#pragma once
#include <memory_resource>
#include "Pair.h"

namespace Seele
{
template <
    typename KeyType,
    typename NodeData,
    typename KeyFun,
    typename Compare,
    typename Allocator>
struct Tree
{
protected:
    struct Node
    {
        Node(Node* left, Node* right, const NodeData& nodeData)
            : leftChild(left)
            , rightChild(right)
            , data(nodeData)
        {}
        Node(Node* left, Node* right, NodeData&& nodeData)
            : leftChild(left)
            , rightChild(right)
            , data(std::move(nodeData))
        {}
        Node* leftChild;
        Node* rightChild;
        NodeData data;
    };
    using NodeAlloc = std::allocator_traits<Allocator>::template rebind_alloc<Node>;
public:
    template<typename IterType>
    class IteratorBase
    {
    public:
        using iterator_category = std::bidirectional_iterator_tag;
        using value_type = IterType;
        using difference_type = std::ptrdiff_t;
        using reference = IterType&;
        using pointer = IterType*;

        constexpr IteratorBase(Node* x = nullptr, Array<Node*>&& beginIt = Array<Node*>())
            : node(x), traversal(std::move(beginIt))
        {
        }
        constexpr IteratorBase(const IteratorBase& i)
            : node(i.node), traversal(i.traversal)
        {
        }
        constexpr IteratorBase(IteratorBase&& i) noexcept
            : node(std::move(i.node)), traversal(std::move(i.traversal))
        {
        }
        constexpr IteratorBase& operator=(const IteratorBase& other)
        {
            if (this != &other)
            {
                node = other.node;
                traversal = other.traversal;
            }
            return *this;
        }
        constexpr IteratorBase& operator=(IteratorBase&& other) noexcept
        {
            if (this != &other)
            {
                node = std::move(other.node);
                traversal = std::move(other.traversal);
            }
            return *this;
        }
        constexpr reference operator*() const
        {
            return node->data;
        }
        constexpr pointer operator->() const
        {
            return &(node->data);
        }
        constexpr bool operator!=(const IteratorBase& other)
        {
            return node != other.node;
        }
        constexpr bool operator==(const IteratorBase& other)
        {
            return node == other.node;
        }
        constexpr std::strong_ordering operator<=>(const IteratorBase& other)
        {
            return node <=> other.node;
        }
        constexpr IteratorBase& operator++()
        {
            node = node->rightChild;
            while (node != nullptr
                && node->leftChild != nullptr)
            {
                traversal.add(node);
                node = node->leftChild;
            }
            if (node == nullptr
                && traversal.size() > 0)
            {
                node = traversal.back();
                traversal.pop();
            }
            return *this;
        }
        constexpr IteratorBase& operator--()
        {
            node = node->leftChild;
            while (node != nullptr
                && node->rightChild != nullptr)
            {
                traversal.add(node);
                node = node->rightchild;
            }
            if (node == nullptr
                && traversal.size() > 0)
            {
                node = traversal.back();
                traversal.pop();
            }
            return *this;
        }
        constexpr IteratorBase operator--(int)
        {
            IteratorBase tmp(*this);
            --*this;
            return tmp;
        }
        constexpr IteratorBase operator++(int)
        {
            IteratorBase tmp(*this);
            ++*this;
            return tmp;
        }
        Node* getNode()
        {
            return node;
        }
    private:
        Node* node;
        Array<Node*> traversal;
    };
    using Iterator = IteratorBase<NodeData>;
    using ConstIterator = IteratorBase<const NodeData>;

    using key_type = KeyType;
    using value_type = NodeData;
    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 = Iterator;
    using const_iterator = ConstIterator;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;

