precision highp float;
varying vec2 v_TexCoords;
uniform sampler2D u_InputImage;
uniform float u_Time;

// constants
const float PHI = 1.61803398874989484820459 * 00000.1; // Golden Ratio
const float PI  = 3.14159265358979323846264 * 00000.1; // PI
const float SRT = 1.41421356237309504880169 * 10000.0; // Square Root of Two

//Tweakables
uniform float uLinesStrength;
uniform float uLinesSpeed;
uniform float uNoiseStrength;
uniform float uContrast;

float noise(vec2 coordinate, float seed) {
  seed = u_Time+10.0*100.0+seed;
  return fract(sin(dot(coordinate*(seed + PHI), vec2(PHI, PI)))*SRT);
}

float noise1D(vec2 coordinate, float seed) { 
  seed = floor(u_Time*uLinesSpeed)+8.0+seed;
  return fract(sin(dot(coordinate*(seed + PHI), vec2(PHI, PI)))*SRT);
}

float luma(vec3 color) {
  return dot(vec3(0.299, 0.587, 0.114), color);
}

void main() { 
  vec2 uv = vec2(v_TexCoords.x, 1.0-v_TexCoords.y);
  float seed = mod(u_Time, 10.0);
  vec4 color = texture2D(u_InputImage, uv);
  vec3 n = vec3(noise(uv, seed), noise(uv, 0.2+seed), noise(uv, 0.4+seed)) * uNoiseStrength;
  color = vec4(luma(color.rgb)) + noise1D(vec2(1.0, uv.y), 0.0) * uLinesStrength;
  color.rgb = mix(color.rgb, n, uNoiseStrength);
  vec3 scurve = smoothstep(0.0, 1.0, color.rgb);
  gl_FragColor = vec4(mix(color.rgb, scurve, uContrast), 1.);    
}