/**
 * @author 
 * Supports the use of rational numbers.  This includes methods for the 
 * standard arithmetic operations of add, subtract, multiply and divide.  Included are 
 * helper methods for reducing rational numbers, putting in simples form.
 */
public class Rational implements Comparable<Rational> {

    private Pair<Integer> r=new Pair<Integer>(new Integer(0), new Integer(1));
    private int numerator = r.getFirstElement();
    private int denominator = r.getSecondElement();
    
    
//Constructors

   
/**
 * Postcondition: Creates the canonical zero rational (0/1) 
 */
public Rational() {
    
}

/**
 * 
 * Precondition: <br>
 * Postcondition: Rational created is (n/d) in lowest terms
 * @throws IllegalArgumentException if d==0
 */
public Rational(int n, int d){

	if(d==0){
		throw new IllegalArgumentException();
	}
	if(n==0){
	d=1;
	}
		 this.r.setFirstElement(n);
    	 this.r.setSecondElement(d);
		 this.reduce();

}


//getters
public int getNumerator(){
    
	return numerator;
}


public int getDenominator(){
    
	
	return denominator;
}

//setters
/**
 * 
 * Precondition: <br>
 * Postcondition: changes this so this.getNumerator()==d
 *@param n - int value for the numerator of the rational number
 *
 */
public void setNumerator(int n){
    
	this.r.setFirstElement(n);
	this.reduce();
}

/**
 * 
 * Precondition: d!=0<br>
 * Postcondition: changes this so this.getDenominator()==d
 *@param d - int value for the denominator of the rational number
 *
 */
public void setDenominator(int d){
	
	this.r.setSecondElement(d);
	this.reduce();
    
}

/**
 * 
 * Precondition: r!=null<br>
 * Postcondition: returns the sum of this instance of a rational number and r in simplest terms
 *@param r - a rational number
 *@return this+r
 */
public Rational add(Rational r){
   return new Rational();
}

/**
 * 
 * Precondition: r!=null<br>
 * Postcondition: returns the difference of this instance of a rational number and r in simplest terms 
 *@param r - a rational number
 *@return (this-r)
 */
public Rational substract(Rational r){
    return new Rational();
}

/**
 * 
 * Precondition: r!=null<br>
 * Postcondition: returns the prodcut of this instance of a rational number and r in simplest terms 
 *@param r - a rational number
 *@return (this*r)
 */
public Rational multiply(Rational r){
    return new Rational();
}

/**
 * 
 * Precondition: r!=null && r!=(0/1)<br>
 * Postcondition: returns the quotient of this instance of a rational number and r in simplest terms 
 *@param r - a rational number
 *@return (this/r)
 */
public Rational divide(Rational r){
    return new Rational();
}

/**
 * if a/b<c/d then ad<bc
 * Precondition: <br>
 * Postcondition: 
 * @throws NullPointerException if o is null
 *@param o
 *@return -1 if this<o, 0 if this==o, 1 if this>o
 */
public int compareTo(Rational o) {
    final int LESSTHAN=-1;
    final int EQUAL=0;
    final int GREATERTHAN=1;
    int compare;
    if((o.getNumerator()/o.getDenominator()) < (this.getNumerator()/this.getDenominator())){
    	compare = GREATERTHAN;
    	return compare;
    }
    
   if((o.getNumerator()/o.getDenominator() > this.getNumerator()/this.getDenominator())){
    	compare = LESSTHAN;
    	return compare;
    }
    
    if((o.getNumerator()/o.getDenominator()) == (this.getNumerator()/this.getDenominator())){
    	compare = EQUAL;
    	return compare;
    }
    else
    	return EQUAL;
    //complete the compareTo method.  Use the constants defined above in returning the value
}

/**
 * 
 * Precondition: none<br>
 * Postcondition: return true if this and r are equivalent rational numbers 
 *@param r - a rational number
 *@return (this-r)
 */
public boolean equals(Rational r){
    boolean eql = false;
	if(this == r)
	{
		eql = true;
	}
	
	return eql;
}

//private methods

/** 
 * @see java.lang.Object#toString()
 * Postcondition: The value of the rational number is given as the string
 *         (numerator/denominator) with no blanks.         
 */
public String toString (){
	String str1;
	str1 = ("(" + getNumerator() + "/" + getDenominator() + ")");
    return str1;
}

/**
 * Use gcd to find the greatest commond divisor of the 
 * numerator and denominator.
 * 
 * Precondition: <br>
 * Postcondition: this reduced to lowest terms
 * 
 */
private void reduce(){
    int rd=1;
    int n=this.r.getFirstElement();
    int d=this.r.getSecondElement();
    	if(n!=0 && d!=0)
    	{
    		rd = gcd(n,d);
    	}
    if(rd!=1)
    {
    	n=n/rd;
    	d=d/rd;
    if( (d<0 && n>0) || (d<0 && n<0))
    {
    n=n*-1;
    d=d*-1;
    }
    }
	this.setDenominator(d);
	this.setNumerator(n);
}


/**
 * Description: Recursive version of Euclid's algorithm for finding the greatest common divisor of two integers<br>
 * Precondition: both are positive integers. Call with ABS on each parameter.<br>
 * Postcondition: returns greatest common divisor of a and b
 *@param a
 *@param b
 *@return int which is the greatest common divisor of a and b
 */
//DO NOT MODIFY
private int gcd(int m, int n){
    int m1=Math.abs(m);
    int n1=Math.abs(n);
    if (m1<n1) 
        return gcd(n1, m1);
    else
    	if (m1%n1==0)
            return n1;
       else 
           return gcd(n1, m1%n1);
}

//Needed for junit testing. visibility must be public due to inheritance
//DO NOT MODIFY
 public boolean equals(Object o){
     if (o.getClass() == this.getClass())
         return this.equals((Rational)o);
     else
         return false;
 }
 
  
} // End of Rational class definition