#include "shaders/scene/desaturate.glsl"

vec4 ApplyTextureManipulation(vec4 texel, int blendflags);

// Samples from the base texture according to gzdoom's texture mode.
// In good gzdoom tradition it also does all kinds of unrelated garbage.
vec4 getTexel(vec2 st)
{
	vec4 texel = texture(tex, st);

	// Apply texture modes
	#if defined(TM_STENCIL)
		texel.rgb = vec3(1.0,1.0,1.0);
	#elif defined(TM_OPAQUE)
		texel.a = 1.0;
	#elif defined(TM_INVERSE)
		texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, texel.a);
	#elif defined(TM_ALPHATEXTURE)
		float gray = grayscale(texel);
		texel = vec4(1.0, 1.0, 1.0, gray*texel.a);
	#elif defined(TM_CLAMPY)
		if (st.t < 0.0 || st.t > 1.0)
		{
			texel.a = 0.0;
		}
	#elif defined(TM_INVERTOPAQUE)
		texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, 1.0);
	#elif defined(TM_FOGLAYER)
		return texel;
	#endif

	#if defined(TEXF_ClampY)
		if (st.t < 0.0 || st.t > 1.0)
		{
			texel.a = 0.0;
		}
	#endif

	// 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);
}

const int Tex_Blend_Alpha = 1;
const int Tex_Blend_Screen = 2;
const int Tex_Blend_Overlay = 3;
const int Tex_Blend_Hardlight = 4;

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