/**
 * MIT License
 *
 * Copyright (c) 2017 Thibaut Goetghebuer-Planchon <tessil@gmx.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#ifndef TSL_HOPSCOTCH_MAP_H
#define TSL_HOPSCOTCH_MAP_H

#include <algorithm>
#include <cstddef>
#include <functional>
#include <initializer_list>
#include <list>
#include <memory>
#include <type_traits>
#include <utility>

#include "hopscotch_hash.h"

namespace tsl {

/**
 * Implementation of a hash map using the hopscotch hashing algorithm.
 *
 * The Key and the value T must be either nothrow move-constructible,
 * copy-constructible or both.
 *
 * The size of the neighborhood (NeighborhoodSize) must be > 0 and <= 62 if
 * StoreHash is false. When StoreHash is true, 32-bits of the hash will be
 * stored alongside the neighborhood limiting the NeighborhoodSize to <= 30.
 * There is no memory usage difference between 'NeighborhoodSize 62; StoreHash
 * false' and 'NeighborhoodSize 30; StoreHash true'.
 *
 * Storing the hash may improve performance on insert during the rehash process
 * if the hash takes time to compute. It may also improve read performance if
 * the KeyEqual function takes time (or incurs a cache-miss). If used with
 * simple Hash and KeyEqual it may slow things down.
 *
 * StoreHash can only be set if the GrowthPolicy is set to
 * tsl::power_of_two_growth_policy.
 *
 * GrowthPolicy defines how the map grows and consequently how a hash value is
 * mapped to a bucket. By default the map uses tsl::power_of_two_growth_policy.
 * This policy keeps the number of buckets to a power of two and uses a mask to
 * map the hash to a bucket instead of the slow modulo. You may define your own
 * growth policy, check tsl::power_of_two_growth_policy for the interface.
 *
 * If the destructors of Key or T throw an exception, behaviour of the class is
 * undefined.
 *
 * Iterators invalidation:
 *  - clear, operator=, reserve, rehash: always invalidate the iterators.
 *  - insert, emplace, emplace_hint, operator[]: if there is an effective
 * insert, invalidate the iterators if a displacement is needed to resolve a
 * collision (which mean that most of the time, insert will invalidate the
 * iterators). Or if there is a rehash.
 *  - erase: iterator on the erased element is the only one which become
 * invalid.
 */
template <class Key, class T, class Hash = std::hash<Key>,
          class KeyEqual = std::equal_to<Key>,
          class Allocator = std::allocator<std::pair<Key, T>>,
          unsigned int NeighborhoodSize = 62, bool StoreHash = false,
          class GrowthPolicy = tsl::hh::power_of_two_growth_policy<2>>
class hopscotch_map {
 private:
  template <typename U>
  using has_is_transparent = tsl::detail_hopscotch_hash::has_is_transparent<U>;

  class KeySelect {
   public:
    using key_type = Key;

    const key_type& operator()(const std::pair<Key, T>& key_value) const {
      return key_value.first;
    }

    key_type& operator()(std::pair<Key, T>& key_value) {
      return key_value.first;
    }
  };

  class ValueSelect {
   public:
    using value_type = T;

    const value_type& operator()(const std::pair<Key, T>& key_value) const {
      return key_value.second;
    }

    value_type& operator()(std::pair<Key, T>& key_value) {
      return key_value.second;
    }
  };

  using overflow_container_type = std::list<std::pair<Key, T>, Allocator>;
  using ht = detail_hopscotch_hash::hopscotch_hash<
      std::pair<Key, T>, KeySelect, ValueSelect, Hash, KeyEqual, Allocator,
      NeighborhoodSize, StoreHash, GrowthPolicy, overflow_container_type>;

 public:
  using key_type = typename ht::key_type;
  using mapped_type = T;
  using value_type = typename ht::value_type;
  using size_type = typename ht::size_type;
  using difference_type = typename ht::difference_type;
  using hasher = typename ht::hasher;
  using key_equal = typename ht::key_equal;
  using allocator_type = typename ht::allocator_type;
  using reference = typename ht::reference;
  using const_reference = typename ht::const_reference;
  using pointer = typename ht::pointer;
  using const_pointer = typename ht::const_pointer;
  using iterator = typename ht::iterator;
  using const_iterator = typename ht::const_iterator;

