shader_type canvas_item;

uniform bool bloom_enabled = true;
uniform float bloom_amount: hint_range(0.0, 0.5, 0.01) = 0.5;
uniform float bloom_radius: hint_range(0.0, 10.0, 0.1) = 2.0;

uniform bool chromatic_abberation_enabled = true;
uniform float chromatic_abberation_amount : hint_range(0.0, 10.0, 0.01) = 4.0;

uniform bool scan_lines_enabled = true;
uniform float scan_lines_count : hint_range(0, 180, 1) = 180;
uniform float scan_lines_opacity : hint_range(0.0, 1.0, 0.01) = 1.0;

uniform bool vignette_enabled = true;
uniform float vignette_opacity : hint_range(0.0, 1.0, 0.01) = 0.2;

uniform float boost_intensity : hint_range(1.0, 2.0, 0.01) = 1.2;

const float PI = 3.14159265359;

/**
 * Apply bloom.
 */
vec3 bloom(sampler2D tex, vec2 uv, vec2 pixel_size)
{
	vec3 glow0 = max(textureLod(tex, uv + vec2(-pixel_size.x, 0), bloom_radius).rgb - bloom_amount, vec3(0.0));
	vec3 glow1 = max(textureLod(tex, uv + vec2(pixel_size.x,  0), bloom_radius).rgb - bloom_amount, vec3(0.0));
	vec3 glow2 = max(textureLod(tex, uv + vec2(0, -pixel_size.y), bloom_radius).rgb - bloom_amount, vec3(0.0));
	vec3 glow3 = max(textureLod(tex, uv + vec2(0,  pixel_size.y), bloom_radius).rgb - bloom_amount, vec3(0.0));
	
	return 0.25 * (glow0 + glow1 + glow2 + glow3);
}

/**
 * Apply chromatic abberation the the given texture.
 */
vec3 chromatic_abberation(sampler2D tex, vec2 uv, vec2 screen_size) {
	float adjusted_amount = chromatic_abberation_amount / screen_size.x;

	vec3 color;

	color.r = texture(tex, vec2(clamp(uv.x + adjusted_amount, 0.0, 1.0), uv.y)).r;
	color.g = texture(tex,                                                  uv).g;
	color.b = texture(tex, vec2(clamp(uv.x - adjusted_amount, 0.0, 1.0), uv.y)).b;

	return color;
}

/**
 * Apply scan lines
 */
vec3 scan_lines(vec3 color, vec2 uv) {
	float strength = clamp(sin(uv.y * scan_lines_count * PI * 2.0), 0.65, 0.85);
	vec3 scan_line = vec3(pow(strength, scan_lines_opacity));
	return color * scan_line * boost_intensity;
}

/**
 * Apply a vignette.
 */
vec3 vignette(vec3 color, vec2 uv, vec2 screen_size) {
	float vignette = uv.x * uv.y * (1.0 - uv.x) * (1.0 - uv.y);
	vignette = clamp(pow((screen_size.x / 4.0) * vignette, vignette_opacity), 0.0, 1.0);
	return color * vignette;
}

void fragment() {
	vec3 color = texture(SCREEN_TEXTURE, SCREEN_UV).rgb;
	vec2 screen_size = 1.0 / SCREEN_PIXEL_SIZE;

	vec3 bloom_color = bloom(SCREEN_TEXTURE, SCREEN_UV, SCREEN_PIXEL_SIZE);
	vec3 scan_lines_color = scan_lines(color, SCREEN_UV);

	color = mix(color, chromatic_abberation(SCREEN_TEXTURE, SCREEN_UV, screen_size), float(chromatic_abberation_enabled));
	color = mix(color, bloom_color, 0.5 * float(bloom_enabled));
	color = color + scan_lines(color, SCREEN_UV) * float(scan_lines_enabled);
	color = color * vignette(color, SCREEN_UV, screen_size);

	COLOR = vec4(color, 1.0);
}