/**
 * A class to implement a "regular polygon" This is an N-gon
 * in which every side is of equal length and every interior angle is the 
 * same.
 * @author gtowell
 * Created: 10/12/2020
 */
public class RegularPolygon extends GeometricObject {
    /** The number of sides in the regular N-gon */
    int numSides;
    /** The length of every side */
    int sideLength;
    
    /**
     * Make a regular polygon.  Note that this is a static method.  It needs to be as 
     * we will use this method to create instances rather than directly using the constructor.
     * Not directly using constructor so that we can return different instances depending on
     * the number of sides.
     * @param n  the number of sides
     * @param l the length of the side
     * @return an instance of either regular polygon OR something that extends RegularPolygon
     */
    public static RegularPolygon regularPolygonBuilder(int n, int l) {
        if (n==4)
            return new SquareRP(l);
        else
            return new RegularPolygon(n, l);
    }

    /**
     * NOTE PROTECTED.  We do not want this to be used by anyone outside of this 
     * class or descendants.  Rather use regularPolygonBuilder
     * @param n the number of sides
     * @param l the length of sides
     */
    protected RegularPolygon(int n, int l) {
        sideLength=l;
        numSides=n;
    }

    /** The perimiter 
     * @return the perimiter
     */
    public int getPerimiter() {
        return numSides*sideLength;
    }

    /** 
     * A complex formula but it works for all regular N-gons
     * @return the area
     */
    public int getArea() {
        return (int)((sideLength*sideLength*numSides) / (4*Math.tan(Math.PI/numSides)));
    }
}