vector.hpp

#pragma once
 
#include <iterator>
#include <type_traits>
#include <utility>
#include <memory>
#include <memory_resource>
#include <initializer_list>
#include <algorithm>
#include <span>
#include <limits>
#include <optional>
 
#include <cstdint>
#include <cstddef>
#include <cstring>
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES && (__cplusplus <= 202002L || !__has_include(<ranges>) || !defined(__cpp_lib_containers_ranges))
#  undef PLUGIFY_STRING_CONTAINERS_RANGES
#  define PLUGIFY_STRING_CONTAINERS_RANGES 0
#endif
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
#  include <ranges>
#endif
 
#include "macro.hpp"
 
namespace plg {
    template<typename Allocator>
    struct vector_iterator {
        using allocator_traits = std::allocator_traits<Allocator>;
    public:
        using iterator_category = std::random_access_iterator_tag;
        using value_type = typename allocator_traits::value_type;
        using difference_type = std::ptrdiff_t;
        using pointer = typename allocator_traits::pointer;
        using reference = value_type&;
    protected:
        pointer _current;
    public:
        constexpr vector_iterator() = default;
        constexpr vector_iterator(const vector_iterator& other) = default;
        constexpr vector_iterator(vector_iterator&& other) = default;
        constexpr vector_iterator(pointer ptr)
            : _current(ptr) {}
        constexpr vector_iterator& operator=(const vector_iterator& other) = default;
        constexpr vector_iterator& operator=(vector_iterator&& other) = default;
#if __cpp_constexpr >= 201907L
        constexpr 
#endif
        ~vector_iterator() = default;
    public:
        constexpr reference operator*() const noexcept {
            return *_current;
        }
        constexpr pointer operator->() const noexcept {
            return _current;
        }
        constexpr vector_iterator& operator++() noexcept {
            ++_current;
            return *this;
        }
        constexpr vector_iterator operator++(int) const noexcept {
            return vector_iterator(_current++);
        }
        constexpr vector_iterator& operator--() noexcept {
            --_current;
            return *this;
        }
        constexpr vector_iterator operator--(int) const noexcept {
            return vector_iterator(_current--);
        }
        constexpr vector_iterator& operator+=(const difference_type n) noexcept {
            _current += n;
            return *this;
        }
        constexpr vector_iterator operator+(const difference_type n) const noexcept {
            vector_iterator temp = *this;
            return temp += n;
        }
        constexpr vector_iterator& operator-=(const difference_type n) noexcept {
            _current -= n;
            return *this;
        }
        constexpr vector_iterator operator-(const difference_type n) const noexcept {
            vector_iterator temp = *this;
            return temp -= n;
        }
        constexpr reference operator[](const difference_type n) const noexcept {
            return _current[n];
        }
        template<typename Alloc>
        constexpr friend typename vector_iterator<Alloc>::difference_type operator-(const vector_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
        template<typename Alloc>
        constexpr friend bool operator==(const vector_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
#if __cpp_impl_three_way_comparison
        template<typename Alloc>
        constexpr friend auto operator<=>(const vector_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
        [[nodiscard]] operator const pointer() const noexcept {
            return _current;
        }
#endif // __cpp_impl_three_way_comparison
        [[nodiscard]] pointer base() const noexcept {
            return _current;
        }
    };
 
    template<typename Allocator>
    [[nodiscard]] constexpr typename vector_iterator<Allocator>::difference_type operator-(const vector_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        using difference_type = typename vector_iterator<Allocator>::difference_type;
        return difference_type(lhs.base() - rhs.base());
    }
    template<typename Allocator>
    [[nodiscard]] constexpr bool operator==(const vector_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        return lhs.base() == rhs.base();
    }
 
#if __cpp_impl_three_way_comparison
    template<typename Allocator>
    [[nodiscard]] constexpr auto operator<=>(const vector_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        return lhs.base() <=> rhs.base();
    }
#endif // __cpp_impl_three_way_comparison
 
