// wind — generated from https://github.com/gl-transitions/gl-transitions/blob/master/transitions/wind.glsl
// Author: gre
// License: MIT
// Description: A ragged left-to-right wipe, as if the image was blown away by the wind

uniform shader _from;
uniform shader _to;
uniform float2 _resolution;
uniform float progress;
uniform float ratio;

vec4 getFromColor(vec2 uv) { return vec4(unpremul(_from.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }
vec4 getToColor(vec2 uv) { return vec4(unpremul(_to.eval(vec2(uv.x, 1.0 - uv.y) * _resolution))); }

uniform float size; 

uniform int reversed; 

float rand (vec2 co) {
  return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

vec4 transition (vec2 uv) {
  float x = (reversed != 0) ? 1. - uv.x : uv.x;
  float r = rand(vec2(0, uv.y));
  float m = smoothstep(0.0, -size, x*(1.0-size) + size*r - (progress * (1.0 + size)));
  return mix(
    getFromColor(uv),
    getToColor(uv),
    m
  );
}

half4 main(float2 _coord) {
  vec2 _uv = _coord / _resolution;
  vec4 _c = clamp(transition(vec2(_uv.x, 1.0 - _uv.y)), 0.0, 1.0);
  return half4(_c.rgb * _c.a, _c.a);
}