layout(location = 0) in vec4 vTexCoord;
layout(location = 1) in vec4 vColor;
layout(location = 2) in vec4 pixelpos;
layout(location = 3) in vec3 glowdist;
layout(location = 4) in vec3 gradientdist;
layout(location = 5) in vec4 vWorldNormal;
layout(location = 6) in vec4 vEyeNormal;

#ifdef NO_CLIPDISTANCE_SUPPORT
layout(location = 7) in vec4 ClipDistanceA;
layout(location = 8) in vec4 ClipDistanceB;
#endif

layout(location=0) out vec4 FragColor;
#ifdef GBUFFER_PASS
layout(location=1) out vec4 FragFog;
layout(location=2) out vec4 FragNormal;
#endif

struct Material
{
	vec4 Base;
	vec4 Bright;
	vec3 Normal;
	vec3 Specular;
	float Glossiness;
	float SpecularLevel;
	float Metallic;
	float Roughness;
	float AO;
};

vec4 Process(vec4 color);
vec4 ProcessTexel();
Material ProcessMaterial();
vec4 ProcessLight(Material mat, vec4 color);
vec3 ProcessMaterialLight(Material material, vec3 color);

//===========================================================================
//
// Color to grayscale
//
//===========================================================================

float grayscale(vec4 color)
{
	return dot(color.rgb, vec3(0.3, 0.56, 0.14));
}

//===========================================================================
//
// Desaturate a color
//
//===========================================================================

vec4 dodesaturate(vec4 texel, float factor)
{
	if (factor != 0.0)
	{
		float gray = grayscale(texel);
		return mix (texel, vec4(gray,gray,gray,texel.a), factor);
	}
	else
	{
		return texel;
	}
}

//===========================================================================
//
// Desaturate a color
//
//===========================================================================

vec4 desaturate(vec4 texel)
{
	return dodesaturate(texel, uDesaturationFactor);
}

//===========================================================================
//
// Texture tinting code originally from JFDuke but with a few more options
//
//===========================================================================

const int Tex_Blend_Alpha = 1;
const int Tex_Blend_Screen = 2;
const int Tex_Blend_Overlay = 3;
const int Tex_Blend_Hardlight = 4;
 
 vec4 ApplyTextureManipulation(vec4 texel, int blendflags)
 {
	// Step 1: desaturate according to the material's desaturation factor. 
	texel = dodesaturate(texel, uTextureModulateColor.a);
	
	// Step 2: Invert if requested
	if ((blendflags & 8) != 0)
	{
		texel.rgb = vec3(1.0 - texel.r, 1.0 - texel.g, 1.0 - texel.b);
	}
	
	// Step 3: Apply additive color
	texel.rgb += uTextureAddColor.rgb;
	
	// Step 4: Colorization, including gradient if set.
	texel.rgb *= uTextureModulateColor.rgb;
	
	// Before applying the blend the value needs to be clamped to [0..1] range.
	texel.rgb = clamp(texel.rgb, 0.0, 1.0);
	
	// Step 5: Apply a blend. This may just be a translucent overlay or one of the blend modes present in current Build engines.
	if ((blendflags & 7) != 0)
	{
		vec3 tcol = texel.rgb * 255.0;	// * 255.0 to make it easier to reuse the integer math.
		vec4 tint = uTextureBlendColor * 255.0;

		switch (blendflags & 7)
		{
			default:
				tcol.b = tcol.b * (1.0 - uTextureBlendColor.a) + tint.b * uTextureBlendColor.a;
				tcol.g = tcol.g * (1.0 - uTextureBlendColor.a) + tint.g * uTextureBlendColor.a;
				tcol.r = tcol.r * (1.0 - uTextureBlendColor.a) + tint.r * uTextureBlendColor.a;
				break;
			// The following 3 are taken 1:1 from the Build engine
			case Tex_Blend_Screen:
				tcol.b = 255.0 - (((255.0 - tcol.b) * (255.0 - tint.r)) / 256.0);
				tcol.g = 255.0 - (((255.0 - tcol.g) * (255.0 - tint.g)) / 256.0);
				tcol.r = 255.0 - (((255.0 - tcol.r) * (255.0 - tint.b)) / 256.0);
				break;
			case Tex_Blend_Overlay:
				tcol.b = tcol.b < 128.0? (tcol.b * tint.b) / 128.0 : 255.0 - (((255.0 - tcol.b) * (255.0 - tint.b)) / 128.0);
				tcol.g = tcol.g < 128.0? (tcol.g * tint.g) / 128.0 : 255.0 - (((255.0 - tcol.g) * (255.0 - tint.g)) / 128.0);
				tcol.r = tcol.r < 128.0? (tcol.r * tint.r) / 128.0 : 255.0 - (((255.0 - tcol.r) * (255.0 - tint.r)) / 128.0);
				break;
			case Tex_Blend_Hardlight:
				tcol.b = tint.b < 128.0 ? (tcol.b * tint.b) / 128.0 : 255.0 - (((255.0 - tcol.b) * (255.0 - tint.b)) / 128.0);
				tcol.g = tint.g < 128.0 ? (tcol.g * tint.g) / 128.0 : 255.0 - (((255.0 - tcol.g) * (255.0 - tint.g)) / 128.0);
				tcol.r = tint.r < 128.0 ? (tcol.r * tint.r) / 128.0 : 255.0 - (((255.0 - tcol.r) * (255.0 - tint.r)) / 128.0);
				break;
		}
		texel.rgb = tcol / 255.0;
	}
	return texel;
}