  /*
   * Constructors
   */
  hopscotch_map() noexcept(std::is_nothrow_default_constructible<ht>::value)
      : m_ht() {}

  explicit hopscotch_map(size_type bucket_count, const Hash& hash = Hash(),
                         const KeyEqual& equal = KeyEqual(),
                         const Allocator& alloc = Allocator())
      : m_ht(bucket_count, hash, equal, alloc, ht::DEFAULT_MAX_LOAD_FACTOR) {}

  hopscotch_map(size_type bucket_count, const Allocator& alloc)
      : hopscotch_map(bucket_count, Hash(), KeyEqual(), alloc) {}

  hopscotch_map(size_type bucket_count, const Hash& hash,
                const Allocator& alloc)
      : hopscotch_map(bucket_count, hash, KeyEqual(), alloc) {}

  explicit hopscotch_map(const Allocator& alloc)
      : hopscotch_map(ht::DEFAULT_INIT_BUCKETS_SIZE, alloc) {}

  hopscotch_map(const hopscotch_map& other, const Allocator& alloc)
      : m_ht(other.m_ht, alloc) {}

  template <class InputIt>
  hopscotch_map(InputIt first, InputIt last,
                size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
                const Hash& hash = Hash(), const KeyEqual& equal = KeyEqual(),
                const Allocator& alloc = Allocator())
      : hopscotch_map(bucket_count, hash, equal, alloc) {
    insert(first, last);
  }

  template <class InputIt>
  hopscotch_map(InputIt first, InputIt last, size_type bucket_count,
                const Allocator& alloc)
      : hopscotch_map(first, last, bucket_count, Hash(), KeyEqual(), alloc) {}

  template <class InputIt>
  hopscotch_map(InputIt first, InputIt last, size_type bucket_count,
                const Hash& hash, const Allocator& alloc)
      : hopscotch_map(first, last, bucket_count, hash, KeyEqual(), alloc) {}

  hopscotch_map(std::initializer_list<value_type> init,
                size_type bucket_count = ht::DEFAULT_INIT_BUCKETS_SIZE,
                const Hash& hash = Hash(), const KeyEqual& equal = KeyEqual(),
                const Allocator& alloc = Allocator())
      : hopscotch_map(init.begin(), init.end(), bucket_count, hash, equal,
                      alloc) {}

  hopscotch_map(std::initializer_list<value_type> init, size_type bucket_count,
                const Allocator& alloc)
      : hopscotch_map(init.begin(), init.end(), bucket_count, Hash(),
                      KeyEqual(), alloc) {}

  hopscotch_map(std::initializer_list<value_type> init, size_type bucket_count,
                const Hash& hash, const Allocator& alloc)
      : hopscotch_map(init.begin(), init.end(), bucket_count, hash, KeyEqual(),
                      alloc) {}

  hopscotch_map& operator=(std::initializer_list<value_type> ilist) {
    m_ht.clear();

    m_ht.reserve(ilist.size());
    m_ht.insert(ilist.begin(), ilist.end());

    return *this;
  }

  allocator_type get_allocator() const { return m_ht.get_allocator(); }

  /*
   * Iterators
   */
  iterator begin() noexcept { return m_ht.begin(); }
  const_iterator begin() const noexcept { return m_ht.begin(); }
  const_iterator cbegin() const noexcept { return m_ht.cbegin(); }

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

  /*
   * Capacity
   */
  bool empty() const noexcept { return m_ht.empty(); }
  size_type size() const noexcept { return m_ht.size(); }
  size_type max_size() const noexcept { return m_ht.max_size(); }