    template<typename Allocator>
    struct vector_const_iterator {
        using allocator_traits = std::allocator_traits<Allocator>;
    public:
        using iterator_category = std::random_access_iterator_tag;
        using value_type = typename allocator_traits::value_type;
        using difference_type = std::ptrdiff_t;
        using pointer = typename allocator_traits::const_pointer;
        using reference = const value_type&;
    protected:
        pointer _current;
    public:
        constexpr vector_const_iterator() = default;
        constexpr vector_const_iterator(const vector_const_iterator& other) = default;
        constexpr vector_const_iterator(vector_const_iterator&& other) = default;
        constexpr vector_const_iterator(pointer ptr)
            : _current(ptr) {}
        constexpr vector_const_iterator(const vector_iterator<Allocator>& other)  // allow only iterator to const_iterator conversion
            : _current(other.base()) {}
        constexpr vector_const_iterator& operator=(const vector_const_iterator& other) = default;
        constexpr vector_const_iterator& operator=(vector_const_iterator&& other) = default;
#if __cpp_constexpr >= 201907L
        constexpr 
#endif
        ~vector_const_iterator() = default;
    public:
        constexpr reference operator*() const noexcept {
            return *_current;
        }
        constexpr pointer operator->() const noexcept {
            return _current;
        }
        constexpr vector_const_iterator& operator++() noexcept {
            ++_current;
            return *this;
        }
        constexpr vector_const_iterator operator++(int) const noexcept {
            return vector_const_iterator(_current++);
        }
        constexpr vector_const_iterator& operator--() noexcept {
            --_current;
            return *this;
        }
        constexpr vector_const_iterator operator--(int) const noexcept {
            return vector_const_iterator(_current--);
        }
        constexpr vector_const_iterator& operator+=(const difference_type n) noexcept {
            _current += n;
            return *this;
        }
        constexpr vector_const_iterator operator+(const difference_type n) const noexcept {
            vector_const_iterator temp = *this;
            return temp += n;
        }
        constexpr vector_const_iterator& operator-=(const difference_type n) noexcept {
            _current -= n;
            return *this;
        }
        constexpr vector_const_iterator operator-(const difference_type n) const noexcept {
            vector_const_iterator temp = *this;
            return temp -= n;
        }
        constexpr reference operator[](const difference_type n) const noexcept {
            return _current[n];
        }
        template<typename Alloc>
        constexpr friend typename vector_const_iterator<Alloc>::difference_type operator-(const vector_const_iterator<Alloc>& lhs, const vector_const_iterator<Alloc>& rhs) noexcept;
        template<typename Alloc>
        constexpr friend bool operator==(const vector_const_iterator<Alloc>& lhs, const vector_const_iterator<Alloc>& rhs) noexcept;
#if __cpp_impl_three_way_comparison
        template<typename Alloc>
        constexpr friend auto operator<=>(const vector_const_iterator<Alloc>& lhs, const vector_const_iterator<Alloc>& rhs) noexcept;
#endif // __cpp_impl_three_way_comparison
        template<typename Alloc>
        constexpr friend typename vector_const_iterator<Alloc>::difference_type operator-(const vector_const_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
        template<typename Alloc>
        constexpr friend bool operator==(const vector_const_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
#if __cpp_impl_three_way_comparison
        template<typename Alloc>
        constexpr friend auto operator<=>(const vector_const_iterator<Alloc>& lhs, const vector_iterator<Alloc>& rhs) noexcept;
        [[nodiscard]] operator const pointer() const noexcept {
            return _current;
        }
#endif // __cpp_impl_three_way_comparison
        [[nodiscard]] pointer base() const noexcept {
            return _current;
        }
    };
 
    template<typename Allocator>
    [[nodiscard]] constexpr typename vector_const_iterator<Allocator>::difference_type operator-(const vector_const_iterator<Allocator>& lhs, const vector_const_iterator<Allocator>& rhs) noexcept {
        using difference_type = typename vector_const_iterator<Allocator>::difference_type;
        return difference_type(lhs.base() - rhs.base());
    }
    template<typename Allocator>
    [[nodiscard]] constexpr bool operator==(const vector_const_iterator<Allocator>& lhs, const vector_const_iterator<Allocator>& rhs) noexcept {
        return lhs.base() == rhs.base();
    }
#if __cpp_impl_three_way_comparison
    template<typename Allocator>
    [[nodiscard]] constexpr auto operator<=>(const vector_const_iterator<Allocator>& lhs, const vector_const_iterator<Allocator>& rhs) noexcept {
        return lhs.base() <=> rhs.base();
    }
#endif // __cpp_impl_three_way_comparison
    template<typename Allocator>
    [[nodiscard]] constexpr typename vector_const_iterator<Allocator>::difference_type operator-(const vector_const_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        using difference_type = typename vector_const_iterator<Allocator>::difference_type;
        return difference_type(lhs.base() - rhs.base());
    }
    template<typename Allocator>
    [[nodiscard]] constexpr bool operator==(const vector_const_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        return lhs.base() == rhs.base();
    }
#if __cpp_impl_three_way_comparison
    template<typename Allocator>
    [[nodiscard]] constexpr auto operator<=>(const vector_const_iterator<Allocator>& lhs, const vector_iterator<Allocator>& rhs) noexcept {
        return lhs.base() <=> rhs.base();
    }
#endif // __cpp_impl_three_way_comparison
 
    namespace detail {
        struct initialized_value_tag {};
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
        template<typename Range, typename Type>
        concept vector_compatible_range = std::ranges::input_range<Range> && std::convertible_to<std::ranges::range_reference_t<Range>, Type>;
#endif
    } // namespace detail
 
