/********************************************
 * LightSensor is a class to intialize
 * and manage one of the Lego Brick RCX optical sensors.
 *
 * Typical use is to put the LegoBrick over "white" space and 
 * then call the defineWhite() routine.
 * After that, calls to seesWhite() will return true
 * if getValue() sees a shade within "tolerance" of 
 * that value, so that the lego robot can tell whether its
 * over a shiny or dark patch of floor.
 * 
 * The "black" colors works the same way.  These names are
 * arbitrary; the reflectivity to match is set by what
 * the sensor is looking at.
 * 
 * The code from the caller might look something like this.
 *
 *     // Put the robot on a white patch.  Push the PRGM button.
 *     // Put it somewhere else.  Push the RUN button.
 *     LightSensor ls = new LightSensor(Sensor.S3);
 *     while (true) {
 *      if (Button.PRGM.isPressed()){ ls.defineWhite(); }
 *      if (Button.RUN.isPressed()) {
 *          // run around the floor ... 
 *          if ( ls.seesWhite() ) {  // we're over a white patch }
 *      }
 *     }
 *
 * @author Jim Mahoney
 * @version 1.0, Oct 11 2002
 ********************************************/
import josx.platform.rcx.*;

public class LightSensor {
   
    private int whiteValue;  // 0 - 100 percent, high values are whiter.
    private int blackValue;  // ditto
    private int tolerance;   // how close for a color match
    private Sensor mySensor;

    LightSensor(Sensor theSensor){
	mySensor = theSensor;
        mySensor.setTypeAndMode(SensorConstants.SENSOR_TYPE_LIGHT,
				SensorConstants.SENSOR_MODE_PCT); //PCT=percent
	mySensor.activate();
	whiteValue = 80;  // very reflective
	blackValue = 20;  // very absorbing
	tolerance  = 3;
    }

    public void setTolerance(int theTolerance){
	tolerance = theTolerance;
    }
    public void defineWhite(){
	whiteValue = mySensor.readValue();
    }
    public void defineWhite(int white){
	whiteValue = white;
    }
    public void defineBlack(){
	blackValue = mySensor.readValue();
    }
    public void defineBlack(int black){
	blackValue = black;
    }
    public void lowerBlack(){
	blackValue -= tolerance;
    }

    public void raiseWhite(){
	whiteValue += tolerance;
    }

    public boolean seesWhite(){
	return Math.abs(mySensor.readValue()-whiteValue) <= tolerance;
    }

    public boolean seesBlack(){
	return Math.abs(mySensor.readValue()-blackValue) <= tolerance;
    }

    public int getValue(){
	return mySensor.readValue();
    }

    public void turnOn(){
	mySensor.activate();
    }

    public void turnOff(){
	mySensor.passivate();
    }

    public void displayValue(){
	LCD.showNumber(mySensor.readValue());
    }

}