//
//  trie.hpp
//  trie
//
//  Created by Sam Jaffe on 6/16/17.
//

#pragma once

#include "pointers/const_propogating_ptr.hpp"
#include "pointers/not_null.hpp"
#include "pointers/value_ptr.hpp"
#include <map>

template <typename K, typename V, typename Compare = std::less<K>>
class trie;

template <typename Trie, typename Iter>
class trie_iterator;
template <typename Trie, typename Iter>
class trie_reverse_iterator;

template <typename K, typename V, typename Compare>
class trie {
private:
  using self_t = trie<K, V, Compare>;
  using layer_t = value_ptr<self_t>;
  using backing_t = std::map<K, const_propogating_ptr<layer_t>, Compare>;
  template <typename KS>
  using is_collection_t = typename std::enable_if<std::is_same<K, std::decay_t<decltype(*std::begin(std::declval<KS>()))>>::value>::type;

public:
  using key_type = K;
  using mapped_type = V;
  using key_compare = Compare;
  
  using local_iterator = typename backing_t::iterator;
  using local_const_iterator = typename backing_t::const_iterator;
  using local_reverse_iterator = typename backing_t::reverse_iterator;
  using local_const_reverse_iterator = typename backing_t::const_reverse_iterator;
  
  using iterator = trie_iterator<self_t, local_iterator>;
  using const_iterator = trie_iterator<self_t const, local_const_iterator>;
  using post_iterator = trie_iterator<self_t, local_reverse_iterator>;
  using const_post_iterator = trie_iterator<self_t const, local_const_reverse_iterator>;
  using reverse_iterator = trie_reverse_iterator<self_t, local_reverse_iterator>;
  using const_reverse_iterator = trie_reverse_iterator<self_t const,  local_const_reverse_iterator>;
public:
  trie() = default;
  trie(mapped_type const & value);
  trie(trie const & other);
  trie(trie && other) = default;
  ~trie();
  self_t & operator=(mapped_type const & value);
  self_t & operator=(trie const & value);
  self_t & operator=(trie && value) = default;

  operator mapped_type &() { return value_; }
  operator mapped_type const &() const { return value_; }
  mapped_type & value() { return value_; }
  mapped_type const & value() const { return value_; }
  
  template <typename KS, typename = is_collection_t<KS>>
  self_t & operator[](KS const & keys);
  self_t & operator[](key_type const & key);
  self_t & operator[](std::initializer_list<key_type> key);
  
  template <typename KS>
  std::pair<iterator, bool> insert(KS const & keys, mapped_type const & value);
  std::pair<iterator, bool> insert(key_type const & key, mapped_type const & value);
  std::pair<iterator, bool> insert(std::initializer_list<key_type> keys, mapped_type const & value);
  
  iterator begin() { return {this}; }
  iterator end() { return {}; }
  const_iterator begin() const { return {this}; }
  const_iterator end() const { return {}; }
  const_iterator cbegin() const { return begin(); }
  const_iterator cend() const { return end(); }
  reverse_iterator rbegin() { return {this}; }
  reverse_iterator rend() { return {}; }
  const_reverse_iterator rbegin() const { return {this}; }
  const_reverse_iterator rend() const { return {}; }
  const_reverse_iterator crbegin() const { return rbegin(); }
  const_reverse_iterator crend() const { return rend(); }
  
  local_iterator local_begin() { return impl_.begin(); }
  local_iterator local_end() { return impl_.end(); }
  local_const_iterator local_begin() const { return impl_.begin(); }
  local_const_iterator local_end() const { return impl_.end(); }

  local_reverse_iterator local_rbegin() { return impl_.rbegin(); }
  local_reverse_iterator local_rend() { return impl_.rend(); }
  local_const_reverse_iterator local_rbegin() const { return impl_.rbegin(); }
  local_const_reverse_iterator local_rend() const { return impl_.rend(); }
  
  void clear();
private:
  template <typename... Args>
  void insert_impl(std::pair<iterator, bool> & out, key_type const & key, Args &&... args);
  
  friend bool operator==(trie const & lhs, trie const & rhs) {
    if (lhs.value() != rhs.value()) { return false; }
    auto it1 = ++lhs.begin(), it2 = ++rhs.begin(), end1 = lhs.end(), end2 = lhs.end();
    for ( ; it1 != end1 && it2 != end2; ++it1, ++it2 ) {
      if (it1.keys.back() != it2.keys.back()) { return false; }
      else if (*it1 != *it2) { return false; }
    }
    return it1 == end1 && it2 == end2;
  }
  friend void swap(trie & lhs, trie & rhs) {
    using std::swap;
    swap(lhs.value_, rhs.value_);
    swap(lhs.impl_, rhs.impl_);
  }
  mapped_type value_;
  backing_t impl_;
};

#include "trie_impl.hpp"