/*
   Copyright (C) 2001-2006, William Joseph.
   All Rights Reserved.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined( INCLUDED_CONTAINER_HASHTABLE_H )
#define INCLUDED_CONTAINER_HASHTABLE_H

#include <cstddef>
#include <algorithm>
#include <functional>
#include <memory>
#include "debugging/debugging.h"

namespace HashTableDetail
{
inline std::size_t next_power_of_two( std::size_t size ){
	std::size_t result = 1;
	while ( result < size )
	{
		result <<= 1;
	}
	return result;
}

struct BucketNodeBase
{
	BucketNodeBase* next;
	BucketNodeBase* prev;
};

inline void list_initialise( BucketNodeBase& self ){
	self.next = self.prev = &self;
}

inline void list_swap( BucketNodeBase& self, BucketNodeBase& other ){
	BucketNodeBase tmp( self );
	if ( other.next == &other ) {
		list_initialise( self );
	}
	else
	{
		self = other;
		self.next->prev = self.prev->next = &self;
	}
	if ( tmp.next == &self ) {
		list_initialise( other );
	}
	else
	{
		other = tmp;
		other.next->prev = other.prev->next = &other;
	}
}

inline void node_link( BucketNodeBase* node, BucketNodeBase* next ){
	node->next = next;
	node->prev = next->prev;
	next->prev = node;
	node->prev->next = node;
}
inline void node_unlink( BucketNodeBase* node ){
	node->prev->next = node->next;
	node->next->prev = node->prev;
}

template<typename Key, typename Value>
struct KeyValue
{
	const Key key;
	Value value;

	KeyValue( const Key& key_, const Value& value_ )
		: key( key_ ), value( value_ ){
	}
};

template<typename Key, typename Value, typename Hash>
struct BucketNode : public BucketNodeBase
{
	Hash m_hash;
	KeyValue<Key, Value> m_value;

	BucketNode( Hash hash, const Key& key, const Value& value )
		: m_hash( hash ), m_value( key, value ){
	}
	BucketNode* getNext() const {
		return static_cast<BucketNode*>( next );
	}
	BucketNode* getPrev() const {
		return static_cast<BucketNode*>( prev );
	}
};

template<typename Key, typename Value, typename Hash>
class BucketIterator
{
typedef BucketNode<Key, Value, Hash> Node;
Node* m_node;

void increment(){
	m_node = m_node->getNext();
}

public:
typedef std::forward_iterator_tag iterator_category;
typedef std::ptrdiff_t difference_type;
typedef difference_type distance_type;
typedef KeyValue<Key, Value> value_type;
typedef value_type* pointer;
typedef value_type& reference;

BucketIterator( Node* node ) : m_node( node ){
}

Node* node(){
	return m_node;
}

bool operator==( const BucketIterator& other ) const {
	return m_node == other.m_node;
}
bool operator!=( const BucketIterator& other ) const {
	return !operator==( other );
}
BucketIterator& operator++(){
	increment();
	return *this;
}
BucketIterator operator++( int ){
	BucketIterator tmp = *this;
	increment();
	return tmp;
}
value_type& operator*() const {
	return m_node->m_value;
}
value_type* operator->() const {
	return &( operator*() );
}
};
}


/// A hash-table container which maps keys to values.
///
/// - Inserting or removing elements does not invalidate iterators.
/// - Inserting or retrieving an element for a given key takes O(1) time on average.
/// - Elements are stored in no particular order.
///
/// \param Key Uniquely identifies a value. Must provide a copy-constructor.
/// \param Value The value to be stored . Must provide a default-constructor and a copy-constructor.
/// \param Hasher Must provide 'std::size_t operator()(const Key&) const' which always returns the same result if the same argument is given.
/// \param KeyEqual Must provide 'bool operator==(const Key&, const Key&) const' which returns true only if both arguments are equal.
///
/// \dontinclude container/hashtable.cpp
/// \skipline HashTable example
/// \until end example
template<typename Key, typename Value, typename Hasher, typename KeyEqual = std::equal_to<Key> >
class HashTable : private KeyEqual, private Hasher
{
typedef typename Hasher::hash_type hash_type;
typedef HashTableDetail::KeyValue<Key, Value> KeyValue;
typedef HashTableDetail::BucketNode<Key, Value, hash_type> BucketNode;

inline BucketNode* node_create( hash_type hash, const Key& key, const Value& value ){
	return new BucketNode( hash, key, value );
}
inline void node_destroy( BucketNode* node ){
	delete node;
}

typedef BucketNode* Bucket;

static Bucket* buckets_new( std::size_t count ){
	Bucket* buckets = new Bucket[count];
	std::uninitialized_fill( buckets, buckets + count, Bucket( 0 ) );
	return buckets;
}
static void buckets_delete( Bucket* buckets ){
	delete[] buckets;
}

std::size_t m_bucketCount;
Bucket* m_buckets;
std::size_t m_size;
HashTableDetail::BucketNodeBase m_list;

