/*
*
*    This program 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.
*
*    This program 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 this program; if not, write to the Free Software Foundation,
*    Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
*    In addition, as a special exception, the author gives permission to
*    link the code of this program with the Half-Life Game Engine ("HL
*    Engine") and Modified Game Libraries ("MODs") developed by Valve,
*    L.L.C ("Valve").  You must obey the GNU General Public License in all
*    respects for all of the code used other than the HL Engine and MODs
*    from Valve.  If you modify this file, you may extend this exception
*    to your version of the file, but you are not obligated to do so.  If
*    you do not wish to do so, delete this exception statement from your
*    version.
*
*/

#pragma once

#include "osconfig.h"
#include "basetypes.h"
#include "utlmemory.h"

// This is a useful macro to iterate from head to tail in a linked list.
#define FOR_EACH_LL(listName, iteratorName)\
	for (int iteratorName = listName.Head(); iteratorName != listName.InvalidIndex(); iteratorName = listName.Next(iteratorName))

#define INVALID_LLIST_IDX ((I)~0)

// class CUtlLinkedList:
// description:
//		A lovely index-based linked list! T is the class type, I is the index
//		type, which usually should be an unsigned short or smaller.
template <class T, class I = unsigned short>
class CUtlLinkedList
{
public:
	typedef T ElemType_t;
	typedef I IndexType_t;

	// constructor, destructor
	CUtlLinkedList(int growSize = 0, int initSize = 0);
	CUtlLinkedList(void *pMemory, int memsize);
	~CUtlLinkedList();

	// gets particular elements
	T&       Element(I i);
	T const& Element(I i) const;
	T&       operator[](I i);
	T const& operator[](I i) const;

	// Make sure we have a particular amount of memory
	void EnsureCapacity(int num);

	// Memory deallocation
	void Purge();

	// Delete all the elements then call Purge.
	void PurgeAndDeleteElements();

	// Insertion methods....
	I InsertBefore(I before);
	I InsertAfter(I after);
	I AddToHead();
	I AddToTail();

	I InsertBefore(I before, T const& src);
	I InsertAfter(I after, T const& src);
	I AddToHead(T const& src);
	I AddToTail(T const& src);

	// Find an element and return its index or InvalidIndex() if it couldn't be found.
	I Find(const T &src) const;

	// Look for the element. If it exists, remove it and return true. Otherwise, return false.
	bool FindAndRemove(const T &src);

	// Removal methods
	void Remove(I elem);
	void RemoveAll();

	// Allocation/deallocation methods
	// If multilist == true, then list list may contain many
	// non-connected lists, and IsInList and Head + Tail are meaningless...
	I Alloc(bool multilist = false);
	void Free(I elem);

	// list modification
	void LinkBefore(I before, I elem);
	void LinkAfter(I after, I elem);
	void Unlink(I elem);
	void LinkToHead(I elem);
	void LinkToTail(I elem);

	// invalid index
	inline static I InvalidIndex() { return INVALID_LLIST_IDX; }
	inline static size_t ElementSize() { return sizeof(ListElem_t); }

	// list statistics
	int Count() const;
	I MaxElementIndex() const;

	// Traversing the list
	I Head() const;
	I Tail() const;
	I Previous(I i) const;
	I Next(I i) const;

	// Are nodes in the list or valid?
	bool IsValidIndex(I i) const;
	bool IsInList(I i) const;

protected:
	// What the linked list element looks like
	struct ListElem_t
	{
		T m_Element;
		I m_Previous;
		I m_Next;

	private:
		// No copy constructor for these...
		ListElem_t(const ListElem_t&);
	};

	// constructs the class
	I AllocInternal(bool multilist = false);
	void ConstructList();

	// Gets at the list element....
	ListElem_t& InternalElement(I i) { return m_Memory[i]; }
	ListElem_t const& InternalElement(I i) const { return m_Memory[i]; }

	void ResetDbgInfo()
	{
		m_pElements = m_Memory.Base();
	}

	// copy constructors not allowed
	CUtlLinkedList(CUtlLinkedList<T, I> const& list) { Assert(0); }

