// commenting everything out when I commit so all commits my code technically
// compiles
#include <algorithm>
#include <cstddef>
#include <deque>
#include <initializer_list>
#include <iterator>
#include <optional>
#include <stdexcept>
#include <utility>
#include <vector>

// everything is super interconnected so some forward declarations are needed at
// various points
namespace cs440 {

template <typename Key_T, typename Mapped_T> class Map;

namespace {
enum class Color { Red, Black };
template <typename Key_T, typename Mapped_T> struct BookKeeping {
  friend class Map<Key_T, Mapped_T>;
  using ValueType = std::pair<const Key_T, Mapped_T>;
  Map<Key_T, Mapped_T> &parent;
  ValueType value;
  std::size_t self;
  Color color;

  std::optional<std::size_t> next;
  std::optional<std::size_t> prev;
};
} // namespace
// https://en.wikipedia.org/wiki/Red%E2%80%93black_tree
template <typename Key_T, typename Mapped_T> class Map {
private:
  using ValueType = std::pair<const Key_T, Mapped_T>;
  // idx 0 = root
  // left = parent * 2 + 1
  // right = parent * 2 + 2
  std::vector<std::optional<BookKeeping<Key_T, Mapped_T>>> store;
  std::vector<Color> coloration;

public:
  class Iterator;
  class ConstIterator;
  class ReverseIterator;

  friend class Iterator;
  friend class ConstIterator;
  friend class ReverseIterator;
  friend struct BookKeeping<Key_T, Mapped_T>;
  // TODO: Iterator functionality
  class Iterator {
    friend class Map<Key_T, Mapped_T>;
    friend struct BookKeeping<Key_T, Mapped_T>;

  public:
  private:
    enum class PastElem { start, end, neither };
    // pointer needed so we can replace as needed
    BookKeeping<Key_T, Mapped_T> *parent;

    // TODO: next/prev found in bookkeeping
    // Note: only used when past first/last element
    PastElem use;
    std::optional<std::size_t> next_or_prev;
    Iterator(std::optional<BookKeeping<Key_T, Mapped_T>> &parent)
        : parent{&parent}, use{PastElem::neither}, next_or_prev{std::nullopt} {}

  public:
    Iterator() = delete;
    ConstIterator to_const() const { return ConstIterator(*this); }
    Iterator &operator++() { return *this; }
    Iterator operator++(int) {
      Iterator tmp = *this;
      ++(*this);
      return tmp;
    }
    Iterator &operator--() { return *this; }
    Iterator operator--(int) {
      Iterator tmp = *this;
      --(*this);
      return tmp;
    }
    ValueType &operator*() const { return parent.parent.at(parent.self); }
    ValueType *operator->() const { return &**this; }
    friend bool operator==(Iterator const &lhs, Iterator const &rhs) {
      return lhs.store_iter == rhs.store_iter;
    }
    friend bool operator!=(Iterator const &lhs, Iterator const &rhs) {
      return lhs.store_iter != rhs.store_iter;
    }
    friend bool operator==(ConstIterator const &lhs, Iterator const &rhs) {
      return lhs == rhs.to_const();
    }
    friend bool operator!=(ConstIterator const &lhs, Iterator const &rhs) {
      return lhs != rhs.to_const();
    }
    friend bool operator==(Iterator const &lhs, ConstIterator const &rhs) {
      return lhs.to_const() == rhs;
    }
    friend bool operator!=(Iterator const &lhs, ConstIterator const &rhs) {
      return lhs.to_const() != rhs;
    }
  };
  class ConstIterator {
  public:
    friend class Map<Key_T, Mapped_T>;
    friend class Iterator;
    using underlying = Iterator;

  private:
    underlying store_iter;
    ConstIterator(underlying iter) : store_iter{iter} {}

