#version 440

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

layout(std140, binding = 0) uniform buf {
    mat4 qt_Matrix;
    float qt_Opacity;
    float uSize;
    float uWavePhase;
    vec4 uResolution;
    vec4 uC0;
    vec4 uC1;
    vec4 uC2;
};

float sdHexagon(vec2 p, float r) {
    const vec3 k = vec3(-0.866025404, 0.5, 0.577350269);
    p = abs(p);
    p -= 2.0 * min(dot(k.xy, p), 0.0) * k.xy;
    p -= vec2(clamp(p.x, -k.z * r, k.z * r), r);
    return length(p) * sign(p.y);
}

// Rainbow from angle — color picker style
vec3 hsv2rgb(float h) {
    return clamp(abs(mod(h * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0, 0.0, 1.0);
}

void main() {
    vec2 res = uResolution.xy;
    vec2 frag = qt_TexCoord0 * res;

    float dx = uSize * 1.5;
    float dy = uSize * 1.7320508;

    float col = round(frag.x / dx);
    float yoff = mod(col, 2.0) != 0.0 ? dy * 0.5 : 0.0;
    float row = round((frag.y - yoff) / dy);
    vec2 center = vec2(col * dx, row * dy + yoff);

    // Wave factor
    float dist = center.x - uWavePhase;
    float wf = exp(-dist * dist / 9000.0);

    float baseR = uSize * 0.48;
    float inradius = baseR * (1.0 + 0.35 * wf);

    vec2 p = frag - center;
    float d = sdHexagon(p.yx, inradius);  // swap for flat-top

    if (d > 0.0) {
        fragColor = vec4(0.0);
        return;
    }

    // Gradient color
    float fx = clamp(center.x / res.x, 0.0, 1.0);
    vec3 rgb = fx < 0.5
        ? mix(uC0.rgb, uC1.rgb, fx * 2.0)
        : mix(uC1.rgb, uC2.rgb, (fx - 0.5) * 2.0);

    // Alpha from distance to center
    float fy = clamp(center.y / res.y, 0.0, 1.0);
    float dc = length(vec2(fx - 0.5, fy - 0.5));
    float a = 0.03 + dc * 0.06;

    // Wave brighten
    rgb = min(rgb + vec3(0.3 * wf), vec3(1.0));
    a += 0.12 * wf;

    // Rainbow shimmer on hex edges when wave passes
    float edgeWidth = 2.0;
    float edgeFactor = smoothstep(-edgeWidth, 0.0, d);  // 0 at interior, 1 at edge
    if (wf > 0.01 && edgeFactor > 0.0) {
        // Angle around hex center → hue
        float angle = atan(p.y, p.x);
        float hue = (angle + 3.14159) / 6.28318;
        // Shift hue by position so neighboring hexes have different phase
        hue = fract(hue + center.x * 0.003 + center.y * 0.005);
        vec3 rainbow = hsv2rgb(hue);

        float shimmer = edgeFactor * wf;
        rgb = mix(rgb, rainbow, shimmer * 0.8);
        a = mix(a, 0.5, shimmer * 0.6);
    }

    // Anti-alias outer edge
    float aa = 1.0 - smoothstep(-1.0, 0.0, d);
    a *= aa;

    fragColor = vec4(rgb * a, a) * qt_Opacity;
}