    // vector
    // based on implementations from libc++, libstdc++ and Microsoft STL
    template<typename T, typename Allocator = std::allocator<T>>
    class vector {
        using allocator_traits = std::allocator_traits<Allocator>;
    public:
        using value_type = T;
        using allocator_type = Allocator;
        using size_type = typename allocator_traits::size_type;
        using difference_type = typename allocator_traits::difference_type;
        using reference = value_type&;
        using const_reference = const value_type&;
        using pointer = typename allocator_traits::pointer;
        using const_pointer = typename allocator_traits::const_pointer;
        using iterator = vector_iterator<Allocator>;
        using const_iterator = vector_const_iterator<Allocator>;
        using reverse_iterator = std::reverse_iterator<iterator>;
        using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
    protected:
        PLUGIFY_NO_UNIQUE_ADDRESS
        allocator_type _allocator;
        pointer _begin;
        pointer _end;
        pointer _capacity;
 
    private:
        constexpr static size_type growth_factor = 2; // When resizing, what number to scale by
 
        constexpr void copy_constructor(const vector& other) {
            const size_type capacity = other.capacity();
            _begin = allocator_traits::allocate(_allocator, capacity);
            std::uninitialized_copy(other.begin(), other.end(), begin());
            _end = _begin + other.size();
            _capacity = _begin + capacity;
        }
 
        template<PLUGIFY_INPUT_ITERATOR InputIterator>
        constexpr void range_constructor(InputIterator first, InputIterator last) {
            const size_type count = static_cast<size_type>(std::distance(first, last));
            _begin = allocator_traits::allocate(_allocator, count);
            std::uninitialized_copy(first, last, _begin);
            _capacity = _begin + count;
            _end = _begin + count;
        }
 
        [[nodiscard]] constexpr bool is_full() const {
            return _end == _capacity;
        }
 
        [[nodiscard]] constexpr size_type calculate_new_capacity() const {
            const size_type old_capacity = capacity();
            return old_capacity == 0 ? 1 : growth_factor * old_capacity;
        }
 
        [[nodiscard]] constexpr iterator const_iterator_cast(const_iterator iter) noexcept {
            return begin() + (iter - cbegin());
        }
 
        constexpr void reallocate(size_type new_capacity) {
            reallocate(new_capacity, [](pointer const) {});
        }
 
        template<typename F>
        constexpr void reallocate(size_type new_capacity, const F& construct) {
            const size_type old_size = size();
            const size_type old_capacity = capacity();
            PLUGIFY_ASSERT(new_capacity >= old_size, "plg::vector::reallocate(): resulted vector size would exceed size()", std::length_error);
            if (new_capacity == old_capacity)
                return;
 
            pointer const new_begin = allocator_traits::allocate(_allocator, new_capacity);
            construct(new_begin);
            std::uninitialized_move(_begin, _end, new_begin);
            std::destroy(_begin, _end);
            allocator_traits::deallocate(_allocator, _begin, capacity());
            _begin = new_begin;
            _end = _begin + old_size;
            _capacity = _begin + new_capacity;
        }
 
        template<typename F>
        constexpr void emplace_at_end(const F& construct) {
            if (is_full()) {
                reallocate(calculate_new_capacity(), construct);
            } else {
                construct(_begin);
            }
        }
 
        template<typename V>
        constexpr void resize_to(size_type count, const V& value) {
            if (count < size()) {
                std::destroy(_begin + count, _end);
                _end = _begin + count;
            } else if (count > size()) {
                const size_type old_size = size();
                auto construct = [&](pointer const data) {
                    if constexpr (std::is_same_v<V, T>) {
                        std::uninitialized_fill(data + old_size, data + count, value);
                    } else {
                        std::uninitialized_value_construct(data + old_size, data + count);
                    }
                };
                if (count > capacity()) {
                    reallocate(count, construct);
                } else {
                    construct(_begin);
                }
                _end = _begin + count;
            }
        }
 
        constexpr void swap_without_allocator(vector&& other) noexcept {
            using std::swap;
            swap(_begin, other._begin);
            swap(_end, other._end);
            swap(_capacity, other._capacity);
        }
 
    public:
        // constructor
        constexpr vector() noexcept(std::is_nothrow_default_constructible<Allocator>::value)
            : _allocator(Allocator()), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
        }
 
        constexpr explicit vector(const Allocator& allocator) noexcept
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
        }
 
        constexpr vector(size_type count, const T& value, const Allocator& allocator = Allocator())
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::vector(): constructed vector size would exceed max_size()", std::length_error);
            _begin = allocator_traits::allocate(_allocator, count);
            std::uninitialized_fill_n(_begin, count, value);
            _capacity = _begin + count;
            _end = _begin + count;
        }
 
        constexpr explicit vector(size_type count, const Allocator& allocator = Allocator())
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::vector(): constructed vector size would exceed max_size()", std::length_error);
            _begin = allocator_traits::allocate(_allocator, count);
            std::uninitialized_value_construct_n(_begin, count);
            _capacity = _begin + count;
            _end = _begin + count;
        }
 
        template<PLUGIFY_INPUT_ITERATOR InputIterator>
        constexpr vector(InputIterator first, InputIterator last, const Allocator& allocator = Allocator())
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            PLUGIFY_ASSERT(static_cast<size_type>(std::distance(first, last)) <= max_size(), "plg::vector::vector(): constructed vector size would exceed max_size()", std::length_error);
            range_constructor(first, last);
        }
 
