// -*- C++ -*-
///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2026 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.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef GSL_DYN_ARRAY_H
#define GSL_DYN_ARRAY_H

#include "./assert"
#include "./narrow"
#include "./util"

#include <algorithm>
#include <iterator>
#include <memory>
#include <type_traits>
#include <vector>

#if defined(__cpp_lib_ranges) && (__cpp_lib_ranges >= 201911L)
#include <ranges>
#endif /* __cpp_lib_ranges >= 201911L */

namespace gsl
{
template <typename T, typename Allocator = std::allocator<T>>
class dyn_array;

namespace details
{
    template <typename T, typename Allocator = std::allocator<T>>
    class dyn_array_base : public Allocator
    {
        using pointer = T*;
        using size_type = std::size_t;

        template <typename... Args>
        GSL_CONSTEXPR_SINCE_CPP20 void construct(pointer ptr, Args&&... args)
        {
            std::allocator_traits<Allocator>::construct(static_cast<Allocator&>(*this), ptr,
                                                        std::forward<Args>(args)...);
        }

        GSL_CONSTEXPR_SINCE_CPP20 void destroy(pointer ptr)
        {
            std::allocator_traits<Allocator>::destroy(static_cast<Allocator&>(*this), ptr);
        }

        GSL_CONSTEXPR_SINCE_CPP20 void destroy_range(pointer first, pointer last)
        {
            for (; first != last; ++first) { destroy(first); }
        }

        GSL_CONSTEXPR_SINCE_CPP20 void rollback_construction(pointer first, pointer last)
        {
            destroy_range(first, last);
            std::allocator_traits<Allocator>::deallocate(static_cast<Allocator&>(*this), _data,
                                                         _count);
            _data = nullptr;
            _count = 0;
        }

    protected:
        constexpr auto data() const { return _data; }

        constexpr auto count() const { return _count; }

        GSL_CONSTEXPR_SINCE_CPP20 void resize(size_type count)
        {
            // This should only be called when constructing a non-forward iterator.
            // It neither frees nor copies `_data`.
            Expects(_data == nullptr && _count == 0);
            if (count != 0)
            {
                _data = std::allocator_traits<Allocator>::allocate(static_cast<Allocator&>(*this),
                                                                   count);
                _count = count;
            }
        }

        GSL_CONSTEXPR_SINCE_CPP20 void fill(pointer first, size_type count, const T& value)
        {
            pointer current = first;
            try
            {
                for (size_type i = 0; i < count; ++i, ++current) { construct(current, value); }
            } catch (...)
            {
                rollback_construction(first, current);
                throw;
            }
        }

        template <typename InputIt>
        GSL_CONSTEXPR_SINCE_CPP20 void copy(InputIt first, InputIt last, pointer output)
        {
            pointer current = output;
            try
            {
                for (; first != last; ++first, ++current) { construct(current, *first); }
            } catch (...)
            {
                rollback_construction(output, current);
                throw;
            }
        }

        GSL_CONSTEXPR_SINCE_CPP20 void default_construct(pointer first, size_type count)
        {
            pointer current = first;
            try
            {
                for (size_type i = 0; i < count; ++i, ++current) { construct(current); }
            } catch (...)
            {
                rollback_construction(first, current);
                throw;
            }
        }

    private:
        pointer _data;
        size_type _count;

    public:
        constexpr dyn_array_base(const Allocator& alloc)
            : Allocator{alloc}, _data{nullptr}, _count{0}
        {
            Ensures((_count == 0 && _data == nullptr) || (_count > 0 && _data != nullptr));
        }

        constexpr dyn_array_base(size_type count, const Allocator& alloc)
            : Allocator{alloc}
            , _data{count == 0 ? nullptr
                               : std::allocator_traits<Allocator>::allocate(
                                     static_cast<Allocator&>(*this), count)}
            , _count{count}
        {
            Ensures((_count == 0 && _data == nullptr) || (_count > 0 && _data != nullptr));
        }

        GSL_CONSTEXPR_SINCE_CPP20 ~dyn_array_base()
        {
            if (_data)
            {
                if (!std::is_trivially_destructible<T>::value)
                {
                    destroy_range(_data, _data + _count);
                }
                std::allocator_traits<Allocator>::deallocate(static_cast<Allocator&>(*this), _data,
                                                             _count);
            }
        }
    };

    template <typename T>
    class dyn_array_iterator
    {
        using size_type = std::size_t;

    public:
        using difference_type = std::ptrdiff_t;
        using value_type = T;
        using pointer = T*;
        using reference = T&;
        using const_reference = const T&;
        using iterator_category = std::random_access_iterator_tag;

#if defined(__cpp_lib_ranges) && (__cpp_lib_ranges >= 201911L)
        constexpr dyn_array_iterator() = default;
#endif /* __cpp_lib_ranges >= 201911L */

        constexpr operator dyn_array_iterator<const T>() const { return {_ptr, _pos, _end_pos}; }

