#version 430 core

in vec2 vTex;
in vec3 vWorldNormal;
in vec3 vWorldPos;

out vec4 fragColor;

// One 2D texture per draw call — same binding point as mesh.frag so the
// C# side can use the same TextureCache without a texture-array pipeline.
uniform sampler2D uDiffuse;

// Translucency kind — matches TranslucencyKind C# enum (same as mesh.frag):
//   0 = Opaque     — depth write+test, no blend; shader never discards
//   1 = ClipMap    — alpha-key discard at 0.5 (doors, windows, vegetation)
//   2 = AlphaBlend — GL blending handles compositing; do NOT discard
//   3 = Additive   — GL additive blending; do NOT discard
//   4 = InvAlpha   — GL inverted-alpha blending; do NOT discard
uniform int uTranslucencyKind;

// Phase G.1+G.2: shared scene-lighting UBO (see mesh.frag for layout docs).
struct Light {
    vec4 posAndKind;
    vec4 dirAndRange;
    vec4 colorAndIntensity;
    vec4 coneAngleEtc;
};
layout(std140, binding = 1) uniform SceneLighting {
    Light uLights[8];
    vec4  uCellAmbient;
    vec4  uFogParams;
    vec4  uFogColor;
    vec4  uCameraAndTime;
};

vec3 accumulateLights(vec3 N, vec3 worldPos) {
    vec3 lit = uCellAmbient.xyz;
    int activeLights = int(uCellAmbient.w);
    for (int i = 0; i < 8; ++i) {
        if (i >= activeLights) break;

        int kind = int(uLights[i].posAndKind.w);
        vec3 Lcol = uLights[i].colorAndIntensity.xyz * uLights[i].colorAndIntensity.w;

        if (kind == 0) {
            vec3 Ldir = -uLights[i].dirAndRange.xyz;
            float ndl = max(0.0, dot(N, Ldir));
            lit += Lcol * ndl;
        } else {
            vec3 toL = uLights[i].posAndKind.xyz - worldPos;
            float d  = length(toL);
            float range = uLights[i].dirAndRange.w;
            if (d < range && range > 1e-3) {
                vec3 Ldir = toL / max(d, 1e-4);
                float ndl = max(0.0, dot(N, Ldir));
                float atten = 1.0;
                if (kind == 2) {
                    float cos_edge = cos(uLights[i].coneAngleEtc.x * 0.5);
                    float cos_l    = dot(-Ldir, uLights[i].dirAndRange.xyz);
                    atten *= (cos_l > cos_edge) ? 1.0 : 0.0;
                }
                lit += Lcol * ndl * atten;
            }
        }
    }
    return lit;
}

vec3 applyFog(vec3 lit, vec3 worldPos) {
    int mode = int(uFogParams.w);
    if (mode == 0) return lit;
    float d = length(worldPos - uCameraAndTime.xyz);
    float fogStart = uFogParams.x;
    float fogEnd   = uFogParams.y;
    float span = max(1e-3, fogEnd - fogStart);
    float fog = clamp((d - fogStart) / span, 0.0, 1.0);
    return mix(lit, uFogColor.xyz, fog);
}

void main() {
    vec4 color = texture(uDiffuse, vTex);

    // Alpha cutout only for clip-map surfaces (doors, windows, vegetation).
    if (uTranslucencyKind == 1 && color.a < 0.5) discard;

    vec3 N = normalize(vWorldNormal);
    vec3 lit = accumulateLights(N, vWorldPos);

    // Lightning flash — additive scene bump.
    lit += uFogParams.z * vec3(0.6, 0.6, 0.75);

    // Retail clamp per-channel to 1.0 (r13 §13.1).
    lit = min(lit, vec3(1.0));

    vec3 rgb = color.rgb * lit;
    rgb = applyFog(rgb, vWorldPos);
    fragColor = vec4(rgb, color.a);
}