        constexpr vector(const vector& other)
            : _allocator(other.get_allocator()), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            copy_constructor(other);
        }
 
        constexpr vector(const vector& other, const Allocator& allocator)
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            copy_constructor(other);
        }
 
        constexpr vector(vector&& other) noexcept(std::is_nothrow_move_constructible<Allocator>::value)
            : _allocator(Allocator()), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            swap(other);
        }
 
        constexpr vector(vector&& other, const Allocator& allocator)
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            if constexpr (allocator_traits::is_always_equal::value) {
                swap_without_allocator(std::move(other));
            } else {
                if (get_allocator() == other.get_allocator()) {
                    swap_without_allocator(std::move(other));
                } else {
                    const size_type capacity = other.capacity();
                    _begin = allocator_traits::allocate(_allocator, capacity);
                    std::uninitialized_move(other.begin(), other.end(), begin());
                    _end = _begin + other.size();
                    _capacity = _begin + capacity;
                }
            }
        }
 
        constexpr vector(std::initializer_list<T> list, const Allocator& allocator = Allocator())
            : _allocator(allocator), _begin{nullptr}, _end{nullptr}, _capacity{nullptr} {
            PLUGIFY_ASSERT(list.size() <= max_size(), "plg::vector::vector(): constructed vector size would exceed max_size()", std::length_error);
            range_constructor(list.begin(), list.end());
        }
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
        template<detail::vector_compatible_range<T> Range>
        constexpr vector(std::from_range_t, Range&& range, const Allocator& alloc = Allocator())
            : vector(std::ranges::begin(range), std::ranges::end(range), alloc) {}
#endif // PLUGIFY_VECTOR_CONTAINERS_RANGES
 
        // destructor
#if __cpp_constexpr >= 201907L
        constexpr 
#endif
        ~vector() {
            std::destroy(_begin, _end);
            allocator_traits::deallocate(_allocator, _begin, capacity());
        }
 
        // operator=
        constexpr vector& operator=(const vector& other) {
            if (this == &other) [[unlikely]] {
                return *this;
            }
 
            clear();
            if constexpr (allocator_traits::propagate_on_container_copy_assignment::value) {
                if constexpr (!allocator_traits::is_always_equal::value) {
                    if (get_allocator() != other.get_allocator()) {
                        allocator_traits::deallocate(_allocator, _begin, capacity());
                    }
                }
                _allocator = other.get_allocator();
            }
 
            assign(other.begin(), other.end());
            return *this;
        }
 
        constexpr vector& operator=(vector&& other) noexcept(
                std::allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
                std::allocator_traits<Allocator>::is_always_equal::value) {
            if (this == &other) [[unlikely]] {
                return *this;
            }
 
            clear();
            if constexpr (allocator_traits::propagate_on_container_move_assignment::value) {
                if constexpr (!allocator_traits::is_always_equal::value) {
                    if (get_allocator() != other.get_allocator()) {
                        allocator_traits::deallocate(_allocator, _begin, capacity());
                    }
                }
                _allocator = other.get_allocator();
            }
 
            if constexpr (allocator_traits::propagate_on_container_move_assignment::value || allocator_traits::is_always_equal::value) {
                swap_without_allocator(std::move(other));
            } else {
                if (get_allocator() == other.get_allocator()) {
                    swap_without_allocator(std::move(other));
                } else {
                    assign(std::make_move_iterator(other.begin()), std::make_move_iterator(other.end()));
                    other.clear();
                }
            }
            return *this;
        }
 
        constexpr vector& operator=(std::initializer_list<T> list) {
            assign(list.begin(), list.end());
            return *this;
        }
 
        // assign
        constexpr void assign(size_type count, const T& value) {
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::assign(): resulted vector size would exceed max_size()", std::length_error);
            if (count > capacity()) {
                pointer const new_begin = allocator_traits::allocate(_allocator, count);
                std::uninitialized_fill_n(new_begin, count, value);
                std::destroy(_begin, _end);
                allocator_traits::deallocate(_allocator, _begin, capacity());
                _begin = new_begin;
                _capacity = _begin + count;
            } else if (size() >= count) {
                std::fill_n(_begin, count, value);
                std::destroy(_begin + count, _end);
            } else {
                std::fill_n(_begin, size(), value);
                std::uninitialized_fill_n(_begin + size(), count - size(), value);
            }
            _end = _begin + count;
        }
 
        template<PLUGIFY_INPUT_ITERATOR InputIterator>
        constexpr void assign(InputIterator first, InputIterator last) {
            const size_type count = static_cast<size_type>(std::distance(first, last));
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::assign(): resulted vector size would exceed max_size()", std::length_error);
            if (count > capacity()) {
                pointer const new_begin = allocator_traits::allocate(_allocator, count);
                std::uninitialized_copy(first, last, new_begin);
                std::destroy(_begin, _end);
                allocator_traits::deallocate(_allocator, _begin, capacity());
                _begin = new_begin;
                _capacity = _begin + count;
            } else if (size() >= count) {
                std::copy(first, last, _begin);
                std::destroy(_begin + count, _end);
            } else {
                std::copy(first, first + size(), _begin);
                std::uninitialized_copy(first + size(), last, _begin + size());
            }
            _end = _begin + count;
        }
 
