, 0> cs{arr};
            CHECK(cs.size() == 0 && cs.data() == arr.data());
        }

        // TODO This is currently an unsupported scenario. We will come back to it as we revise
        // the multidimensional interface and what transformations between dimensionality look like
        //{
        //    multi_span<int, 2, 2> s{arr};
        //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
        //}

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<int, 5> s{arr};
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_an_array = []() { return std::array<int, 4>{1, 2, 3, 4}; };
            auto take_a_span = [](multi_span<int> s) { (void) s; };
            // try to take a temporary std::array
            take_a_span(get_an_array());
#endif
        }
    }

    TEST(from_const_std_array_constructor)
    {
        const std::array<int, 4> arr = {1, 2, 3, 4};

        {
            multi_span<const int> s{arr};
            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
        }

        {
            multi_span<const int, 4> s{arr};
            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
        }

        {
            multi_span<const int, 2> s{arr};
            CHECK(s.size() == 2 && s.data() == arr.data());
        }

        {
            multi_span<const int, 0> s{arr};
            CHECK(s.size() == 0 && s.data() == arr.data());
        }

        // TODO This is currently an unsupported scenario. We will come back to it as we revise
        // the multidimensional interface and what transformations between dimensionality look like
        //{
        //    multi_span<int, 2, 2> s{arr};
        //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
        //}

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<const int, 5> s{arr};
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_an_array = []() -> const std::array<int, 4> { return {1, 2, 3, 4}; };
            auto take_a_span = [](multi_span<const int> s) { (void) s; };
            // try to take a temporary std::array
            take_a_span(get_an_array());
#endif
        }
    }

    TEST(from_container_constructor)
    {
        std::vector<int> v = {1, 2, 3};
        const std::vector<int> cv = v;

        {
            multi_span<int> s{v};
            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data());

            multi_span<const int> cs{v};
            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(v.size()) && cs.data() == v.data());
        }

        std::string str = "hello";
        const std::string cstr = "hello";

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<char> s{str};
            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(str.size()) && s.data() == str.data());
#endif
            multi_span<const char> cs{str};
            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(str.size()) && cs.data() == str.data());
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            multi_span<char> s{cstr};
#endif
            multi_span<const char> cs{cstr};
            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
                  cs.data() == cstr.data());
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_temp_vector = []() -> std::vector<int> { return {}; };
            auto use_span = [](multi_span<int> s) { (void) s; };
            use_span(get_temp_vector());
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_temp_string = []() -> std::string { return {}; };
            auto use_span = [](multi_span<char> s) { (void) s; };
            use_span(get_temp_string());
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_temp_vector = []() -> const std::vector<int> { return {}; };
            auto use_span = [](multi_span<const char> s) { (void) s; };
            use_span(get_temp_vector());
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            auto get_temp_string = []() -> const std::string { return {}; };
            auto use_span = [](multi_span<const char> s) { (void) s; };
            use_span(get_temp_string());
#endif
        }

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            std::map<int, int> m;
            multi_span<int> s{m};
#endif
        }
    }

    TEST(from_convertible_span_constructor)
    {
#ifdef CONFIRM_COMPILATION_ERRORS
        multi_span<int, 7, 4, 2> av1(nullptr, b1);

        auto f = [&]() { multi_span<int, 7, 4, 2> av1(nullptr); };
        CHECK_THROW(f(), fail_fast);
#endif

#ifdef CONFIRM_COMPILATION_ERRORS
        static_bounds<size_t, 7, dynamic_range, 2> b12(b11);
        b12 = b11;
        b11 = b12;

        multi_span<int, dynamic_range> av1 = nullptr;
        multi_span<int, 7, dynamic_range, 2> av2(av1);
        multi_span<int, 7, 4, 2> av2(av1);
#endif

        multi_span<DerivedClass> avd;
#ifdef CONFIRM_COMPILATION_ERRORS
        multi_span<BaseClass> avb = avd;
#endif
        multi_span<const DerivedClass> avcd = avd;
        (void) avcd;
    }

