#[set(everything)]
const constants: {
	screen_size_inv: float2;
	current_mip_level: int;
	sample_scale: float;
	bloom_strength: float;
};

#[set(everything)]
const sampler_linear: sampler;

#[set(everything)]
const tex: tex2d;

struct vert_in {
	pos: float2;
}

struct vert_out {
	pos: float4;
	tex: float2;
}

fun bloom_upsample_pass_vert(input: vert_in): vert_out {
	var output: vert_out;
	output.tex = input.pos.xy * 0.5 + 0.5;
	output.tex.y = 1.0 - output.tex.y;
	output.pos = float4(input.pos.xy, 0.0, 1.0);
	return output;
}

fun clamp_coord(coord: float2, texel_size: float2): float2 {
	var lo: float2 = texel_size * 1.5;
	var hi: float2 = float2(1.0, 1.0) - lo;
	return float2(clamp(coord.x, lo.x, hi.x), clamp(coord.y, lo.y, hi.y));
}

fun upsample_dual_filter(tex_coord: float2, texel_size: float2): float3 {
	var delta: float2 = texel_size * constants.sample_scale;

	var result: float3;
	result  = sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(-delta.x * 2.0, 0.0), texel_size), 0.0).rgb;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(-delta.x, delta.y),   texel_size), 0.0).rgb * 2.0;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(0.0, delta.y * 2.0),  texel_size), 0.0).rgb;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + delta,                       texel_size), 0.0).rgb * 2.0;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(delta.x * 2.0, 0.0),  texel_size), 0.0).rgb;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(delta.x, -delta.y),   texel_size), 0.0).rgb * 2.0;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord + float2(0.0, -delta.y * 2.0), texel_size), 0.0).rgb;
	result += sample_lod(tex, sampler_linear, clamp_coord(tex_coord - delta,                       texel_size), 0.0).rgb * 2.0;

	return result * (1.0 / 12.0);
}

fun bloom_upsample_pass_frag(input: vert_out): float4 {
	var color: float4;
	color.rgb = upsample_dual_filter(input.tex, constants.screen_size_inv);

	if (constants.current_mip_level == 0) {
		color.rgb = color.rgb * float3(constants.bloom_strength, constants.bloom_strength, constants.bloom_strength);
	}

	color.a = 1.0;
	return color;
}

#[pipe]
struct pipe {
	vertex = bloom_upsample_pass_vert;
	fragment = bloom_upsample_pass_frag;
}