// 
//---------------------------------------------------------------------------
//
// Copyright(C) 2015 Christopher Bruns
// All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see http://www.gnu.org/licenses/
//
//--------------------------------------------------------------------------
//
/*
** gl_stereo3d.cpp
** Stereoscopic 3D API
**
*/

#include "gl_system.h"
#include "gl_renderer.h"
#include "gl_renderbuffers.h"
#include "hw_vrmodes.h"
#include "gl_framebuffer.h"
#include "gl_postprocessstate.h"
#include "gl_framebuffer.h"
#include "gl_shaderprogram.h"
#include "gl_buffers.h"


EXTERN_CVAR(Int, vr_mode)
EXTERN_CVAR(Float, vid_saturation)
EXTERN_CVAR(Float, vid_brightness)
EXTERN_CVAR(Float, vid_contrast)
EXTERN_CVAR(Int, gl_satformula)
EXTERN_CVAR(Int, gl_dither_bpc)

void UpdateVRModes(bool considerQuadBuffered = true);

namespace OpenGLRenderer
{

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentAnaglyph(bool r, bool g, bool b)
{
	mBuffers->BindOutputFB();
	ClearBorders();

	glColorMask(r, g, b, 1);
	mBuffers->BindEyeTexture(0, 0);
 	DrawPresentTexture(screen->mOutputLetterbox, true);

	glColorMask(!r, !g, !b, 1);
	mBuffers->BindEyeTexture(1, 0);
	DrawPresentTexture(screen->mOutputLetterbox, true);

	glColorMask(1, 1, 1, 1);
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentSideBySide(int vrmode)
{
	if (vrmode == VR_SIDEBYSIDEFULL || vrmode == VR_SIDEBYSIDESQUISHED)
	{
		mBuffers->BindOutputFB();
		ClearBorders();

		// Compute screen regions to use for left and right eye views
		int leftWidth = screen->mOutputLetterbox.width / 2;
		int rightWidth = screen->mOutputLetterbox.width - leftWidth;
		IntRect leftHalfScreen = screen->mOutputLetterbox;
		leftHalfScreen.width = leftWidth;
		IntRect rightHalfScreen = screen->mOutputLetterbox;
		rightHalfScreen.width = rightWidth;
		rightHalfScreen.left += leftWidth;

		mBuffers->BindEyeTexture(0, 0);
		DrawPresentTexture(leftHalfScreen, true);

		mBuffers->BindEyeTexture(1, 0);
		DrawPresentTexture(rightHalfScreen, true);
	}
	else if (vrmode == VR_SIDEBYSIDELETTERBOX)
	{
		mBuffers->BindOutputFB();
		screen->mOutputLetterbox.top = screen->mOutputLetterbox.height;

		ClearBorders();
		screen->mOutputLetterbox.top = 0;  //reset so screenshots can be taken

		// Compute screen regions to use for left and right eye views
		int leftWidth = screen->mOutputLetterbox.width / 2;
		int rightWidth = screen->mOutputLetterbox.width - leftWidth;
		//cut letterbox height in half
		int height = screen->mOutputLetterbox.height / 2;
		int top = height * .5;
		IntRect leftHalfScreen = screen->mOutputLetterbox;
		leftHalfScreen.width = leftWidth;
		leftHalfScreen.height = height;
		leftHalfScreen.top = top;
		IntRect rightHalfScreen = screen->mOutputLetterbox;
		rightHalfScreen.width = rightWidth;
		rightHalfScreen.left += leftWidth;
		//give it those cinematic black bars on top and bottom
		rightHalfScreen.height = height;
		rightHalfScreen.top = top;

		mBuffers->BindEyeTexture(0, 0);
		DrawPresentTexture(leftHalfScreen, true);

		mBuffers->BindEyeTexture(1, 0);
		DrawPresentTexture(rightHalfScreen, true);
	}
}


//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentTopBottom()
{
	mBuffers->BindOutputFB();
	ClearBorders();