#if defined(_MSC_VER) && defined(__cpp_lib_ranges) && (__cpp_lib_ranges >= 201911L)
        constexpr operator pointer() const { return _ptr + gsl::narrow<size_type>(_pos); }
#endif /* defined(_MSC_VER) && __cpp_lib_ranges >= 201911L */

        constexpr auto operator==(const dyn_array_iterator& other) const
        {
            Expects(_ptr == other._ptr);
            Expects(_end_pos == other._end_pos);
            return _pos == other._pos;
        }

        constexpr auto operator!=(const dyn_array_iterator& other) const
        {
            return !(*this == other);
        }

        constexpr auto operator*() const -> reference
        {
            Expects(_ptr != nullptr);
            Expects(_pos < _end_pos);
            return _ptr[_pos];
        }

        constexpr auto operator++() -> dyn_array_iterator&
        {
            Expects(_pos < _end_pos);
            ++_pos;
            return *this;
        }

        constexpr auto operator++(int)
        {
            ++(*this);
            return dyn_array_iterator{_ptr, _pos - 1, _end_pos};
        }

        constexpr auto operator--() -> dyn_array_iterator&
        {
            Expects(_pos > 0);
            --_pos;
            return *this;
        }

        constexpr auto operator--(int)
        {
            --(*this);
            return dyn_array_iterator{_ptr, _pos + 1, _end_pos};
        }

        constexpr auto operator+=(difference_type diff) -> dyn_array_iterator&
        {
            auto new_pos = gsl::narrow<difference_type>(_pos) + diff;
            Expects(new_pos >= 0);
            Expects(new_pos <= gsl::narrow<difference_type>(_end_pos));
            _pos = gsl::narrow<size_type>(new_pos);
            return *this;
        }

        constexpr auto operator-=(difference_type diff) -> dyn_array_iterator&
        {
            auto new_pos = gsl::narrow<difference_type>(_pos) - diff;
            Expects(new_pos >= 0);
            Expects(new_pos <= gsl::narrow<difference_type>(_end_pos));
            _pos = gsl::narrow<size_type>(new_pos);
            return *this;
        }

        constexpr auto operator+(difference_type diff) const
        {
            auto new_pos = gsl::narrow<difference_type>(_pos) + diff;
            return dyn_array_iterator{_ptr, gsl::narrow<size_type>(new_pos), _end_pos};
        }

        constexpr auto operator-(difference_type diff) const { return *this + (-diff); }

        constexpr auto operator-(const dyn_array_iterator& other) const
        {
            Expects(_ptr == other._ptr);
            Expects(_end_pos == other._end_pos);
            return gsl::narrow<difference_type>(_pos) - gsl::narrow<difference_type>(other._pos);
        }

        constexpr auto operator[](size_type pos) -> reference
        {
            Expects(_pos + pos < _end_pos);
            return _ptr[_pos + pos];
        }

        constexpr auto operator[](size_type pos) const -> const_reference
        {
            return const_cast<dyn_array_iterator&>(*this).operator[](pos);
        }

    private:
        constexpr dyn_array_iterator(pointer ptr, size_type pos, size_type end_pos)
            : _ptr{ptr}, _pos{pos}, _end_pos{end_pos}
        {
            Ensures((_ptr != nullptr && _end_pos > 0) || (_ptr == nullptr && _end_pos == 0));
            Ensures(_pos <= _end_pos);
        }

        pointer _ptr{};
        size_type _pos{};
        size_type _end_pos{};

        template <typename, typename>
        friend class ::gsl::dyn_array;
    };
} // namespace details

template <typename T, typename Allocator>
class dyn_array : private details::dyn_array_base<T, Allocator>
{
    using base = details::dyn_array_base<T, Allocator>;
    using pointer = T*;

public:
    using value_type = T;
    using reference = T&;
    using const_reference = const T&;
    using iterator = details::dyn_array_iterator<T>;
    using const_iterator = details::dyn_array_iterator<const T>;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
    using difference_type = std::ptrdiff_t;
    using size_type = std::size_t;

    using allocator_type = Allocator;

    explicit constexpr dyn_array(const Allocator& alloc = {}) : base{alloc} {}

    constexpr dyn_array(size_type count, const T& value, const Allocator& alloc = {})
        : base{count, alloc}
    {
        base::fill(data(), size(), value);
    }

    template <typename InputIt,
              std::enable_if_t<details::is_fwd_iterator<InputIt>::value, bool> = true>
    constexpr dyn_array(InputIt first, InputIt last, const Allocator& alloc = {})
        : base{gsl::narrow<size_type>(std::distance(first, last)), alloc}
    {
        base::copy(first, last, data());
    }

    template <typename InputIt, std::enable_if_t<!details::is_fwd_iterator<InputIt>::value &&
                                                     details::is_iterator<InputIt>::value,
                                                 bool> = true>
    constexpr dyn_array(InputIt first, InputIt last, const Allocator& alloc = {}) : dyn_array{alloc}
    {
        std::vector<T> tmp(first, last);
        base::resize(tmp.size());
        base::copy(std::begin(tmp), std::end(tmp), data());
    }

