in vec4 pixelpos;
in vec2 glowdist;


#ifdef SHADER_STORAGE_LIGHTS
	layout(std430, binding = 3) buffer ParameterBuffer
	{
		vec4 lights[];
	};
#elif defined MAXLIGHTS128
	uniform vec4 lights[256];
#else
	uniform vec4 lights[128];
#endif


uniform sampler2D tex;

vec4 Process(vec4 color);
vec4 ProcessTexel();
vec4 ProcessLight(vec4 color);


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

vec4 desaturate(vec4 texel)
{
	if (uDesaturationFactor > 0.0)
	{
		float gray = (texel.r * 0.3 + texel.g * 0.56 + texel.b * 0.14);	
		return mix (texel, vec4(gray,gray,gray,texel.a), uDesaturationFactor);
	}
	else
	{
		return texel;
	}
}

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

vec4 getTexel(vec2 st)
{
	vec4 texel = texture2D(tex, st);
	
	//
	// Apply texture modes
	//
	switch (uTextureMode)
	{
		case 1:
			texel.rgb = vec3(1.0,1.0,1.0);
			break;
			
		case 2:
			texel.a = 1.0;
			break;
			
		case 3:
			texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, texel.a);
			break;
	}
	texel *= uObjectColor;

	return desaturate(texel);
}

//===========================================================================
//
// Doom lighting equation ripped from EDGE.
// Big thanks to EDGE developers for making the only port
// that actually replicates software renderer's lighting in OpenGL.
// Float version.
// Basically replace int with float and divide all constants by 31.
//
//===========================================================================

float R_DoomLightingEquation(float light, float dist)
{
	// Changing this constant gives results very similar to changing r_visibility.
	// Default is 232, it seems to give exactly the same light bands as software renderer.
	#define DOOMLIGHTFACTOR 232.0

	/* L in the range 0 to 63 */
	float L = light * 63.0/31.0;

	float min_L = clamp(36.0/31.0 - L, 0.0, 1.0);

	// Fix objects getting totally black when close.
	if (dist < 0.0001)
		dist = 0.0001;

	float scale = 1.0 / dist;
	float index = (59.0/31.0 - L) - (scale * DOOMLIGHTFACTOR/31.0 - DOOMLIGHTFACTOR/31.0);

	/* result is colormap index (0 bright .. 31 dark) */
	return clamp(index, min_L, 1.0);
}

//===========================================================================
//
// 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(float fogdist, float fogfactor)
{
	vec4 color = gl_Color;
	
	if (uLightLevel >= 0.0)
	{
		float newlightlevel = 1.0 - R_DoomLightingEquation(uLightLevel, gl_FragCoord.z);
		color.rgb *= newlightlevel;
	}
	else if (uFogEnabled > 0.0)
	{
		// 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(color);

	//
	// apply dynamic lights (except additive)
	//
	
	vec4 dynlight = uDynLightColor;

	if (uLightRange.z > uLightRange.x)
	{
		//
		// modulated lights
		//
		for(int i=uLightRange.x; i<uLightRange.y; i+=2)
		{
			vec4 lightpos = lights[i];
			vec4 lightcolor = lights[i+1];
			
			lightcolor.rgb *= max(lightpos.w - distance(pixelpos.xyz, lightpos.xyz),0.0) / lightpos.w;
			dynlight.rgb += lightcolor.rgb;
		}
		//
		// subtractive lights
		//
		for(int i=uLightRange.y; i<uLightRange.z; i+=2)
		{
			vec4 lightpos = lights[i];
			vec4 lightcolor = lights[i+1];
			
			lightcolor.rgb *= max(lightpos.w - distance(pixelpos.xyz, lightpos.xyz),0.0) / lightpos.w;
			dynlight.rgb -= lightcolor.rgb;
		}
	}
	color.rgb = clamp(color.rgb + desaturate(dynlight).rgb, 0.0, 1.4);
	
	// prevent any unintentional messing around with the alpha.
	return vec4(color.rgb, gl_Color.a);
}

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

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


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

void main()
{
#ifndef NO_DISCARD
	// clip plane emulation for plane reflections. These are always perfectly horizontal so a simple check of the pixelpos's y coordinate is sufficient.
	if (pixelpos.y > uClipHeightTop) discard;
	if (pixelpos.y < uClipHeightBottom) discard;
#endif

	vec4 frag = ProcessTexel();
	
#ifndef NO_DISCARD
	// alpha testing
	if (frag.a <= uAlphaThreshold) discard;
#endif


	switch (uFixedColormap)
	{
		case 0:
		{
			float fogdist = 0.0;
			float fogfactor = 0.0;
			

			
			//
			// calculate fog factor
			//
			if (uFogEnabled != 0)
			{
				if (uFogEnabled == 1 || uFogEnabled == -1) 
				{
					fogdist = pixelpos.w;
				}
				else 
				{
					fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
				}
				fogfactor = exp2 (uFogDensity * fogdist);
			}
			
			
			frag *= getLightColor(fogdist, fogfactor);
			
			if (uLightRange.w > uLightRange.z)
			{
				vec4 addlight = vec4(0.0,0.0,0.0,0.0);
			
				//
				// additive lights - these can be done after the alpha test.
				//
				for(int i=uLightRange.z; i<uLightRange.w; i+=2)
				{
					vec4 lightpos = lights[i];
					vec4 lightcolor = lights[i+1];
					
					lightcolor.rgb *= max(lightpos.w - distance(pixelpos.xyz, lightpos.xyz),0.0) / lightpos.w;
					addlight.rgb += lightcolor.rgb;
				}
				frag.rgb = clamp(frag.rgb + desaturate(addlight).rgb, 0.0, 1.0);
			}

			//
			// colored fog
			//
			if (uFogEnabled < 0) 
			{
				frag = applyFog(frag, fogfactor);
			}
			
			break;
		}
		
		case 1:
		{
			float gray = (frag.r * 0.3 + frag.g * 0.56 + frag.b * 0.14);	
			vec4 cm = uFixedColormapStart + gray * uFixedColormapRange;
			frag = vec4(clamp(cm.rgb, 0.0, 1.0), frag.a*gl_Color.a);
			break;
		}
		
		case 2:
		{
			frag = frag * uFixedColormapStart;
			frag.a *= gl_Color.a;
			break;
		}

		case 3:
		{
			float fogdist;
			float fogfactor;
			
			//
			// calculate fog factor
			//
			if (uFogEnabled == -1) 
			{
				fogdist = pixelpos.w;
			}
			else 
			{
				fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
			}
			fogfactor = exp2 (uFogDensity * fogdist);
			
			frag = vec4(uFogColor.rgb, (1.0 - fogfactor) * frag.a * 0.75 * gl_Color.a);
			break;
		}
	}
	gl_FragColor = frag;
}