/*
	This file is part of Fennix Kernel.

	Fennix Kernel is free software: you can redistribute it and/or
	modify it under the terms of the GNU General Public License as
	published by the Free Software Foundation, either version 3 of
	the License, or (at your option) any later version.

	Fennix Kernel is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
*/

#pragma once

#include <memory>
#include <functional>
#include <initializer_list>
#include <compare>
#include <iterator>
#include <limits>
#include <utility>
#include <type_traits>
#include <algorithm>
#include <vector>

namespace std
{
	template <class T, class Allocator = std::allocator<T>>
	class forward_list
	{
	public:
		using value_type = T;
		using allocator_type = Allocator;
		using size_type = std::size_t;
		using difference_type = std::ptrdiff_t;
		using reference = value_type &;
		using const_reference = const value_type &;
		using pointer = std::allocator_traits<Allocator>::pointer;
		using const_pointer = std::allocator_traits<Allocator>::const_pointer;
		using iterator_category = std::forward_iterator_tag;
		// using iterator = value_type;
		// using const_iterator = const value_type;

	private:
		struct node
		{
			node *Next;
			value_type Value;

			template <class... Args>
			node(node *next, Args &&...args)
				: Next(next), Value(std::forward<Args>(args)...) {}
		};

		using node_allocator_type = typename std::allocator_traits<Allocator>::template rebind_alloc<node>;
		node_allocator_type NodeAlloc;
		node *Head; /* Points to dummy node (before first element) */

		node *__CreateNode(const T &value)
		{
			node *n = std::allocator_traits<node_allocator_type>::allocate(NodeAlloc, 1);
			try
			{
				std::allocator_traits<node_allocator_type>::construct(NodeAlloc, n, nullptr, value);
			}
			catch (...)
			{
				std::allocator_traits<node_allocator_type>::deallocate(NodeAlloc, n, 1);
				throw;
			}
			return n;
		}

		node *__CreateNode(T &&value)
		{
			node *n = std::allocator_traits<node_allocator_type>::allocate(NodeAlloc, 1);
			try
			{
				std::allocator_traits<node_allocator_type>::construct(NodeAlloc, n, nullptr, std::move(value));
			}
			catch (...)
			{
				std::allocator_traits<node_allocator_type>::deallocate(NodeAlloc, n, 1);
				throw;
			}
			return n;
		}

		template <class... Args>
		node *__CreateNodeEmplace(Args &&...args)
		{
			node *n = std::allocator_traits<node_allocator_type>::allocate(NodeAlloc, 1);
			try
			{
				std::allocator_traits<node_allocator_type>::construct(NodeAlloc, n, nullptr, std::forward<Args>(args)...);
			}
			catch (...)
			{
				std::allocator_traits<node_allocator_type>::deallocate(NodeAlloc, n, 1);
				throw;
			}
			return n;
		}

		void __DestroyNode(node *n)
		{
			std::allocator_traits<node_allocator_type>::destroy(NodeAlloc, n);
			std::allocator_traits<node_allocator_type>::deallocate(NodeAlloc, n, 1);
		}

		void __ClearNodes(node *start)
		{
			while (start)
			{
				node *next = start->Next;
				__DestroyNode(start);
				start = next;
			}
		}

	public:
		class iterator
		{
			friend class forward_list;
			node *ptr;

		public:
			typedef std::forward_iterator_tag iterator_category;
			typedef T value_type;
			typedef std::ptrdiff_t difference_type;
			typedef T *pointer;
			typedef T &reference;
			using self_type = iterator;

			iterator() : ptr(nullptr) {}
			iterator(node *p) : ptr(p) {}
			iterator(const iterator &other) = default;
			iterator &operator=(const iterator &other) = default;
			~iterator() = default;

			reference operator*() { return ptr->Value; }
			pointer operator->() { return &(ptr->Value); }
			const_reference operator*() const { return ptr->Value; }
			const_pointer operator->() const { return &(ptr->Value); }

			self_type &operator++()
			{
				ptr = ptr->Next;
				return *this;
			}

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

			bool operator==(const self_type &other) const { return ptr == other.ptr; }
			bool operator!=(const self_type &other) const { return ptr != other.ptr; }
		};

		class const_iterator
		{
			friend class forward_list;
			const node *ptr;

		public:
			typedef std::forward_iterator_tag iterator_category;
			typedef T value_type;
			typedef std::ptrdiff_t difference_type;
			typedef const T *pointer;
			typedef const T &reference;
			using self_type = const_iterator;

			const_iterator() : ptr(nullptr) {}
			const_iterator(const node *p) : ptr(p) {}
			const_iterator(const iterator &it) : ptr(it.ptr) {}
			const_iterator(const const_iterator &other) = default;
			const_iterator &operator=(const const_iterator &other) = default;
			~const_iterator() = default;

			reference operator*() const { return ptr->Value; }
			pointer operator->() const { return &(ptr->Value); }

			self_type &operator++()
			{
				ptr = ptr->Next;
				return *this;
			}

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

			bool operator==(const self_type &other) const { return ptr == other.ptr; }
			bool operator!=(const self_type &other) const { return ptr != other.ptr; }
		};

