#version 450

layout(location = 0) in vec2 coords;

layout(location = 0) out vec4 outColor;

layout(push_constant) uniform p_constants_t
{
    uint frame;
    uint test;
    float time;
    float targetNits;
};

vec3 nitsToPq(vec3 nits)
{
    vec3 y = clamp(nits / 10000.0, vec3(0.0), vec3(1.0));
    const float c1 = 0.8359375;
    const float c2 = 18.8515625;
    const float c3 = 18.6875;
    const float m1 = 0.1593017578125;
    const float m2 = 78.84375;
    vec3 num = c1 + c2 * pow(y, vec3(m1));
    vec3 den = 1.0 + c3 * pow(y, vec3(m1));
    vec3 n = pow(num / den, vec3(m2));
    return n;
}

vec3 pqToNits(vec3 pq)
{
    const float c1 = 0.8359375;
    const float c2 = 18.8515625;
    const float c3 = 18.6875;

    const float oo_m1 = 1.0 / 0.1593017578125;
    const float oo_m2 = 1.0 / 78.84375;

    vec3 num = max(pow(pq, vec3(oo_m2)) - c1, vec3(0.0));
    vec3 den = c2 - c3 * pow(pq, vec3(oo_m2));

    return 10000.0 * pow(num / den, vec3(oo_m1));
}

float gold_noise(vec2 xy, float seed)
{
    const float PHI = 1.61803398874989484820459;
    return fract(tan(distance(xy*PHI, xy)*seed)*xy.x);
}

float positive_mod(float flX, float flPeriod)
{
	float flVal = mod( flX, flPeriod );
	return ( flVal < 0 ) ? flVal + flPeriod : abs( flVal ); // fabs fixes -0
}

vec3 hsv_to_rgb(vec3 hsv)
{
    if ( abs( hsv.y ) < 0.0000001 )
    {
       return vec3( hsv.z ) ;
    }

    float flHue = positive_mod( hsv.x, 1.f );
    flHue *= 6.f;

    int i = int(floor(flHue));        // integer part
	float f = fract(flHue);    // fractional part

	float p = hsv.z * ( 1.f - hsv.y );
	float q = hsv.z * ( 1.f - hsv.y * f );
	float t = hsv.z * ( 1.f - hsv.y * ( 1.f - f ) );

	switch(i)
	{
	case 0: return vec3( hsv.z, t, p ); break;
	case 1: return vec3( q, hsv.z, p ); break;
	case 2: return vec3( p, hsv.z, t ); break;
	case 3: return vec3( p, q, hsv.z ); break;
	case 4: return vec3( t, p, hsv.z ); break;
	case 5: return vec3( hsv.z, p, q ); break;
	}

    return vec3( 0 );
}

void main()
{
    outColor = vec4(0.0, 0.0, 0.0, 1.0);
    int nextTest = 0;

    if (test == nextTest++)
    {
        const vec3 start = vec3(0.0);
        const vec3 end   = vec3(targetNits);

        vec3 color = mix(start, end, coords.x);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        const vec3 start = vec3(0.0);
        const vec3 end   = vec3(targetNits);

        vec3 color = mix(start, end, coords.x);
        if (coords.y < 1.0 / 3.0)
            color.gb = vec2(0.0);
        else if (coords.y < 2.0 / 3.0)
            color.rb = vec2(0.0);
        else
            color.rg = vec2(0.0);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        const vec3 start = vec3(0.0);
        const vec3 end   = vec3(hsv_to_rgb(vec3(coords.y, 1.0, 1.0)) * targetNits);

        vec3 color = mix(start, end, coords.x);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        const vec3 start = vec3(0.0);
        const vec3 end   = vec3(targetNits);

        vec3 color = mix(start, end, coords.x);
        if (coords.y < 1.0 / 3.0)
            color.gb = vec2(0.0);
        else if (coords.y < 2.0 / 3.0)
            color.rb = vec2(0.0);
        else
            color.rg = vec2(0.0);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        vec3 color = vec3(0.0);
        if ((int(gl_FragCoord.x) & 1) == 0)
            color = vec3(targetNits);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        vec3 color = vec3(0.0);
        if ((int(gl_FragCoord.y) & 1) == 0)
            color = vec3(targetNits);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        vec3 color = vec3(0.0);
        if ((int(gl_FragCoord.x) & 1) == 0 && (int(gl_FragCoord.y) & 1) == 0)
            color = vec3(targetNits);

        outColor = vec4(nitsToPq(color), 1.0);
    }
    else if (test == nextTest++)
    {
        const vec3 barycentrics = vec3(1.0 - coords.x - coords.y, coords.x, coords.y) * targetNits;

        outColor = vec4(nitsToPq(barycentrics), 1.0);
    }
    else if (test == nextTest++)
    {
        float value = ((frame & 1) == 0) ? targetNits : 0.0;

        outColor = vec4(nitsToPq(vec3(value)), 1.0);
    }
    else if (test == nextTest++)
    {
        float value = ((frame & 1) == 0) ? targetNits : 0.0;

        outColor = vec4(nitsToPq(vec3(value, 0, 0)), 1.0);
    }
    else if (test == nextTest++)
    {
        float value = ((frame & 1) == 0) ? targetNits : 0.0;

        outColor = vec4(nitsToPq(vec3(0, value, 0)), 1.0);
    }
    else if (test == nextTest++)
    {
        float value = ((frame & 1) == 0) ? targetNits : 0.0;

        outColor = vec4(nitsToPq(vec3(0, 0, value)), 1.0);
    }
    else if (test == nextTest++)
    {
        const float seed = fract(time);

        vec3 value = vec3(gold_noise(gl_FragCoord.xy, seed + 0.2)) * targetNits;

        outColor = vec4(nitsToPq(value), 1.0);
    }
    else if (test == nextTest++)
    {
        const float seed = fract(time);

        vec3 value = vec3(
            gold_noise(gl_FragCoord.xy, seed + 0.1),
            gold_noise(gl_FragCoord.xy, seed + 0.2),
            gold_noise(gl_FragCoord.xy, seed + 0.3)) * targetNits;

        outColor = vec4(nitsToPq(value), 1.0);
    }
}