#include <metal_stdlib>
using namespace metal;

// New Leaked 3I/Atlas NASA Footage — msm01
// MSL port of dbz.vk.glsl.

struct ShadertoyUBO {
    float iTime;
    float2 iResolution;
};

struct PassthroughVOut {
    float4 pos [[position]];
    float2 uv;
};

constant float NBCaps = 3.0;

static float2x2 r2d(float a) {
    float c = cos(a), s = sin(a);
    return float2x2(c, s, -s, c);
}

static float hash12(float2 p) {
    float3 p3 = fract(float3(p.xyx) * 0.1031);
    p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.x + p3.y) * p3.z);
}

static float fbm(float2 v_p) {
    float pvpx = v_p.x;
    float2 V1 = float2(floor(pvpx));
    float2 V2 = float2(floor(pvpx + 1.0));
    return mix(hash12(V1), hash12(V2), smoothstep(0.0, 1.0, fract(pvpx)));
}

#define S(a,b,c) smoothstep(a,b,c)

fragment float4 dbz_fs(PassthroughVOut in [[stage_in]],
                       constant ShadertoyUBO& U [[buffer(0)]]) {
    float2 fragCoord = in.uv * U.iResolution;
    float2 p = float2((1.0 / U.iResolution.y) * (fragCoord.x - U.iResolution.x / 2.0),
                      fragCoord.y / U.iResolution.y - 0.5);

    p.x = -p.x;
    p *= 150.0;

    float4 col = float4(0.05, 0.05, 0.15, 1.0);

    float2 save1 = p;

    p = p * r2d(-0.05);
    col = mix(col, float4(0.2, 0.3, 0.5, 1.0),
              smoothstep(75.0, 0.0, abs(p.y - 5.0 * fbm(float2(0.01 * (p.x - 33.333 * U.iTime))) + 3.5)));
    p = p * r2d(0.05);

    p = p * r2d(-0.05);
    p *= 0.35;
    p += float2(-5.0 * U.iTime, 0.0);

    float2 b = fract(5.0 * p);
    p = floor(5.0 * p);
    if (fbm(float2(p.x * p.y)) > 0.996) {
        col += clamp(1.0 - pow(3.0 * length(b + float2(-0.5)), 0.5), 0.0, 1.0);
    }

    p = save1;
    float2 save3;

    float Nb_Capsules = clamp(NBCaps, 0.0, 4.0);
    for (float i = 0.0; i < Nb_Capsules; i++) {
        p = save1;
        p = p * r2d(-0.05);
        p *= 2.5;
        p *= 1.0 - 0.25 * i;
        p += float2(150.0 * fbm(float2(0.15 * U.iTime + i * 54.321)) - 75.0,
                    50.0 * sin(0.25 * U.iTime + i * 54.321) - 25.0);
        save3 = p;

        p *= 0.04;
        p.y = abs(p.y);

        if (p.x > 0.0) {
            col += float4(0.0, 1.0, 0.5, 1.0) * smoothstep(0.2, 0.0, abs(p.y - 0.05 * fbm(float2(1.5 * p.x - 40.0 * U.iTime))) - 0.05) * smoothstep(29.0, 0.0, abs(p.x));
            col += float4(1.0, 1.0, 1.0, 1.0) * smoothstep(0.1, 0.0, abs(p.y - 0.05 * fbm(float2(1.5 * p.x - 40.0 * U.iTime))) - 0.05) * smoothstep(29.0, 0.0, abs(p.x));
        }

        p = save3;
        p.y = abs(p.y);
        p += float2(-10.0, 0.0);
        p *= float2(0.75, 1.0);

        col += 0.8 * float4(0.0, 1.0, 0.5, 1.0) * S(20.0, 0.0, length(p) - 25.0 + 7.0 * sin(0.30 * length(p) * atan2(p.y, p.x) + 55.0 * U.iTime));
        col += 0.8 * float4(1.0, 1.0, 1.0, 1.0) * S(20.0, 0.0, length(p) - 20.0 + 7.0 * sin(0.30 * length(p) * atan2(p.y, p.x) + 55.0 * U.iTime));

        p = save3;

        col = mix(col, float4(1.0), 0.5 * S(10.0, 0.0, length(p + float2(5.0, 0.0)) - 20.0) * abs(sin(50.0 * U.iTime)));
        col = mix(col, float4(1.0), 0.5 * S(20.0, 0.0, length(p + float2(5.0, 0.0)) - 20.0));
        col = mix(col, float4(1.0), S(0.01, 0.0, length(p) - 20.0));

        if (length(p) - 20.0 < 0.0) {
            col = mix(col, float4(0.65, 0.68, 0.68 + 0.1 * (3.0 - i), 1.0), S(0.5, 0.0, length(p - float2(2.0, 0.0)) - 17.0));
            if (S(0.0, 1.0, length(float2(3.0, 2.0) * p + float2(33.5, 0.0)) - 23.0) > 0.0) {
                col = mix(col, float4(0.45, 0.55, 0.55 + 0.1 * (3.0 - i), 1.0),
                          0.75 * S(0.5, 0.0, length(p - float2(2.0, 0.0) + 0.5 * fbm(float2(4.5 * atan2(p.y, p.x)))) - 9.0));
            }

            col = mix(col, float4(0.0), S(0.2, 0.0, abs(length(p) - 19.9) - 0.20));
            col = mix(col, float4(0.5, 0.2, 0.3, 1.0)
                          - S(5.0, 0.0, length(p + float2(-6.0, 15.0)) - 20.0)
                          - S(0.25, 0.0, abs(length(p + float2(0.0, 3.0)) - 15.0) - 0.4)
                          - S(0.0, 1.5, p.y - 8.5)
                          + 0.25 * float4(1.0, 0.5, 0.0, 1.0) * S(10.0, 0.0, abs(p.y))
                          ,
                          S(0.5, 0.0, length(float2(3.0, 2.0) * p + float2(35.0, 0.0)) - 19.9));

            col = mix(col, float4(0.0, 0.0, 0.0, 1.0), S(1.0, 0.0, abs(length(float2(3.0, 2.0) * p + float2(35.0, 0.0)) - 19.9) - 0.1));
            col = mix(col, float4(0.0, 0.0, 0.0, 1.0), S(1.0, 0.0, abs(length(float2(3.0, 2.0) * p + float2(33.5, 0.0)) - 23.0) - 0.1));

            if (p.y > 0.0) col = mix(col, float4(0.0, 0.0, 0.0, 1.0), S(1.0, 0.0, abs(length(float2(3.0, 2.0) * p + float2(29.0, 0.0)) - 30.0) - 0.1));
            if (p.y < 0.0) col = mix(col, float4(0.0, 0.0, 0.0, 1.0), S(1.0, 0.0, abs(length(float2(3.0, 2.0) * p + float2(-31.0, 0.0)) - 30.0) - 0.1));
        }
    }

    return clamp(col, 0.0, 1.0);
}