[[block]]
struct Globals {
    transform: mat4x4<f32>;
};

[[group(0), binding(0)]] var<uniform> globals: Globals;
[[group(0), binding(1)]] var u_sampler: sampler;
[[group(1), binding(0)]] var u_texture: texture_2d_array<f32>;

struct VertexInput {
    [[location(0)]] v_pos: vec2<f32>;
    [[location(1)]] pos: vec2<f32>;
    [[location(2)]] scale: vec2<f32>;
    [[location(3)]] atlas_pos: vec2<f32>;
    [[location(4)]] atlas_scale: vec2<f32>;
    [[location(5)]] layer: i32;
};

struct VertexOutput {
    [[builtin(position)]] position: vec4<f32>;
    [[location(0)]] uv: vec2<f32>;
    [[location(1)]] layer: f32; // this should be an i32, but naga currently reads that as requiring interpolation.
};

[[stage(vertex)]]
fn vs_main(input: VertexInput) -> VertexOutput {
    var out: VertexOutput;

    out.uv = vec2<f32>(input.v_pos * input.atlas_scale + input.atlas_pos);
    out.layer = f32(input.layer);

    var transform: mat4x4<f32> = mat4x4<f32>(
        vec4<f32>(input.scale.x, 0.0, 0.0, 0.0),
        vec4<f32>(0.0, input.scale.y, 0.0, 0.0),
        vec4<f32>(0.0, 0.0, 1.0, 0.0),
        vec4<f32>(input.pos, 0.0, 1.0)
    );

    out.position = globals.transform * transform * vec4<f32>(input.v_pos, 0.0, 1.0);

    return out;
}

[[stage(fragment)]]
fn fs_main(input: VertexOutput) -> [[location(0)]] vec4<f32> {
    return textureSample(u_texture, u_sampler, input.uv, i32(input.layer));
}