    TEST(copy_move_and_assignment)
    {
        multi_span<int> s1;
        CHECK(s1.empty());

        int arr[] = {3, 4, 5};

        multi_span<const int> s2 = arr;
        CHECK(s2.length() == 3 && s2.data() == &arr[0]);

        s2 = s1;
        CHECK(s2.empty());

        auto get_temp_span = [&]() -> multi_span<int> { return {&arr[1], 2}; };
        auto use_span = [&](multi_span<const int> s) { CHECK(s.length() == 2 && s.data() == &arr[1]); };
        use_span(get_temp_span());

        s1 = get_temp_span();
        CHECK(s1.length() == 2 && s1.data() == &arr[1]);
    }

    template <class Bounds>
    void fn(const Bounds&)
    {
        static_assert(Bounds::static_size == 60, "static bounds is wrong size");
    }
    TEST(as_multi_span_reshape)
    {
        int a[3][4][5];
        auto av = as_multi_span(a);
        fn(av.bounds());
        auto av2 = as_multi_span(av, dim<60>());
        auto av3 = as_multi_span(av2, dim<3>(), dim<4>(), dim<5>());
        auto av4 = as_multi_span(av3, dim<4>(), dim(3), dim<5>());
        auto av5 = as_multi_span(av4, dim<3>(), dim<4>(), dim<5>());
        auto av6 = as_multi_span(av5, dim<12>(), dim(5));

        fill(av6.begin(), av6.end(), 1);

        auto av7 = as_bytes(av6);

        auto av8 = as_multi_span<int>(av7);

        CHECK(av8.size() == av6.size());
        for (auto i = 0; i < av8.size(); i++) {
            CHECK(av8[i] == 1);
        }
    }

    TEST(first)
    {
        int arr[5] = {1, 2, 3, 4, 5};

        {
            multi_span<int, 5> av = arr;
            CHECK((av.first<2>().bounds() == static_bounds<2>()));
            CHECK(av.first<2>().length() == 2);
            CHECK(av.first(2).length() == 2);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.first<0>().bounds() == static_bounds<0>()));
            CHECK(av.first<0>().length() == 0);
            CHECK(av.first(0).length() == 0);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.first<5>().bounds() == static_bounds<5>()));
            CHECK(av.first<5>().length() == 5);
            CHECK(av.first(5).length() == 5);
        }

        {
            multi_span<int, 5> av = arr;
#ifdef CONFIRM_COMPILATION_ERRORS
            CHECK(av.first<6>().bounds() == static_bounds<6>());
            CHECK(av.first<6>().length() == 6);
            CHECK(av.first<-1>().length() == -1);
#endif
            CHECK_THROW(av.first(6).length(), fail_fast);
        }

        {
            multi_span<int, dynamic_range> av;
            CHECK((av.first<0>().bounds() == static_bounds<0>()));
            CHECK(av.first<0>().length() == 0);
            CHECK(av.first(0).length() == 0);
        }
    }

    TEST(last)
    {
        int arr[5] = {1, 2, 3, 4, 5};

        {
            multi_span<int, 5> av = arr;
            CHECK((av.last<2>().bounds() == static_bounds<2>()));
            CHECK(av.last<2>().length() == 2);
            CHECK(av.last(2).length() == 2);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.last<0>().bounds() == static_bounds<0>()));
            CHECK(av.last<0>().length() == 0);
            CHECK(av.last(0).length() == 0);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.last<5>().bounds() == static_bounds<5>()));
            CHECK(av.last<5>().length() == 5);
            CHECK(av.last(5).length() == 5);
        }

        {
            multi_span<int, 5> av = arr;
#ifdef CONFIRM_COMPILATION_ERRORS
            CHECK((av.last<6>().bounds() == static_bounds<6>()));
            CHECK(av.last<6>().length() == 6);
#endif
            CHECK_THROW(av.last(6).length(), fail_fast);
        }

        {
            multi_span<int, dynamic_range> av;
            CHECK((av.last<0>().bounds() == static_bounds<0>()));
            CHECK(av.last<0>().length() == 0);
            CHECK(av.last(0).length() == 0);
        }
    }

    TEST(subspan)
    {
        int arr[5] = {1, 2, 3, 4, 5};

