#ifndef INCLUDED_TRNX_VECTOR
#define INCLUDED_TRNX_VECTOR

#include <cstddef>
#include <exception>
#include <iterator>
#include <type_traits>
#include <memory>
#include <trnx_vector_impl.h>

namespace trnx {

template <typename T>
class vector
{
public:
    typedef T              value_type;
    typedef std::size_t    size_type;
    typedef std::ptrdiff_t difference_type;
    typedef T&             reference;
    typedef const T&       const_reference;
    typedef T*             pointer;
    typedef const T*       const_pointer;

private:
    size_type d_size;
    size_type d_capacity;
    typedef detail::uninitialized<T> buff_type[];
    std::unique_ptr<buff_type> d_buff;
        // `uninitialized<T>` represents enough uninitialized storage for an
        // instance of `T`. The lifetime of the `T` instance is controlled
        // manually via the `.construct` and `.destroy` member functions.
        // An initialized instance can be accessed through `.get`.

public:
    typedef detail::iter_impl<detail::uninitialized<T> >       iterator;            //CHG
    typedef detail::iter_impl<const detail::uninitialized<T> > const_iterator;      //CHG
        // `iter_impl` is an iterator type that automatically transforms
        // `uninitialized<T>*` into `T*` when dereferencing.

    vector() : d_size(0), d_capacity(0), d_buff(nullptr)
    {
        // A default-constructed vector is empty and has no allocated buffer.
    }

    vector(const vector& rhs)
        : d_size(rhs.d_size),
          d_capacity(rhs.d_capacity),

          // Allocate enough space for `rhs.d_size` items.
          d_buff(std::make_unique<buff_type>(rhs.d_size))
    {
        // Copy-construct all of `rhs`'s elements into the current buffer.
        for(size_type i = 0; i < d_size; ++i)
        {
            d_buff[i].construct(rhs.d_buff[i].get());
        }
    }

    ~vector()
    {
        // Destroy all elements in the vector. In the Standard, the order of
        // destruction is unspecified.
        for(size_type i = 0; i < d_size; ++i)
        {
            d_buff[i].destroy();
        }
    }

    vector<T>& operator=(const vector<T>& rhs);
        // The copy-constructor allocates enough memory to store `rhs`'s
        // elements in a new buffer, copies over the current elements to the
        // new buffer, and finally sets `d_buff` to point to the new buffer.

    size_type size() const     { return d_size; }
    size_type capacity() const { return d_capacity; }
    bool empty() const         { return d_size == 0; }

    iterator begin()       { return iterator(d_buff.get()); }
    iterator begin() const { return iterator(d_buff.get()); }

    iterator end()         { return iterator(d_buff.get() + d_size); }
    iterator end() const   { return iterator(d_buff.get() + d_size); }

    const_iterator cbegin() const { return const_iterator(d_buff.get()); }
    const_iterator cend() const   { return const_iterator(d_buff.get() + d_size); }

    reference front()             { return d_buff[0].get(); }
    const_reference front() const { return d_buff[0].get(); }

    reference back()              { return d_buff[d_size - 1].get(); }
    const_reference back() const  { return d_buff[d_size - 1].get(); }

    reference operator[](size_type i)             { return d_buff[i].get(); }
    const_reference operator[](size_type i) const { return d_buff[i].get(); }

    reference at(size_type i)
    {
        if(i >= d_size)
        {
            throw std::out_of_range("Index out of range");
        }
        else
        {
            return d_buff[i].get();
        }
    }

    const_reference at(size_type i) const
    {
        // The following use of `const_cast` is legal and simply prevents code
        // repetition with the non-`const` version of `at`.
        return const_cast<vector<T>&>(*this).at(i);
    }

    void push_back(const T& item);
    void push_back(T&& item);
    void pop_back();
    void clear();
    void reserve(size_type new_capacity);
};

template <typename T>
void vector<T>::push_back(const T& item)
{
    if(d_size >= d_capacity)
    {
        const size_type new_capacity = (d_capacity == 0) ? 1
                                                         : d_capacity * 2;

        reserve(new_capacity);
    }

    d_buff[d_size++].construct(item);
}

template <typename T>
void vector<T>::push_back(T&& item)
{
    if(d_size >= d_capacity)
    {
        const size_type new_capacity = (d_capacity == 0) ? 1
                                                         : d_capacity * 2;

        reserve(new_capacity);
    }

    d_buff[d_size++].construct(std::move(item));
}

template <typename T>
void vector<T>::pop_back()
{
    BSLS_ASSERT(!empty());

    d_buff[d_size - 1].destroy();
    --d_size;
}

template <typename T>
void vector<T>::clear()
{
    // Destroy all existing elements
    for(size_type i = 0; i < d_size; ++i)
    {
        d_buff[i].destroy();
    }

    // Set size to zero, but leave capacity unchanged
    d_size = 0;
}

template <typename T>
vector<T>& vector<T>::operator=(const vector& rhs)
{
    // Prevent self-assignment
    if(&rhs != this)
    {
        // Destroy all existing elements and set size to zero
        clear();

        // Reserve if necessary
        reserve(rhs.d_size);

        // Copy elements from `rhs`
        for(size_type i = 0; i < rhs.d_size; ++i)
        {
            d_buff[i].construct(rhs.d_buff[i].get());
        }

        // Update size
        d_size = rhs.d_size;
    }

    return *this;
}

template <typename T>
void vector<T>::reserve(size_type new_capacity)
{
    // Exit early if there's no need to reserve more memory
    if(new_capacity <= d_capacity) { return; }

    // Allocate a new buffer
    auto buff = std::make_unique<buff_type>(new_capacity);

    // Copy-construct existing elements into the new buffer and destroy them
    // in the old one
    for(size_type i = 0; i < d_size; ++i)
    {
        buff[i].construct(std::move(d_buff[i].get()));
        d_buff[i].destroy();
    }

    // Deallocate old buffer, set the owned buffer to `buff`
    d_buff = std::move(buff);

    // Update capacity
    d_capacity = new_capacity;
}

} // close namespace trnx

#endif