package graphics;

public class Shader
{
  //toony effect by rounding colors off
  public static int colorMask = 0;

  public static double[] shade(Vector3 normal, Material material, Light[] lights, int[] ambient)
  {
    Vector3 eye = new Vector3(0, 0, 1); //eye/camera is at the origin

    return shade(eye, normal, material, lights, ambient);
  }

  public static double[] shade(Vector3 eye, Vector3 normal, Material material, Light[] lights, int[] ambient)
  {
    //eye.normalize();

    double r = 0, g = 0, b = 0;

    for (int li = 0; li < lights.length; li++)
    {
      //colors for this light
      double lr = 0, lg = 0, lb = 0;

      //diffuse shading
      // f is L dot N
      double fDiff = normal.dotProduct( lights[li].getDirectionVector() );
      if (fDiff < 0) fDiff = 0;

      lr += fDiff * material.diffuseColor[0];
      lg += fDiff * material.diffuseColor[1];
      lb += fDiff * material.diffuseColor[2];

      //specular shading
      //R = 2*f*N - L
      //Ls = [rs,gs,bs]max(0, E ∙ R)^p
      Vector3 R = new Vector3(normal); //copy normal vector
      R.scale(-2 * fDiff); // r is now -2fN
      R.add( lights[li].getDirectionVector() ); //r is now L - 2fN
      R.scale(-1);
      //R.normalize();

      double fSpec = Math.pow(eye.dotProduct(R), material.shininess); //E ∙ R
      if (fSpec < 0) fSpec = 0;
//System.err.println("fSpec = " + fSpec);

      lr += fSpec * material.specularColor[0];
      lg += fSpec * material.specularColor[1];
      lb += fSpec * material.specularColor[2];

      //factor in light source, but
      //scale back down (compare 0.5 * 0.5 with (128 * 128)/256)
      lr *= lights[li].color[0] / 256.0;
      lg *= lights[li].color[1] / 256.0;
      lb *= lights[li].color[2] / 256.0;

      //add the light to object's light
      r += lr; g += lg; b += lb;
    }

    //add ambient component
    r += ambient[0]; g += ambient[1]; b += ambient[2];

    if (r > 255) r = 255; if (g > 255) g = 255; if (b > 255) b = 255;

    //make it look cartoony by quantizing colors
    if (colorMask > 0)
    {
      r = (int)r & colorMask;
      g = (int)g & colorMask;
      b = (int)b & colorMask;
    }

    return new double[] {r, g, b};
  }

}