//===========================================================================
//
// This function is common for all (non-special-effect) fragment shaders
//
//===========================================================================

vec4 getTexel(vec2 st)
{
	vec4 texel = texture(tex, st);
	
	//
	// Apply texture modes
	//
	switch (uTextureMode)
	{
		case 1:	// TM_STENCIL
			texel.rgb = vec3(1.0,1.0,1.0);
			break;
			
		case 2:	// TM_OPAQUE
			texel.a = 1.0;
			break;
			
		case 3:	// TM_INVERSE
			texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, texel.a);
			break;
			
		case 4:	// TM_ALPHATEXTURE
		{
			float gray = grayscale(texel);
			texel = vec4(1.0, 1.0, 1.0, gray*texel.a);
			break;
		}
			
		case 5:	// TM_CLAMPY
			if (st.t < 0.0 || st.t > 1.0)
			{
				texel.a = 0.0;
			}
			break;
			
		case 6: // TM_OPAQUEINVERSE
			texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, 1.0);
			break;
			
		case 7: //TM_FOGLAYER 
			return texel;

	}
	
	// Apply the texture modification colors.
	int blendflags = int(uTextureAddColor.a);	// this alpha is unused otherwise
	if (blendflags != 0)	
	{
		// only apply the texture manipulation if it contains something.
		texel = ApplyTextureManipulation(texel, blendflags);
	}

	// Apply the Doom64 style material colors on top of everything from the texture modification settings.
	// This may be a bit redundant in terms of features but the data comes from different sources so this is unavoidable.
	texel.rgb += uAddColor.rgb;
	if (uObjectColor2.a == 0.0) texel *= uObjectColor;
	else texel *= mix(uObjectColor, uObjectColor2, gradientdist.z);

	// Last but not least apply the desaturation from the sector's light.
	return desaturate(texel);
}

//===========================================================================
//
// Vanilla Doom wall colormap equation
//
//===========================================================================
float R_WallColormap(float lightnum, float z, vec3 normal)
{
	// R_ScaleFromGlobalAngle calculation
	float projection = 160.0; // projection depends on SCREENBLOCKS!! 160 is the fullscreen value
	vec2 line_v1 = pixelpos.xz; // in vanilla this is the first curline vertex
	vec2 line_normal = normal.xz;
	float texscale = projection * clamp(dot(normalize(uCameraPos.xz - line_v1), line_normal), 0.0, 1.0) / z;

	float lightz = clamp(16.0 * texscale, 0.0, 47.0);

	// scalelight[lightnum][lightz] lookup
	float startmap = (15.0 - lightnum) * 4.0;
	return startmap - lightz * 0.5;
}

//===========================================================================
//
// Vanilla Doom plane colormap equation
//
//===========================================================================
float R_PlaneColormap(float lightnum, float z)
{
	float lightz = clamp(z / 16.0f, 0.0, 127.0);

	// zlight[lightnum][lightz] lookup
	float startmap = (15.0 - lightnum) * 4.0;
	float scale = 160.0 / (lightz + 1.0);
	return startmap - scale * 0.5;
}