#pragma region Constructors

		forward_list() : NodeAlloc(), Head(__CreateNodeEmplace()) {}

		explicit forward_list(const Allocator &alloc) : NodeAlloc(alloc), Head(__CreateNodeEmplace()) {}

		explicit forward_list(size_type count, const Allocator &alloc = Allocator())
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (size_type i = 0; i < count; ++i)
			{
				cur->Next = __CreateNode(T());
				cur = cur->Next;
			}
		}

		forward_list(size_type count, const T &value, const Allocator &alloc = Allocator())
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (size_type i = 0; i < count; ++i)
			{
				cur->Next = __CreateNode(value);
				cur = cur->Next;
			}
		}

		template <class InputIt, typename = std::enable_if_t<!std::is_integral<InputIt>::value>>
		forward_list(InputIt first, InputIt last, const Allocator &alloc = Allocator())
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (; first != last; ++first)
			{
				cur->Next = __CreateNode(*first);
				cur = cur->Next;
			}
		}

		forward_list(const forward_list &other)
			: NodeAlloc(std::allocator_traits<Allocator>::select_on_container_copy_construction(other.NodeAlloc)), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (node *n = other.Head->Next; n; n = n->Next)
			{
				cur->Next = __CreateNode(n->Value);
				cur = cur->Next;
			}
		}

		forward_list(forward_list &&other)
			: NodeAlloc(std::move(other.NodeAlloc)), Head(other.Head)
		{
			other.Head = nullptr;
		}

		forward_list(const forward_list &other, const std::type_identity_t<Allocator> &alloc)
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (node *n = other.Head->Next; n; n = n->Next)
			{
				cur->Next = __CreateNode(n->Value);
				cur = cur->Next;
			}
		}

		forward_list(forward_list &&other, const std::type_identity_t<Allocator> &alloc)
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			if (other.empty())
				return;

			node *cur = Head;
			for (node *n = other.Head->Next; n; n = n->Next)
			{
				cur->Next = __CreateNode(std::move(n->Value));
				cur = cur->Next;
			}
			other.clear();
		}

		forward_list(std::initializer_list<T> init, const Allocator &alloc = Allocator())
			: NodeAlloc(alloc), Head(__CreateNodeEmplace())
		{
			node *cur = Head;
			for (const auto &v : init)
			{
				cur->Next = __CreateNode(v);
				cur = cur->Next;
			}
		}

		~forward_list()
		{
			if (Head == nullptr)
				return;

			clear();
			__DestroyNode(Head);
			Head = nullptr;
		}

#pragma endregion Constructors

		forward_list &operator=(const forward_list &other)
		{
			if (this != &other)
			{
				clear();
				node *cur = Head;
				for (node *n = other.Head->Next; n; n = n->Next)
				{
					cur->Next = __CreateNode(n->Value);
					cur = cur->Next;
				}
			}
			return *this;
		}

		forward_list &operator=(forward_list &&other) noexcept(std::allocator_traits<Allocator>::is_always_equal::value)
		{
			if (this != &other)
			{
				clear();
				__DestroyNode(Head);
				Head = other.Head;
				NodeAlloc = std::move(other.NodeAlloc);
				other.Head = nullptr;
			}
			return *this;
		}

		forward_list &operator=(std::initializer_list<value_type> ilist)
		{
			clear();
			node *cur = Head;
			for (const auto &v : ilist)
			{
				cur->Next = __CreateNode(v);
				cur = cur->Next;
			}
			return *this;
		}

		void assign(size_type count, const T &value)
		{
			clear();
			node *cur = Head;
			for (size_type i = 0; i < count; ++i)
			{
				cur->Next = __CreateNode(value);
				cur = cur->Next;
			}
		}

		template <class InputIt>
		void assign(InputIt first, InputIt last)
		{
			clear();
			node *cur = Head;
			for (; first != last; ++first)
			{
				cur->Next = __CreateNode(*first);
				cur = cur->Next;
			}
		}

		void assign(std::initializer_list<T> ilist)
		{
			clear();
			node *cur = Head;
			for (const auto &v : ilist)
			{
				cur->Next = __CreateNode(v);
				cur = cur->Next;
			}
		}

		allocator_type get_allocator() const noexcept { return allocator_type(NodeAlloc); }

#pragma region Element Access

		reference front() { return Head->Next->Value; }
		const_reference front() const { return Head->Next->Value; }