        constexpr void assign(std::initializer_list<T> list) {
            assign(list.begin(), list.end());
        }
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
        template<detail::vector_compatible_range<T> Range>
        constexpr void assign_range(Range&& range) {
            assign(std::ranges::begin(range), std::ranges::end(range));
        }
#endif // PLUGIFY_VECTOR_CONTAINERS_RANGES
 
        // get_allocator
        [[nodiscard]] constexpr allocator_type get_allocator() const {
            return _allocator;
        }
 
        // element access
        [[nodiscard]] constexpr reference at(size_type position) {
            PLUGIFY_ASSERT(position < size(), "plg::vector::at(): input index is out of bounds", std::out_of_range);
            return *(_begin + position);
        }
 
        [[nodiscard]] constexpr const_reference at(size_type position) const {
            PLUGIFY_ASSERT(position < size(), "plg::vector::at(): input index is out of bounds", std::out_of_range);
            return *(_begin + position);
        }
 
        [[nodiscard]] constexpr reference operator[](size_type position) noexcept {
            return *(_begin + position);
        }
 
        [[nodiscard]] constexpr const_reference operator[](size_type position) const noexcept {
            return *(_begin + position);
        }
 
        [[nodiscard]] constexpr reference front() {
            PLUGIFY_ASSERT(!empty(), "plg::vector::front(): vector is empty", std::length_error);
            return *_begin;
        }
 
        [[nodiscard]] constexpr const_reference front() const {
            PLUGIFY_ASSERT(!empty(), "plg::vector::front(): vector is empty", std::length_error);
            return *_begin;
        }
 
        [[nodiscard]] constexpr reference back() {
            PLUGIFY_ASSERT(!empty(), "plg::vector::back(): vector is empty", std::length_error);
            return *(_end - 1);
        }
 
        [[nodiscard]] constexpr const_reference back() const {
            PLUGIFY_ASSERT(!empty(), "plg::vector::back(): vector is empty", std::length_error);
            return *(_end - 1);
        }
 
        [[nodiscard]] constexpr T* data() noexcept {
            return _begin;
        }
 
        [[nodiscard]] constexpr const T* data() const noexcept {
            return _begin;
        }
 
        // iterators
        [[nodiscard]] constexpr iterator begin() noexcept {
            return iterator(_begin);
        }
 
        [[nodiscard]] constexpr const_iterator begin() const noexcept {
            return const_iterator(_begin);
        }
 
        [[nodiscard]] constexpr const_iterator cbegin() const noexcept {
            return const_iterator(_begin);
        }
 
        [[nodiscard]] constexpr iterator end() noexcept {
            return iterator(_end);
        }
 
        [[nodiscard]] constexpr const_iterator end() const noexcept {
            return const_iterator(_end);
        }
 
        [[nodiscard]] constexpr const_iterator cend() const noexcept {
            return const_iterator(_end);
        }
 
        [[nodiscard]] constexpr reverse_iterator rbegin() noexcept {
            return reverse_iterator(_end);
        }
 
        [[nodiscard]] constexpr const_reverse_iterator rbegin() const noexcept {
            return const_reverse_iterator(_end);
        }
 
        [[nodiscard]] constexpr const_reverse_iterator crbegin() const noexcept {
            return const_reverse_iterator(_end);
        }
 
        [[nodiscard]] constexpr reverse_iterator rend() noexcept {
            return reverse_iterator(_begin);
        }
 
        [[nodiscard]] constexpr const_reverse_iterator rend() const noexcept {
            return const_reverse_iterator(_begin);
        }
 
        [[nodiscard]] constexpr const_reverse_iterator crend() const noexcept {
            return const_reverse_iterator(_begin);
        }
 
        // capacity
        [[nodiscard]] constexpr bool empty() const {
            return (_begin == _end);
        }
 
        [[nodiscard]] constexpr size_type size() const noexcept {
            return static_cast<size_type>(_end - _begin);
        }
 
        [[nodiscard]] constexpr size_type max_size() const noexcept {
            return allocator_traits::max_size(_allocator);
        }
 
        constexpr void reserve(size_type new_capacity) {
            PLUGIFY_ASSERT(new_capacity <= max_size(), "plg::vector::reserve(): allocated memory size would exceed max_size()", std::length_error);
            if (new_capacity > capacity()) {
                reallocate(new_capacity);
            }
        }
 