    constexpr Tree() noexcept
        : alloc(NodeAlloc())
        , root(nullptr)
        , beginIt(nullptr)
        , endIt(nullptr)
        , iteratorsDirty(true)
        , _size(0)
        , comp(Compare())
    {
    }
    constexpr explicit Tree(const Compare& comp, const Allocator& alloc = Allocator()) noexcept(noexcept(Allocator()))
        : alloc(alloc)
        , root(nullptr)
        , beginIt(nullptr)
        , endIt(nullptr)
        , iteratorsDirty(true)
        , _size(0)
        , comp(comp)
    {
    }
    constexpr explicit Tree(const Allocator& alloc) noexcept(noexcept(Compare()))
        : alloc(alloc)
        , root(nullptr)
        , beginIt(nullptr)
        , endIt(nullptr)
        , iteratorsDirty(true)
        , _size(0)
        , comp(Compare())
    {
    }
    constexpr Tree(const Tree& other)
        : alloc(other.alloc)
        , root(nullptr)
        , iteratorsDirty(true)
        , _size()
        , comp(other.comp)
    {
        for (const auto& elem : other)
        {
            insert(elem);
        }
    }
    constexpr Tree(Tree&& other) noexcept
        : alloc(std::move(other.alloc))
        , root(std::move(other.root))
        , iteratorsDirty(true)
        , _size(std::move(other._size))
        , comp(std::move(other.comp))
    {
        other._size = 0;
    }
    constexpr ~Tree() noexcept
    {
        clear();
    }
    constexpr Tree& operator=(const Tree& other)
    {
        if (this != &other)
        {
            clear();
            if constexpr (std::allocator_traits<allocator_type>::propagate_on_container_copy_assignment::value)
            {
                alloc = other.alloc;
            }
            for (const auto& elem : other)
            {
                insert(elem);
            }
            markIteratorsDirty();
        }
        return *this;
    }
    constexpr Tree& operator=(Tree&& other) noexcept
    {
        if (this != &other)
        {
            clear();
            if constexpr (std::allocator_traits<allocator_type>::propagate_on_container_move_assignment::value)
            {
                alloc = std::move(other.alloc);
            }
            root = std::move(other.root);
            _size = std::move(other._size);
            comp = std::move(other.comp);
            other._size = 0;
            markIteratorsDirty();
        }
        return *this;
    }
    constexpr void clear()
    {
        while (_size > 0)
        {
            root = _remove(root, keyFun(root->data));
        }
        root = nullptr;
        markIteratorsDirty();
    }
    constexpr iterator begin()
    {
        if (iteratorsDirty)
        {
            refreshIterators();
        }
        return beginIt;
    }
    constexpr iterator end()
    {
        if (iteratorsDirty)
        {
            refreshIterators();
        }
        return endIt;
    }
    constexpr iterator begin() const
    {
        if (iteratorsDirty)
        {
            return calcBeginIterator();
        }
        return beginIt;
    }
    constexpr iterator end() const
    {
        if (iteratorsDirty)
        {
            return calcEndIterator();
        }
        return endIt;
    }
    constexpr bool empty() const
    {
        return _size == 0;
    }
    constexpr size_type size() const
    {
        return _size;
    }
protected:
    constexpr iterator find(const key_type& key)
    {
        root = _splay(root, key);
        if (root == nullptr || !equal(root->data, key))
        {
            return end();
        }
        return iterator(root);
    }
    constexpr iterator find(const key_type& key) const
    {
        Node* it = root;
        while (it != nullptr && !equal(it->data, key))
        {
            if (comp(key, keyFun(it->data)))
            {
                it = it->leftChild;
            }
            else
            {
                it = it->rightChild;
            }
        }
        if (it == nullptr)
        {
            return end();
        }
        return iterator(it);
    }
    constexpr Pair<iterator, bool> insert(const NodeData& data)
    {
        auto [r, inserted] = _insert(root, data);
        root = r;
        return Pair<iterator, bool>(iterator(root), inserted);
    }
    constexpr Pair<iterator, bool> insert(NodeData&& data)
    {
        auto [r, inserted] = _insert(root, std::move(data));
        root = r;
        return Pair<iterator, bool>(iterator(root), inserted);
    }
    constexpr iterator remove(const key_type& key)
    {
        root = _remove(root, key);
        return iterator(root);
    }
private:
    void verifyTree()
    {
        size_t numElems = 0;
        for (const auto& it : *this)
        {
            numElems++;
        }
        assert(numElems == _size);
    }
    void markIteratorsDirty()
    {
        iteratorsDirty = true;
    }
    void refreshIterators()
    {
        beginIt = calcBeginIterator();
        endIt = calcEndIterator();
        iteratorsDirty = false;
    }
    constexpr Iterator calcBeginIterator() const
    {
        Node* begin = root;
        Array<Node*> beginTraversal;
        while (begin != nullptr)
        {
            beginTraversal.add(begin);
            begin = begin->leftChild;
        }
        if (!beginTraversal.empty())
        {
            begin = beginTraversal.back();
            beginTraversal.pop();
        }
        return Iterator(begin, std::move(beginTraversal));
    }
    constexpr Iterator calcEndIterator() const
    {
        Node* endIndex = root;
        Array<Node*> endTraversal;
        while (endIndex != nullptr)
        {
            endTraversal.add(endIndex);
            endIndex = endIndex->rightChild;
        }
        return Iterator(endIndex, std::move(endTraversal));
    }
    NodeAlloc alloc;
    Node* root;
    Iterator beginIt;
    Iterator endIt;
    bool iteratorsDirty;
    size_type _size;
    Compare comp;
    KeyFun keyFun = KeyFun();
    Node* rotateLeft(Node* x)
    {
        Node* y = x->rightChild;
        x->rightChild = y->leftChild;
        y->leftChild = x;
        return y;
    }
    Node* rotateRight(Node* x)
    {
        Node* y = x->leftChild;
        x->leftChild = y->rightChild;
        y->rightChild = x;
        return y;
    }
    template<class NodeDataType>
    Pair<Node*, bool> _insert(Node* r, NodeDataType&& data)
    {
        markIteratorsDirty();
        if (r == nullptr)
        {
            root = alloc.allocate(1);
            std::allocator_traits<NodeAlloc>::construct(alloc, root, nullptr, nullptr, std::forward<NodeDataType>(data));
            _size++;
            return Pair<Node*, bool>(root, true);
        }
        r = _splay(r, keyFun(data));

