struct VertexShaderOut {
    @builtin(position) position: vec4<f32>,
    @location(0) texcoord: vec2<f32>
}

struct FrameUniforms {
    camera_transform: mat3x3f,
    viewport_size: vec2f,
}
struct LocalUniforms {
    transform: mat3x3f,
}
@group(0) @binding(2) var<uniform> frame_uni: FrameUniforms;
@group(0) @binding(3) var<uniform> local_uni: LocalUniforms;

@vertex fn vs(
    @builtin(vertex_index) vertexIndex : u32
) -> VertexShaderOut {
    let pos = array(
            vec2<f32>(-0.5, -0.5),
            vec2<f32>(0.5, -0.5),
            vec2<f32>(-0.5, 0.5),
            vec2<f32>(-0.5, 0.5),
            vec2<f32>(0.5, -0.5),
            vec2<f32>(0.5, 0.5)
        );

    var vsOutput: VertexShaderOut;

    let homogeneous_position = frame_uni.camera_transform * local_uni.transform * vec3f(pos[vertexIndex], 1);
    let position = homogeneous_position.xy / homogeneous_position.z;
    // convert from pixels to 0.0 to 1.0
    let zeroToOne = position / frame_uni.viewport_size;
    // convert from 0 - 1 to 0 - 2
    let zeroToTwo = zeroToOne * 2.0;
    // convert from 0 - 2 to -1 - +1 (clip space)
    let flippedClipSpace = zeroToTwo - 1.0;
    // flip Y
    let clipSpace = flippedClipSpace * vec2f(1, -1);

    vsOutput.position = vec4f(clipSpace, 0.0, 1.0);
    vsOutput.texcoord = pos[vertexIndex] + vec2f(0.5, 0.5);

    return vsOutput;
}

@group(0) @binding(0) var tex_sampler: sampler;
@group(0) @binding(1) var tex: texture_2d<f32>;

@fragment fn fs(fsInput: VertexShaderOut) -> @location(0) vec4<f32> {
    return textureSample(tex, tex_sampler, fsInput.texcoord);
}