import java.io.*;
import java.lang.*;

/**
  * DirectionalLight represents a light source that illuminates along
  * parallel rays.
  *
  * @author Anthony Steed
  * @version 1.0
  */

public class DirectionalLight extends Light {
  /**
    * Stores the direction the light travels in.
    */
  public Vector Direction;

  /**
    * Create a default light.
    */
  public DirectionalLight() {
    Intensity = new Colour(1.0,1.0,1.0);
    Direction = new Vector(1.0,1.0,1.0);
  }
    
  /**
    * Create a new directional light that shines along given
    * direction vector.
    * @param v the direction of the light rays
    */
  public DirectionalLight(Vector v) {
    Intensity = new Colour(1.0,1.0,1.0);
    Direction = v;
  }

  /**
    * Read the light from the given source.
    * @param is the source to read from.
    * @exception java.io.IOException
    * if the light can not be read.
    * @exception java.io.NumberFormatException
    * if there a number format error is encountered.
    */
  public void read(SceneReader is) 
    throws IOException, NumberFormatException {
      Intensity.read(is);
      Direction.read(is);
  }

  /**
    * Write the light to the given destination
    * @param os  The destination to write to
    * @exception java.io.IOException
    * if the write fails.
    */
  public void write(SceneWriter os) throws IOException {
    Intensity.write(os);
    os.writeChar(' ');
    Direction.write(os);
  }

  /** 
    * Print a human readable version of the light definition to the
    * given destination
    * @param os  The destination to write to
    * @exception java.io.IOException
    * if the write fails.
    */
  public void print(SceneWriter os) throws IOException {
    os.writeString("Directional light with colour: ");
    Intensity.print(os);
    os.writeString(" and direction: ");
    Direction.print(os);
    os.writeString("\n");
  }
}