/* Input */
varying vec4 v_Color;
varying vec2 v_Texcoord0;
uniform sampler2D u_Texture0;
uniform int u_Time;

/* Curvature */
const float Curvature = 6.0;

/* Color bleeding */
const float color_bleeding = 1.1;
const float bleeding_range = 1.3;

vec2 crt_coords(vec2 uv, float bend)
{
    uv -= 0.5;
    uv *= 2.;
    uv.x *= 1. + pow(abs(uv.y)/bend, 2.);
    uv.y *= 1. + pow(abs(uv.x)/bend, 2.);

    uv /= 2.;
    return uv + .5;
}

float vignette(vec2 uv, float size, float smoothness, float edgeRounding)
{
    uv -= .5;
    uv *= size;
    float amount = sqrt(pow(abs(uv.x), edgeRounding) + pow(abs(uv.y), edgeRounding));
    return smoothstep(0., smoothness, 1.0 - amount);
}

vec4 get_color_bleeding(vec4 current_color,vec4 color_left)
{
    vec4 c = current_color*vec4(color_bleeding, 0.5, 1.0-color_bleeding, 1);
    vec4 l = color_left*vec4(1.0-color_bleeding, 0.5, color_bleeding, 1);
    return c + l;
}

float random(vec2 uv)
{
    return fract(sin(dot(uv * 0.05, vec2(12.9898, 78.233) * float(u_Time))) * 438.5453) * 1.9;
}

float noise(vec2 uv)
{
    vec2 i = floor(uv);
    vec2 f = fract(uv);
    
    float a = random(i);
    float b = random(i + vec2(1.,0.));
    float c = random(i + vec2(0., 1.));
    float d = random(i + vec2(1.));
    
    vec2 u = smoothstep(0., 1., f);
    
    return mix(a,b, u.x) + (c - a) * u.y * (1. - u.x) + (d - b) * u.x * u.y; 
}

void main()
{
    /* screen curvature */
    vec2 xy;
    vec4 col;
    if (c_curvature == 1) {
        xy =  crt_coords(v_Texcoord0, Curvature);
        col = v_Color * vignette(xy, 1.9, 0.6, Curvature*2.0);
    } else {
        xy = v_Texcoord0;
        col = v_Color;
    }

    /* screen noise */
    vec4 color;
    if (c_noise == 1) {
        color = mix(col, vec4(noise(xy * 75.)), 0.05);
    } else {
        color = col;
    }

    /* Color bleeding */
    vec4 p;
    if (c_color_bleed == 1) {
        float pixel_size = 1.0/float(c_WindowWidth)*bleeding_range;
        vec4 current_color = texture2D(u_Texture0, xy) * color;
        vec4 color_left = texture2D(u_Texture0, vec2(xy.x-pixel_size, xy.y)) * color;
        p = get_color_bleeding(current_color, color_left);
    } else {
        p = texture2D(u_Texture0, xy) * color;
    }

    /* Add scanlines */
    if (c_scanlines == 1) {
        float r = float(c_WindowHeight / 216);
        float f = mod(gl_FragCoord.y, r) / r;
        gl_FragColor = mix(p, vec4(p.rgb * 0.5, p.a), f);
    } else {
        gl_FragColor = p;
    }
}