  public:
    ConstIterator() = delete;
    friend bool operator==(ConstIterator const &lhs, ConstIterator const &rhs) {
      return lhs.store_iter == rhs.store_iter;
    }
    ConstIterator &operator++() {
      ++this->store_iter;
      return *this;
    }
    ConstIterator operator++(int) {
      ConstIterator tmp = *this;
      this->store_iter++;
      return tmp;
    }
    ConstIterator &operator--() {
      --this->store_iter;
      return *this;
    }
    ConstIterator operator--(int) {
      ConstIterator tmp = *this;
      this->store_iter--;
      return tmp;
    }
    const ValueType &operator*() const { return *this->store_iter; }
    const ValueType *operator->() const {
      // I find this rather funny
      return this->store_iter.operator->();
    }
    friend bool operator!=(ConstIterator const &lhs, ConstIterator const &rhs) {
      return lhs.store_iter != rhs.store_iter;
    }
  };
  class ReverseIterator {
  public:
    friend class Map<Key_T, Mapped_T>;
    using underlying = typename std::vector<std::optional<ValueType>>::iterator;

  private:
    underlying store_iter;

  public:
    ReverseIterator() = delete;
    ReverseIterator(underlying store_iter) : store_iter{store_iter} {}
    ReverseIterator &operator++() {}
    ReverseIterator operator++(int) {}
    ReverseIterator &operator--() {}
    ReverseIterator operator--(int) {}
    ValueType &operator*() const {}
    ValueType *operator->() const {}
    friend bool operator==(ReverseIterator const &lhs,
                           ReverseIterator const &rhs) {
      return lhs.store_iter == rhs.store_iter;
    }
    friend bool operator!=(ConstIterator const &lhs, ConstIterator const &rhs) {
      return lhs.store_iter != rhs.store_iter;
    }
  };
  Map() : store{} {}
  Map(const Map &rhs) : store{rhs.store} {}
  Map &operator=(const Map &rhs) { this->store = rhs.store; }
  Map(std::initializer_list<ValueType> elems) : store{} {
    this->insert(elems.begin(), elems.end());
  }
  // who cares we're using vector
  ~Map() {}

  size_t size() const {
    std::size_t count = 0;
    for (auto &m_pair : this->store) {
      count += m_pair.has_value() ? 1 : 0;
    }
    return count;
  }
  bool empty() const { return this->store.empty(); }
  // TODO: Iterator creation
  Iterator begin() {}
  Iterator end() {}
  ConstIterator begin() const {}
  ConstIterator end() const {}
  ConstIterator cbegin() const {}
  ConstIterator cend() const {}
  ReverseIterator rbegin() {}
  ReverseIterator rend() {}
  // TODO: actually return an iterator from find and deal with error cases
  // correctly, also need to update for new bookkeeping type
  Iterator find(const Key_T &key) {
    std::size_t idx = 0;
    while (store[idx].first != key) {
      if (idx >= store.size()) {
        return this->end();
      }
      if (store[idx].first < key) {
        idx = idx * 2 + 1;
      } else {
        idx = idx * 2 + 2;
      }
    }
  }
  ConstIterator find(const Key_T &key) const {
    std::size_t idx = 0;
    while (store[idx].first != key) {
      if (idx >= store.size()) {
        return this->end();
      }
      if (store[idx].first < key) {
        idx = idx * 2 + 1;
      } else {
        idx = idx * 2 + 2;
      }
    }
  }

  Mapped_T &at(const Key_T &key) {
    std::size_t i = 0;
    while (this->store.at(i).has_value()) {
      switch (true) {
      case this->store.at(i).first == key:
        return this->store.at(i).second;
      case this->store.at(i).first < key:
        i = 2 * i + 1;
        break;
      case this->store.at(i).first > key:
        i = 2 * i + 2;
        break;
      }
    }
    throw std::out_of_range{""};
  }
  const Mapped_T &at(const Key_T &key) const { return this->at(key); }
  Mapped_T &operator[](const Key_T &key) { return this->at(key); }