        {
            multi_span<int, 5> av = arr;
            CHECK((av.subspan<2, 2>().bounds() == static_bounds<2>()));
            CHECK((av.subspan<2, 2>().length() == 2));
            CHECK(av.subspan(2, 2).length() == 2);
            CHECK(av.subspan(2, 3).length() == 3);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
            CHECK((av.subspan<0, 0>().length() == 0));
            CHECK(av.subspan(0, 0).length() == 0);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.subspan<0, 5>().bounds() == static_bounds<5>()));
            CHECK((av.subspan<0, 5>().length() == 5));
            CHECK(av.subspan(0, 5).length() == 5);
            CHECK_THROW(av.subspan(0, 6).length(), fail_fast);
            CHECK_THROW(av.subspan(1, 5).length(), fail_fast);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK((av.subspan<5, 0>().bounds() == static_bounds<0>()));
            CHECK((av.subspan<5, 0>().length() == 0));
            CHECK(av.subspan(5, 0).length() == 0);
            CHECK_THROW(av.subspan(6, 0).length(), fail_fast);
        }

        {
            multi_span<int, dynamic_range> av;
            CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
            CHECK((av.subspan<0, 0>().length() == 0));
            CHECK(av.subspan(0, 0).length() == 0);
            CHECK_THROW((av.subspan<1, 0>().length()), fail_fast);
        }

        {
            multi_span<int> av;
            CHECK(av.subspan(0).length() == 0);
            CHECK_THROW(av.subspan(1).length(), fail_fast);
        }

        {
            multi_span<int> av = arr;
            CHECK(av.subspan(0).length() == 5);
            CHECK(av.subspan(1).length() == 4);
            CHECK(av.subspan(4).length() == 1);
            CHECK(av.subspan(5).length() == 0);
            CHECK_THROW(av.subspan(6).length(), fail_fast);
            auto av2 = av.subspan(1);
            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
        }

        {
            multi_span<int, 5> av = arr;
            CHECK(av.subspan(0).length() == 5);
            CHECK(av.subspan(1).length() == 4);
            CHECK(av.subspan(4).length() == 1);
            CHECK(av.subspan(5).length() == 0);
            CHECK_THROW(av.subspan(6).length(), fail_fast);
            auto av2 = av.subspan(1);
            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
        }
    }

    TEST(rank)
    {
        int arr[2] = {1, 2};

        {
            multi_span<int> s;
            CHECK(s.rank() == 1);
        }

        {
            multi_span<int, 2> s = arr;
            CHECK(s.rank() == 1);
        }

        int arr2d[1][1] = {};
        {
            multi_span<int, 1, 1> s = arr2d;
            CHECK(s.rank() == 2);
        }
    }

    TEST(extent)
    {
        {
            multi_span<int> s;
            CHECK(s.extent() == 0);
            CHECK(s.extent(0) == 0);
            CHECK_THROW(s.extent(1), fail_fast);
#ifdef CONFIRM_COMPILATION_ERRORS
            CHECK(s.extent<1>() == 0);
#endif
        }

        {
            multi_span<int, 0> s;
            CHECK(s.extent() == 0);
            CHECK(s.extent(0) == 0);
            CHECK_THROW(s.extent(1), fail_fast);
        }

        {
            int arr2d[1][2] = {};

            multi_span<int, 1, 2> s = arr2d;
            CHECK(s.extent() == 1);
            CHECK(s.extent<0>() == 1);
            CHECK(s.extent<1>() == 2);
            CHECK(s.extent(0) == 1);
            CHECK(s.extent(1) == 2);
            CHECK_THROW(s.extent(3), fail_fast);
        }

        {
            int arr2d[1][2] = {};

            multi_span<int, 0, 2> s = arr2d;
            CHECK(s.extent() == 0);
            CHECK(s.extent<0>() == 0);
            CHECK(s.extent<1>() == 2);
            CHECK(s.extent(0) == 0);
            CHECK(s.extent(1) == 2);
            CHECK_THROW(s.extent(3), fail_fast);
        }
    }

    TEST(operator_function_call)
    {
        int arr[4] = {1, 2, 3, 4};

        {
            multi_span<int> s = arr;
            CHECK(s(0) == 1);
            CHECK_THROW(s(5), fail_fast);
        }

        int arr2d[2][3] = {1, 2, 3, 4, 5, 6};

