#ifdef HAS_NORMALMAP
uniform sampler2D m_NormalMap;
#endif
#ifdef HAS_FOAMMAP
uniform sampler2D m_FoamMap;
#endif

uniform vec4  m_Tint;
uniform float m_FoamAmount;

in vec2 vUV;
in vec2 vTex1;
in vec2 vTex2;

out vec4 outFragColor;

void main() {
    // ── Randabstand: 0 = Mitte, 1 = Rand ─────────────────────────────────────
    float edgeDist = abs(vUV.x * 2.0 - 1.0);

    // ── Tiefengradient ────────────────────────────────────────────────────────
    // Ränder heller/transparenter (flaches Ufer), Mitte dunkler (tief)
    vec3  baseColor = m_Tint.rgb * (1.0 - edgeDist * 0.45);
    float baseAlpha = m_Tint.a * smoothstep(0.0, 0.18, 1.0 - edgeDist);

    // ── Dual-Layer Normal-Map: Specular + Wellenhelligkeit ────────────────────
    float specular = 0.0;
    float ripple   = 0.0;
#ifdef HAS_NORMALMAP
    vec3 n1 = texture(m_NormalMap, vTex1).rgb * 2.0 - 1.0;
    vec3 n2 = texture(m_NormalMap, vTex2).rgb * 2.0 - 1.0;
    vec3 n  = normalize(n1 + n2);

    // Feste Sonnenrichtung – gut für Bachlauf-Optik
    vec3 sunDir = normalize(vec3(0.5, 1.0, 0.3));
    specular = pow(max(0.0, dot(n, sunDir)), 22.0);
    // Wellenhelligkeit variiert den Basiston leicht
    ripple = dot(n, vec3(0.0, 1.0, 0.0)) * 0.10;
#endif

    // ── Schaum ────────────────────────────────────────────────────────────────
    // Uferschaum wird stärker je näher am Rand; Wasserfälle extra
    float foamEdge = smoothstep(0.55, 1.0, edgeDist);
    float foamMask = clamp(foamEdge + m_FoamAmount * 0.75, 0.0, 1.0);

#ifdef HAS_FOAMMAP
    float foamSample = texture(m_FoamMap, vTex1 * 0.4).r;
    foamMask *= foamSample;
#else
    // Prozeduraler Fallback wenn keine Schaumtextur geladen
    float procFoam = (sin(vTex1.x * 6.283) * 0.5 + 0.5)
                   * (sin(vTex1.y * 3.141) * 0.5 + 0.5);
    foamMask *= procFoam;
#endif

    // ── Zusammenführen ────────────────────────────────────────────────────────
    vec3  waterColor = baseColor + ripple + vec3(0.35, 0.45, 0.55) * specular;
    vec3  finalColor = mix(waterColor, vec3(1.0), foamMask);
    float finalAlpha = max(baseAlpha, foamMask * 0.9);

    outFragColor = vec4(clamp(finalColor, 0.0, 1.0), finalAlpha);
}