	CUtlMemory<ListElem_t> m_Memory;
	I m_Head;
	I m_Tail;
	I m_FirstFree;
	I m_ElementCount;  // The number actually in the list
	I m_TotalElements; // The number allocated

	// For debugging purposes;
	// it's in release builds so this can be used in libraries correctly
	ListElem_t *m_pElements;
};

// Constructor, Destructor
template <class T, class I>
CUtlLinkedList<T, I>::CUtlLinkedList(int growSize, int initSize) :
m_Memory(growSize, initSize)
{
	ConstructList();
	ResetDbgInfo();
}

template <class T, class I>
CUtlLinkedList<T, I>::CUtlLinkedList(void *pMemory, int memsize) :
m_Memory((ListElem_t *)pMemory, memsize / sizeof(ListElem_t))
{
	ConstructList();
	ResetDbgInfo();
}

template <class T, class I>
CUtlLinkedList<T, I>::~CUtlLinkedList()
{
	RemoveAll();
}

template <class T, class I>
void CUtlLinkedList<T, I>::ConstructList()
{
	m_Head = InvalidIndex();
	m_Tail = InvalidIndex();
	m_FirstFree = InvalidIndex();
	m_ElementCount = m_TotalElements = 0;
}

// Gets particular elements
template <class T, class I>
inline T& CUtlLinkedList<T, I>::Element(I i)
{
	return m_Memory[i].m_Element;
}

template <class T, class I>
inline T const& CUtlLinkedList<T, I>::Element(I i) const
{
	return m_Memory[i].m_Element;
}

template <class T, class I>
inline T& CUtlLinkedList<T, I>::operator[](I i)
{
	return m_Memory[i].m_Element;
}

template <class T, class I>
inline T const& CUtlLinkedList<T, I>::operator[](I i) const
{
	return m_Memory[i].m_Element;
}

// List statistics
template <class T, class I>
inline int CUtlLinkedList<T, I>::Count() const
{
	return m_ElementCount;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::MaxElementIndex() const
{
	return m_Memory.NumAllocated();
}

// Traversing the list
template <class T, class I>
inline I CUtlLinkedList<T, I>::Head() const
{
	return m_Head;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::Tail() const
{
	return m_Tail;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::Previous(I i) const
{
	Assert(IsValidIndex(i));
	return InternalElement(i).m_Previous;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::Next(I i) const
{
	Assert(IsValidIndex(i));
	return InternalElement(i).m_Next;
}

// Are nodes in the list or valid?
template <class T, class I>
inline bool CUtlLinkedList<T, I>::IsValidIndex(I i) const
{
	return (i < m_TotalElements) && (i >= 0) &&
		((m_Memory[i].m_Previous != i) || (m_Memory[i].m_Next == i));
}

template <class T, class I>
inline bool CUtlLinkedList<T, I>::IsInList(I i) const
{
	return (i < m_TotalElements) && (i >= 0) && (Previous(i) != i);
}

// Makes sure we have enough memory allocated to store a requested # of elements
template< class T, class I >
void CUtlLinkedList<T, I>::EnsureCapacity(int num)
{
	m_Memory.EnsureCapacity(num);
	ResetDbgInfo();
}

// Deallocate memory
template <class T, class I>
void CUtlLinkedList<T, I>::Purge()
{
	RemoveAll();
	m_Memory.Purge();
	m_FirstFree = InvalidIndex();
	m_TotalElements = 0;
	ResetDbgInfo();

}

template<class T, class I>
void CUtlLinkedList<T, I>::PurgeAndDeleteElements()
{
	int iNext;
	for (int i = Head(); i != InvalidIndex(); i = iNext)
	{
		iNext = Next(i);
		delete Element(i);
	}

	Purge();
}

// Node allocation/deallocation
template <class T, class I>
I CUtlLinkedList<T, I>::AllocInternal(bool multilist)
{
	I elem;
	if (m_FirstFree == InvalidIndex())
	{
		// Nothing in the free list; add.
		// Since nothing is in the free list, m_TotalElements == total # of elements
		// the list knows about.
		if (m_TotalElements == m_Memory.NumAllocated())
			m_Memory.Grow();