        {
            multi_span<int, 2, 3> s = arr2d;
            CHECK(s(0, 0) == 1);
            CHECK(s(1, 2) == 6);
        }
    }

    TEST(comparison_operators)
    {
        {
            int arr[10][2];
            auto s1 = as_multi_span(arr);
            multi_span<const int, dynamic_range, 2> s2 = s1;

            CHECK(s1 == s2);

            multi_span<int, 20> s3 = as_multi_span(s1, dim(20));
            CHECK(s3 == s2 && s3 == s1);
        }

        {
            multi_span<int> s1 = nullptr;
            multi_span<int> s2 = nullptr;
            CHECK(s1 == s2);
            CHECK(!(s1 != s2));
            CHECK(!(s1 < s2));
            CHECK(s1 <= s2);
            CHECK(!(s1 > s2));
            CHECK(s1 >= s2);
            CHECK(s2 == s1);
            CHECK(!(s2 != s1));
            CHECK(!(s2 < s1));
            CHECK(s2 <= s1);
            CHECK(!(s2 > s1));
            CHECK(s2 >= s1);
        }

        {
            int arr[] = {2, 1}; // bigger

            multi_span<int> s1 = nullptr;
            multi_span<int> s2 = arr;

            CHECK(s1 != s2);
            CHECK(s2 != s1);
            CHECK(!(s1 == s2));
            CHECK(!(s2 == s1));
            CHECK(s1 < s2);
            CHECK(!(s2 < s1));
            CHECK(s1 <= s2);
            CHECK(!(s2 <= s1));
            CHECK(s2 > s1);
            CHECK(!(s1 > s2));
            CHECK(s2 >= s1);
            CHECK(!(s1 >= s2));
        }

        {
            int arr1[] = {1, 2};
            int arr2[] = {1, 2};
            multi_span<int> s1 = arr1;
            multi_span<int> s2 = arr2;

            CHECK(s1 == s2);
            CHECK(!(s1 != s2));
            CHECK(!(s1 < s2));
            CHECK(s1 <= s2);
            CHECK(!(s1 > s2));
            CHECK(s1 >= s2);
            CHECK(s2 == s1);
            CHECK(!(s2 != s1));
            CHECK(!(s2 < s1));
            CHECK(s2 <= s1);
            CHECK(!(s2 > s1));
            CHECK(s2 >= s1);
        }

        {
            int arr[] = {1, 2, 3};

            multi_span<int> s1 = {&arr[0], 2}; // shorter
            multi_span<int> s2 = arr; // longer

            CHECK(s1 != s2);
            CHECK(s2 != s1);
            CHECK(!(s1 == s2));
            CHECK(!(s2 == s1));
            CHECK(s1 < s2);
            CHECK(!(s2 < s1));
            CHECK(s1 <= s2);
            CHECK(!(s2 <= s1));
            CHECK(s2 > s1);
            CHECK(!(s1 > s2));
            CHECK(s2 >= s1);
            CHECK(!(s1 >= s2));
        }

        {
            int arr1[] = {1, 2}; // smaller
            int arr2[] = {2, 1}; // bigger

            multi_span<int> s1 = arr1;
            multi_span<int> s2 = arr2;

            CHECK(s1 != s2);
            CHECK(s2 != s1);
            CHECK(!(s1 == s2));
            CHECK(!(s2 == s1));
            CHECK(s1 < s2);
            CHECK(!(s2 < s1));
            CHECK(s1 <= s2);
            CHECK(!(s2 <= s1));
            CHECK(s2 > s1);
            CHECK(!(s1 > s2));
            CHECK(s2 >= s1);
            CHECK(!(s1 >= s2));
        }
    }

    TEST(basics)
    {
        auto ptr = as_multi_span(new int[10], 10);
        fill(ptr.begin(), ptr.end(), 99);
        for (int num : ptr) {
            CHECK(num == 99);
        }

        delete[] ptr.data();
    }

    TEST(bounds_checks)
    {
        int arr[10][2];
        auto av = as_multi_span(arr);

        fill(begin(av), end(av), 0);

        av[2][0] = 1;
        av[1][1] = 3;