#if defined(__cpp_lib_containers_ranges) && (__cpp_lib_containers_ranges >= 202202L)
    template <typename InputRg>
        requires(std::ranges::input_range<InputRg>)
    constexpr dyn_array(std::from_range_t, InputRg&& rg, const Allocator& alloc = {})
        : base{gsl::narrow<size_type>(std::size(rg)), alloc}
    {
        base::copy(std::ranges::begin(rg), std::ranges::end(rg), data());
    }
#endif /* __cpp_lib_containers_ranges >= 202202L */

    constexpr explicit dyn_array(size_type count, const Allocator& alloc = {}) : base{count, alloc}
    {
        base::default_construct(data(), size());
    }

    constexpr dyn_array(const dyn_array& other, const Allocator& alloc = {})
        : dyn_array(other.begin(), other.end(), alloc)
    {}

    constexpr dyn_array(std::initializer_list<T> init, const Allocator& alloc = {})
        : dyn_array(init.begin(), init.end(), alloc)
    {}

    constexpr dyn_array(dyn_array&&) = delete;
    dyn_array& operator=(dyn_array&&) = delete;

    constexpr auto operator==(const dyn_array& other) const
    {
        return size() == other.size() && std::equal(begin(), end(), other.begin(), other.end());
    }

    constexpr auto operator!=(const dyn_array& other) const { return !(*this == other); }

    constexpr auto size() const { return base::count(); }

    constexpr auto empty() const { return size() == 0; }

    constexpr auto max_size() const { return static_cast<size_type>(-1); }

    constexpr auto get_allocator() -> Allocator& { return *this; }

    constexpr auto operator[](size_type pos) -> reference
    {
        Expects(pos < size());
        return data()[pos];
    }

    constexpr auto operator[](size_type pos) const -> const_reference
    {
        return const_cast<dyn_array&>(*this)[pos];
    }

    constexpr auto data() { return base::data(); }
    constexpr auto data() const -> const T* { return const_cast<dyn_array&>(*this).data(); }

    constexpr auto begin() { return iterator{data(), 0, size()}; }
    constexpr auto begin() const { return const_iterator{data(), 0, size()}; }
    constexpr auto cbegin() const { return begin(); }

    constexpr auto rbegin() { return reverse_iterator{end()}; }
    constexpr auto rbegin() const { return const_reverse_iterator{end()}; }
    constexpr auto crbegin() const { return rbegin(); }

#ifdef _MSC_VER
    constexpr auto _Unchecked_begin() { return data(); }
    constexpr auto _Unchecked_begin() const -> const T*
    {
        return const_cast<dyn_array&>(*this)._Unchecked_begin();
    }
#endif /* _MSC_VER */

    constexpr auto end() { return iterator{data(), size(), size()}; }
    constexpr auto end() const { return const_iterator{data(), size(), size()}; }
    constexpr auto cend() const { return end(); }

    constexpr auto rend() { return reverse_iterator{begin()}; }
    constexpr auto rend() const { return const_reverse_iterator{begin()}; }
    constexpr auto crend() const { return rend(); }

#ifdef _MSC_VER
    constexpr auto _Unchecked_end() { return data() + size(); }
    constexpr auto _Unchecked_end() const -> const T*
    {
        return const_cast<dyn_array&>(*this)._Unchecked_end();
    }
#endif /* _MSC_VER */
};

#if defined(__cpp_deduction_guides) && (__cpp_deduction_guides >= 201703L)

template <class InputIt,
          class Alloc = std::allocator<typename std::iterator_traits<InputIt>::value_type>>
dyn_array(InputIt, InputIt, Alloc = {})
    -> dyn_array<typename std::iterator_traits<InputIt>::value_type, Alloc>;

#if defined(__cpp_lib_containers_ranges) && (__cpp_lib_containers_ranges >= 202202L)
template <std::ranges::input_range InputRg,
          class Alloc = std::allocator<std::ranges::range_value_t<InputRg>>>
dyn_array(std::from_range_t, InputRg&&, Alloc = {})
    -> dyn_array<std::ranges::range_value_t<InputRg>, Alloc>;
#endif /* __cpp_lib_containers_ranges >= 202202L */

#endif /* __cpp_deduction_guides >= 201703L */
} // namespace gsl

#endif /* defined(GSL_DYN_ARRAY_H) */