        if (equal(r->data, keyFun(data)))
            return Pair<Node*, bool>(r, false);

        Node* newNode = alloc.allocate(1);
        std::allocator_traits<NodeAlloc>::construct(alloc, newNode, nullptr, nullptr, std::forward<NodeDataType>(data));

        if (comp(keyFun(newNode->data), keyFun(r->data)))
        {
            newNode->rightChild = r;
            newNode->leftChild = r->leftChild;
            r->leftChild = nullptr;
        }
        else
        {
            newNode->leftChild = r;
            newNode->rightChild = r->rightChild;
            r->rightChild = nullptr;
        }
        _size++;
        return Pair<Node*, bool>(newNode, true);
    }
    template<class K>
    Node* _remove(Node* r, K&& key)
    {
        markIteratorsDirty();
        Node* temp;
        if (r == nullptr)
            return nullptr;

        r = _splay(r, key);

        if (!equal(r->data, key))
            return r;

        if (r->leftChild == nullptr)
        {
            temp = r;
            r = r->rightChild;
        }
        else
        {
            temp = r;

            r = _splay(r->leftChild, key);
            r->rightChild = temp->rightChild;
        }
        std::allocator_traits<NodeAlloc>::destroy(alloc, temp);
        alloc.deallocate(temp, 1);
        _size--;
        return r;
    }
    template<class K>
    Node* _splay(Node* r, K&& key)
    {
        markIteratorsDirty();
        if (r == nullptr || equal(r->data, key))
        {
            return r;
        }
        if (comp(key, keyFun(r->data)))
        {
            if (r->leftChild == nullptr)
                return r;

            if (comp(key, keyFun(r->leftChild->data)))
            {
                r->leftChild->leftChild = _splay(r->leftChild->leftChild, key);

                r = rotateRight(r);
            }
            else if (comp(keyFun(r->leftChild->data), key))
            {
                r->leftChild->rightChild = _splay(r->leftChild->rightChild, key);

                if (r->leftChild->rightChild != nullptr)
                {
                    r->leftChild = rotateLeft(r->leftChild);
                }
            }
            return (r->leftChild == nullptr) ? r : rotateRight(r);
        }
        else
        {
            if (r->rightChild == nullptr)
                return r;

            if (comp(key, keyFun(r->rightChild->data)))
            {
                r->rightChild->leftChild = _splay(r->rightChild->leftChild, key);

                if (r->rightChild->leftChild != nullptr)
                {
                    r->rightChild = rotateRight(r->rightChild);
                }
            }
            else if (comp(keyFun(r->rightChild->data), key))
            {
                r->rightChild->rightChild = _splay(r->rightChild->rightChild, key);

                r = rotateLeft(r);
            }
            return (r->rightChild == nullptr) ? r : rotateLeft(r);
        }
    }
    template<typename K>
    bool equal(const NodeData& a, K&& b) const
    {
        return !comp(keyFun(a), b) && !comp(b, keyFun(a));
    }
};
} // namespace Seele