uniform sampler2D m_ExploreMap;
uniform float     m_Time;
uniform vec2      m_OverlayOrigin;
uniform vec2      m_OverlaySize;
uniform float     m_FadePx;

in  vec2 texCoord;
out vec4 outFragColor;

// ── Procedural Value Noise ────────────────────────────────────────────────────

float hash(vec2 p) {
    vec3 p3 = fract(vec3(p.xyx) * vec3(0.1031, 0.1030, 0.0973));
    p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.x + p3.y) * p3.z);
}

float vnoise(vec2 p) {
    vec2 i = floor(p);
    vec2 f = fract(p);
    f = f * f * (3.0 - 2.0 * f);
    return mix(
        mix(hash(i),                hash(i + vec2(1.0, 0.0)), f.x),
        mix(hash(i + vec2(0.0,1.0)), hash(i + vec2(1.0, 1.0)), f.x),
        f.y);
}

// FBM: 3 Oktaven
float fbm(vec2 p) {
    float v = 0.0;
    v += vnoise(p)                           * 0.500;
    v += vnoise(p * 2.1 + vec2(1.7,  9.2))  * 0.250;
    v += vnoise(p * 4.3 + vec2(8.3,  2.8))  * 0.125;
    return v / 0.875;
}

// ── Hauptprogramm ─────────────────────────────────────────────────────────────

void main() {

    // Weichgezeichnete Erkundungsmaske (3×3-Kernel, 8-Texel-Radius = ~32 m)
    float ts = 8.0 / 512.0;
    float density =
        texture(m_ExploreMap, texCoord + vec2(-ts,-ts)).a +
        texture(m_ExploreMap, texCoord + vec2(0.0,-ts)).a +
        texture(m_ExploreMap, texCoord + vec2( ts,-ts)).a +
        texture(m_ExploreMap, texCoord + vec2(-ts, 0.0)).a +
        texture(m_ExploreMap, texCoord             ).a +
        texture(m_ExploreMap, texCoord + vec2( ts, 0.0)).a +
        texture(m_ExploreMap, texCoord + vec2(-ts,  ts)).a +
        texture(m_ExploreMap, texCoord + vec2(0.0,  ts)).a +
        texture(m_ExploreMap, texCoord + vec2( ts,  ts)).a;
    density /= 9.0;

    // Vollständig erkundet → diesen Fragment überspringen
    if (density <= 0.0) { discard; }

    // ── Animierter Nebel mit Domain-Warping ───────────────────────────────────

    float t  = m_Time * 0.18;
    vec2  uv = texCoord;

    // Erste Warp-Schicht: langsam driftende Wirbel
    vec2 q = vec2(
        fbm(uv * 2.5 + vec2(t * 0.40, t * 0.15)),
        fbm(uv * 2.5 + vec2(t * 0.15, t * 0.30) + vec2(5.2, 1.3))
    );

    // Zweite Warp-Schicht: gibt Tiefe und Komplexität
    vec2 r = vec2(
        fbm(uv * 2.0 + q * 0.9 + vec2(1.7, 9.2) + vec2(t * 0.10, 0.0)),
        fbm(uv * 2.0 + q * 0.9 + vec2(8.3, 2.8) + vec2(0.0, t * 0.08))
    );

    // Finaler Noise-Wert [0..1]
    float f = fbm(uv * 3.0 + r * 1.2 + vec2(t * 0.05, t * 0.04));

    // ── Farbe + Alpha ─────────────────────────────────────────────────────────

    // Dunkles Blaugrau – etwas heller an den "Schwaden"
    vec3 fogColor = mix(
        vec3(0.04, 0.05, 0.09),    // tiefer Schatten
        vec3(0.11, 0.13, 0.20),    // heller Dunst
        f
    );

    // Weich-Übergang am Overlay-Rand (Screen-Space, zoom-unabhängig)
    float distL    = gl_FragCoord.x - m_OverlayOrigin.x;
    float distR    = (m_OverlayOrigin.x + m_OverlaySize.x) - gl_FragCoord.x;
    float distB    = gl_FragCoord.y - m_OverlayOrigin.y;
    float distT    = (m_OverlayOrigin.y + m_OverlaySize.y) - gl_FragCoord.y;
    float edgeFade = clamp(min(min(distL, distR), min(distB, distT)) / m_FadePx, 0.0, 1.0);

    // Alpha: voll opak im unentdeckten Innern, weicher Rand durch Kernel + Edge-Fade
    float alpha = density * (0.88 + f * 0.12) * edgeFade;

    outFragColor = vec4(fogColor, alpha);
}