//! ref: https://www.w3.org/TR/WGSL/
use my_wgsl::*;

#[wgsl_decl_struct]
pub struct PointLight {
    position: vec3f,
    color: vec3f,
}

#[wgsl_decl_struct]
pub struct LightStorage {
    pointCount: u32,
    point: array<PointLight>,
}

fn main() {
    let mut builder = Builder::new();

    wgsl_structs![builder, PointLight, LightStorage];

    wgsl_bind!(
        builder, group(0) binding(0) var<storage> lights : LightStorage
    );
    wgsl_bind!(
        builder, group(1) binding(0) var baseColorSampler : sampler
    );
    wgsl_bind!(
        builder, group(1) binding(1) var baseColorTexture : texture_2d<f32>
    );

    wgsl_fn!(builder,
        #[fragment]
        fn fragmentMain(#[location(0)] worldPos : vec3f,
                        #[location(1)] normal : vec3f,
                        #[location(2)] uv : vec2f) -> #[location(0)] vec4f {
            // Sample the base color of the surface from a texture.
            let baseColor = textureSample(baseColorTexture, baseColorSampler, uv);

            let N = normalize(normal);
            var surfaceColor = vec3f(0);

            // Loop over the scene point lights.
            for (var i = 0u; i < lights.pointCount; ++i) {
                let worldToLight = lights.point[i].position - worldPos;
                let dist = length(worldToLight);
                let dir = normalize(worldToLight);

                // Determine the contribution of this light to the surface color.
                let radiance = lights.point[i].color * (1 / pow(dist, 2));
                let nDotL = max(dot(N, dir), 0);

                // Accumulate light contribution to the surface color.
                surfaceColor += baseColor.rgb * radiance * nDotL;
            }

            // Return the accumulated surface color.
            return vec4(surfaceColor, baseColor.a);
        }
    );

    let wgsl: String = builder.build_pretty();
    println!("{}", wgsl);
}