  /*
   * Modifiers
   */
  void clear() noexcept { m_ht.clear(); }

  std::pair<iterator, bool> insert(const value_type& value) {
    return m_ht.insert(value);
  }

  template <class P, typename std::enable_if<std::is_constructible<
                         value_type, P&&>::value>::type* = nullptr>
  std::pair<iterator, bool> insert(P&& value) {
    return m_ht.insert(std::forward<P>(value));
  }

  std::pair<iterator, bool> insert(value_type&& value) {
    return m_ht.insert(std::move(value));
  }

  iterator insert(const_iterator hint, const value_type& value) {
    return m_ht.insert(hint, value);
  }

  template <class P, typename std::enable_if<std::is_constructible<
                         value_type, P&&>::value>::type* = nullptr>
  iterator insert(const_iterator hint, P&& value) {
    return m_ht.insert(hint, std::forward<P>(value));
  }

  iterator insert(const_iterator hint, value_type&& value) {
    return m_ht.insert(hint, std::move(value));
  }

  template <class InputIt>
  void insert(InputIt first, InputIt last) {
    m_ht.insert(first, last);
  }

  void insert(std::initializer_list<value_type> ilist) {
    m_ht.insert(ilist.begin(), ilist.end());
  }

  template <class M>
  std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj) {
    return m_ht.insert_or_assign(k, std::forward<M>(obj));
  }

  template <class M>
  std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj) {
    return m_ht.insert_or_assign(std::move(k), std::forward<M>(obj));
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class M, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  std::pair<iterator, bool> insert_or_assign(K&& k, M&& obj) {
    return m_ht.insert_or_assign(std::forward<K>(k), std::forward<M>(obj));
  }

  template <class M>
  iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj) {
    return m_ht.insert_or_assign(hint, k, std::forward<M>(obj));
  }

  template <class M>
  iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj) {
    return m_ht.insert_or_assign(hint, std::move(k), std::forward<M>(obj));
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class M, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  iterator insert_or_assign(const_iterator hint, K&& k, M&& obj) {
    return m_ht.insert_or_assign(hint, std::forward<K>(k),
                                 std::forward<M>(obj));
  }

  /**
   * Due to the way elements are stored, emplace will need to move or copy the
   * key-value once. The method is equivalent to
   * insert(value_type(std::forward<Args>(args)...));
   *
   * Mainly here for compatibility with the std::unordered_map interface.
   */
  template <class... Args>
  std::pair<iterator, bool> emplace(Args&&... args) {
    return m_ht.emplace(std::forward<Args>(args)...);
  }

  /**
   * Due to the way elements are stored, emplace_hint will need to move or copy
   * the key-value once. The method is equivalent to insert(hint,
   * value_type(std::forward<Args>(args)...));
   *
   * Mainly here for compatibility with the std::unordered_map interface.
   */
  template <class... Args>
  iterator emplace_hint(const_iterator hint, Args&&... args) {
    return m_ht.emplace_hint(hint, std::forward<Args>(args)...);
  }

  template <class... Args>
  std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args) {
    return m_ht.try_emplace(k, std::forward<Args>(args)...);
  }

  template <class... Args>
  std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args) {
    return m_ht.try_emplace(std::move(k), std::forward<Args>(args)...);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class... Args, class KE = KeyEqual,
      typename std::enable_if<
          has_is_transparent<KE>::value &&
          !std::is_convertible<K&&, iterator>::value &&
          !std::is_convertible<K&&, const_iterator>::value>::type* = nullptr>
  std::pair<iterator, bool> try_emplace(K&& k, Args&&... args) {
    return m_ht.try_emplace(std::forward<K>(k), std::forward<Args>(args)...);
  }

  template <class... Args>
  iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args) {
    return m_ht.try_emplace(hint, k, std::forward<Args>(args)...);
  }

  template <class... Args>
  iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args) {
    return m_ht.try_emplace(hint, std::move(k), std::forward<Args>(args)...);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class... Args, class KE = KeyEqual,
      typename std::enable_if<
          has_is_transparent<KE>::value &&
          !std::is_convertible<K&&, iterator>::value &&
          !std::is_convertible<K&&, const_iterator>::value>::type* = nullptr>
  iterator try_emplace(const_iterator hint, K&& k, Args&&... args) {
    return m_ht.try_emplace(hint, std::forward<K>(k),
                            std::forward<Args>(args)...);
  }

  iterator erase(iterator pos) { return m_ht.erase(pos); }
  iterator erase(const_iterator pos) { return m_ht.erase(pos); }
  iterator erase(const_iterator first, const_iterator last) {
    return m_ht.erase(first, last);
  }
  size_type erase(const key_type& key) { return m_ht.erase(key); }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup to the value if you already have the hash.
   */
  size_type erase(const key_type& key, std::size_t precalculated_hash) {
    return m_ht.erase(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  size_type erase(const K& key) {
    return m_ht.erase(key);
  }