		Assert(m_TotalElements != InvalidIndex());

		elem = (I)m_TotalElements;
		m_TotalElements++;

		if (elem == InvalidIndex())
		{
			Error("CUtlLinkedList overflow!\n");
		}
	}
	else
	{
		elem = m_FirstFree;
		m_FirstFree = InternalElement(m_FirstFree).m_Next;
	}

	if (!multilist)
		InternalElement(elem).m_Next = InternalElement(elem).m_Previous = elem;
	else
		InternalElement(elem).m_Next = InternalElement(elem).m_Previous = InvalidIndex();

	ResetDbgInfo();
	return elem;
}

template <class T, class I>
I CUtlLinkedList<T, I>::Alloc(bool multilist)
{
	I elem = AllocInternal(multilist);
	Construct(&Element(elem));

	return elem;
}

template <class T, class I>
void CUtlLinkedList<T, I>::Free(I elem)
{
	Assert(IsValidIndex(elem));
	Unlink(elem);

	ListElem_t &internalElem = InternalElement(elem);
	Destruct(&internalElem.m_Element);
	internalElem.m_Next = m_FirstFree;
	m_FirstFree = elem;
}

// Insertion methods; allocates and links (uses default constructor)
template <class T, class I>
I CUtlLinkedList<T, I>::InsertBefore(I before)
{
	// Make a new node
	I newNode = AllocInternal();

	// Link it in
	LinkBefore(before, newNode);

	// Construct the data
	Construct(&Element(newNode));

	return newNode;
}

template <class T, class I>
I CUtlLinkedList<T, I>::InsertAfter(I after)
{
	// Make a new node
	I newNode = AllocInternal();

	// Link it in
	LinkAfter(after, newNode);

	// Construct the data
	Construct(&Element(newNode));

	return newNode;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::AddToHead()
{
	return InsertAfter(InvalidIndex());
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::AddToTail()
{
	return InsertBefore(InvalidIndex());
}

// Insertion methods; allocates and links (uses copy constructor)
template <class T, class I>
I CUtlLinkedList<T, I>::InsertBefore(I before, T const& src)
{
	// Make a new node
	I newNode = AllocInternal();

	// Link it in
	LinkBefore(before, newNode);

	// Construct the data
	CopyConstruct(&Element(newNode), src);

	return newNode;
}

template <class T, class I>
I CUtlLinkedList<T, I>::InsertAfter(I after, T const& src)
{
	// Make a new node
	I newNode = AllocInternal();

	// Link it in
	LinkAfter(after, newNode);

	// Construct the data
	CopyConstruct(&Element(newNode), src);

	return newNode;
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::AddToHead(T const& src)
{
	return InsertAfter(InvalidIndex(), src);
}

template <class T, class I>
inline I CUtlLinkedList<T, I>::AddToTail(T const& src)
{
	return InsertBefore(InvalidIndex(), src);
}

// Removal methods
template<class T, class I>
I CUtlLinkedList<T, I>::Find(const T &src) const
{
	for (I i = Head(); i != InvalidIndex(); i = Next(i))
	{
		if (Element(i) == src)
			return i;
	}

	return InvalidIndex();
}

template<class T, class I>
bool CUtlLinkedList<T, I>::FindAndRemove(const T &src)
{
	I i = Find(src);
	if (i == InvalidIndex())
	{
		return false;
	}
	else
	{
		Remove(i);
		return true;
	}
}

template <class T, class I>
void CUtlLinkedList<T, I>::Remove(I elem)
{
	Free(elem);
}

template <class T, class I>
void CUtlLinkedList<T, I>::RemoveAll()
{
	if (m_TotalElements == 0)
		return;

	// Put everything into the free list
	I prev = InvalidIndex();
	for (int i = (int)m_TotalElements; --i >= 0;)
	{
		// Invoke the destructor
		if (IsValidIndex((I)i))
			Destruct(&Element((I)i));

		// next points to the next free list item
		InternalElement((I)i).m_Next = prev;

