#pragma once

#if !defined(BAD_APPLE_OS_STRING_INCLUDED)
#define BAD_APPLE_OS_STRING_INCLUDED

#include <cstddef>
#include <cstring>
#include <utility>
#include <vector>

namespace std
{
template<typename CharT>
class char_traits {};

template<>
class char_traits<char>
{
public:
    using char_type = char;
    using int_type = int;
    using off_type = std::ptrdiff_t; // TODO: should be std::streamoff?
    // TODO: ??
};

template<typename CharT, typename Traits = char_traits<CharT>> // TODO: Allocator
class basic_string
{
public:
    using traits_type = Traits;
    using value_type = CharT;
    using size_type = size_t;
    using difference_type = ptrdiff_t;
    using reference = value_type&;
    using const_reference = const value_type&;
    using pointer = value_type*;
    using const_pointer = const value_type*;
    using iterator = pointer;
    using const_iterator = const_pointer;
private:
    vector<value_type> _data;
public:
    constexpr basic_string() noexcept : basic_string("") {}
    constexpr basic_string(const basic_string& other) = default;
    constexpr basic_string(basic_string&& other) = default;
    constexpr basic_string(size_type count, value_type chr) : _data(count, chr) {}
    constexpr basic_string(const basic_string& other, size_type pos, size_type count = npos)
        : basic_string(other.substr(pos, count)) {}
    constexpr basic_string(const value_type* str, size_type count)
    {
        _data.resize(count + 1);
        for (size_type idx = 0; idx < count; ++idx) {
            _data[idx] = str[idx];
        }
        _data[count] = value_type(0);
    }
    constexpr basic_string(const value_type* str) : basic_string(str, strlen(str)) {} // NOLINT
    // TODO: all the other constructors
    constexpr basic_string& operator=(const basic_string& other) = default;
    constexpr basic_string& operator=(basic_string&& other) = default;
    constexpr basic_string& operator=(const value_type* str)
    {
        const size_t count = strlen(str);
        _data.resize(count + 1);
        for (size_type idx = 0; idx < count; ++idx) {
            _data[idx] = str[idx];
        }
        _data[count] = value_type(0);
        return *this;
    }
    constexpr basic_string& operator=(value_type chr)
    {
        _data.resize(2);
        _data[0] = chr;
        _data[1] = value_type(0);
        return *this;
    }
    constexpr basic_string& operator=(std::nullptr_t) = delete;

    constexpr basic_string& operator+=(value_type chr) noexcept
    {
        return append(chr);
    }
    constexpr basic_string& operator+=(const basic_string& other) noexcept
    {
        return append(other);
    }

    [[nodiscard]] constexpr reference operator[](size_type pos) noexcept { return _data[pos]; }
    [[nodiscard]] constexpr const_reference operator[](size_type pos) const noexcept { return _data[pos]; }

    // TODO: the range check should actually also fail for the \0 in the end
    [[nodiscard]] constexpr reference at(size_type pos) { return _data.at(pos); }
    [[nodiscard]] constexpr const_reference at(size_type pos) const { return _data.at(pos); }

    [[nodiscard]] constexpr reference front() noexcept { return _data.front(); }
    [[nodiscard]] constexpr const_reference front() const noexcept { return _data.front(); }

    [[nodiscard]] constexpr reference back() noexcept { return _data.at(size() - 1); }
    [[nodiscard]] constexpr const_reference back() const noexcept { return _data.at(size() - 1); }

    [[nodiscard]] constexpr pointer data() noexcept { return _data.data(); }
    [[nodiscard]] constexpr const_pointer data() const noexcept { return _data.data(); }

    [[nodiscard]] constexpr const_pointer c_str() const noexcept { return data(); }

    [[nodiscard]] constexpr iterator begin() noexcept { return _data.begin(); }
    [[nodiscard]] constexpr const_iterator begin() const noexcept { return _data.begin(); }
    [[nodiscard]] constexpr const_iterator cbegin() const noexcept { return _data.begin(); }
    [[nodiscard]] constexpr iterator end() noexcept { return _data.end() - 1; }
    [[nodiscard]] constexpr const_iterator end() const noexcept { return _data.end() - 1; }
    [[nodiscard]] constexpr const_iterator cend() const noexcept { return _data.end() - 1; }

    [[nodiscard]] constexpr bool empty() const noexcept { return size() == 0; }
    [[nodiscard]] constexpr size_type size() const noexcept { return _data.size() - 1; }
    [[nodiscard]] constexpr size_type max_size() const noexcept { return _data.max_size() - 1; }
    constexpr void reserve(size_type newCapacity) noexcept { _data.reserve(newCapacity + 1); }
    [[nodiscard]] constexpr size_type capacity() const noexcept { return _data.capacity() - 1; }
    constexpr void shrink_to_fit() noexcept { _data.shrink_to_fit(); }

    constexpr void clear() { *this = ""; }
    constexpr void resize(size_type count, value_type chr = value_type())
    {
        _data.resize(count + 1, chr);
        _data.back() = value_type(0);
    }

    constexpr basic_string& append(value_type chr) noexcept
    {
        _data.back() = chr;
        _data.push_back(value_type());
        return *this;
    }
    constexpr basic_string& append(const basic_string& other) noexcept
    {
        _data.reserve(_data.size() + other.size());
        _data.resize(_data.size() - 1);
        for (char chr : other)
        {
            _data.push_back(chr);
        }
        _data.push_back(value_type());
        return *this;
    }
    constexpr void pop_back() noexcept
    {
        _data.pop_back();
        _data.back() = value_type();
    }

    static inline size_type npos = size_type(-1);
};
using string = basic_string<char>;
}

#endif // !defined(BAD_APPLE_OS_STRING_INCLUDED)