local shader = [[ 
extern Image diffuse;
extern vec2 mouse; 
extern number i ; 

vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
{
   vec3 light_vec = vec3(mouse,1);
   vec3 light_direction = light_vec - vec3(pixel_coords, 0);
   float distance = length(light_direction);
   light_direction = normalize(light_direction);

   vec3 normal = Texel(texture, texture_coords).xyz;
   normal.y = 1 - normal.y;
   normal = normalize(mix(vec3(-1), vec3(1), normal));

   //float attenuation = 1/(7e-5*pow(distance, 2));
   float attenuation = 5000/pow(distance, 2);
   //float attenuation = 1;

   float diffuse_term = clamp(attenuation * dot(normal, light_direction), 0.0, 1.0);

   vec3 dark_color = vec3(0.0, 0.0, 1);
   //vec3 light_color = vec3(0.6, 0.6, 0.0);
   vec3 light_color = vec3(0.8, 0.8, 0.0);
   vec3 ambient = mix(dark_color, light_color, diffuse_term) * 0.20;

   // the shaded cel has a light value of 0.5, the light cel has a light value of 1
   float cel_diffuse_term = smoothstep(0.49, 0.52, diffuse_term)/2 + 0.5;
   //float cel_diffuse_term = step(0.5, diffuse_term)/2 + 0.5;

   return vec4((cel_diffuse_term * Texel(diffuse, texture_coords).rgb) + ambient, Texel(texture, texture_coords).a);
   //return vec4(ambient+Texel(diffuse, texture_coords).rgb/100, Texel(texture, texture_coords).a);

}
]]

local shader2 = [[ 
extern Image diffuse;
vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
{
	return Texel(diffuse, texture_coords);
}	
]] 

local lighningShader = [[ 
extern vec2 iResolution; // 分辨率, pixels
extern number iTime;  // 秒数, seconds
// Lightning shader
// rand,noise,fmb functions from https://www.shadertoy.com/view/Xsl3zN
// jerome

float rand(vec2 n) {
    return fract(sin(dot(n, vec2(12.9898, 4.1414))) * 43758.5453);
}

float noise(vec2 n) {
    const vec2 d = vec2(0.0, 1.0);
    vec2 b = floor(n), f = smoothstep(vec2(0.0), vec2(1.0), fract(n));
    return mix(mix(rand(b), rand(b + d.yx), f.x), mix(rand(b + d.xy), rand(b + d.yy), f.x), f.y);
}

float fbm(vec2 n) {
    float total = 0.0, amplitude = 1.0;
    for (int i = 0; i < 7; i++) {
        total += noise(n) * amplitude;
        n += n;
        amplitude *= 0.5;
    }
    return total;
}

vec4 effect(vec4 outcolor, Image img, vec2 texture_coords, vec2 pixel_coords)
//void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec4 col = vec4(0,0,0,1);
    vec2 uv = pixel_coords.xy * 1.0 / iResolution.xy;
   
   
    // draw a line, left side is fixed
    vec2 t = uv * vec2(2.0,1.0) - iTime*3.0;
    vec2 t2 = (vec2(1,-1) + uv) * vec2(2.0,1.0) - iTime*3.0; // a second strand
   
    // draw the lines,
//  this make the left side fixed, can be useful
//  float ycenter = mix( 0.5, 0.25 + 0.25*fbm( t ), uv.x*4.0);
//    float ycenter2 = mix( 0.5, 0.25 + 0.25*fbm( t2 ), uv.x*4.0);
    float ycenter = fbm(t)*0.5;
    float ycenter2= fbm(t2)*0.5;

    // falloff
    float diff = abs(uv.y - ycenter);
    float c1 = 1.0 - mix(0.0,1.0,diff*20.0);
   
    float diff2 = abs(uv.y - ycenter2);
    float c2 = 1.0 - mix(0.0,1.0,diff2*20.0);
   
    float c = max(c1,c2);
    col = vec4(c*0.6,0.2*c2,c,1.0); // purple color
    //fragColor = col;
	return col; 
}
]]

local jg = jin.graphics
local effect =  jg.Shader(shader) 
local effect2 = jg.Shader(shader2)
local lightning = jg.Shader(lighningShader)
local diffuse = jg.Image("treestump_diffuse.png")
local img = jg.Image("treestump.png")
local img2 = jg.Image("lightning.png")
local ww, wh = jg.size() 
local scale = 2 
ww = ww / scale 
wh = wh / scale 
jin.core.onLoad = function() 
	jg.use(lightning)
	lightning:send("vec2", "iResolution", ww, wh)
	jg.unuse()
end 
jin.core.onEvent = function(e) 
	if e.type == "quit" then 
		jin.core.quit() 
	end 
end 
local mx, my 
local c = 0
local t = 0;
jin.core.onUpdate = function(dt) 
	t = t + dt
	mx, my = jin.mouse.position() 
	mx = mx / 2 
	my = my / 2
	my = wh - my
	c = c + 1
	if c == 50 then 
		print(1/dt)
		c = 0
	end 
end 
img:setAnchor(16, 16)
local cvs = jg.Canvas(320, 240)
local i = 0

jin.core.onDraw = function() 
--	if true then return end
	i = i + 0.001
	jg.bind(cvs)
		jg.draw(img, 10, 10)
		-- jg.use(lightning)
			-- lightning:send("number", "iTime", t)
			-- lightning:send("Image", "img", img2)
			-- jg.draw(img2, 20, 20)
		-- jg.unuse()
	jg.unbind()	
	jg.draw(cvs, 0, 0, 2, 2)
end