		// Indicates it's in the free list
		InternalElement((I)i).m_Previous = (I)i;
		prev = (I)i;
	}

	// First free points to the first element
	m_FirstFree = 0;

	// Clear everything else out
	m_Head = InvalidIndex();
	m_Tail = InvalidIndex();
	m_ElementCount = 0;
}

// list modification
template <class T, class I>
void CUtlLinkedList<T, I>::LinkBefore(I before, I elem)
{
	Assert(IsValidIndex(elem));

	// Unlink it if it's in the list at the moment
	Unlink(elem);

	ListElem_t& newElem = InternalElement(elem);

	// The element *after* our newly linked one is the one we linked before.
	newElem.m_Next = before;

	if (before == InvalidIndex())
	{
		// In this case, we're linking to the end of the list, so reset the tail
		newElem.m_Previous = m_Tail;
		m_Tail = elem;
	}
	else
	{
		// Here, we're not linking to the end. Set the prev pointer to point to
		// the element we're linking.
		Assert(IsInList(before));
		ListElem_t& beforeElem = InternalElement(before);
		newElem.m_Previous = beforeElem.m_Previous;
		beforeElem.m_Previous = elem;
	}

	// Reset the head if we linked to the head of the list
	if (newElem.m_Previous == InvalidIndex())
		m_Head = elem;
	else
		InternalElement(newElem.m_Previous).m_Next = elem;

	// one more element baby
	m_ElementCount++;
}

template <class T, class I>
void CUtlLinkedList<T, I>::LinkAfter(I after, I elem)
{
	Assert(IsValidIndex(elem));

	// Unlink it if it's in the list at the moment
	if (IsInList(elem))
		Unlink(elem);

	ListElem_t& newElem = InternalElement(elem);

	// The element *before* our newly linked one is the one we linked after
	newElem.m_Previous = after;
	if (after == InvalidIndex())
	{
		// In this case, we're linking to the head of the list, reset the head
		newElem.m_Next = m_Head;
		m_Head = elem;
	}
	else
	{
		// Here, we're not linking to the end. Set the next pointer to point to
		// the element we're linking.
		Assert(IsInList(after));
		ListElem_t& afterElem = InternalElement(after);
		newElem.m_Next = afterElem.m_Next;
		afterElem.m_Next = elem;
	}

	// Reset the tail if we linked to the tail of the list
	if (newElem.m_Next == InvalidIndex())
		m_Tail = elem;
	else
		InternalElement(newElem.m_Next).m_Previous = elem;

	// one more element baby
	m_ElementCount++;
}

template <class T, class I>
void CUtlLinkedList<T, I>::Unlink(I elem)
{
	Assert(IsValidIndex(elem));
	if (IsInList(elem))
	{
		ListElem_t *pBase = m_Memory.Base();
		ListElem_t *pOldElem = &pBase[elem];

		// If we're the first guy, reset the head
		// otherwise, make our previous node's next pointer = our next
		if (pOldElem->m_Previous != INVALID_LLIST_IDX)
		{
			pBase[pOldElem->m_Previous].m_Next = pOldElem->m_Next;
		}
		else
		{
			m_Head = pOldElem->m_Next;
		}

		// If we're the last guy, reset the tail
		// otherwise, make our next node's prev pointer = our prev
		if (pOldElem->m_Next != INVALID_LLIST_IDX)
		{
			pBase[pOldElem->m_Next].m_Previous = pOldElem->m_Previous;
		}
		else
		{
			m_Tail = pOldElem->m_Previous;
		}

		// This marks this node as not in the list,
		// but not in the free list either
		pOldElem->m_Previous = pOldElem->m_Next = elem;

		// One less puppy
		m_ElementCount--;
	}
}

template <class T, class I>
inline void CUtlLinkedList<T, I>::LinkToHead(I elem)
{
	LinkAfter(InvalidIndex(), elem);
}

template <class T, class I>
inline void CUtlLinkedList<T, I>::LinkToTail(I elem)
{
	LinkBefore(InvalidIndex(), elem);
}