  /**
   * @copydoc erase(const K& key)
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup to the value if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  size_type erase(const K& key, std::size_t precalculated_hash) {
    return m_ht.erase(key, precalculated_hash);
  }

  void swap(hopscotch_map& other) noexcept(noexcept(other.m_ht.swap(m_ht))) {
    other.m_ht.swap(m_ht);
  }

  /*
   * Lookup
   */
  T& at(const Key& key) { return m_ht.at(key); }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  T& at(const Key& key, std::size_t precalculated_hash) {
    return m_ht.at(key, precalculated_hash);
  }

  const T& at(const Key& key) const { return m_ht.at(key); }

  /**
   * @copydoc at(const Key& key, std::size_t precalculated_hash)
   */
  const T& at(const Key& key, std::size_t precalculated_hash) const {
    return m_ht.at(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  T& at(const K& key) {
    return m_ht.at(key);
  }

  /**
   * @copydoc at(const K& key)
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  T& at(const K& key, std::size_t precalculated_hash) {
    return m_ht.at(key, precalculated_hash);
  }

  /**
   * @copydoc at(const K& key)
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  const T& at(const K& key) const {
    return m_ht.at(key);
  }

  /**
   * @copydoc at(const K& key, std::size_t precalculated_hash)
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  const T& at(const K& key, std::size_t precalculated_hash) const {
    return m_ht.at(key, precalculated_hash);
  }

  T& operator[](const Key& key) { return m_ht[key]; }
  T& operator[](Key&& key) { return m_ht[std::move(key)]; }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  T& operator[](K&& key) {
    return m_ht[std::forward<K>(key)];
  }

  size_type count(const Key& key) const { return m_ht.count(key); }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  size_type count(const Key& key, std::size_t precalculated_hash) const {
    return m_ht.count(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  size_type count(const K& key) const {
    return m_ht.count(key);
  }

  /**
   * @copydoc count(const K& key) const
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  size_type count(const K& key, std::size_t precalculated_hash) const {
    return m_ht.count(key, precalculated_hash);
  }

  iterator find(const Key& key) { return m_ht.find(key); }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  iterator find(const Key& key, std::size_t precalculated_hash) {
    return m_ht.find(key, precalculated_hash);
  }

  const_iterator find(const Key& key) const { return m_ht.find(key); }

  /**
   * @copydoc find(const Key& key, std::size_t precalculated_hash)
   */
  const_iterator find(const Key& key, std::size_t precalculated_hash) const {
    return m_ht.find(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  iterator find(const K& key) {
    return m_ht.find(key);
  }

  /**
   * @copydoc find(const K& key)
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  iterator find(const K& key, std::size_t precalculated_hash) {
    return m_ht.find(key, precalculated_hash);
  }

  /**
   * @copydoc find(const K& key)
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  const_iterator find(const K& key) const {
    return m_ht.find(key);
  }

  /**
   * @copydoc find(const K& key)
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  const_iterator find(const K& key, std::size_t precalculated_hash) const {
    return m_ht.find(key, precalculated_hash);
  }

  bool contains(const Key& key) const { return m_ht.contains(key); }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  bool contains(const Key& key, std::size_t precalculated_hash) const {
    return m_ht.contains(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  bool contains(const K& key) const {
    return m_ht.contains(key);
  }

  /**
   * @copydoc contains(const K& key) const
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  bool contains(const K& key, std::size_t precalculated_hash) const {
    return m_ht.contains(key, precalculated_hash);
  }

  std::pair<iterator, iterator> equal_range(const Key& key) {
    return m_ht.equal_range(key);
  }

  /**
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  std::pair<iterator, iterator> equal_range(const Key& key,
                                            std::size_t precalculated_hash) {
    return m_ht.equal_range(key, precalculated_hash);
  }

  std::pair<const_iterator, const_iterator> equal_range(const Key& key) const {
    return m_ht.equal_range(key);
  }

