#version 440

layout(location = 0) in vec2 qt_TexCoord0;
layout(location = 0) out vec4 fragColor;

// NOTE: std140 layout. Order/types must match the ShaderEffect properties by name.
layout(std140, binding = 0) uniform buf {
    mat4  qt_Matrix;
    float qt_Opacity;
    vec2  itemSize;   // full ShaderEffect size in px (rect + glow padding)
    vec2  rectSize;   // size of the target rectangle in px
    float radius;     // corner radius of the target rectangle in px
    float glowSize;   // how far the glow extends outside the rectangle (px)
    float innerGlow;  // how far the glow bleeds inside (px), 0 = none
    float lineWidth;  // width of the bright edge line (px), 0 = none
    float phase;      // 0..1, loops seamlessly
    float intensity;  // overall brightness
    vec4  color1;
    vec4  color2;
    vec4  color3;
    vec4  color4;
};

const float TAU = 6.28318530718;

// Signed distance to a rounded box centred at the origin. <0 inside, >0 outside.
float sdRoundBox(vec2 p, vec2 halfSize, float r)
{
    vec2 q = abs(p) - (halfSize - r);
    return length(max(q, 0.0)) + min(max(q.x, q.y), 0.0) - r;
}

// Cyclic 4-colour gradient, t is wrapped to [0,1)
vec3 palette(float t)
{
    t = fract(t) * 4.0;
    float f = smoothstep(0.0, 1.0, fract(t));
    if (t < 1.0) return mix(color1.rgb, color2.rgb, f);
    if (t < 2.0) return mix(color2.rgb, color3.rgb, f);
    if (t < 3.0) return mix(color3.rgb, color4.rgb, f);
    return mix(color4.rgb, color1.rgb, f);
}

// Cheap hash for dithering (avoids banding in soft gradients)
float hash(vec2 p)
{
    return fract(sin(dot(p, vec2(12.9898, 78.233))) * 43758.5453);
}

void main()
{
    // Pixel position relative to the centre of the item
    vec2 p = (qt_TexCoord0 - 0.5) * itemSize;

    float r = clamp(radius, 0.0, min(rectSize.x, rectSize.y) * 0.5);
    float d = sdRoundBox(p, rectSize * 0.5, r);

    // ---- colour: rotates around the rectangle, slightly wobbling ----
    float ang = atan(p.y, p.x);
    float a2  = phase * TAU;
    float u = ang / TAU + 0.5 + phase;
    u += 0.07 * sin(ang * 2.0 + a2) + 0.04 * sin(ang * 3.0 - a2 * 2.0);
    vec3 col = palette(u);

    // ---- intensity falloff ----
    float g = 0.0;
    if (d > 0.0) {
        float t = clamp(d / max(glowSize, 0.001), 0.0, 1.0);
        g = pow(1.0 - t, 3.0);
    } else if (innerGlow > 0.0) {
        g = exp(d / innerGlow * 3.0);
    }

    // Slow "breathing" so the glow feels alive
    float pulse = 0.9 + 0.1 * sin(a2 * 2.0 + ang);
    g *= pulse;

    // Crisp bright line along the edge
    float line = 0.0;
    if (lineWidth > 0.0)
        line = 1.0 - smoothstep(0.0, lineWidth, abs(d));

    float a = clamp(g * intensity + line * 0.9, 0.0, 1.0);

    // Brighten the colour a bit where the line is
    col = mix(col, vec3(1.0), line * 0.25);

    a += (hash(gl_FragCoord.xy) - 0.5) / 255.0;
    a = clamp(a, 0.0, 1.0);

    // Premultiplied alpha output
    fragColor = vec4(col * a, a) * qt_Opacity;
}