#version 430

// Adapted from: https://www.shadertoy.com/view/4sf3Dr

layout (binding = 0) uniform sampler2D sprite;

layout (location = 0) in vec4 color;
layout (location = 1) in vec2 uv;

layout (location = 0) out vec4 texel;

layout (binding = 0) uniform Effect {
	float screen_width;
	float screen_height;
	float time;
};

vec3 scanline(vec2 coord, vec3 screen) {
	screen.rgb -= sin((coord.y + (time * 29.0))) * 0.02;
	return screen;
}

vec2 crt(vec2 coord, float bend) {
	// put in symmetrical coords
	coord = (coord - 0.5) * 2.0;

	coord *= 1.0;

	// deform coords
	coord.x *= 1.0 + pow((abs(coord.y) / bend), 2.0);
	coord.y *= 1.0 + pow((abs(coord.x) / bend), 2.0);

	// transform back to 0.0 - 1.0 space
	coord  = (coord / 2.0) + 0.5;

	return coord;
}

void main() {
	vec2 crtCoords = crt(uv, 4.8);

	// Split the color channels
	texel.rgb = texture(sprite, crtCoords).rgb;
	texel.a = 1;

	vec2 screenSpace = crtCoords * vec2(screen_width, screen_height);
	texel.rgb = scanline(screenSpace, texel.rgb);
}