/*
     File: CAThreadSafeList.h
 Abstract: Part of CoreAudio Utility Classes
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*/
#ifndef __CAThreadSafeList_h__
#define __CAThreadSafeList_h__

#include "CAAtomicStack.h"

//  linked list of T's
//	T must define operator ==
template <class T>
class TThreadSafeList {
private:
	enum EEventType { kAdd, kRemove, kClear };
	class Node {
	public:
		Node *		mNext;
		EEventType	mEventType;
		T			mObject;

		Node *&	next() { return mNext; }
	};

public:
	class iterator {
	public:
		iterator() { }
		iterator(Node *n) : mNode(n) { }

		bool operator == (const iterator &other) const { return this->mNode == other.mNode; }
		bool operator != (const iterator &other) const { return this->mNode != other.mNode; }

		T & operator * () const { return mNode->mObject; }

		iterator & operator ++ () { mNode = mNode->next(); return *this; }	// preincrement
		iterator operator ++ (int) { iterator tmp = *this; mNode = mNode->next(); return tmp; } // postincrement

	private:
		Node *		mNode;
	};

	TThreadSafeList() { }
	~TThreadSafeList()
	{
		mActiveList.free_all();
		mPendingList.free_all();
		mFreeList.free_all();
	}

	// These may be called on any thread

	void	deferred_add(const T &obj)	// can be called on any thread
	{
		Node *node = AllocNode();
		node->mEventType = kAdd;
		node->mObject = obj;
		mPendingList.push_atomic(node);
		//mPendingList.dump("pending after add");
	}

	void	deferred_remove(const T &obj)	// can be called on any thread
	{
		Node *node = AllocNode();
		node->mEventType = kRemove;
		node->mObject = obj;
		mPendingList.push_atomic(node);
		//mPendingList.dump("pending after remove");
	}

	void	deferred_clear()					// can be called on any thread
	{
		Node *node = AllocNode();
		node->mEventType = kClear;
		mPendingList.push_atomic(node);
	}

	// These must be called from only one thread

	void	update()		// must only be called from one thread
	{
		NodeStack reversed;
		Node *event, *node, *next;
		bool workDone = false;

		// reverse the events so they are in order
		event = mPendingList.pop_all();
		while (event != NULL) {
			next = event->mNext;
			reversed.push_NA(event);
			event = next;
			workDone = true;
		}
		if (workDone) {
			//reversed.dump("pending popped");
			//mActiveList.dump("active before update");

			// now process them
			while ((event = reversed.pop_NA()) != NULL) {
				switch (event->mEventType) {
				case kAdd:
					{
						Node **pnode;
						bool needToInsert = true;
						for (pnode = mActiveList.phead(); *pnode != NULL; pnode = &node->mNext) {
							node = *pnode;
							if (node->mObject == event->mObject) {
								//printf("already active!!!\n");
								FreeNode(event);
								needToInsert = false;
								break;
							}
						}
						if (needToInsert) {
							// link the new event in at the end of the active list
							*pnode = event;
							event->mNext = NULL;
						}
					}
					break;
				case kRemove:
					// find matching node in the active list, remove it
					for (Node **pnode = mActiveList.phead(); *pnode != NULL; ) {
						node = *pnode;
						if (node->mObject == event->mObject) {
							*pnode = node->mNext;	// remove from linked list
							FreeNode(node);
							break;
						}
						pnode = &node->mNext;
					}
					// dispose the request node
					FreeNode(event);
					break;
				case kClear:
					for (node = mActiveList.head(); node != NULL; ) {
						next = node->mNext;
						FreeNode(node);
						node = next;
					}
					FreeNode(event);
					break;
				default:
					//printf("invalid node type %d!\n", event->mEventType);
					break;
				}
			}
			//mActiveList.dump("active after update");
		}
	}

	iterator begin() const {
		//mActiveList.dump("active at begin");
		return iterator(mActiveList.head());
	}
	iterator end() const { return iterator(NULL); }


private:
	Node *	AllocNode()
	{
		Node *node = mFreeList.pop_atomic();
		if (node == NULL)
			node = (Node *)CA_malloc(sizeof(Node));
		return node;
	}

	void	FreeNode(Node *node)
	{
		mFreeList.push_atomic(node);
	}

private:
	class NodeStack : public TAtomicStack<Node> {
	public:
		void free_all() {
			Node *node;
			while ((node = this->pop_NA()) != NULL)
				free(node);
		}

		Node **	phead() { return &this->mHead; }
		Node *	head() const { return this->mHead; }
	};

	NodeStack	mActiveList;	// what's actually in the container - only accessed on one thread
	NodeStack	mPendingList;	// add or remove requests - threadsafe
	NodeStack	mFreeList;		// free nodes for reuse - threadsafe
};

#endif // __CAThreadSafeList_h__
