shader_type sky;

#include "res://addons/rokojori_action_library/Runtime/Shading/Library/Math.gdshaderinc"
#include "res://addons/rokojori_action_library/Runtime/Shading/Library/Transform.gdshaderinc"
#include "res://addons/rokojori_action_library/Runtime/Shading/Library/Noise.gdshaderinc"

uniform int vertical_sections = 21;
uniform float star_size = 0.02;
uniform float star_falloff = 4.;
uniform float margin = 0.05; // How far the star is from the edge of it's section. Avoids artifacts at the edge of sections.

uniform sampler2D verticalColor: source_color;
uniform float starOpacity = 0;
uniform float starsNoiseScale = 1;
uniform float starsNoiseDivision = 1;
uniform vec2 starsNoiseOffset =vec2(0,0);

vec2 get_partition( vec2 sky_coords ) 
{
	// Separate the sphere into sections of roughly equal width and height.
	float y = sky_coords.y * 2. - 1.;
	float section_y = ceil(abs(y) * float(vertical_sections)) / float(vertical_sections);
	float horizontal_sections = max(4., ceil(float(vertical_sections) * 4. * cos(section_y * PI / 2.)));
	horizontal_sections = horizontal_sections > 0. ? horizontal_sections : 1.;
	return vec2(sky_coords.x * horizontal_sections, y * float(vertical_sections));
}

vec2 rand_vec2(vec2 xy) 
{
  float rand1 = fract(sin(dot(xy, vec2(11.9131, 81.2317))) *  57183.77193);
  float rand2 = fract(sin(dot(xy, vec2(16.8131, 91.2327))) *  37113.66193);
	return vec2(rand1, rand2) * ( 1. - margin * 2.) + margin;
}

float star_brightness(vec2 sky_coords) 
{
	vec2 partitions = get_partition(sky_coords);
	vec2 partition_index = floor(partitions);
	vec2 inner_coord = fract(partitions);
	vec2 star_coord = rand_vec2(partition_index);
	float dist = length(inner_coord - star_coord);
  
	return pow(star_size / dist, star_falloff);
  
}

void sky() 
{
  vec3 stars= clamp( vec3( star_brightness( SKY_COORDS ) ), vec3(0,0,0), vec3(1,1,1) );
  float starsLight = random( ( starsNoiseOffset+ SKY_COORDS ) * starsNoiseScale / starsNoiseDivision );
	COLOR = stars* starOpacity * starsLight + texture( verticalColor, SKY_COORDS ).rgb ;
  // vec3( star_brightness( SKY_COORDS ) );
}