precision mediump float;

uniform sampler2D uMap;
uniform vec3 uHighlightColor;
uniform float uHighlightIntensity;

varying vec2 vUv;
varying vec3 vNormal;
varying float vHighlightStrength;
varying float vGlitchStrength;

const vec3 LIGHT_DIR = vec3(0.8, 0.85, 1.0);
const float AMBIENT_INTENSITY = 0.95;
const float DIFFUSE_INTENSITY = 0.1;
const float SHIFT_OFFSET = 0.075;

void main() {
  // --- 1. Texture Sampling with RGB Shift ---
  float shift = vGlitchStrength * SHIFT_OFFSET;

  float r = texture2D(uMap, vUv + vec2(shift, 0.0)).r;
  float g = texture2D(uMap, vUv).g;
  float b = texture2D(uMap, vUv - vec2(shift, 0.0)).b;

  vec4 texColor = vec4(r, g, b, 1.0);

  // --- 2. Lighting  ---
  vec3 normLightDir = normalize(LIGHT_DIR);

  float diff = max(dot(vNormal, normLightDir), 0.0);

  vec3 ambient = vec3(AMBIENT_INTENSITY);
  vec3 diffuse = vec3(DIFFUSE_INTENSITY) * diff;

  vec3 lighting = ambient + diffuse;

  vec3 finalColor = texColor.rgb * lighting;

  // --- 3. Highlight Composition ---
  float effectIntensity = vHighlightStrength * uHighlightIntensity;

  finalColor = mix(finalColor, uHighlightColor, effectIntensity);

  gl_FragColor = vec4(finalColor, texColor.a);
}