  /**
   * @copydoc equal_range(const Key& key, std::size_t precalculated_hash)
   */
  std::pair<const_iterator, const_iterator> equal_range(
      const Key& key, std::size_t precalculated_hash) const {
    return m_ht.equal_range(key, precalculated_hash);
  }

  /**
   * This overload only participates in the overload resolution if the typedef
   * KeyEqual::is_transparent exists. If so, K must be hashable and comparable
   * to Key.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  std::pair<iterator, iterator> equal_range(const K& key) {
    return m_ht.equal_range(key);
  }

  /**
   * @copydoc equal_range(const K& key)
   *
   * Use the hash value 'precalculated_hash' instead of hashing the key. The
   * hash value should be the same as hash_function()(key). Useful to speed-up
   * the lookup if you already have the hash.
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  std::pair<iterator, iterator> equal_range(const K& key,
                                            std::size_t precalculated_hash) {
    return m_ht.equal_range(key, precalculated_hash);
  }

  /**
   * @copydoc equal_range(const K& key)
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  std::pair<const_iterator, const_iterator> equal_range(const K& key) const {
    return m_ht.equal_range(key);
  }

  /**
   * @copydoc equal_range(const K& key, std::size_t precalculated_hash)
   */
  template <
      class K, class KE = KeyEqual,
      typename std::enable_if<has_is_transparent<KE>::value>::type* = nullptr>
  std::pair<const_iterator, const_iterator> equal_range(
      const K& key, std::size_t precalculated_hash) const {
    return m_ht.equal_range(key, precalculated_hash);
  }

  /*
   * Bucket interface
   */
  size_type bucket_count() const { return m_ht.bucket_count(); }
  size_type max_bucket_count() const { return m_ht.max_bucket_count(); }

  /*
   *  Hash policy
   */
  float load_factor() const { return m_ht.load_factor(); }
  float max_load_factor() const { return m_ht.max_load_factor(); }
  void max_load_factor(float ml) { m_ht.max_load_factor(ml); }

  void rehash(size_type count_) { m_ht.rehash(count_); }
  void reserve(size_type count_) { m_ht.reserve(count_); }

  /*
   * Observers
   */
  hasher hash_function() const { return m_ht.hash_function(); }
  key_equal key_eq() const { return m_ht.key_eq(); }

  /*
   * Other
   */

  /**
   * Convert a const_iterator to an iterator.
   */
  iterator mutable_iterator(const_iterator pos) {
    return m_ht.mutable_iterator(pos);
  }

  size_type overflow_size() const noexcept { return m_ht.overflow_size(); }

  friend bool operator==(const hopscotch_map& lhs, const hopscotch_map& rhs) {
    if (lhs.size() != rhs.size()) {
      return false;
    }

    for (const auto& element_lhs : lhs) {
      const auto it_element_rhs = rhs.find(element_lhs.first);
      if (it_element_rhs == rhs.cend() ||
          element_lhs.second != it_element_rhs->second) {
        return false;
      }
    }

    return true;
  }

  friend bool operator!=(const hopscotch_map& lhs, const hopscotch_map& rhs) {
    return !operator==(lhs, rhs);
  }

  friend void swap(hopscotch_map& lhs,
                   hopscotch_map& rhs) noexcept(noexcept(lhs.swap(rhs))) {
    lhs.swap(rhs);
  }

 private:
  ht m_ht;
};

/**
 * Same as `tsl::hopscotch_map<Key, T, Hash, KeyEqual, Allocator,
 * NeighborhoodSize, StoreHash, tsl::hh::prime_growth_policy>`.
 */
template <class Key, class T, class Hash = std::hash<Key>,
          class KeyEqual = std::equal_to<Key>,
          class Allocator = std::allocator<std::pair<Key, T>>,
          unsigned int NeighborhoodSize = 62, bool StoreHash = false>
using hopscotch_pg_map =
    hopscotch_map<Key, T, Hash, KeyEqual, Allocator, NeighborhoodSize,
                  StoreHash, tsl::hh::prime_growth_policy>;

}  // end namespace tsl

#endif