        [[nodiscard]] constexpr size_type capacity() const noexcept {
            return static_cast<size_type>(_capacity - _begin);
        }
 
        constexpr void shrink_to_fit() {
            reallocate(size());
        }
 
        // modifiers
        constexpr void clear() noexcept {
            std::destroy(_begin, _end);
            _end = _begin;
        }
 
        constexpr iterator insert(const_iterator position, const T& value) {
            return emplace(position, value);
        }
 
        constexpr iterator insert(const_iterator position, T&& value) {
            return emplace(position, std::move(value));
        }
 
        constexpr iterator insert(const_iterator position, size_type count, const T& value) {
            const size_type sz = size();
            const size_type new_size = sz + count;
            PLUGIFY_ASSERT(new_size <= max_size(), "plg::vector::insert(): resulted vector size would exceed max_size()", std::length_error);
            const size_type position_distance = static_cast<size_type>(position - cbegin());
            PLUGIFY_ASSERT(position_distance <= sz, "plg::vector::insert(): pos out of range", std::out_of_range);
            if (count != 0) {
                if (new_size > capacity()) {
                    pointer const new_begin = allocator_traits::allocate(_allocator, new_size);
                    pointer const old_position = _begin + position_distance;
                    std::uninitialized_move(_begin, old_position, new_begin);
                    pointer const new_position = new_begin + position_distance;
                    std::uninitialized_fill_n(new_position, count, value);
                    std::uninitialized_move(old_position, _end, new_position + count);
                    std::destroy(_begin, _end);
                    allocator_traits::deallocate(_allocator, _begin, capacity());
                    _begin = new_begin;
                    _end = _begin + new_size;
                    _capacity = _end;
                } else {
                    pointer const pointer_position = _begin + position_distance;
                    std::uninitialized_fill_n(_end, count, value);
                    _end += count;
                    std::rotate(pointer_position, _end - count, _end);
                }
            }
            return begin() + position_distance;
        }
 
        template<PLUGIFY_INPUT_ITERATOR InputIterator>
        constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last) {
            const size_type sz = size();
            const size_type count = static_cast<size_type>(std::distance(first, last));
            const size_type new_size = sz + count;
            PLUGIFY_ASSERT(new_size <= max_size(), "plg::vector::insert(): resulted vector size would exceed max_size()", std::length_error);
            const size_type position_distance = static_cast<size_type>(position - cbegin());
            PLUGIFY_ASSERT(position_distance <= sz, "plg::vector::insert(): pos out of range", std::out_of_range);
            if (count != 0) {
                if (new_size > capacity()) {
                    pointer const new_begin = allocator_traits::allocate(_allocator, new_size);
                    pointer const old_position = _begin + position_distance;
                    pointer const new_position = new_begin + position_distance;
                    std::uninitialized_move(_begin, old_position, new_begin);
                    std::uninitialized_copy(first, last, new_position);
                    std::uninitialized_move(old_position, _end, new_position + count);
                    std::destroy(_begin, _end);
                    allocator_traits::deallocate(_allocator, _begin, capacity());
                    _begin = new_begin;
                    _end = _begin + new_size;
                    _capacity = _end;
                } else {
                    pointer const pointer_position = _begin + position_distance;
                    std::uninitialized_copy(first, last, _end);
                    _end += count;
                    std::rotate(pointer_position, _end - count, _end);
                }
            }
            return begin() + position_distance;
        }
 
        constexpr iterator insert(const_iterator position, std::initializer_list<T> list) {
            return insert(position, list.begin(), list.end());
        }
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
        template<detail::vector_compatible_range<T> Range>
        constexpr iterator insert_range(const_iterator pos, Range&& range) {
            return insert(pos - begin(), std::ranges::begin(range), std::ranges::end(range));
        }
#endif // PLUGIFY_VECTOR_CONTAINERS_RANGES
 
        template<typename... Args>
        iterator emplace(const_iterator position, Args&&... args) {
            const size_type sz = size();
            const size_type new_size = sz + 1;
            PLUGIFY_ASSERT(new_size <= max_size(), "plg::vector::emplace(): resulted vector size would exceed max_size()", std::length_error);
            const size_type position_distance = static_cast<size_type>(position - cbegin());
            PLUGIFY_ASSERT(position_distance <= sz, "plg::vector::emplace(): pos out of range", std::out_of_range);
            if (position == cend()) {
                emplace_back(std::forward<Args>(args)...);
            } else {
                if (is_full()) {
                    const size_type new_capacity = calculate_new_capacity();
                    pointer const new_begin = allocator_traits::allocate(_allocator, new_capacity);
                    pointer const old_position = _begin + position_distance;
                    pointer const new_position = new_begin + position_distance;
                    std::uninitialized_move(_begin, old_position, new_begin);
                    PLUGIFY_CONSTRUCT_AT(new_position, std::forward<Args>(args)...);
                    std::uninitialized_move(old_position, _end, new_position + 1);
                    std::destroy(_begin, _end);
                    allocator_traits::deallocate(_allocator, _begin, capacity());
                    _begin = new_begin;
                    _end = _begin + new_size;
                    _capacity = _begin + new_capacity;
                } else {
                    pointer const pointer_position = _begin + position_distance;
                    PLUGIFY_CONSTRUCT_AT(_end, std::forward<Args>(args)...);
                    ++_end;
                    std::rotate(pointer_position, _end - 1, _end);
                }
            }
            return begin() + position_distance;
        }
 
