// Copyright (c) 2023 Lachlan McDonald
// This work is licensed under the MIT License (MIT)
// https://github.com/lachlanmcdonald/magicavoxel-shaders
//
// xs primitive/greebles1 [Mode] [Count] [Width] [Height] [Depth] [Seed]
//
// xs_begin
// author : '@lmcdx.bsky.social'
// arg : { name = 'Mode'  var = 'm_mode'  range = '0 1'  value = '0'  step = '1'  precision = '0' }
// arg : { name = 'Count'  var = 'm_count'  range = '1 256'  value = '32'  step = '8'  precision = '0' }
// arg : { name = 'Width'  var = 'm_width'  range = '1 256'  value = '4'  step = '1'  precision = '0' }
// arg : { name = 'Height'  var = 'm_height'  range = '1 256'  value = '4'  step = '1'  precision = '0' }
// arg : { name = 'Depth'  var = 'm_depth'  range = '1 256'  value = '4'  step = '1'  precision = '0' }
// arg : { name = 'Seed'  var = 'global_seed'  range = '1 100'  value = '1'  step = '1'  precision = '0' }
// xs_end

int mode = int(m_mode);
int count = int(m_count);

vec3 dim_min = vec3(1.0);
vec3 dim_max = vec3(m_width, m_height, m_depth);

bool no_axis_mode = all(equal(ivec3(i_axis), ivec3(0)));
bvec3 axis_mode = no_axis_mode ? bvec3(true) : equal(ivec3(i_axis), ivec3(1));

struct Box {
	ivec3 lower;
	ivec3 upper;
};

float hash(vec2 p) {
	p += global_seed;
	return fract(1e4 * sin(17.0 * p.x + p.y * 0.1) * (0.1 + abs(sin(p.y * 13.0 + p.x))));
}

float roundf(float f) {
	return fract(f) > 0.5 ? ceil(f) : floor(f);
}

int imix(float a, float b, float f) {
	return int(roundf(mix(a, b, f)));
}

float max3(vec3 a) {
	return max(max(a.x, a.y), a.z);
}

Box region(vec3 dim_min, vec3 dim_max, float iter, float seed) {
	float max_size = max3(i_volume_size);

	float r[5];
	r[0] = hash(vec2(iter * seed));
	r[1] = hash(vec2(iter * seed + 16.0 * 1.0));
	r[2] = hash(vec2(iter * seed + 16.0 * 2.0));
	r[3] = hash(vec2(iter * seed + 16.0 * 3.0));
	r[4] = hash(vec2(iter * seed + 16.0 * 4.0));

	int x = imix(0.0, max_size, r[0]);
	int y = imix(0.0, max_size, r[1]);

	ivec3 p = ivec3(x, y, 0);
	ivec3 dim = ivec3(imix(dim_min.x, dim_max.x, r[2]),
					  imix(dim_min.y, dim_max.y, r[3]),
					  imix(dim_min.z, dim_max.z, r[4]));

	ivec3 lower = p - ivec3(floor(vec3(dim) / 2.0));
	ivec3 upper = p + ivec3(ceil(vec3(dim) / 2.0));

	return Box(lower, upper);
}

bool lowerRegion(ivec3 iv, vec3 dim_min, vec3 dim_max, float seed) {
	for (int i = 0; i < count; i += 1) {
		Box j = region(dim_min, dim_max, float(i), seed);

		if (all(greaterThanEqual(iv, j.lower)) && all(lessThan(iv, j.upper))) {
			return true;
		}
	}
	return false;
}

bool upperRegion(ivec3 iv, vec3 dim_min, vec3 dim_max, float seed) {
	for (int i = 0; i < count; i += 1) {
		Box j = region(dim_min, dim_max, float(i), seed);

		if (all(greaterThan(iv, j.lower)) && all(lessThanEqual(iv, j.upper))) {
			return true;
		}
	}
	return false;
}

float map(vec3 v) {
	ivec3 iv = ivec3(v);
	ivec3 ivs = ivec3(i_volume_size);

	if (axis_mode.x) {
		if (lowerRegion(iv.zyx, dim_min.yxz, dim_max.yxz, 64.0 * 1.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
		if (upperRegion((ivs - iv).zyx, dim_min.yxz, dim_max.yxz, 64.0 * 2.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
	}
	if (axis_mode.y) {
		if (lowerRegion(iv.xzy, dim_min.xyz, dim_max.xyz, 64.0 * 3.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
		if (upperRegion((ivs - iv).xzy, dim_min.xyz, dim_max.xyz, 64.0 * 4.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
	}
	if (axis_mode.z) {
		if (lowerRegion(iv, dim_min.yxz, dim_max.yxz, 64.0 * 5.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
		if (upperRegion(ivs - iv, dim_min.yxz, dim_max.yxz, 64.0 * 6.0)) {
			return (mode == 0) ? 0.0 : i_color_index;
		}
	}

	return (mode == 0) ? i_color_index : 0.0;
}