//===========================================================================
//
// zdoom colormap equation
//
//===========================================================================
float R_ZDoomColormap(float light, float z)
{
	float L = light * 255.0;
	float vis = min(uGlobVis / z, 24.0 / 32.0);
	float shade = 2.0 - (L + 12.0) / 128.0;
	float lightscale = shade - vis;
	return lightscale * 31.0;
}

float R_DoomColormap(float light, float z)
{
	if ((uPalLightLevels >> 16) == 16) // gl_lightmode 16
	{
		float lightnum = clamp(light * 15.0, 0.0, 15.0);

		if (dot(vWorldNormal.xyz, vWorldNormal.xyz) > 0.5)
		{
			vec3 normal = normalize(vWorldNormal.xyz);
			return mix(R_WallColormap(lightnum, z, normal), R_PlaneColormap(lightnum, z), abs(normal.y));
		}
		else // vWorldNormal is not set on sprites
		{
			return R_PlaneColormap(lightnum, z);
		}
	}
	else
	{
		return R_ZDoomColormap(light, z);
	}
}

//===========================================================================
//
// Doom software lighting equation
//
//===========================================================================
float R_DoomLightingEquation(float light)
{
	// z is the depth in view space, positive going into the screen
	float z;
	if (((uPalLightLevels >> 8)  & 0xff) == 2)
	{
		z = distance(pixelpos.xyz, uCameraPos.xyz);
	}
	else 
	{
		z = pixelpos.w;
	}

	float colormap = R_DoomColormap(light, z);

	if ((uPalLightLevels & 0xff) != 0)
		colormap = floor(colormap) + 0.5;

	// Result is the normalized colormap index (0 bright .. 1 dark)
	return clamp(colormap, 0.0, 31.0) / 32.0;
}

//===========================================================================
//
// Check if light is in shadow according to its 1D shadow map
//
//===========================================================================

#ifdef SUPPORTS_SHADOWMAPS

float shadowDirToU(vec2 dir)
{
	if (abs(dir.y) > abs(dir.x))
	{
		float x = dir.x / dir.y * 0.125;
		if (dir.y >= 0.0)
			return 0.125 + x;
		else
			return (0.50 + 0.125) + x;
	}
	else
	{
		float y = dir.y / dir.x * 0.125;
		if (dir.x >= 0.0)
			return (0.25 + 0.125) - y;
		else
			return (0.75 + 0.125) - y;
	}
}

vec2 shadowUToDir(float u)
{
	u *= 4.0;
	vec2 raydir;
	switch (int(u))
	{
	case 0: raydir = vec2(u * 2.0 - 1.0, 1.0); break;
	case 1: raydir = vec2(1.0, 1.0 - (u - 1.0) * 2.0); break;
	case 2: raydir = vec2(1.0 - (u - 2.0) * 2.0, -1.0); break;
	case 3: raydir = vec2(-1.0, (u - 3.0) * 2.0 - 1.0); break;
	}
	return raydir;
}

float sampleShadowmap(vec3 planePoint, float v)
{
	float bias = 1.0;
	float negD = dot(vWorldNormal.xyz, planePoint);

	vec3 ray = planePoint;

	vec2 isize = textureSize(ShadowMap, 0);
	float scale = float(isize.x) * 0.25;

	// Snap to shadow map texel grid
	if (abs(ray.z) > abs(ray.x))
	{
		ray.y = ray.y / abs(ray.z);
		ray.x = ray.x / abs(ray.z);
		ray.x = (floor((ray.x + 1.0) * 0.5 * scale) + 0.5) / scale * 2.0 - 1.0;
		ray.z = sign(ray.z);
	}
	else
	{
		ray.y = ray.y / abs(ray.x);
		ray.z = ray.z / abs(ray.x);
		ray.z = (floor((ray.z + 1.0) * 0.5 * scale) + 0.5) / scale * 2.0 - 1.0;
		ray.x = sign(ray.x);
	}

	float t = negD / dot(vWorldNormal.xyz, ray) - bias;
	vec2 dir = ray.xz * t;

	float u = shadowDirToU(dir);
	float dist2 = dot(dir, dir);
	return step(dist2, texture(ShadowMap, vec2(u, v)).x);
}

float sampleShadowmapPCF(vec3 planePoint, float v)
{
	float bias = 1.0;
	float negD = dot(vWorldNormal.xyz, planePoint);

	vec3 ray = planePoint;

	if (abs(ray.z) > abs(ray.x))
		ray.y = ray.y / abs(ray.z);
	else
		ray.y = ray.y / abs(ray.x);

	vec2 isize = textureSize(ShadowMap, 0);
	float scale = float(isize.x);
	float texelPos = floor(shadowDirToU(ray.xz) * scale);

	float sum = 0.0;
	float step_count = uShadowmapFilter;
		
