#pragma once

#include <gp/containers/buffer.hpp>
#include <gp/utils/allocators/allocator.hpp>

#include <initializer_list>

namespace gp{
	/**
	 * @brief A vector type most similar to that of the standard library
	 * Always uses polymorphic allocation, no small value optimization
	 *
	 * @tparam T 
	 */
	template<typename T>
	class vector final {
		T* ary = nullptr;
		size_t sz = 0;
		size_t cap = 0;
		gp::reference_wrapper<allocator> alloc;
	public:
		using associated_iterator = pointer_iterator<T, 1>;
		using associated_const_iterator = const_pointer_iterator<T, 1>;
		using associated_riterator = pointer_iterator<T, -1>;
		using associated_const_riterator = const_pointer_iterator<T, -1>;

		/**
		 * @brief Construct a new vector object from an allocator
		 * 
		 * @param v the allocator
		 */
		vector(allocator& v) 
		: ary()
		, alloc(v)
		{}

		/**
		 * @brief Construct a new vector object from another vector, copying it
		 * 
		 * @param oth the other vector
		 */
		vector(vector& oth)
		: alloc(oth.alloc)
		{
			sz = 0;
			cap = 0;
			ary = nullptr;
			gp_config::assertion(reserve(oth.size()), "could not reserve space on building");
			sz = oth.size();
			cap = oth.size();
			auto it_l = begin();
			auto it_o = oth.cbegin();
			for(size_t i = 0; i < sz; ++i)
			{
				new(&*(it_l++)) T(*(it_o++));
			}
		}

		/**
		 * @brief Construct a new vector object by moving objects out of another vector
		 * 
		 * @param oth 
		 */
		vector(vector&& oth)
		: ary(oth.ary)
		, sz(oth.sz)
		, cap(oth.cap)
		, alloc(oth.alloc)
		{
			oth.ary = nullptr;
		}

		/**
		 * @brief Copy assignment 
		 * 
		 * @param oth 
		 * @return vector& the reference to this changed vector
		 */
		vector& operator=(vector& oth)
		{
			gp_config::assertion(reserve(oth.size()), "could not reserve space on assign");
			for(size_t i = 0; i < gp::min(sz, oth.sz); ++i)
			{
				new(ary+i) T(oth[i]);
			}
			if(sz < oth.sz) {
				for(size_t i = sz; i < oth.sz; ++i) {
					new(ary+i) T(oth[i]);
				}
			} else if(sz > oth.sz) {
				for(size_t i = oth.sz; i < sz; ++i) {
					ary[i]->~T();
				}
			}
			sz = oth.sz;
			return *this;
		}

		/**
		 * @brief Move assignment
		 *
		 * Will not change the allocator of the local vector, is EXPENSIVE if the both vectors have different allocators
		 * 
		 * @param oth 
		 * @return vector& 
		 */
		vector& operator=(vector&& oth)
		{
			if(&alloc.get() == &oth.alloc.get())
			{
				gp::swap(ary, oth.ary);
				gp::swap(sz, oth.sz);
				gp::swap(cap, oth.cap);
			} else {
				for(auto& elem : *this) {
					elem->~T();
				}
				sz = 0;
				if(capacity()<oth.size()) {
					reserve(oth.size());
				}
				size_t idx = 0;
				for(auto& elem : oth) {
					new(ary+idx) T(gp::move(elem));
					elem.~T();
				}
				sz = idx;
				oth.sz = 0;
			}
			return *this;
		}

		constexpr T& operator[] (size_t off)
		{
			if constexpr (gp_config::has_buffer_bounds)
			{
				gp_config::assertion(
					off < sz,
					"Array bounds infringed"
				);
			}
			return ary[off];
		}

		~vector()
		{
			if(ary)
			{
				for(auto& elem : *this) {
					elem.~T();
				}
				gp_config::assertion(alloc.get().deallocate(ary), "could not deallocate");
			}
		}

		/**
		 * @brief Ensures the vector can hold at least 1 more element
		 * 
		 * @return true if it is at least now possible to fit one more element
		 * @return false if fiting one more element is not possible even now
		 */
		bool grow() {
			if(sz == cap) return reserve(1 + sz + (sz >> 1));
			return true;
		}