        // out of bounds
        CHECK_THROW(av[1][3] = 3, fail_fast);
        CHECK_THROW((av[{1, 3}] = 3), fail_fast);

        CHECK_THROW(av[10][2], fail_fast);
        CHECK_THROW((av[{10, 2}]), fail_fast);

        CHECK_THROW(av[-1][0], fail_fast);
        CHECK_THROW((av[{-1, 0}]), fail_fast);

        CHECK_THROW(av[0][-1], fail_fast);
        CHECK_THROW((av[{0, -1}]), fail_fast);
    }

    void overloaded_func(multi_span<const int, dynamic_range, 3, 5> exp, int expected_value)
    {
        for (auto val : exp) {
            CHECK(val == expected_value);
        }
    }

    void overloaded_func(multi_span<const char, dynamic_range, 3, 5> exp, char expected_value)
    {
        for (auto val : exp) {
            CHECK(val == expected_value);
        }
    }

    void fixed_func(multi_span<int, 3, 3, 5> exp, int expected_value)
    {
        for (auto val : exp) {
            CHECK(val == expected_value);
        }
    }

    TEST(span_parameter_test)
    {
        auto data = new int[4][3][5];

        auto av = as_multi_span(data, 4);

        CHECK(av.size() == 60);

        fill(av.begin(), av.end(), 34);

        int count = 0;
        for_each(av.rbegin(), av.rend(), [&](int val) { count += val; });
        CHECK(count == 34 * 60);
        overloaded_func(av, 34);

        overloaded_func(as_multi_span(av, dim(4), dim(3), dim(5)), 34);

        // fixed_func(av, 34);
        delete[] data;
    }

    TEST(md_access)
    {
        auto width = 5, height = 20;

        auto imgSize = width * height;
        auto image_ptr = new int[imgSize][3];

        // size check will be done
        auto image_view =
            as_multi_span(as_multi_span(image_ptr, imgSize), dim(height), dim(width), dim<3>());

        iota(image_view.begin(), image_view.end(), 1);

        int expected = 0;
        for (auto i = 0; i < height; i++) {
            for (auto j = 0; j < width; j++) {
                CHECK(expected + 1 == image_view[i][j][0]);
                CHECK(expected + 2 == image_view[i][j][1]);
                CHECK(expected + 3 == image_view[i][j][2]);

                auto val = image_view[{i, j, 0}];
                CHECK(expected + 1 == val);
                val = image_view[{i, j, 1}];
                CHECK(expected + 2 == val);
                val = image_view[{i, j, 2}];
                CHECK(expected + 3 == val);

                expected += 3;
            }
        }
    }

    TEST(as_multi_span)
    {
        {
            int* arr = new int[150];

            auto av = as_multi_span(arr, dim<10>(), dim(3), dim<5>());

            fill(av.begin(), av.end(), 24);
            overloaded_func(av, 24);

            delete[] arr;

            array<int, 15> stdarr{0};
            auto av2 = as_multi_span(stdarr);
            overloaded_func(as_multi_span(av2, dim(1), dim<3>(), dim<5>()), 0);

            string str = "ttttttttttttttt"; // size = 15
            auto t = str.data();
            (void) t;
            auto av3 = as_multi_span(str);
            overloaded_func(as_multi_span(av3, dim(1), dim<3>(), dim<5>()), 't');
        }

        {
            string str;
            multi_span<char> strspan = as_multi_span(str);
            (void) strspan;
            const string cstr;
            multi_span<const char> cstrspan = as_multi_span(cstr);
            (void) cstrspan;
        }

        {
            int a[3][4][5];
            auto av = as_multi_span(a);
            const int(*b)[4][5];
            b = a;
            auto bv = as_multi_span(b, 3);

            CHECK(av == bv);

            const std::array<double, 3> arr = {0.0, 0.0, 0.0};
            auto cv = as_multi_span(arr);
            (void) cv;

            vector<float> vec(3);
            auto dv = as_multi_span(vec);
            (void) dv;

#ifdef CONFIRM_COMPILATION_ERRORS
            auto dv2 = as_multi_span(std::move(vec));
#endif
        }
    }