	texelPos -= step_count + 0.5;
	for (float x = -step_count; x <= step_count; x++)
	{
		float u = fract(texelPos / scale);
		vec2 dir = shadowUToDir(u);

		ray.x = dir.x;
		ray.z = dir.y;
		float t = negD / dot(vWorldNormal.xyz, ray) - bias;
		dir = ray.xz * t;

		float dist2 = dot(dir, dir);
		sum += step(dist2, texture(ShadowMap, vec2(u, v)).x);
		texelPos++;
	}
	return sum / (uShadowmapFilter * 2.0 + 1.0);
}

float shadowmapAttenuation(vec4 lightpos, float shadowIndex)
{
	if (shadowIndex >= 1024.0)
		return 1.0; // No shadowmap available for this light

	vec3 planePoint = pixelpos.xyz - lightpos.xyz;
	planePoint += 0.01; // nudge light position slightly as Doom maps tend to have their lights perfectly aligned with planes

	if (dot(planePoint.xz, planePoint.xz) < 1.0)
		return 1.0; // Light is too close

	float v = (shadowIndex + 0.5) / 1024.0;

	if (uShadowmapFilter <= 0)
	{
		return sampleShadowmap(planePoint, v);
	}
	else
	{
		return sampleShadowmapPCF(planePoint, v);
	}
}

float shadowAttenuation(vec4 lightpos, float lightcolorA)
{
	float shadowIndex = abs(lightcolorA) - 1.0;
	return shadowmapAttenuation(lightpos, shadowIndex);
}

#else

float shadowAttenuation(vec4 lightpos, float lightcolorA)
{
	return 1.0;
}

#endif

float spotLightAttenuation(vec4 lightpos, vec3 spotdir, float lightCosInnerAngle, float lightCosOuterAngle)
{
	vec3 lightDirection = normalize(lightpos.xyz - pixelpos.xyz);
	float cosDir = dot(lightDirection, spotdir);
	return smoothstep(lightCosOuterAngle, lightCosInnerAngle, cosDir);
}

//===========================================================================
//
// Adjust normal vector according to the normal map
//
//===========================================================================

#if defined(NORMALMAP)
mat3 cotangent_frame(vec3 n, vec3 p, vec2 uv)
{
	// get edge vectors of the pixel triangle
	vec3 dp1 = dFdx(p);
	vec3 dp2 = dFdy(p);
	vec2 duv1 = dFdx(uv);
	vec2 duv2 = dFdy(uv);

	// solve the linear system
	vec3 dp2perp = cross(n, dp2); // cross(dp2, n);
	vec3 dp1perp = cross(dp1, n); // cross(n, dp1);
	vec3 t = dp2perp * duv1.x + dp1perp * duv2.x;
	vec3 b = dp2perp * duv1.y + dp1perp * duv2.y;

	// construct a scale-invariant frame
	float invmax = inversesqrt(max(dot(t,t), dot(b,b)));
	return mat3(t * invmax, b * invmax, n);
}

vec3 ApplyNormalMap(vec2 texcoord)
{
	#define WITH_NORMALMAP_UNSIGNED
	#define WITH_NORMALMAP_GREEN_UP
	//#define WITH_NORMALMAP_2CHANNEL

	vec3 interpolatedNormal = normalize(vWorldNormal.xyz);

	vec3 map = texture(normaltexture, texcoord).xyz;
	#if defined(WITH_NORMALMAP_UNSIGNED)
	map = map * 255./127. - 128./127.; // Math so "odd" because 0.5 cannot be precisely described in an unsigned format
	#endif
	#if defined(WITH_NORMALMAP_2CHANNEL)
	map.z = sqrt(1 - dot(map.xy, map.xy));
	#endif
	#if defined(WITH_NORMALMAP_GREEN_UP)
	map.y = -map.y;
	#endif

	mat3 tbn = cotangent_frame(interpolatedNormal, pixelpos.xyz, vTexCoord.st);
	vec3 bumpedNormal = normalize(tbn * map);
	return bumpedNormal;
}
#else
vec3 ApplyNormalMap(vec2 texcoord)
{
	return normalize(vWorldNormal.xyz);
}
#endif

