#version 450

layout(std140, set = 0, binding = 0) uniform UBO
{
   mat4 MVP;
   vec4 OutputSize;
   vec4 OriginalSize;
   vec4 SourceSize;
} global;

#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;

void main()
{
   gl_Position = global.MVP * Position;
   vTexCoord   = TexCoord;
}

/*
    CRT Shader by EasyMode
    License: GPL

    A flat CRT shader ideally for 1080p or higher displays.

    Recommended Settings:

    Video
    - Aspect Ratio:  4:3
    - Integer Scale: Off

    Shader
    - Filter: Nearest
    - Scale:  Don't Care

    Example RGB Mask Parameter Settings:

    Aperture Grille (Default)
    - Dot Width:  1
    - Dot Height: 1
    - Stagger:    0

    Lottes' Shadow Mask
    - Dot Width:  2
    - Dot Height: 1
    - Stagger:    3
*/

#pragma stage fragment
layout(location = 0) in  vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

#define SHARPNESS_H                 0.5 
#define SHARPNESS_V                 1.0 
#define MASK_STRENGTH               0.3 
#define MASK_DOT_WIDTH              1.0 
#define MASK_DOT_HEIGHT             1.0 
#define MASK_STAGGER                0.0 
#define MASK_SIZE                   1.0 
#define SCANLINE_STRENGTH           1.0 
#define SCANLINE_BEAM_WIDTH_MIN     1.5
#define SCANLINE_BEAM_WIDTH_MAX     1.5 
#define SCANLINE_BRIGHT_MIN         0.35
#define SCANLINE_BRIGHT_MAX         0.65 
#define SCANLINE_CUTOFF             400.0 
#define GAMMA_INPUT                 2.0 
#define GAMMA_OUTPUT                1.8 
#define BRIGHT_BOOST                1.2 
#define DILATION                    1.0 

#define FIX(c) max(abs(c), 1e-5)
#define PI 3.141592653589

#define TEX2D(c) dilate(texture(Source, c))

// Set to 0 to use linear filter and gain speed
#define ENABLE_LANCZOS 1

vec4 dilate(vec4 col)
{
    vec4 x = mix(vec4(1.0), col, DILATION);

    return col * x;
}

float curve_distance(float x, float sharp)
{

/*
    apply half-circle s-curve to distance for sharper (more pixelated) interpolation
    single line formula for Graph Toy:
    0.5 - sqrt(0.25 - (x - step(0.5, x)) * (x - step(0.5, x))) * sign(0.5 - x)
*/

    float x_step = step(0.5, x);
    float curve = 0.5 - sqrt(0.25 - (x - x_step) * (x - x_step)) * sign(0.5 - x);

    return mix(x, curve, sharp);
}

mat4x4 get_color_matrix(vec2 co, vec2 dx)
{
    return mat4x4(TEX2D(co - dx), TEX2D(co), TEX2D(co + dx), TEX2D(co + 2.0 * dx));
}

vec3 filter_lanczos(vec4 coeffs, mat4x4 color_matrix)
{
    vec4 col        = coeffs * color_matrix;
    vec4 sample_min = min(color_matrix[1], color_matrix[2]);
    vec4 sample_max = max(color_matrix[1], color_matrix[2]);

    col = clamp(col, sample_min, sample_max);

    return col.rgb;
}

/* main_fragment */
void main()
{
    vec2 dx     = vec2(global.SourceSize.z, 0.0);
    vec2 dy     = vec2(0.0, global.SourceSize.w);
    vec2 pix_co = vTexCoord * global.SourceSize.xy - vec2(0.5, 0.5);
    vec2 tex_co = (floor(pix_co) + vec2(0.5, 0.5)) * global.SourceSize.zw;
    vec2 dist   = fract(pix_co);
    float curve_x;
    vec3 col, col2;

#if ENABLE_LANCZOS
    curve_x = curve_distance(dist.x, SHARPNESS_H * SHARPNESS_H);

    vec4 coeffs = PI * vec4(1.0 + curve_x, curve_x, 1.0 - curve_x, 2.0 - curve_x);

    coeffs = FIX(coeffs);
    coeffs = 2.0 * sin(coeffs) * sin(coeffs * 0.5) / (coeffs * coeffs);
    coeffs /= dot(coeffs, vec4(1.0));

    col  = filter_lanczos(coeffs, get_color_matrix(tex_co, dx));
    col2 = filter_lanczos(coeffs, get_color_matrix(tex_co + dy, dx));
#else
    curve_x = curve_distance(dist.x, SHARPNESS_H);

    col  = mix(TEX2D(tex_co).rgb,      TEX2D(tex_co + dx).rgb,      curve_x);
    col2 = mix(TEX2D(tex_co + dy).rgb, TEX2D(tex_co + dx + dy).rgb, curve_x);
#endif

    col = mix(col, col2, curve_distance(dist.y, SHARPNESS_V));
    col = pow(col, vec3(GAMMA_INPUT / (DILATION + 1.0)));

    float luma        = dot(vec3(0.2126, 0.7152, 0.0722), col);
    float bright      = (max(col.r, max(col.g, col.b)) + luma) * 0.5;
    float scan_bright = clamp(bright, SCANLINE_BRIGHT_MIN, SCANLINE_BRIGHT_MAX);
    float scan_beam   = clamp(bright * SCANLINE_BEAM_WIDTH_MAX, SCANLINE_BEAM_WIDTH_MIN, SCANLINE_BEAM_WIDTH_MAX);
    float scan_weight = 1.0 - pow(cos(vTexCoord.y * 2.0 * PI * global.SourceSize.y) * 0.5 + 0.5, scan_beam) * SCANLINE_STRENGTH;

    float mask   = 1.0 - MASK_STRENGTH;    
    vec2 mod_fac = floor(vTexCoord * global.OutputSize.xy * global.SourceSize.zw * (global.SourceSize.xy * vec2(MASK_SIZE, MASK_DOT_HEIGHT * MASK_SIZE)));
    int dot_no   = int(mod((mod_fac.x + mod(mod_fac.y, 2.0) * MASK_STAGGER) / MASK_DOT_WIDTH, 3.0));
    vec3 mask_weight;

    if      (dot_no == 0) mask_weight = vec3(1.0,  mask, mask);
    else if (dot_no == 1) mask_weight = vec3(mask, 1.0,  mask);
    else                  mask_weight = vec3(mask, mask, 1.0);

    if (global.SourceSize.y >= SCANLINE_CUTOFF) 
        scan_weight = 1.0;

    col2 = col.rgb;
    col *= vec3(scan_weight);
    col  = mix(col, col2, scan_bright);
    col *= mask_weight;
    col  = pow(col, vec3(1.0 / GAMMA_OUTPUT));

    FragColor = vec4(col * BRIGHT_BOOST, 1.0);
}