BucketNode* getFirst(){
	return static_cast<BucketNode*>( m_list.next );
}
BucketNode* getLast(){
	return static_cast<BucketNode*>( &m_list );
}

public:

typedef KeyValue value_type;
typedef HashTableDetail::BucketIterator<Key, Value, hash_type> iterator;

private:

void initialise(){
	list_initialise( m_list );
}
hash_type hashKey( const Key& key ){
	return Hasher::operator()( key );
}

std::size_t getBucketId( hash_type hash ) const {
	return hash & ( m_bucketCount - 1 );
}
Bucket& getBucket( hash_type hash ){
	return m_buckets[getBucketId( hash )];
}
BucketNode* bucket_find( Bucket bucket, hash_type hash, const Key& key ){
	std::size_t bucketId = getBucketId( hash );
	for ( iterator i( bucket ); i != end(); ++i )
	{
		hash_type nodeHash = i.node()->m_hash;

		if ( getBucketId( nodeHash ) != bucketId ) {
			return 0;
		}

		if ( nodeHash == hash && KeyEqual::operator()( ( *i ).key, key ) ) {
			return i.node();
		}
	}
	return 0;
}
BucketNode* bucket_insert( Bucket& bucket, BucketNode* node ){
	// link node into list
	node_link( node, bucket_next( bucket ) );
	bucket = node;
	return node;
}
BucketNode* bucket_next( Bucket& bucket ){
	Bucket* end = m_buckets + m_bucketCount;
	for ( Bucket* i = &bucket; i != end; ++i )
	{
		if ( *i != 0 ) {
			return *i;
		}
	}
	return getLast();
}

void buckets_resize( std::size_t count ){
	BucketNode* first = getFirst();
	BucketNode* last = getLast();

	buckets_delete( m_buckets );

	m_bucketCount = count;

	m_buckets = buckets_new( m_bucketCount );
	initialise();

	for ( BucketNode* i = first; i != last; )
	{
		BucketNode* node = i;
		i = i->getNext();
		bucket_insert( getBucket( ( *node ).m_hash ), node );
	}
}
void size_increment(){
	if ( m_size == m_bucketCount ) {
		buckets_resize( m_bucketCount == 0 ? 8 : m_bucketCount << 1 );
	}
	++m_size;
}
void size_decrement(){
	--m_size;
}

HashTable( const HashTable& other );
HashTable& operator=( const HashTable& other );
public:
HashTable() : m_bucketCount( 0 ), m_buckets( 0 ), m_size( 0 ){
	initialise();
}
HashTable( std::size_t bucketCount ) : m_bucketCount( HashTableDetail::next_power_of_two( bucketCount ) ), m_buckets( buckets_new( m_bucketCount ) ), m_size( 0 ){
	initialise();
}
~HashTable(){
	for ( BucketNode* i = getFirst(); i != getLast(); )
	{
		BucketNode* node = i;
		i = i->getNext();
		node_destroy( node );
	}
	buckets_delete( m_buckets );
}

iterator begin(){
	return iterator( getFirst() );
}
iterator end(){
	return iterator( getLast() );
}

bool empty() const {
	return m_size == 0;
}
std::size_t size() const {
	return m_size;
}

/// \brief Returns an iterator pointing to the value associated with \p key if it is contained by the hash-table, else \c end().
iterator find( const Key& key ){
	hash_type hash = hashKey( key );
	if ( m_bucketCount != 0 ) {
		Bucket bucket = getBucket( hash );
		if ( bucket != 0 ) {
			BucketNode* node = bucket_find( bucket, hash, key );
			if ( node != 0 ) {
				return iterator( node );
			}
		}
	}

	return end();
}
/// \brief Adds \p value to the hash-table associated with \p key if it does not exist.
iterator insert( const Key& key, const Value& value ){
	hash_type hash = hashKey( key );
	if ( m_bucketCount != 0 ) {
		Bucket& bucket = getBucket( hash );
		if ( bucket != 0 ) {
			BucketNode* node = bucket_find( bucket, hash, key );
			if ( node != 0 ) {
				return iterator( node );
			}
		}
	}

	size_increment();
	return iterator( bucket_insert( getBucket( hash ), node_create( hash, key, value ) ) );
}

/// \brief Removes the value pointed to by \p i from the hash-table.
///
/// \p i must be a deferenceable iterator into the hash-table.
void erase( iterator i ){
	Bucket& bucket = getBucket( i.node()->m_hash );
	BucketNode* node = i.node();

	// if this was the last node in the bucket
	if ( bucket == node ) {
		bucket = ( node->getNext() == getLast() || &getBucket( node->getNext()->m_hash ) != &bucket ) ? 0 : node->getNext();
	}

	node_unlink( node );
	ASSERT_MESSAGE( node != 0, "tried to erase a non-existent key/value" );
	node_destroy( node );

	size_decrement();
}

/// \brief Returns the value identified by \p key if it is contained by the hash-table, else inserts and returns a new default-constructed value associated with \p key.
Value& operator[]( const Key& key ){
	hash_type hash = hashKey( key );
	if ( m_bucketCount != 0 ) {
		Bucket& bucket = getBucket( hash );
		if ( bucket != 0 ) {
			BucketNode* node = bucket_find( bucket, hash, key );
			if ( node != 0 ) {
				return node->m_value.value;
			}
		}
	}
	size_increment();
	return bucket_insert( getBucket( hash ), node_create( hash, key, Value() ) )->m_value.value;
}
/// \brief Removes the value associated with \p key from the hash-table.
void erase( const Key& key ){
	erase( find( key ) );
}
/// \brief Swaps the contents of the hash-table with \p other.
void swap( HashTable& other ){
	std::swap( m_buckets, other.m_buckets );
	std::swap( m_bucketCount, other.m_bucketCount );
	std::swap( m_size, other.m_size );
	HashTableDetail::list_swap( m_list, other.m_list );
}
/// \brief Removes all values from the hash-table.
void clear(){
	HashTable tmp;
	tmp.swap( *this );
}
};

#endif