//===========================================================================
//
// Calculate light
//
// It is important to note that the light color is not desaturated
// due to ZDoom's implementation weirdness. Everything that's added
// on top of it, e.g. dynamic lights and glows are, though, because
// the objects emitting these lights are also.
//
// This is making this a bit more complicated than it needs to
// because we can't just desaturate the final fragment color.
//
//===========================================================================

vec4 getLightColor(Material material, float fogdist, float fogfactor)
{
	vec4 color = vColor;
	
	if (uLightLevel >= 0.0)
	{
		float newlightlevel = 1.0 - R_DoomLightingEquation(uLightLevel);
		color.rgb *= newlightlevel;
	}
	else if (uFogEnabled > 0)
	{
		// brightening around the player for light mode 2
		if (fogdist < uLightDist)
		{
			color.rgb *= uLightFactor - (fogdist / uLightDist) * (uLightFactor - 1.0);
		}
		
		//
		// apply light diminishing through fog equation
		//
		color.rgb = mix(vec3(0.0, 0.0, 0.0), color.rgb, fogfactor);
	}
	
	//
	// handle glowing walls
	//
	if (uGlowTopColor.a > 0.0 && glowdist.x < uGlowTopColor.a)
	{
		color.rgb += desaturate(uGlowTopColor * (1.0 - glowdist.x / uGlowTopColor.a)).rgb;
	}
	if (uGlowBottomColor.a > 0.0 && glowdist.y < uGlowBottomColor.a)
	{
		color.rgb += desaturate(uGlowBottomColor * (1.0 - glowdist.y / uGlowBottomColor.a)).rgb;
	}
	color = min(color, 1.0);

	//
	// apply brightmaps (or other light manipulation by custom shaders.
	//
	color = ProcessLight(material, color);

	//
	// apply dynamic lights
	//
	return vec4(ProcessMaterialLight(material, color.rgb), material.Base.a * vColor.a);
}

//===========================================================================
//
// Applies colored fog
//
//===========================================================================

vec4 applyFog(vec4 frag, float fogfactor)
{
	return vec4(mix(uFogColor.rgb, frag.rgb, fogfactor), frag.a);
}

//===========================================================================
//
// The color of the fragment if it is fully occluded by ambient lighting
//
//===========================================================================

vec3 AmbientOcclusionColor()
{
	float fogdist;
	float fogfactor;
			
	//
	// calculate fog factor
	//
	if (uFogEnabled == -1) 
	{
		fogdist = max(16.0, pixelpos.w);
	}
	else 
	{
		fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
	}
	fogfactor = exp2 (uFogDensity * fogdist);
			
	return mix(uFogColor.rgb, vec3(0.0), fogfactor);
}

//===========================================================================
//
// Main shader routine
//
//===========================================================================

void main()
{
#ifdef NO_CLIPDISTANCE_SUPPORT
	if (ClipDistanceA.x < 0 || ClipDistanceA.y < 0 || ClipDistanceA.z < 0 || ClipDistanceA.w < 0 || ClipDistanceB.x < 0) discard;
#endif

	Material material = ProcessMaterial();
	vec4 frag = material.Base;
	
#ifndef NO_ALPHATEST
	if (frag.a <= uAlphaThreshold) discard;
#endif

	if (uFogEnabled != -3)	// check for special 2D 'fog' mode.
	{
		float fogdist = 0.0;
		float fogfactor = 0.0;
		
		//
		// calculate fog factor
		//
		if (uFogEnabled != 0)
		{
			if (uFogEnabled == 1 || uFogEnabled == -1) 
			{
				fogdist = max(16.0, pixelpos.w);
			}
			else 
			{
				fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
			}
			fogfactor = exp2 (uFogDensity * fogdist);
		}
		
		if (uTextureMode != 7)
		{
			frag = getLightColor(material, fogdist, fogfactor);
			//
			// colored fog
			//
			if (uFogEnabled < 0) 
			{
				frag = applyFog(frag, fogfactor);
			}
		}
		else
		{
			frag = vec4(uFogColor.rgb, (1.0 - fogfactor) * frag.a * 0.75 * vColor.a);
		}
	}
	else // simple 2D (uses the fog color to add a color overlay)
	{
		if (uTextureMode == 7)
		{
			float gray = grayscale(frag);
			vec4 cm = (uObjectColor + gray * (uAddColor - uObjectColor)) * 2;
			frag = vec4(clamp(cm.rgb, 0.0, 1.0), frag.a);
		}
			frag = frag * ProcessLight(material, vColor);
		frag.rgb = frag.rgb + uFogColor.rgb;
	}
	FragColor = frag;
#ifdef GBUFFER_PASS
	FragFog = vec4(AmbientOcclusionColor(), 1.0);
	FragNormal = vec4(vEyeNormal.xyz * 0.5 + 0.5, 1.0);
#endif
}