        constexpr iterator erase(const_iterator position) {
            iterator nonconst_position = const_iterator_cast(position);
            if (nonconst_position + 1 != end()) {
                std::rotate(nonconst_position, nonconst_position + 1, end());
            }
            --_end;
            std::destroy_at(_end);
            return nonconst_position;
        }
 
        constexpr iterator erase(const_iterator first, const_iterator last) {
            PLUGIFY_ASSERT(first <= last, "plg::vector::erase(): called with invalid range", std::out_of_range);
            iterator nonconst_first = const_iterator_cast(first);
            iterator nonconst_last = const_iterator_cast(last);
            if (nonconst_first != nonconst_last) {
                if (nonconst_last != end()) {
                    std::rotate(nonconst_first, nonconst_last, end());
                }
                _end = nonconst_first.base() + static_cast<size_type>(end() - nonconst_last);
                std::destroy(_end, _end + static_cast<size_type>(std::distance(first, last)));
            }
            return nonconst_first;
        }
 
        constexpr void push_back(const T& value) {
            const size_type sz = size();
            PLUGIFY_ASSERT(sz + 1 <= max_size(), "plg::vector::push_back(): resulted vector size would exceed max_size()", std::length_error);
            emplace_at_end([&](pointer const data) {
                PLUGIFY_CONSTRUCT_AT(data + sz, value);
            });
            ++_end;
        }
 
        constexpr void push_back(T&& value) {
            const size_type sz = size();
            PLUGIFY_ASSERT(sz + 1 <= max_size(), "plg::vector::push_back(): resulted vector size would exceed max_size()", std::length_error);
            emplace_at_end([&](pointer const data) {
                PLUGIFY_CONSTRUCT_AT(data + sz, std::move(value));
            });
            ++_end;
        }
 
        template<typename... Args>
        constexpr reference emplace_back(Args&&... args) {
            const size_type sz = size();
            PLUGIFY_ASSERT(sz + 1 <= max_size(), "plg::vector::emplace_back(): resulted vector size would exceed max_size()", std::length_error);
            emplace_at_end([&](pointer const data) {
                PLUGIFY_CONSTRUCT_AT(data + sz, std::forward<Args>(args)...);
            });
            ++_end;
            return back();
        }
 
        constexpr void pop_back() {
            PLUGIFY_ASSERT(!empty(), "plg::vector::pop_back(): vector is empty", std::length_error);
            --_end;
            std::destroy_at(_end);
        }
 
        constexpr void resize(size_type count) {
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::resize(): allocated memory size would exceed max_size()", std::length_error);
            resize_to(count, detail::initialized_value_tag{});
        }
 
        constexpr void resize(size_type count, const T& value) {
            PLUGIFY_ASSERT(count <= max_size(), "plg::vector::resize(): allocated memory size would exceed max_size()", std::length_error);
            resize_to(count, value);
        }
 
        constexpr vector& operator+=(const T& value) {
            push_back(value);
            return *this;
        }
 
        constexpr vector& operator+=(T&& value) {
            push_back(std::move(value));
            return *this;
        }
 
        constexpr vector& operator+=(const vector& other) {
            insert(end(), other.begin(), other.end());
            return *this;
        }
 
        constexpr vector& operator+=(vector&& other) {
            if (this == &other) [[unlikely]] {
                return *this;
            }
 
            insert(end(), std::make_move_iterator(other.begin()), std::make_move_iterator(other.end()));
            return *this;
        }
 
#if PLUGIFY_VECTOR_CONTAINERS_RANGES
        template<detail::vector_compatible_range<T> Range>
        constexpr void append_range(Range&& range) {
            return insert(end(), std::ranges::begin(range), std::ranges::end(range));
        }
#endif // PLUGIFY_VECTOR_CONTAINERS_RANGES
 
        constexpr void swap(vector& other) noexcept(std::allocator_traits<Allocator>::propagate_on_container_swap::value || std::allocator_traits<Allocator>::is_always_equal::value) {
            using std::swap;
            if constexpr (allocator_traits::propagate_on_container_swap::value) {
                swap(_allocator, other._allocator);
            }
            swap(_begin, other._begin);
            swap(_end, other._end);
            swap(_capacity, other._capacity);
        }
 
