out vec4 outcolor;
in vec2 frag_texture_coord;

uniform sampler2D source;
uniform bool horizontal;

// ========== QUALITY SETTINGS ==========
// Change this to switch between quality levels:
// 0 = Fastest (5-tap, best for integrated GPUs)
// 1 = Medium quality (9-tap, good balance)
// 2 = High quality (17-tap, beautiful bloom but expensive)
#define BLUR_QUALITY 2

#if BLUR_QUALITY == 0
	// 5-tap gaussian blur (3 samples each direction)
	const int SAMPLE_COUNT = 3;
	const float weight[3] = float[](0.3829249226, 0.2419707245, 0.0606531529);
	const float blur_radius = 1.0;
#elif BLUR_QUALITY == 1
	// 9-tap gaussian blur (5 samples each direction)
	const int SAMPLE_COUNT = 5;
	const float weight[5] = float[](0.227027, 0.1945946, 0.1216216, 0.054054, 0.016216);
	const float blur_radius = 1.0;
#else
	// 17-tap gaussian blur (9 samples each direction)
	const int SAMPLE_COUNT = 9;
	const float weight[9] = float[](0.1964825501511404, 0.1782316199485724, 0.12149164501415554, 0.0652229951888931, 0.027835877787234808, 0.009270061520867907, 0.0024201487396289743, 0.0004963317290261215, 0.0000801326238056394);
	const float blur_radius = 1.0;
#endif

void main() {
	vec2 tex_offset = 1.0 / vec2(textureSize(source, 0));
	vec3 result = texture(source, frag_texture_coord).rgb * weight[0];

	if(horizontal) {
		for(int i = 1; i < SAMPLE_COUNT; ++i) {
			float offset = tex_offset.x * float(i) * blur_radius;
			result += texture(source, frag_texture_coord + vec2(offset, 0.0)).rgb * weight[i];
			result += texture(source, frag_texture_coord - vec2(offset, 0.0)).rgb * weight[i];
		}
	} else {
		for(int i = 1; i < SAMPLE_COUNT; ++i) {
			float offset = tex_offset.y * float(i) * blur_radius;
			result += texture(source, frag_texture_coord + vec2(0.0, offset)).rgb * weight[i];
			result += texture(source, frag_texture_coord - vec2(0.0, offset)).rgb * weight[i];
		}
	}

	outcolor = vec4(result, 1.0);
}