#version 400

in vec4 v_position; // view space position

uniform sampler2D s_normalDepthTex;  	// Normals and Depth

uniform mat4 u_worldTrans;
uniform mat4 u_projTrans;
uniform mat4 u_viewTrans;
uniform mat4 u_projViewTrans;

uniform vec3 u_lightPosition;
uniform vec3 u_lightDiffuse = vec3(1.0,1.0,0);
uniform vec3 u_lightSpecular = vec3(1.0,1.0,1.0);
uniform vec3 u_lightAttenuation = vec3(0.2,0,0.2);
uniform float u_lightIntensity = 1;
uniform float u_lightRadius = 50f;

uniform vec2 u_inverseScreenSize;
uniform float u_farDistance;


void main()
{
  vec2 texCoord = gl_FragCoord.xy * u_inverseScreenSize.xy;

  float linearDepth = texture2D(s_normalDepthTex, texCoord.st).a;
  vec3 lightPos = (u_viewTrans * vec4(u_lightPosition,1)).rgb;

  // vector to far plane
  vec3 viewRay = vec3(v_position.xy * (u_farDistance/v_position.z), u_farDistance);
  // scale viewRay by linear depth to get view space position
  vec3 vertex = viewRay * linearDepth;
  vec3 normal = texture2D(s_normalDepthTex, texCoord.st).xyz;

  vec3 ambient = vec3(0.0, 0.0, 0.0);
  vec3 diffuse = vec3(0.0, 0.0, 0.0);
  vec3 specular = vec3(0.0, 0.0, 0.0);

  vec3 lightDir = lightPos - vertex;

  float distance = length(lightDir);
	float fallof = max(0.0, 1.0 - distance / u_lightRadius);


  gl_FragColor = vec4(fallof,fallof,fallof, 1.0);
}