#include "CHCTraverser.h"
#include "SceneEntity.h"


namespace CHCDemoEngine
{

CHCTraverser::CHCTraverser() 
{}


OcclusionQuery *CHCTraverser::IssueOcclusionQueryWithGeometry(BvhNode *node)
{
	// render out what is left in the qeue
	if (mUseRenderQueue) ApplyRenderQueue();

	OcclusionQuery *query = mQueryHandler.RequestQuery();
	query->AddNode(node);

	++ mStats.mNumIssuedQueries;

	query->BeginQuery();

	RenderNode(node);
	if (mUseRenderQueue) ApplyRenderQueue();

	query->EndQuery();

	return query;
}


void CHCTraverser::Traverse()
{
	//-- PART 1: process finished occlusion queries
	while (!mDistanceQueue.empty() || !mQueryQueue.empty())
	{
		while (!mQueryQueue.empty() && 
			   (mQueryQueue.front()->ResultAvailable() || mDistanceQueue.empty()))
		{
			OcclusionQuery *query = mQueryQueue.front();
			mQueryQueue.pop();
			
			// wait until result available
			int visiblePixels = query->GetQueryResult();

			if (visiblePixels > mVisibilityThreshold)
			{
				BvhNode *node = query->GetFrontNode();
				node->SetAssumedVisibleFrameId(mFrameId + mAssumedVisibleFrames);

				node->SetVisible(true);
				mBvh->MakeParentsVisible(node);
				TraverseNode(node);
			}
			else
			{
				
				++ mStats.mNumQueryCulledNodes;
			}
		}	

		//-- PART 2: hierarchical traversal
		if (!mDistanceQueue.empty())
		{
			BvhNode *node = mDistanceQueue.top();
			mDistanceQueue.pop();
	
			if (mBvh->IsWithinViewFrustum(node))
			{
				// for near plane intersecting bounding box possible 
				// wrong results => skip occlusion query
				if (IntersectsNearPlane(node))
				{
					// update node's visited flag
					node->SetLastVisitedFrame(mFrameId);
					node->SetVisible(true);
					mBvh->MakeParentsVisible(node);

					TraverseNode(node);
				}
				else
				{		
					// identify previously visible nodes
					const bool wasVisible = node->IsVisible() && (node->GetLastVisitedFrame() == mFrameId - 1);
					
					// identify nodes that we cannot skip queries for
					const bool queryFeasible = (!wasVisible || 
						(node->IsVirtualLeaf() && (node->GetAssumedVisibleFrameId() <= mFrameId)));

					// update node's visited flag
					node->SetLastVisitedFrame(mFrameId);
					
					// skip testing previously visible interior nodes
					if (queryFeasible)
					{
						OcclusionQuery *query;

						// if this node is a previous visible leaf:
						// leaves will be rendered anyway => we can directly query the real geometry 
						if (wasVisible && mUseOptimization)
							query = IssueOcclusionQueryWithGeometry(node);
						else
							query = IssueOcclusionQuery(node);

						mQueryQueue.push(query);
					}
					else
					{
						if (node->IsVirtualLeaf())
						{
							node->SetVisible(true);
							mBvh->MakeParentsVisible(node);
						} 
						else // reset visibility classification
						{
							node->SetVisible(false);
						}
					}

					// always traverse a node if it was visible
					if (wasVisible)
						TraverseNode(node);
				}
			}
			else
			{
				// for stats
				++ mStats.mNumFrustumCulledNodes;
			}
		}
	}
}

}