    TEST(empty_spans)
    {
        {
            multi_span<int, 0> empty_av(nullptr);

            CHECK(empty_av.bounds().index_bounds() == index<1>{0});
            CHECK_THROW(empty_av[0], fail_fast);
            CHECK_THROW(empty_av.begin()[0], fail_fast);
            CHECK_THROW(empty_av.cbegin()[0], fail_fast);
            for (auto& v : empty_av) {
                (void) v;
                CHECK(false);
            }
        }

        {
            multi_span<int> empty_av = {};
            CHECK(empty_av.bounds().index_bounds() == index<1>{0});
            CHECK_THROW(empty_av[0], fail_fast);
            CHECK_THROW(empty_av.begin()[0], fail_fast);
            CHECK_THROW(empty_av.cbegin()[0], fail_fast);
            for (auto& v : empty_av) {
                (void) v;
                CHECK(false);
            }
        }
    }

    TEST(index_constructor)
    {
        auto arr = new int[8];
        for (int i = 0; i < 4; ++i) {
            arr[2 * i] = 4 + i;
            arr[2 * i + 1] = i;
        }

        multi_span<int, dynamic_range> av(arr, 8);

        ptrdiff_t a[1] = {0};
        index<1> i = a;

        CHECK(av[i] == 4);

        auto av2 = as_multi_span(av, dim<4>(), dim(2));
        ptrdiff_t a2[2] = {0, 1};
        index<2> i2 = a2;

        CHECK(av2[i2] == 0);
        CHECK(av2[0][i] == 4);

        delete[] arr;
    }

    TEST(index_constructors)
    {
        {
            // components of the same type
            index<3> i1(0, 1, 2);
            CHECK(i1[0] == 0);

            // components of different types
            size_t c0 = 0;
            size_t c1 = 1;
            index<3> i2(c0, c1, 2);
            CHECK(i2[0] == 0);

            // from array
            index<3> i3 = {0, 1, 2};
            CHECK(i3[0] == 0);

            // from other index of the same size type
            index<3> i4 = i3;
            CHECK(i4[0] == 0);

            // default
            index<3> i7;
            CHECK(i7[0] == 0);

            // default
            index<3> i9 = {};
            CHECK(i9[0] == 0);
        }

        {
            // components of the same type
            index<1> i1(0);
            CHECK(i1[0] == 0);

            // components of different types
            size_t c0 = 0;
            index<1> i2(c0);
            CHECK(i2[0] == 0);

            // from array
            index<1> i3 = {0};
            CHECK(i3[0] == 0);

            // from int
            index<1> i4 = 0;
            CHECK(i4[0] == 0);

            // from other index of the same size type
            index<1> i5 = i3;
            CHECK(i5[0] == 0);

            // default
            index<1> i8;
            CHECK(i8[0] == 0);

            // default
            index<1> i9 = {};
            CHECK(i9[0] == 0);
        }

#ifdef CONFIRM_COMPILATION_ERRORS
        {
            index<3> i1(0, 1);
            index<3> i2(0, 1, 2, 3);
            index<3> i3 = {0};
            index<3> i4 = {0, 1, 2, 3};
            index<1> i5 = {0, 1};
        }
#endif
    }

    TEST(index_operations)
    {
        ptrdiff_t a[3] = {0, 1, 2};
        ptrdiff_t b[3] = {3, 4, 5};
        index<3> i = a;
        index<3> j = b;

        CHECK(i[0] == 0);
        CHECK(i[1] == 1);
        CHECK(i[2] == 2);

        {
            index<3> k = i + j;

            CHECK(i[0] == 0);
            CHECK(i[1] == 1);
            CHECK(i[2] == 2);
            CHECK(k[0] == 3);
            CHECK(k[1] == 5);
            CHECK(k[2] == 7);
        }

        {
            index<3> k = i * 3;

            CHECK(i[0] == 0);
            CHECK(i[1] == 1);
            CHECK(i[2] == 2);
            CHECK(k[0] == 0);
            CHECK(k[1] == 3);
            CHECK(k[2] == 6);
        }

        {
            index<3> k = 3 * i;