		/**
		 * @brief Reserves space so that the capacity is at least equal to the provided value.
		 * 
		 * This will never shrink the datastructure
		 *
		 * @param new_cap the new capacity
		 * @return true on success
		 * @return false on failure
		 */
		bool reserve(size_t new_cap) {
			if(new_cap <= cap) return true;

			size_t new_data_size = new_cap*sizeof(T);

			if(alloc.get().try_reallocate(ary, new_data_size)) return true;

			if(T* new_ary = (T*)alloc.get().allocate(new_data_size); new_ary) {
				auto new_it = new_ary;
				for(auto& elem : *this) {
					new(new_it++) T(gp::move(elem));
				}

				if(ary != nullptr) gp_config::assertion(alloc.get().deallocate(ary), "failed to deallocate old range");

				ary = new_ary;
				cap = new_cap;

				return true;
			}

			return false;
		}

		constexpr const T& operator[] (size_t off) const
		{
			if constexpr (gp_config::has_buffer_bounds)
			{
				gp_config::assertion(
					off < sz,
					"Array bounds infringed"
				);
			}
			return ary[off];
		}

		constexpr size_t size() const
		{
			return sz;
		}

		constexpr size_t capacity() const
		{
			return cap;
		}

		/**
		 * @brief Adds the provided value to the vector
		 * 
		 * @param value 
		 * @return true on success
		 * @return false on failure
		 */
		constexpr bool push_back(T& value) {
			if(grow()) {
				new(ary+sz) T(value);
				sz++;
				return true;
			}
			return false;
		}


		/**
		 * @brief Moves the provided value to the vector
		 * 
		 * @param value 
		 * @return true on success
		 * @return false on failure
		 */
		constexpr bool push_back(T&& value) {
			if(grow()) {
				new(ary+sz) T(gp::move(value));
				sz++;
				return true;
			}
			return false;
		}

		/**
		 * @brief Constructs a new element at the end of the vector
		 * 
		 * @param value the parameters to be sent to the constructor of T
		 * @return true on success
		 * @return false on failure
		 */
		template<typename ...U>
		constexpr bool emplace_back(U&&... value) {
			if(grow()) {
				new(ary+sz) T(gp::forward<U>(value)...);
				sz++;
				return true;
			}
			return false;
		}

		/**
		 * @brief moves the last element of the vector out if it exists, returning an optional.
		 * 
		 * @return constexpr gp::optional<T> contains a value if it existed, else it is empty
		 */
		constexpr gp::optional<T> pop_back() {
			if(sz == 0) return gp::nullopt;
			sz--;
			gp::optional<T> ret_val = gp::move(ary[sz]);
			ary[sz]->~T();
			return gp::move(ret_val);
		}

		void remove(pointer_iterator<T, 1> it) {
			for(auto step = it + 1; step<end(); step++) {
				(*it++) = gp::move(*step);
			}
			*rbegin().~T();
			sz -= 1;
		}

		constexpr pointer_iterator<T, 1> begin()
		{
			return associated_iterator(&ary[0]);
		}

		constexpr pointer_iterator<T, 1> end()
		{
			return associated_iterator(&ary[sz]);
		}

		constexpr const_pointer_iterator<T, 1> cbegin() const
		{
			return associated_const_iterator(&ary[0]);
		}

		constexpr const_pointer_iterator<T, 1> cend() const
		{
			return associated_const_iterator(&ary[sz]);
		}

		constexpr pointer_iterator<T, -1> rbegin()
		{
			return associated_riterator(&ary[sz-1]);
		}

		constexpr pointer_iterator<T, -1> rend()
		{
			return associated_riterator(ary-1);
		}

		constexpr const_pointer_iterator<T, -1> crbegin() const
		{
			return associated_const_riterator(&ary[sz-1]);
		}

		constexpr const_pointer_iterator<T, -1> crend() const
		{
			return associated_const_riterator(ary-1);
		}

		constexpr bool operator==(const vector& oth) const
		{
			for(size_t idx = 0; idx<sz; idx++)
			{
				if(ary[idx] != oth.ary[idx])
				{
					return false;
				}
			}
			return true;
		}

		constexpr bool operator!=(const vector& oth) const
		{
			return !(*this == oth);
		}

		/**
		 * @brief Provides a span access to the vector
		 * 
		 * @return A buffer of the vector. 
		 * It is invalidated by any operation that may change the size of the vector.
		 */
		gp::buffer<T> as_buffer()
		{
			return gp::buffer<T>{(T*)ary, (T*)ary+sz};
		}
	};
}