/// Defines: 
/// - VPASS or HPASS
/// - COL_RGBA or COL_RGB or COL_R
/// - SAMPLES is a number of 3 or 5 or 7 or 9
/// - BLURRING_DIST is optional and it's extra pixels to move the blurring

#pragma anki start vertexShader

layout(location = 0) in vec2 position;

out vec2 vTexCoords;

void main()
{
	vTexCoords = position;
	gl_Position = vec4(position * 2.0 - 1.0, 0.0, 1.0);
}

#pragma anki start fragmentShader

#define DEFAULT_FLOAT_PRECISION mediump
#pragma anki include "shaders/Common.glsl"

// Preprocessor switches sanity checks
#if !defined(VPASS) && !defined(HPASS)
#	error See file
#endif

#if !(defined(COL_RGBA) || defined(COL_RGB) || defined(COL_R))
#	error See file
#endif

#if !defined(IMG_DIMENSION)
#	error See file
#endif

#if !defined(SAMPLES)
#	error See file
#endif

uniform mediump sampler2D img; ///< Input FAI

in vec2 vTexCoords;

#if !defined(BLURRING_DIST)
#	define BLURRING_DIST 0.0
#endif

// Determine color type
#if defined(COL_RGBA)
#	define COL_TYPE vec4
#elif defined(COL_RGB)
#	define COL_TYPE vec3
#elif defined(COL_R)
#	define COL_TYPE float
#endif

// Determine tex fetch
#if defined(COL_RGBA)
#	define TEX_FETCH rgba
#elif defined(COL_RGB)
#	define TEX_FETCH rgb
#elif defined(COL_R)
#	define TEX_FETCH r
#endif

// Calc the kernel. Use offsets of 3 to take advantage of bilinear filtering
#define BLURRING(val, sign_) ((float(val) * (float(BLURRING_DIST) + 1.0) / float(IMG_DIMENSION)) * float(sign_))

#if defined(VPASS)
#	define BLURRING_OFFSET_X(val, sign_) BLURRING(val, sign_)
#	define BLURRING_OFFSET_Y(val, sign_) 0.0
#else
#	define BLURRING_OFFSET_X(val, sign_) 0.0
#	define BLURRING_OFFSET_Y(val, sign_) BLURRING(val, sign_)
#endif

#define BLURRING_OFFSET(v, s) vec2(BLURRING_OFFSET_X(v, s), BLURRING_OFFSET_Y(v, s))

#if SAMPLES == 3
const vec2 kernel[SAMPLES] = vec2[](
	BLURRING_OFFSET(1, -1),
	BLURRING_OFFSET(0, 1),
	BLURRING_OFFSET(1, 1));
#elif SAMPLES == 5
const vec2 kernel[SAMPLES] = vec2[](
	BLURRING_OFFSET(2, -1),
	BLURRING_OFFSET(1, -1),
	BLURRING_OFFSET(0, 0),
	BLURRING_OFFSET(1, 1),
	BLURRING_OFFSET(2, 1));
#elif SAMPLES == 7
const vec2 kernel[SAMPLES] = vec2[](
	BLURRING_OFFSET(3, -1),
	BLURRING_OFFSET(2, -1),
	BLURRING_OFFSET(1, -1),
	BLURRING_OFFSET(0, 1),
	BLURRING_OFFSET(1, 1),
	BLURRING_OFFSET(2, 1),
	BLURRING_OFFSET(3, 1));
#elif SAMPLES == 9
const vec2 kernel[SAMPLES] = vec2[](
	BLURRING_OFFSET(4, -1),
	BLURRING_OFFSET(3, -1),
	BLURRING_OFFSET(2, -1),
	BLURRING_OFFSET(1, -1),
	BLURRING_OFFSET(0, 1),
	BLURRING_OFFSET(1, 1),
	BLURRING_OFFSET(2, 1),
	BLURRING_OFFSET(3, 1),
	BLURRING_OFFSET(4, 1));
#endif

layout(location = 0) out COL_TYPE fFragColor;

void main()
{
	// Get the first
	COL_TYPE col = textureFai(img, vTexCoords + kernel[0]).TEX_FETCH;

	// Get the rest of the samples
	for(int i = 1; i < SAMPLES; i++)
	{
		col += textureFai(img, vTexCoords + kernel[i]).TEX_FETCH;
	}

	fFragColor = col * (1.0 / float(SAMPLES));
}