#pragma endregion Element Access

#pragma region Iterators

		iterator before_begin() noexcept { return iterator(Head); }
		const_iterator before_begin() const noexcept { return const_iterator(Head); }
		const_iterator cbefore_begin() const noexcept { return const_iterator(Head); }

		iterator begin() noexcept { return Head ? iterator(Head->Next) : iterator(nullptr); }
		const_iterator begin() const noexcept { return Head ? const_iterator(Head->Next) : iterator(nullptr); }
		const_iterator cbegin() const noexcept { return Head ? const_iterator(Head->Next) : iterator(nullptr); }

		iterator end() noexcept { return iterator(nullptr); }
		const_iterator end() const noexcept { return const_iterator(nullptr); }
		const_iterator cend() const noexcept { return const_iterator(nullptr); }

#pragma endregion Iterators

#pragma region Capacity

		bool empty() const noexcept { return Head->Next == nullptr; }
		size_type max_size() const noexcept { return std::numeric_limits<size_type>::max(); }

#pragma endregion Capacity

#pragma region Modifiers

		void clear() noexcept
		{
			node *cur = Head->Next;
			Head->Next = nullptr;
			__ClearNodes(cur);
		}

		iterator insert_after(const_iterator pos, const T &value)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *n = __CreateNode(value);
			n->Next = p->Next;
			p->Next = n;
			return iterator(n);
		}

		iterator insert_after(const_iterator pos, T &&value)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *n = __CreateNode(std::move(value));
			n->Next = p->Next;
			p->Next = n;
			return iterator(n);
		}

		iterator insert_after(const_iterator pos, size_type count, const T &value)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *last = p;

			for (size_type i = 0; i < count; ++i)
			{
				node *n = __CreateNode(value);
				n->Next = last->Next;
				last->Next = n;
				last = n;
			}

			return iterator(last);
		}

		template <class InputIt>
		iterator insert_after(const_iterator pos, InputIt first, InputIt last)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *cur = p;

			for (; first != last; ++first)
			{
				node *n = __CreateNode(*first);
				n->Next = cur->Next;
				cur->Next = n;
				cur = n;
			}

			return iterator(cur);
		}

		iterator insert_after(const_iterator pos, std::initializer_list<T> ilist)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *cur = p;

			for (const auto &v : ilist)
			{
				node *n = __CreateNode(v);
				n->Next = cur->Next;
				cur->Next = n;
				cur = n;
			}

			return iterator(cur);
		}

		template <class... Args>
		iterator emplace_after(const_iterator pos, Args &&...args)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *n = __CreateNodeEmplace(std::forward<Args>(args)...);
			n->Next = p->Next;
			p->Next = n;
			return iterator(n);
		}

		iterator erase_after(const_iterator pos)
		{
			node *p = const_cast<node *>(pos.ptr);
			node *to_delete = p->Next;

			if (to_delete)
			{
				p->Next = to_delete->Next;
				__DestroyNode(to_delete);
			}

			return iterator(p->Next);
		}

		iterator erase_after(const_iterator first, const_iterator last)
		{
			node *p = const_cast<node *>(first.ptr);
			node *end = const_cast<node *>(last.ptr);
			node *cur = p->Next;

			while (cur != end)
			{
				node *next = cur->Next;
				__DestroyNode(cur);
				cur = next;
			}

			p->Next = end;
			return iterator(end);
		}

		void push_front(const T &value) { insert_after(before_begin(), value); }
		void push_front(T &&value) { insert_after(before_begin(), std::move(value)); }

		template <class... Args>
		reference emplace_front(Args &&...args)
		{
			iterator it = emplace_after(before_begin(), std::forward<Args>(args)...);
			return *it;
		}

		void pop_front() { erase_after(before_begin()); }

		void resize(size_type count) { resize(count, T()); }

		void resize(size_type count, const value_type &value)
		{
			node *cur = Head;
			size_type n = 0;

			while (cur->Next && n < count)
			{
				cur = cur->Next;
				++n;
			}

			if (n == count)
			{
				/* Remove remaining */
				__ClearNodes(cur->Next);
				cur->Next = nullptr;
			}
			else
			{
				/* Add more */
				for (; n < count; ++n)
				{
					cur->Next = __CreateNode(value);
					cur = cur->Next;
				}
			}
		}

		void swap(forward_list &other) noexcept(std::allocator_traits<Allocator>::is_always_equal::value)
		{
			std::swap(Head, other.Head);
			/* FIXME FIXME FIXME FIXME */
			// std::swap(NodeAlloc, other.NodeAlloc);
		}