            CHECK(i[0] == 0);
            CHECK(i[1] == 1);
            CHECK(i[2] == 2);
            CHECK(k[0] == 0);
            CHECK(k[1] == 3);
            CHECK(k[2] == 6);
        }

        {
            index<2> k = details::shift_left(i);

            CHECK(i[0] == 0);
            CHECK(i[1] == 1);
            CHECK(i[2] == 2);
            CHECK(k[0] == 1);
            CHECK(k[1] == 2);
        }
    }

    void iterate_second_column(multi_span<int, dynamic_range, dynamic_range> av)
    {
        auto length = av.size() / 2;

        // view to the second column
        auto section = av.section({0, 1}, {length, 1});

        CHECK(section.size() == length);
        for (auto i = 0; i < section.size(); ++i) {
            CHECK(section[i][0] == av[i][1]);
        }

        for (auto i = 0; i < section.size(); ++i) {
            auto idx = index<2>{i, 0}; // avoid braces inside the CHECK macro
            CHECK(section[idx] == av[i][1]);
        }

        CHECK(section.bounds().index_bounds()[0] == length);
        CHECK(section.bounds().index_bounds()[1] == 1);
        for (auto i = 0; i < section.bounds().index_bounds()[0]; ++i) {
            for (auto j = 0; j < section.bounds().index_bounds()[1]; ++j) {
                auto idx = index<2>{i, j}; // avoid braces inside the CHECK macro
                CHECK(section[idx] == av[i][1]);
            }
        }

        size_t check_sum = 0;
        for (auto i = 0; i < length; ++i) {
            check_sum += av[i][1];
        }

        {
            auto idx = 0;
            size_t sum = 0;
            for (auto num : section) {
                CHECK(num == av[idx][1]);
                sum += num;
                idx++;
            }

            CHECK(sum == check_sum);
        }
        {
            size_t idx = length - 1;
            size_t sum = 0;
            for (auto iter = section.rbegin(); iter != section.rend(); ++iter) {
                CHECK(*iter == av[idx][1]);
                sum += *iter;
                idx--;
            }

            CHECK(sum == check_sum);
        }
    }

    TEST(span_section_iteration)
    {
        int arr[4][2] = {{4, 0}, {5, 1}, {6, 2}, {7, 3}};

        // static bounds
        {
            multi_span<int, 4, 2> av = arr;
            iterate_second_column(av);
        }
        // first bound is dynamic
        {
            multi_span<int, dynamic_range, 2> av = arr;
            iterate_second_column(av);
        }
        // second bound is dynamic
        {
            multi_span<int, 4, dynamic_range> av = arr;
            iterate_second_column(av);
        }
        // both bounds are dynamic
        {
            multi_span<int, dynamic_range, dynamic_range> av = arr;
            iterate_second_column(av);
        }
    }

    TEST(dynamic_span_section_iteration)
    {
        auto height = 4, width = 2;
        auto size = height * width;

        auto arr = new int[size];
        for (auto i = 0; i < size; ++i) {
            arr[i] = i;
        }

        auto av = as_multi_span(arr, size);

        // first bound is dynamic
        {
            multi_span<int, dynamic_range, 2> av2 = as_multi_span(av, dim(height), dim(width));
            iterate_second_column(av2);
        }
        // second bound is dynamic
        {
            multi_span<int, 4, dynamic_range> av2 = as_multi_span(av, dim(height), dim(width));
            iterate_second_column(av2);
        }
        // both bounds are dynamic
        {
            multi_span<int, dynamic_range, dynamic_range> av2 = as_multi_span(av, dim(height), dim(width));
            iterate_second_column(av2);
        }

        delete[] arr;
    }

    TEST(span_structure_size)
    {
        double(*arr)[3][4] = new double[100][3][4];
        multi_span<double, dynamic_range, 3, 4> av1(arr, 10);

        struct EffectiveStructure
        {
            double* v1;
            ptrdiff_t v2;
        };
        CHECK(sizeof(av1) == sizeof(EffectiveStructure));

        CHECK_THROW(av1[10][3][4], fail_fast);

        multi_span<const double, dynamic_range, 6, 4> av2 = as_multi_span(av1, dim(5), dim<6>(), dim<4>());
        (void) av2;
    }

