/*
 * utility_ringbuffer.hpp
 *
 *  Created on: Mar 12, 2021
 *      Author: erki
 */

#ifndef UTILITY_RINGBUFFER_HPP_
#define UTILITY_RINGBUFFER_HPP_

#include <array>
#include <iterator>
#include <cstddef>

namespace Utility
{

template<typename T, size_t N>
class Ringbuffer
{
public:
	using value_type = T;
	using size_type = std::size_t;
	using difference_type = std::ptrdiff_t;
	using reference = value_type&;
	using const_reference = const value_type&;
	using pointer = value_type*;
	using const_pointer = const value_type*;

	struct iterator
	{
		using iterator_category = std::forward_iterator_tag;
		using difference_type = std::ptrdiff_t;
		using value_type = T;
		using pointer = value_type*;
		using reference = value_type&;

		iterator(const pointer ptr, const pointer begin, const pointer end)
		  : _ptr(ptr)
		  , _arr_begin(begin)
		  , _arr_end(end)
		{ }
		iterator(const iterator&) = default;
		iterator(iterator&&) noexcept = default;

		iterator& operator=(const iterator&) = default;

		reference operator*() const
		{
			return *_ptr;
		}

		pointer operator->()
		{
			return _ptr;
		}

		iterator& operator++()
		{
			_ptr++;
			if (_ptr == _arr_end)
				_ptr = _arr_begin;

			return *this;
		}

		iterator operator++(int)
		{
			iterator tmp = *this;
			++(*this);
			return tmp;
		}

    iterator operator+(const difference_type n) const
    {
		  const pointer naive = _ptr + n;
      if (naive < _arr_end)
      {
        return iterator(naive, _arr_begin, _arr_end);
      }
      else
      {
        const pointer remainder = pointer(naive - _arr_end);
        return iterator(_arr_begin + difference_type(remainder), _arr_begin, _arr_end);
      }
    }

    iterator operator-(const difference_type n) const
    {
		  const pointer naive = _ptr - n;
		  if (naive >= _arr_begin)
      {
		    return iterator(naive, _arr_begin, _arr_end);
      }
		  else
      {
		    const pointer remainder = pointer(_arr_begin - naive);
		    return iterator(_arr_end - difference_type(remainder), _arr_begin, _arr_end);
      }
    }

		friend bool operator==(const iterator& a, const iterator& b)
		{
			return a._ptr == b._ptr;
		}

		friend bool operator!=(const iterator& a, const iterator& b)
		{
			return a._ptr != b._ptr;
		}

		friend difference_type operator-(const iterator& a, const iterator& b)
    {
		  return a._ptr - b._ptr;
    }

    friend difference_type operator+(const iterator& a, const iterator& b)
    {
		  return a._ptr + b._ptr;
    }

	private:
		pointer _ptr;
		pointer _arr_begin;
		pointer _arr_end;
	};

	Ringbuffer()
	  : _head(&_data[0], &_data[0], &_data[N])
	  , _tail(_head)
	{ }

	Ringbuffer(const Ringbuffer&) = delete;
	Ringbuffer(Ringbuffer&&) noexcept = default;

	iterator begin()
	{
		return _head;
	}

	iterator end()
	{
		return _tail;
	}

	void clear()
  {
	  _head = _tail;
  }

	void push_back(const T& value)
	{
	  if (size() == N)
	    return;

		*_tail = value;
		++_tail;

		if (_tail == _head)
		  _is_full = true;
	}

	template<typename... Args>
	void emplace_back(Args&&... args)
	{
	  if (size() == N)
	    return;

		new (&*_tail)T(std::forward<Args>(args)...);
		++_tail;
	}

	void increment_tail()
	{
	  if (_is_full)
	    ++_head;

	  ++_tail;
	}

	void pop_front()
  {
	  if (empty())
	    return;

    ++_head;
    _is_full = false;
  }

	reference front()
  {
	  return *_head;
  }

  const_reference front() const
  {
	  return *_head;
  }

  reference back()
  {
	  if (empty())
	    return *_tail;
	  else
	    return *(_tail - 1);
  }

  const_reference back() const
  {
    if (empty())
      return *_tail;
    else
      return *(_tail - 1);
  }

  size_type size() const
  {
	  if (_head == _tail)
    {
      if (_is_full)
        return N;
      else
        return 0;
    }

	  const typename Ringbuffer<T, N>::iterator::difference_type distance = _tail - _head;

    if (distance > 0)
    {
      return distance;
    }
    else
    {
      return _head - _tail + 1;
    }
  }

  constexpr size_type max_size() const
  {
    return N;
  }

  bool empty() const
  {
	  return size() == 0;
  }

private:
	std::array<T, N> _data;
	bool _is_full = false;

	iterator _head;
	iterator _tail;
};

}


#endif /* UTILITY_RINGBUFFER_HPP_ */