#ifdef __cpp_lib_span
        constexpr operator std::span<T>() const noexcept {
            return std::span<T>(data(), size());
        }
        constexpr operator std::span<const T>() const noexcept {
            return std::span<const T>(data(), size());
        }
 
        constexpr std::span<const T> span() const noexcept {
            return std::span<const T>(data(), size());
        }
 
        constexpr std::span<T> span() noexcept {
            return std::span<T>(data(), size());
        }
 
        constexpr std::span<const T> const_span() const noexcept {
            return std::span<const T>(data(), size());
        }
 
        template<size_type Size>
        [[nodiscard]] constexpr std::span<T, Size> span_size() noexcept {
            PLUGIFY_ASSERT(size() == Size, "plg::vector::span_size(): const_span_size argument does not match size of vector", std::length_error);
            return std::span<T, Size>(data(), size());
        }
 
        template<size_type Size>
        [[nodiscard]] constexpr std::span<const T, Size> const_span_size() const noexcept {
            PLUGIFY_ASSERT(size() == Size, "plg::vector::const_span_size(): const_span_size argument does not match size of vector", std::length_error);
            return std::span<const T, Size>(data(), size());
        }
 
        [[nodiscard]] constexpr std::span<const std::byte> byte_span() const noexcept {
            return std::as_bytes(span());
        }
 
        [[nodiscard]] constexpr std::span<std::byte> byte_span() noexcept {
            return std::as_writable_bytes(span());
        }
 
        [[nodiscard]] constexpr std::span<const std::byte> const_byte_span() const noexcept {
            return std::as_bytes(span());
        }
#endif // __cpp_lib_span
 
        [[nodiscard]] constexpr bool contains(const T& elem) const {
            return std::find(begin(), end(), elem) != end();
        }
 
        template<typename F>
        [[nodiscard]] constexpr bool contains_if(F predicate) {
            return std::find_if(begin(), end(), predicate) != end();
        }
 
        [[nodiscard]] constexpr auto find(const T& value) const {
            return std::find(begin(), end(), value);
        }
 
        [[nodiscard]] constexpr auto find(const T& value) {
            return std::find(begin(), end(), value);
        }
 
        template<typename F>
        [[nodiscard]] constexpr auto find_if(F predicate) const {
            return std::find_if(begin(), end(), predicate);
        }
 
        template<typename F>
        [[nodiscard]] constexpr auto find_if(F predicate) {
            return std::find_if(begin(), end(), predicate);
        }
 
        [[nodiscard]] constexpr std::optional<size_type> find_index(const T& value) {
            const auto iter = std::find(begin(), end(), value);
            if (iter == end()) {
                return {};
            } else {
                return iter - begin();
            }
        }
 
        [[nodiscard]] constexpr std::optional<size_type> find_index(const T& value) const {
            const auto iter = std::find(begin(), end(), value);
            if (iter == end()) {
                return {};
            } else {
                return iter - begin();
            }
        }
 
        template<typename F>
        [[nodiscard]] constexpr std::optional<size_type> find_index_if(F predicate) {
            const auto iter = std::find_if(begin(), end(), predicate);
            if (iter == end()) {
                return {};
            } else {
                return iter - begin();
            }
        }
 
        template<typename F>
        [[nodiscard]] constexpr std::optional<size_type> find_index_if(F predicate) const {
            const auto iter = std::find_if(begin(), end(), predicate);
            if (iter == end()) {
                return {};
            } else {
                return iter - begin();
            }
        }
    };
 
    // comparisons
    template<typename T, typename Allocator>
    [[nodiscard]] constexpr bool operator==(const vector<T, Allocator>& lhs, const vector<T, Allocator>& rhs) {
        return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
    }
 
#ifdef __cpp_impl_three_way_comparison
    template<typename T, typename Allocator>
    [[nodiscard]] constexpr auto operator<=>(const vector<T, Allocator>& lhs, const vector<T, Allocator>& rhs) {
        return std::lexicographical_compare_three_way(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
    }
#endif // __cpp_impl_three_way_comparison
 
    // global swap for vector
    template<typename T, typename Allocator>
    constexpr void swap(vector<T, Allocator>& lhs, vector<T, Allocator>& rhs) noexcept(noexcept(lhs.swap(rhs))) {
        lhs.swap(rhs);
    }
 
    template<typename T, typename Allocator, typename U>
    constexpr typename vector<T, Allocator>::size_type erase(vector<T, Allocator>& c, const U& value) {
        auto it = std::remove(c.begin(), c.end(), value);
        auto r = std::distance(it, c.end());
        c.erase(it, c.end());
        return r;
    }
 
    template<typename T, typename Allocator, typename Pred>
    constexpr typename vector<T, Allocator>::size_type erase_if(vector<T, Allocator>& c, Pred pred) {
        auto it = std::remove_if(c.begin(), c.end(), pred);
        auto r = std::distance(it, c.end());
        c.erase(it, c.end());
        return r;
    }
 
    // deduction guides
    template<typename InputIterator, typename Allocator = std::allocator<typename std::iterator_traits<InputIterator>::value_type>>
    vector(InputIterator, InputIterator, Allocator = Allocator()) -> vector<typename std::iterator_traits<InputIterator>::value_type, Allocator>;
 
    namespace pmr {
        template<typename T>
        using vector = ::plg::vector<T, std::pmr::polymorphic_allocator<T>>;
    } // namespace pmr
 
} // namespace plg