// XC_BUILTIN_FORWARD_LIT_OPENGL_PS
#version 430
layout(binding = 0) uniform sampler2D uBaseColorTexture;
layout(binding = 1) uniform sampler2D uShadowMapTexture;

layout(std140, binding = 0) uniform PerObjectConstants {
    mat4 gProjectionMatrix;
    mat4 gViewMatrix;
    mat4 gModelMatrix;
    mat4 gNormalMatrix;
};

layout(std140, binding = 1) uniform LightingConstants {
    vec4 gMainLightDirectionAndIntensity;
    vec4 gMainLightColorAndFlags;
};

layout(std140, binding = 2) uniform MaterialConstants {
    vec4 gBaseColorFactor;
};

layout(std140, binding = 3) uniform ShadowReceiverConstants {
    mat4 gWorldToShadowMatrix;
    vec4 gShadowBiasAndTexelSize;
    vec4 gShadowOptions;
};

in vec3 vNormalWS;
in vec2 vTexCoord;
in vec3 vPositionWS;

layout(location = 0) out vec4 fragColor;

float ComputeShadowAttenuation(vec3 positionWS) {
    if (gShadowOptions.x < 0.5) {
        return 1.0;
    }

    vec4 shadowClip = gWorldToShadowMatrix * vec4(positionWS, 1.0);
    if (shadowClip.w <= 0.0) {
        return 1.0;
    }

    vec3 shadowNdc = shadowClip.xyz / shadowClip.w;
    vec2 shadowUv = vec2(
        shadowNdc.x * 0.5 + 0.5,
        shadowNdc.y * 0.5 + 0.5);
    if (shadowUv.x < 0.0 || shadowUv.x > 1.0 ||
        shadowUv.y < 0.0 || shadowUv.y > 1.0 ||
        shadowNdc.z < -1.0 || shadowNdc.z > 1.0) {
        return 1.0;
    }

    float shadowDepth = texture(uShadowMapTexture, shadowUv).r;
    float receiverDepth = shadowNdc.z * 0.5 + 0.5 - gShadowBiasAndTexelSize.x;
    float shadowStrength = clamp(gShadowBiasAndTexelSize.w, 0.0, 1.0);
    return receiverDepth <= shadowDepth ? 1.0 : (1.0 - shadowStrength);
}

void main() {
    vec4 baseColor = texture(uBaseColorTexture, vTexCoord) * gBaseColorFactor;
    if (gMainLightColorAndFlags.w < 0.5) {
        fragColor = baseColor;
        return;
    }

    vec3 normalWS = normalize(vNormalWS);
    vec3 directionToLightWS = normalize(gMainLightDirectionAndIntensity.xyz);
    float diffuse = max(dot(normalWS, directionToLightWS), 0.0);
    float shadowAttenuation = diffuse > 0.0
        ? ComputeShadowAttenuation(vPositionWS)
        : 1.0;
    vec3 lighting = vec3(0.28) +
        gMainLightColorAndFlags.rgb * (diffuse * gMainLightDirectionAndIntensity.w * shadowAttenuation);
    fragColor = vec4(baseColor.rgb * lighting, baseColor.a);
}