    TEST(fixed_size_conversions)
    {
        int arr[] = {1, 2, 3, 4};

        // converting to an multi_span from an equal size array is ok
        multi_span<int, 4> av4 = arr;
        CHECK(av4.length() == 4);

        // converting to dynamic_range a_v is always ok
        {
            multi_span<int, dynamic_range> av = av4;
            (void) av;
        }
        {
            multi_span<int, dynamic_range> av = arr;
            (void) av;
        }

// initialization or assignment to static multi_span that REDUCES size is NOT ok
#ifdef CONFIRM_COMPILATION_ERRORS
        {
            multi_span<int, 2> av2 = arr;
        }
        {
            multi_span<int, 2> av2 = av4;
        }
#endif

        {
            multi_span<int, dynamic_range> av = arr;
            multi_span<int, 2> av2 = av;
            (void) av2;
        }

#ifdef CONFIRM_COMPILATION_ERRORS
        {
            multi_span<int, dynamic_range> av = arr;
            multi_span<int, 2, 1> av2 = av.as_multi_span(dim<2>(), dim<2>());
        }
#endif

        {
            multi_span<int, dynamic_range> av = arr;
            multi_span<int, 2, 1> av2 = as_multi_span(av, dim(2), dim(2));
            auto workaround_macro = [&]() { return av2[{1, 0}] == 2; };
            CHECK(workaround_macro());
        }

        // but doing so explicitly is ok

        // you can convert statically
        {
            multi_span<int, 2> av2 = {arr, 2};
            (void) av2;
        }
        {
            multi_span<int, 1> av2 = av4.first<1>();
            (void) av2;
        }

        // ...or dynamically
        {
            // NB: implicit conversion to multi_span<int,2> from multi_span<int,dynamic_range>
            multi_span<int, 1> av2 = av4.first(1);
            (void) av2;
        }

        // initialization or assignment to static multi_span that requires size INCREASE is not ok.
        int arr2[2] = {1, 2};

#ifdef CONFIRM_COMPILATION_ERRORS
        {
            multi_span<int, 4> av4 = arr2;
        }
        {
            multi_span<int, 2> av2 = arr2;
            multi_span<int, 4> av4 = av2;
        }
#endif
        {
            auto f = [&]() {
                multi_span<int, 4> av9 = {arr2, 2};
                (void) av9;
            };
            CHECK_THROW(f(), fail_fast);
        }

        // this should fail - we are trying to assign a small dynamic a_v to a fixed_size larger one
        multi_span<int, dynamic_range> av = arr2;
        auto f = [&]() {
            multi_span<int, 4> av2 = av;
            (void) av2;
        };
        CHECK_THROW(f(), fail_fast);
    }

    TEST(as_writeable_bytes)
    {
        int a[] = {1, 2, 3, 4};

        {
#ifdef CONFIRM_COMPILATION_ERRORS
            // you should not be able to get writeable bytes for const objects
            multi_span<const int, dynamic_range> av = a;
            auto wav = av.as_writeable_bytes();
#endif
        }

        {
            multi_span<int, dynamic_range> av;
            auto wav = as_writeable_bytes(av);
            CHECK(wav.length() == av.length());
            CHECK(wav.length() == 0);
            CHECK(wav.size_bytes() == 0);
        }

        {
            multi_span<int, dynamic_range> av = a;
            auto wav = as_writeable_bytes(av);
            CHECK(wav.data() == (byte*) &a[0]);
            CHECK(wav.length() == sizeof(a));
        }
    }

    TEST(iterator)
    {
        int a[] = {1, 2, 3, 4};

        {
            multi_span<int, dynamic_range> av = a;
            auto wav = as_writeable_bytes(av);
            for (auto& b : wav) {
                b = byte(0);
            }
            for (size_t i = 0; i < 4; ++i) {
                CHECK(a[i] == 0);
            }
        }

        {
            multi_span<int, dynamic_range> av = a;
            for (auto& n : av) {
                n = 1;
            }
            for (size_t i = 0; i < 4; ++i) {
                CHECK(a[i] == 1);
            }
        }
    }
}

int main(int, const char* []) { return UnitTest::RunAllTests(); }