	// Compute screen regions to use for left and right eye views
	int topHeight = screen->mOutputLetterbox.height / 2;
	int bottomHeight = screen->mOutputLetterbox.height - topHeight;
	IntRect topHalfScreen = screen->mOutputLetterbox;
	topHalfScreen.height = topHeight;
	topHalfScreen.top = topHeight;
	IntRect bottomHalfScreen = screen->mOutputLetterbox;
	bottomHalfScreen.height = bottomHeight;
	bottomHalfScreen.top = 0;

	mBuffers->BindEyeTexture(0, 0);
	DrawPresentTexture(topHalfScreen, true);

	mBuffers->BindEyeTexture(1, 0);
	DrawPresentTexture(bottomHalfScreen, true);
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::prepareInterleavedPresent(FPresentShaderBase& shader)
{
	mBuffers->BindOutputFB();
	ClearBorders();


	// Bind each eye texture, for composition in the shader
	mBuffers->BindEyeTexture(0, 0);
	mBuffers->BindEyeTexture(1, 1);

	glActiveTexture(GL_TEXTURE0);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

	glActiveTexture(GL_TEXTURE1);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

	const IntRect& box = screen->mOutputLetterbox;
	glViewport(box.left, box.top, box.width, box.height);

	shader.Bind();

	if (framebuffer->IsHWGammaActive())
	{
		shader.Uniforms->InvGamma = 1.0f;
		shader.Uniforms->Contrast = 1.0f;
		shader.Uniforms->Brightness = 0.0f;
		shader.Uniforms->Saturation = 1.0f;
	}
	else
	{
		shader.Uniforms->InvGamma = 1.0f / clamp<float>(vid_gamma, 0.1f, 4.f);
		shader.Uniforms->Contrast = clamp<float>(vid_contrast, 0.1f, 3.f);
		shader.Uniforms->Brightness = clamp<float>(vid_brightness, -0.8f, 0.8f);
		shader.Uniforms->Saturation = clamp<float>(vid_saturation, -15.0f, 15.0f);
		shader.Uniforms->GrayFormula = static_cast<int>(gl_satformula);
	}
	shader.Uniforms->HdrMode = 0;
	shader.Uniforms->ColorScale = (gl_dither_bpc == -1) ? 255.0f : (float)((1 << gl_dither_bpc) - 1);
	shader.Uniforms->Scale = {
		screen->mScreenViewport.width / (float)mBuffers->GetWidth(),
		screen->mScreenViewport.height / (float)mBuffers->GetHeight()
	};
	shader.Uniforms->Offset = { 0.0f, 0.0f };
	shader.Uniforms.SetData();
	static_cast<GLDataBuffer*>(shader.Uniforms.GetBuffer())->BindBase();
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentColumnInterleaved()
{
	FGLPostProcessState savedState;
	savedState.SaveTextureBindings(2);
	prepareInterleavedPresent(*mPresent3dColumnShader);

	// Compute absolute offset from top of screen to top of current display window
	// because we need screen-relative, not window-relative, scan line parity

	// Todo:
	//auto clientoffset = screen->GetClientOffset();
	//auto windowHOffset = clientoffset.X % 2;
	int windowHOffset = 0;

	mPresent3dColumnShader->Uniforms->WindowPositionParity = windowHOffset;
	mPresent3dColumnShader->Uniforms.SetData();
	static_cast<GLDataBuffer*>(mPresent3dColumnShader->Uniforms.GetBuffer())->BindBase();

	RenderScreenQuad();
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentRowInterleaved()
{
	FGLPostProcessState savedState;
	savedState.SaveTextureBindings(2);
	prepareInterleavedPresent(*mPresent3dRowShader);

	// Todo:
	//auto clientoffset = screen->GetClientOffset();
	//auto windowVOffset = clientoffset.Y % 2;
	int windowVOffset = 0;

	mPresent3dRowShader->Uniforms->WindowPositionParity =
		(windowVOffset
			+ screen->mOutputLetterbox.height + 1 // +1 because of origin at bottom
			) % 2;

	mPresent3dRowShader->Uniforms.SetData();
	static_cast<GLDataBuffer*>(mPresent3dRowShader->Uniforms.GetBuffer())->BindBase();
	RenderScreenQuad();
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentCheckerInterleaved()
{
	FGLPostProcessState savedState;
	savedState.SaveTextureBindings(2);
	prepareInterleavedPresent(*mPresent3dCheckerShader);

	// Compute absolute offset from top of screen to top of current display window
	// because we need screen-relative, not window-relative, scan line parity

