/**
 * MIT License
 *
 * Copyright (c) 2017 Tessil
 *
 * 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_ROBIN_SET_H
#define TSL_ROBIN_SET_H

#include <cstddef>
#include <functional>
#include <initializer_list>
#include <memory>
#include <type_traits>
#include <utility>
#include "robin_hash.h"

namespace tsl {

  /**
   * Implementation of a hash set using open-adressing and the robin hood
   * hashing algorithm with backward shift deletion.
   *
   * For operations modifying the hash set (insert, erase, rehash, ...), the
   * strong exception guarantee is only guaranteed when the expression
   * `std::is_nothrow_swappable<Key>::value &&
   * std::is_nothrow_move_constructible<Key>::value` is true, otherwise if an
   * exception is thrown during the swap or the move, the hash set may end up in
   * a undefined state. Per the standard a `Key` with a noexcept copy
   * constructor and no move constructor also satisfies the
   * `std::is_nothrow_move_constructible<Key>::value` criterion (and will thus
   * guarantee the strong exception for the set).
   *
   * When `StoreHash` is true, 32 bits of the hash are stored alongside the
   * values. It can improve the performance during lookups if the `KeyEqual`
   * function takes time (or engenders a cache-miss for example) as we then
   * compare the stored hashes before comparing the keys. When
   * `tsl::rh::power_of_two_growth_policy` is used as `GrowthPolicy`, it may
   * also speed-up the rehash process as we can avoid to recalculate the hash.
   * When it is detected that storing the hash will not incur any memory
   * penality due to alignement (i.e.
   * `sizeof(tsl::detail_robin_hash::bucket_entry<ValueType, true>) ==
   * sizeof(tsl::detail_robin_hash::bucket_entry<ValueType, false>)`) and
   * `tsl::rh::power_of_two_growth_policy` is used, the hash will be stored even
   * if `StoreHash` is false so that we can speed-up the rehash (but it will not
   * be used on lookups unless `StoreHash` is true).
   *
   * `GrowthPolicy` defines how the set grows and consequently how a hash value
   * is mapped to a bucket. By default the set uses
   * `tsl::rh::power_of_two_growth_policy`. This policy keeps the number of
   * buckets to a power of two and uses a mask to set the hash to a bucket
   * instead of the slow modulo. Other growth policies are available and you may
   * define your own growth policy, check `tsl::rh::power_of_two_growth_policy`
   * for the interface.
   *
   * If the destructor of `Key` throws an exception, the 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.
   *  - erase: always invalidate the iterators.
   */
  template<class Key, class Hash = std::hash<Key>,
           class KeyEqual = std::equal_to<Key>,
           class Allocator = std::allocator<Key>, bool StoreHash = false,
           class GrowthPolicy = tsl::rh::power_of_two_growth_policy<2>>
  class robin_set {
   private:
    template<typename U>
    using has_is_transparent = tsl::detail_robin_hash::has_is_transparent<U>;

    class KeySelect {
     public:
      using key_type = Key;

      const key_type& operator()(const Key& key) const noexcept {
        return key;
      }

      key_type& operator()(Key& key) noexcept {
        return key;
      }
    };

    using ht =
        detail_robin_hash::robin_hash<Key, KeySelect, void, Hash, KeyEqual,
                                      Allocator, StoreHash, GrowthPolicy>;

   public:
    using key_type = typename ht::key_type;
    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
     */
    robin_set() : robin_set(ht::DEFAULT_INIT_BUCKETS_SIZE) {
    }

    explicit robin_set(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) {
    }

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

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

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

    template<class InputIt>
    robin_set(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())
        : robin_set(bucket_count, hash, equal, alloc) {
      insert(first, last);
    }

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

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

    robin_set(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())
        : robin_set(init.begin(), init.end(), bucket_count, hash, equal,
                    alloc) {
    }

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

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

    robin_set& 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);
    }

    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);
    }

    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());
    }

    /**
     * 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)...);
    }

    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). Usefull 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). Usefull 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(robin_set& other) {
      other.m_ht.swap(m_ht);
    }

    /*
     * Lookup
     */
    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). Usefull 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). Usefull 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). Usefull 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). Usefull 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). Usefull 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);
    }

    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). Usefull 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). Usefull 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);
    }

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

      for (const auto& element_lhs : lhs) {
        const auto it_element_rhs = rhs.find(element_lhs);
        if (it_element_rhs == rhs.cend()) {
          return false;
        }
      }

      return true;
    }

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

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

   private:
    ht m_ht;
  };

  /**
   * Same as `tsl::robin_set<Key, Hash, KeyEqual, Allocator, StoreHash,
   * tsl::rh::prime_growth_policy>`.
   */
  template<class Key, class Hash = std::hash<Key>,
           class KeyEqual = std::equal_to<Key>,
           class Allocator = std::allocator<Key>, bool StoreHash = false>
  using robin_pg_set = robin_set<Key, Hash, KeyEqual, Allocator, StoreHash,
                                 tsl::rh::prime_growth_policy>;

}  // end namespace tsl

#endif
