// 
//---------------------------------------------------------------------------
//
// Copyright(C) 2003-2018 Christoph Oelckers
// 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_decal.cpp
** OpenGL decal processing code
**
*/

#include "doomdata.h"
#include "a_sharedglobal.h"
#include "r_utility.h"
#include "g_levellocals.h"
#include "hwrenderer/textures/hw_material.h"
#include "hwrenderer/utility/hw_cvars.h"
#include "hwrenderer/scene/hw_drawstructs.h"
#include "hwrenderer/scene/hw_drawinfo.h"
#include "hwrenderer/utility/hw_lighting.h"
#include "hwrenderer/data/flatvertices.h"

void GLWall::ProcessDecal(HWDrawInfo *di, DBaseDecal *decal)
{
	line_t * line = seg->linedef;
	side_t * side = seg->sidedef;
	int i;
	float zpos;
	bool flipx, flipy;
	FTextureID decalTile;
	
	
	if (decal->RenderFlags & RF_INVISIBLE) return;
	if (type == RENDERWALL_FFBLOCK && gltexture->isMasked()) return;	// No decals on 3D floors with transparent textures.
	if (seg == nullptr) return;
	
	
	decalTile = decal->PicNum;
	flipx = !!(decal->RenderFlags & RF_XFLIP);
	flipy = !!(decal->RenderFlags & RF_YFLIP);

	
	FTexture *texture = TexMan[decalTile];
	if (texture == NULL) return;

	
	// the sectors are only used for their texture origin coordinates
	// so we don't need the fake sectors for deep water etc.
	// As this is a completely split wall fragment no further splits are
	// necessary for the decal.
	sector_t *frontsector;
	
	// for 3d-floor segments use the model sector as reference
	if ((decal->RenderFlags&RF_CLIPMASK) == RF_CLIPMID) frontsector = decal->Sector;
	else frontsector = seg->frontsector;
	
	switch (decal->RenderFlags & RF_RELMASK)
	{
		default:
			// No valid decal can have this type. If one is encountered anyway
			// it is in some way invalid so skip it.
			return;
			//zpos = decal->z;
			//break;
			
		case RF_RELUPPER:
			if (type != RENDERWALL_TOP) return;
			if (line->flags & ML_DONTPEGTOP)
			{
				zpos = decal->Z + frontsector->GetPlaneTexZ(sector_t::ceiling);
			}
			else
			{
				zpos = decal->Z + seg->backsector->GetPlaneTexZ(sector_t::ceiling);
			}
			break;
		case RF_RELLOWER:
			if (type != RENDERWALL_BOTTOM) return;
			if (line->flags & ML_DONTPEGBOTTOM)
			{
				zpos = decal->Z + frontsector->GetPlaneTexZ(sector_t::ceiling);
			}
			else
			{
				zpos = decal->Z + seg->backsector->GetPlaneTexZ(sector_t::floor);
			}
			break;
		case RF_RELMID:
			if (type == RENDERWALL_TOP || type == RENDERWALL_BOTTOM) return;
			if (line->flags & ML_DONTPEGBOTTOM)
			{
				zpos = decal->Z + frontsector->GetPlaneTexZ(sector_t::floor);
			}
			else
			{
				zpos = decal->Z + frontsector->GetPlaneTexZ(sector_t::ceiling);
			}
	}

	GLDecal &gldecal = *di->AddDecal(type == RENDERWALL_MIRRORSURFACE);
	gldecal.gltexture = FMaterial::ValidateTexture(texture, true);
	gldecal.wall = this;
	gldecal.decal = decal;
	
	if (decal->RenderFlags & RF_FULLBRIGHT)
	{
		gldecal.light = 255;
		gldecal.rel = 0;
	}
	else
	{
		gldecal.light = lightlevel;
		gldecal.rel = rellight + getExtraLight();
	}
	
	gldecal.colormap = Colormap;
	
	if (level.flags3 & LEVEL3_NOCOLOREDSPRITELIGHTING)
	{
		gldecal.colormap.Decolorize();
	}
	
	gldecal.a = decal->Alpha;
	
	// now clip the decal to the actual polygon
	FMaterial *tex = gldecal.gltexture;

	float decalwidth = tex->TextureWidth()  * decal->ScaleX;
	float decalheight = tex->TextureHeight() * decal->ScaleY;
	float decallefto = tex->GetLeftOffset() * decal->ScaleX;
	float decaltopo = tex->GetTopOffset()  * decal->ScaleY;
	
	float leftedge = glseg.fracleft * side->TexelLength;
	float linelength = glseg.fracright * side->TexelLength - leftedge;
	
