/*
 * Moonlight|3D Copyright (C) 2006 The Moonlight|3D team
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Created on Oct 31, 2006
 */
package ml.math;

import ml.core.exceptions.Exception;

public class Vector2D implements Cloneable {
	public double X1, X2;
	
	public Vector2D() {
	}
	
	public Vector2D(double X1, double X2) {
		this.X1=X1;
		this.X2=X2;
	}

	/**
	 * Clear the component values. This sets this vector equal to the
	 * 0 vector.
	 */
	public void clear() {
		X1=0.0;
		X2=0.0;
	}

	/**
	 * Test if this vector is mathematical equal to the given vector,
	 * i.e. if all the components are equal.
	 * 
	 * @param a the vector to test against
	 * @return true if the vectors are equal
	 */
	public boolean equals(Vector2D a) {
		if (X1 != a.X1) {
			return false;
		}
		if (X2 != a.X2) {
			return false;
		}
		return true;
	}

	/**
	 * Return a complete copy of this Vector3D.
	 */
	@Override
	public Vector2D clone() {
		Vector2D ret=null;
		try {
			ret = (Vector2D) super.clone();
		} catch (CloneNotSupportedException e) {
			// cannot happen
		}

		return ret;
	}
	
	/**
	 * Return the absolute value of this vector, i.e. calculate
	 * \f$ \sqrt{x^2 + y^2 + z^2} \f$.
	 * 
	 * @return the absolute value
	 */
	public double abs() {
		return Math.sqrt(X1*X1+X2*X2);
	}
	
	/**
	 * Return a normalised copy of this vector.
	 * 
	 * @return normalised vector
	 */
	public Vector2D norm() {
		Vector2D res=new Vector2D();
		double abs=abs();
		
		res.X1=X1/abs;
		res.X2=X2/abs;
		
		return res;
	}
	
	/**
	 * Add the given vector to this vector and return the result.
	 * 
	 * @param a the vector to add
	 * @return the sum of the two vectors
	 */
	public Vector2D add(Vector2D a) {
		Vector2D res=new Vector2D();
		
		res.X1=X1+a.X1;
		res.X2=X2+a.X2;
		
		return res;
	}
	
	/**
	 * Subtract the given vector from this vector and return
	 * the result.
	 * 
	 * @param a the vector to subtract
	 * @return the difference between the two vectors
	 */
	public Vector2D sub(Vector2D a) {
		Vector2D res=new Vector2D();
		
		res.X1=X1-a.X1;
		res.X2=X2-a.X2;
		
		return res;
	}
	
	/**
	 * Perform scalar multiplication with the given value.
	 * 
	 * @param a the value with which to multiply
	 * @return the multiplied vector
	 */
	public Vector2D multiply(double a) {
		Vector2D res=new Vector2D();
		
		res.X1=X1*a;
		res.X2=X2*a;
		
		return res;
	}

	/**
	 * Perform inner product between this and the given vector
	 * and return the result.
	 * 
	 * @param a the vector to multiply
	 * @return the resulting value
	 */
	public double multiply(Vector2D a) {
		return X1*a.X1+X2*a.X2;
	}

	/**
	 * Return the angle between this and the given vector.
	 * 
	 * @param b the vector to compute the angle to
	 * @return the angle between the vectors
	 * @throws Exception
	 */
	public double angleTo(Vector2D b) throws Exception {
		if (abs() == 0 || b.abs() == 0) {
			throw new Exception("cannot calculate angle to null vector");
		}

		double cosAngle = multiply(b) / (abs() * b.abs());
		double angle = Math.acos(cosAngle);

		return angle;
	}
}