	//auto clientoffset = screen->GetClientOffset();
	//auto windowHOffset = clientoffset.X % 2;
	//auto windowVOffset = clientoffset.Y % 2;
	int windowHOffset = 0;
	int windowVOffset = 0;

	mPresent3dCheckerShader->Uniforms->WindowPositionParity =
		(windowVOffset
			+ windowHOffset
			+ screen->mOutputLetterbox.height + 1 // +1 because of origin at bottom
			) % 2; // because we want the top pixel offset, but gl_FragCoord.y is the bottom pixel offset

	mPresent3dCheckerShader->Uniforms.SetData();
	static_cast<GLDataBuffer*>(mPresent3dCheckerShader->Uniforms.GetBuffer())->BindBase();
	RenderScreenQuad();
}

//==========================================================================
//
// Sometimes the stereo render context is not ready immediately at start up
//
//==========================================================================

bool FGLRenderer::QuadStereoCheckInitialRenderContextState()
{
	// Keep trying until we see at least one good OpenGL context to render to
	bool bQuadStereoSupported = false;
	bool bDecentContextWasFound = false;
	int contextCheckCount = 0;
	if ((!bDecentContextWasFound) && (contextCheckCount < 200))
	{
		contextCheckCount += 1;
		glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);  // This question is about the main screen display context
		GLboolean supportsStereo, supportsBuffered;
		glGetBooleanv(GL_DOUBLEBUFFER, &supportsBuffered);
		if (supportsBuffered) // Finally, a useful OpenGL context
		{
			// This block will be executed exactly ONCE during a game run
			bDecentContextWasFound = true; // now we can stop checking every frame...
										   // Now check whether this context supports hardware stereo
			glGetBooleanv(GL_STEREO, &supportsStereo);
			bQuadStereoSupported = supportsStereo && supportsBuffered;
			if (! bQuadStereoSupported)
				UpdateVRModes(false);
		}
	}
	return bQuadStereoSupported;
}

//==========================================================================
//
//
//
//==========================================================================

void FGLRenderer::PresentQuadStereo()
{
	if (QuadStereoCheckInitialRenderContextState())
	{
		mBuffers->BindOutputFB();

		glDrawBuffer(GL_BACK_LEFT);
		ClearBorders();
		mBuffers->BindEyeTexture(0, 0);
		DrawPresentTexture(screen->mOutputLetterbox, true);

		glDrawBuffer(GL_BACK_RIGHT);
		ClearBorders();
		mBuffers->BindEyeTexture(1, 0);
		DrawPresentTexture(screen->mOutputLetterbox, true);

		glDrawBuffer(GL_BACK);
	}
	else
	{
		mBuffers->BindOutputFB();
		ClearBorders();
		mBuffers->BindEyeTexture(0, 0);
		DrawPresentTexture(screen->mOutputLetterbox, true);
	}
}


void FGLRenderer::PresentStereo()
{
	auto vrmode = VRMode::GetVRMode(true);
	const int eyeCount = vrmode->mEyeCount;
	// Don't invalidate the bound framebuffer (..., false)
	if (eyeCount > 1)
		mBuffers->BlitToEyeTexture(mBuffers->CurrentEye(), false);

	switch (vr_mode)
	{
	default:
		return;

	case VR_GREENMAGENTA:
		PresentAnaglyph(false, true, false);
		break;

	case VR_REDCYAN:
		PresentAnaglyph(true, false, false);
		break;

	case VR_AMBERBLUE:
		PresentAnaglyph(true, true, false);
		break;

	case VR_SIDEBYSIDEFULL:
	case VR_SIDEBYSIDESQUISHED:
	case VR_SIDEBYSIDELETTERBOX:
		PresentSideBySide(vr_mode);
		break;

	case VR_TOPBOTTOM:
		PresentTopBottom();
		break;

	case VR_ROWINTERLEAVED:
		PresentRowInterleaved();
		break;

	case VR_COLUMNINTERLEAVED:
		PresentColumnInterleaved();
		break;

	case VR_CHECKERINTERLEAVED:
		PresentCheckerInterleaved();
		break;

	case VR_QUADSTEREO:
		PresentQuadStereo();
		break;
	}
}

}