	// texel index of the decal's left edge
	float decalpixpos = (float)side->TexelLength * decal->LeftDistance - (flipx ? decalwidth - decallefto : decallefto) - leftedge;
	
	float left, right;
	float lefttex, righttex;
	
	// decal is off the left edge
	if (decalpixpos < 0)
	{
		left = 0;
		lefttex = -decalpixpos;
	}
	else
	{
		left = decalpixpos;
		lefttex = 0;
	}
	
	// decal is off the right edge
	if (decalpixpos + decalwidth > linelength)
	{
		right = linelength;
		righttex = right - decalpixpos;
	}
	else
	{
		right = decalpixpos + decalwidth;
		righttex = decalwidth;
	}
	if (right <= left) return;	// nothing to draw
	
	// one texture unit on the wall as vector
	float vx = (glseg.x2 - glseg.x1) / linelength;
	float vy = (glseg.y2 - glseg.y1) / linelength;
	
	DecalVertex *dv = gldecal.dv;
	dv[1].x = dv[0].x = glseg.x1 + vx * left;
	dv[1].y = dv[0].y = glseg.y1 + vy * left;
	
	dv[3].x = dv[2].x = glseg.x1 + vx * right;
	dv[3].y = dv[2].y = glseg.y1 + vy * right;
	
	zpos += (flipy ? decalheight - decaltopo : decaltopo);
	
	dv[1].z = dv[2].z = zpos;
	dv[0].z = dv[3].z = dv[1].z - decalheight;
	dv[1].v = dv[2].v = tex->GetVT();
	
	dv[1].u = dv[0].u = tex->GetU(lefttex / decal->ScaleX);
	dv[3].u = dv[2].u = tex->GetU(righttex / decal->ScaleX);
	dv[0].v = dv[3].v = tex->GetVB();
	
	// now clip to the top plane
	float vzt = (ztop[1] - ztop[0]) / linelength;
	float topleft = ztop[0] + vzt * left;
	float topright = ztop[0] + vzt * right;
	
	// completely below the wall
	if (topleft < dv[0].z && topright < dv[3].z)
		return;
	
	if (topleft < dv[1].z || topright < dv[2].z)
	{
		// decal has to be clipped at the top
		// let texture clamping handle all extreme cases
		dv[1].v = (dv[1].z - topleft) / (dv[1].z - dv[0].z)*dv[0].v;
		dv[2].v = (dv[2].z - topright) / (dv[2].z - dv[3].z)*dv[3].v;
		dv[1].z = topleft;
		dv[2].z = topright;
	}
	
	// now clip to the bottom plane
	float vzb = (zbottom[1] - zbottom[0]) / linelength;
	float bottomleft = zbottom[0] + vzb * left;
	float bottomright = zbottom[0] + vzb * right;
	
	// completely above the wall
	if (bottomleft > dv[1].z && bottomright > dv[2].z)
		return;
	
	if (bottomleft > dv[0].z || bottomright > dv[3].z)
	{
		// decal has to be clipped at the bottom
		// let texture clamping handle all extreme cases
		dv[0].v = (dv[1].z - bottomleft) / (dv[1].z - dv[0].z)*(dv[0].v - dv[1].v) + dv[1].v;
		dv[3].v = (dv[2].z - bottomright) / (dv[2].z - dv[3].z)*(dv[3].v - dv[2].v) + dv[2].v;
		dv[0].z = bottomleft;
		dv[3].z = bottomright;
	}
	
	
	if (flipx)
	{
		float ur = tex->GetUR();
		for (i = 0; i < 4; i++) dv[i].u = ur - dv[i].u;
	}
	if (flipy)
	{
		float vb = tex->GetVB();
		for (i = 0; i < 4; i++) dv[i].v = vb - dv[i].v;
	}

	gldecal.zcenter = zpos - decalheight * 0.5f;
	
	auto verts = di->AllocVertices(4);
	gldecal.vertindex = verts.second;
	
	for (i = 0; i < 4; i++)
	{
		verts.first[i].Set(dv[i].x, dv[i].z, dv[i].y, dv[i].u, dv[i].v);
	}
}

//==========================================================================
//
//
//
//==========================================================================
void GLWall::ProcessDecals(HWDrawInfo *di)
{
	if (seg->sidedef != nullptr)
	{
		DBaseDecal *decal = seg->sidedef->AttachedDecals;
		while (decal)
		{
			ProcessDecal(di, decal);
			decal = decal->WallNext;
		}
	}
}