#include "DeferredShader.h"
#include "FrameBufferObject.h"
#include "RenderState.h"


using namespace std;


namespace CHCDemoEngine
{


static void PrintGLerror(char *msg)
{
	GLenum errCode;
	const GLubyte *errStr;
	
	if ((errCode = glGetError()) != GL_NO_ERROR) 
	{
		errStr = gluErrorString(errCode);
		fprintf(stderr,"OpenGL ERROR: %s: %s\n", errStr, msg);
	}
}


static CGprogram sCgDeferredProgram;
static CGparameter sColorsTexParam;
static CGparameter sPositionsTexParam;
static CGparameter sNormalsTexParam;


DeferredShader::DeferredShader(int w, int h):
mWidth(w), mHeight(h)
{}


DeferredShader::~DeferredShader()
{
	if (sCgDeferredProgram)
		cgDestroyProgram(sCgDeferredProgram);
}


void DeferredShader::Init(CGcontext context)
{
	
	sCgDeferredProgram = 
		cgCreateProgramFromFile(context, 
								CG_SOURCE,
								"src/shaders/deferred.cg", 
								RenderState::sCgFragmentProfile,
								"main",
								NULL);

	if (sCgDeferredProgram != NULL)
	{
		cgGLLoadProgram(sCgDeferredProgram);

		// we need size of texture for scaling
		sPositionsTexParam = cgGetNamedParameter(sCgDeferredProgram, "positions");  
		sColorsTexParam = cgGetNamedParameter(sCgDeferredProgram, "colors");  
		sNormalsTexParam = cgGetNamedParameter(sCgDeferredProgram, "normals"); 
	}
	else
		cerr << "deferred program failed to load" << endl;


	PrintGLerror("init");
}


void DeferredShader::Render(FrameBufferObject *fbo)
{
	FrameBufferObject::Release();

	GLuint colorsTex = fbo->GetColorBuffer(0)->GetTexture();
	GLuint positionsTex = fbo->GetColorBuffer(1)->GetTexture();
	GLuint normalsTex = fbo->GetColorBuffer(2)->GetTexture();

	glPushAttrib(GL_VIEWPORT_BIT);
	glViewport(0, 0, mWidth, mHeight);

	glDisable(GL_ALPHA_TEST);
	glDisable(GL_TEXTURE_2D);
	glDisable(GL_LIGHTING);
	
	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();

	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();

	const float offs = 0.5f;
	
	glOrtho(-offs, offs, -offs, offs, 0, 1);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	cgGLEnableProfile(RenderState::sCgFragmentProfile);

	cgGLBindProgram(sCgDeferredProgram);

	cgGLSetTextureParameter(sColorsTexParam, colorsTex);
	cgGLEnableTextureParameter(sColorsTexParam);

	cgGLSetTextureParameter(sPositionsTexParam, positionsTex);
	cgGLEnableTextureParameter(sPositionsTexParam);

	cgGLSetTextureParameter(sNormalsTexParam, normalsTex);
	cgGLEnableTextureParameter(sNormalsTexParam);
	
	glColor3f(1.0f, 1.0f, 1.0f);
	
	glBegin(GL_QUADS);

	float offs2 = 0.5f;

	glTexCoord2f(0, 0); glVertex3f(-offs2, -offs2, -0.5f);
	glTexCoord2f(1, 0); glVertex3f( offs2, -offs2, -0.5f);
	glTexCoord2f(1, 1); glVertex3f( offs2,  offs2, -0.5f);
	glTexCoord2f(0, 1); glVertex3f(-offs2,  offs2, -0.5f);

	glEnd();

	cgGLDisableTextureParameter(sColorsTexParam);
	cgGLDisableTextureParameter(sPositionsTexParam);
	cgGLDisableTextureParameter(sNormalsTexParam);

	cgGLDisableProfile(RenderState::sCgFragmentProfile);
	
	glEnable(GL_LIGHTING);
	glDisable(GL_TEXTURE_2D);
	
	glMatrixMode(GL_PROJECTION);
	glPopMatrix();

	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();

	glPopAttrib();

	PrintGLerror("deferred shading");
}


} // namespace