#pragma endregion Modifiers

#pragma region Operations

		void merge(forward_list &other) { merge(other, std::less<T>()); }
		void merge(forward_list &&other) { merge(other, std::less<T>()); }

		template <class Compare>
		void merge(forward_list &other, Compare comp)
		{
			if (this == &other)
				return;

			node *this_prev = Head;
			node *this_cur = Head->Next;
			node *other_cur = other.Head->Next;

			while (this_cur && other_cur)
			{
				if (comp(other_cur->Value, this_cur->Value))
				{
					node *next = other_cur->Next;
					this_prev->Next = other_cur;
					other_cur->Next = this_cur;
					this_prev = other_cur;
					other_cur = next;
				}
				else
				{
					this_prev = this_cur;
					this_cur = this_cur->Next;
				}
			}

			if (other_cur)
				this_prev->Next = other_cur;

			other.Head->Next = nullptr;
		}

		template <class Compare>
		void merge(forward_list &&other, Compare comp) { merge(other, comp); }

		void splice_after(const_iterator pos, forward_list &other)
		{
			if (&other == this || other.empty())
				return;
			splice_after(pos, other, other.before_begin(), other.end());
		}

		void splice_after(const_iterator pos, forward_list &&other) { splice_after(pos, other); }
		void splice_after(const_iterator pos, forward_list &other, const_iterator it) { splice_after(pos, other, it, std::next(it)); }
		void splice_after(const_iterator pos, forward_list &&other, const_iterator it) { splice_after(pos, other, it); }

		void splice_after(const_iterator pos, forward_list &other, const_iterator first, const_iterator last)
		{
			if (first == last)
				return;

			node *p = const_cast<node *>(pos.ptr);
			node *f = const_cast<node *>(first.ptr);
			node *l = const_cast<node *>(last.ptr);

			node *start = f->Next;
			node *end = start;

			if (!start)
				return;

			while (end->Next && end->Next != l)
				end = end->Next;

			f->Next = l;
			node *after = p->Next;
			p->Next = start;
			end->Next = after;
		}

		void splice_after(const_iterator pos, forward_list &&other, const_iterator first, const_iterator last)
		{
			splice_after(pos, other, first, last);
		}

		size_type remove(const T &value)
		{
			size_type count = 0;
			node *prev = Head;
			node *cur = Head->Next;
			while (cur)
			{
				if (cur->Value == value)
				{
					node *to_delete = cur;
					prev->Next = cur->Next;
					cur = cur->Next;
					__DestroyNode(to_delete);
					++count;
				}
				else
				{
					prev = cur;
					cur = cur->Next;
				}
			}
			return count;
		}

		template <class UnaryPred>
		size_type remove_if(UnaryPred p)
		{
			size_type count = 0;
			node *prev = Head;
			node *cur = Head->Next;
			while (cur)
			{
				if (p(cur->Value))
				{
					node *to_delete = cur;
					prev->Next = cur->Next;
					cur = cur->Next;
					__DestroyNode(to_delete);
					++count;
				}
				else
				{
					prev = cur;
					cur = cur->Next;
				}
			}
			return count;
		}

		void reverse() noexcept
		{
			node *prev = nullptr;
			node *cur = Head->Next;
			while (cur)
			{
				node *next = cur->Next;
				cur->Next = prev;
				prev = cur;
				cur = next;
			}
			Head->Next = prev;
		}

		size_type unique() { return unique(std::equal_to<T>()); }

		template <class BinaryPred>
		size_type unique(BinaryPred p)
		{
			size_type count = 0;
			node *cur = Head->Next;
			while (cur && cur->Next)
			{
				if (p(cur->Value, cur->Next->Value))
				{
					node *to_delete = cur->Next;
					cur->Next = to_delete->Next;
					__DestroyNode(to_delete);
					++count;
				}
				else
					cur = cur->Next;
			}
			return count;
		}

		void sort() { sort(std::less<T>()); }

		template <class Compare>
		void sort(Compare comp)
		{
			if (!Head->Next || !Head->Next->Next)
				return;

			std::vector<T> vec;
			for (node *cur = Head->Next; cur; cur = cur->Next)
				vec.push_back(cur->Value);

			std::sort(vec.begin(), vec.end(), comp);
			node *cur = Head->Next;
			for (auto &v : vec)
			{
				cur->Value = v;
				cur = cur->Next;
			}
		}

#pragma endregion Operations
	};

	template <class T, class Alloc>
	bool operator==(const std::forward_list<T, Alloc> &lhs, const std::forward_list<T, Alloc> &rhs)
	{
		return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
	}

	template <class T, class Alloc>
	auto operator<=>(const std::forward_list<T, Alloc> &lhs, const std::forward_list<T, Alloc> &rhs)
	{
		return std::lexicographical_compare_three_way(lhs.begin(), lhs.end(), rhs.begin(), rhs.end(), __synth_three_way);
	}
}