private:
  Color getColor(std::size_t i) {
    if (this->store.size() <= i) {
      return Color::Black;
    }
    if (!this->store.at(i).has_value()) {
      return Color::Black;
    }
    return this->store.at(i).value().color;
  }
  std::size_t find_null(const Key_T &key) {
    std::size_t idx = 0;
    while (store[idx].first != key) {
      if (idx >= store.size()) {
        return this->end();
      }
      if (store[idx].first < key) {
        if (idx * 2 + 1 > store.size() || !store.at(idx * 2 + 1).has_value()) {
          idx = idx * 2 + 1;
          break;
        }
        idx = idx * 2 + 1;
      } else {
        if (idx * 2 + 2 > store.size() || !store.at(idx * 2 + 2).has_value()) {
          idx = idx * 2 + 2;
          break;
        }
        idx = idx * 2 + 2;
      }
    }
    return idx;
  }
  enum class Direction { left, right };
  void insert_helper(std::size_t idx, BookKeeping<Key_T, Mapped_T> to_insert) {
    // might as well make sure
    to_insert.color = Color::Red;
    std::size_t parent_idx;
    Direction relation;
    if (idx % 2 == 1) {
      parent_idx = (idx - 1) / 2;
      relation = Direction::left;
    } else {
      parent_idx = (idx - 1) / 2;
      relation = Direction::right;
    }
    BookKeeping<Key_T, Mapped_T> &parent = this->store.at(parent_idx).value();
  }

public:
  // TODO: single insert
  // OH NO IT SHOULD BE RED-BLACK
  std::pair<Iterator, bool> insert(const ValueType &val) {

    BookKeeping<Key_T, Mapped_T> new_node;
    new_node.color = Color::Red;
    new_node.value = val;
    new_node.parent = *this;

    if (this->store.size() == 0) {
      new_node.self = 0;
      this->store.push_back(new_node);
    }
  }
  template <typename IT_T> void insert(IT_T range_beg, IT_T range_end) {
    std::for_each(range_beg, range_end,
                  [&](ValueType &val) { this->insert(val); });
  }
  // TODO: erase via iterator
  void erase(Iterator pos) {
    // RED BLACK TREE oh no
  }
  void erase(const Key_T &key) { this->erase(this->find(key)); }
  void clear() { this->store = {}; }
  friend bool operator==(const Map &lhs, const Map &rhs) {
    if (lhs.store.size() != rhs.store.size()) {
      return false;
    }
    auto liter = lhs.cbegin();
    auto riter = rhs.cbegin();
    // both must be the same length so this is fine
    while (liter != lhs.cend()) {
      if (*liter != *riter) {
        return false;
      }
      liter++;
      riter++;
    }
    return true;
  }
  friend bool operator!=(const Map &lhs, const Map &rhs) {
    return !(lhs == rhs);
  }
  friend bool operator<(const Map &lhs, const Map &rhs) {
    std::size_t lhs_i = 0;
    std::size_t rhs_i = 0;
    for (; lhs_i < lhs.store.size() && rhs_i < rhs.store.size();
         lhs_i++, rhs_i++) {
      bool lhs_exhaust = false;
      while (!lhs.store[lhs_i].has_value()) {
        lhs_i++;
        if (lhs.store.size() >= lhs_i) {
          lhs_exhaust = true;
          break;
        }
      }

      bool rhs_exhaust = false;
      while (!rhs.store[rhs_i].has_value()) {
        rhs_i++;
        if (rhs.store.size() >= rhs_i) {
          rhs_exhaust = true;
          break;
        }
      }

      if (lhs_exhaust && !rhs_exhaust) {
        return true;
      }
      if (lhs_exhaust || rhs_exhaust) {
        break;
      }
      if (lhs.store[lhs_i] != rhs.store[rhs_i]) {
        return lhs.store[lhs_i] < rhs.store[rhs_i];
      }
    }
    return false;
  }
};
} // namespace cs440