// Lit sphere (Blinn-Phong + HDRI ambient + selection rim). Uniforms in a
// ConstantBuffer (UBO, binding 0) so both backends drive it through the RHI;
// the environment cubemap is a separate sampler at binding 1.
struct Sphere
{
    float4x4 u_view_projection;
    float4x4 u_transform;
    float3   u_color;
    float    u_specular;
    float    u_emission;
    float3   u_light_pos;
    float3   u_camera_pos;
    int      u_is_selected;
    float3   u_outline_color;
    float    u_outline_width;
};
ConstantBuffer<Sphere> su;

struct VSInput  { float3 position : POSITION; float3 normal : NORMAL; };
struct VSOutput { float4 position : SV_Position; float3 normal : TEXCOORD0; float3 worldPos : TEXCOORD1; };

[shader("vertex")]
VSOutput vertexMain(VSInput input)
{
    VSOutput output;
    output.worldPos = mul(su.u_transform, float4(input.position, 1.0)).xyz;
    float3x3 normalMatrix = (float3x3)su.u_transform;
    output.normal   = mul(normalMatrix, input.normal);
    output.position = mul(su.u_view_projection, float4(output.worldPos, 1.0));
    return output;
}

SamplerCube u_HDRIEnvironment;

[shader("fragment")]
float4 fragmentMain(VSOutput input) : SV_Target
{
    float3 normal     = normalize(input.normal);
    float3 lightDir   = normalize(su.u_light_pos - input.worldPos);
    float3 viewDir    = normalize(su.u_camera_pos - input.worldPos);
    float3 reflectDir = reflect(-lightDir, normal);

    float3 hdriLight     = u_HDRIEnvironment.Sample(normal).rgb;
    float  hdriIntensity = 0.3;

    float diff = max(dot(normal, lightDir), 0.0);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32.0);

    float3 diffuse  = su.u_color * (diff + hdriIntensity * hdriLight);
    float3 specular = float3(su.u_specular, su.u_specular, su.u_specular) * spec;
    float3 emission = su.u_color * su.u_emission;

    float3 result = diffuse + specular + emission;

    if (su.u_is_selected > 0)
    {
        float ndotv       = max(dot(normal, viewDir), 0.0);
        float rim         = 1.0 - ndotv;
        float outlineMask = step(1.0 - su.u_outline_width, rim);
        result = lerp(result, su.u_outline_color, outlineMask);
    }

    return float4(result, 1.0);
}