package examples;

// ********************************************************************
// RationalNumber.java Author: Lewis/Loftus
//
// Represents one rational number with a numerator and denominator.
// ********************************************************************

public class RationalNumber
{
	private int numerator, denominator;

	// -----------------------------------------------------------------
	// Constructor: Sets up the rational number by ensuring a nonzero
	// denominator and making only the numerator signed.
	// -----------------------------------------------------------------
	public RationalNumber(int numer, int denom)
	{
		if (denom == 0)
			denom = 1;

		// Make the numerator "store" the sign
		if (denom < 0)
		{
			numer = numer * -1;
			denom = denom * -1;
		}

		numerator = numer;
		denominator = denom;

		reduce();
	}

	// -----------------------------------------------------------------
	// Returns the numerator of this rational number.
	// -----------------------------------------------------------------
	public int getNumerator()
	{
		return numerator;
	}

	// -----------------------------------------------------------------
	// Returns the denominator of this rational number.
	// -----------------------------------------------------------------
	public int getDenominator()
	{
		return denominator;
	}

	// -----------------------------------------------------------------
	// Returns the reciprocal of this rational number.
	// -----------------------------------------------------------------
	public RationalNumber reciprocal()
	{
		return new RationalNumber(denominator, numerator);
	}

	// -----------------------------------------------------------------
	// Adds this rational number to the one passed as a parameter.
	// A common denominator is found by multiplying the individual
	// denominators.
	// -----------------------------------------------------------------
	public RationalNumber add(RationalNumber op2)
	{
		int commonDenominator = denominator * op2.getDenominator();
		int numerator1 = numerator * op2.getDenominator();
		int numerator2 = op2.getNumerator() * denominator;
		int sum = numerator1 + numerator2;

		return new RationalNumber(sum, commonDenominator);
	}

	// -----------------------------------------------------------------
	// Subtracts the rational number passed as a parameter from this
	// rational number.
	// -----------------------------------------------------------------
	public RationalNumber subtract(RationalNumber op2)
	{
		int commonDenominator = denominator * op2.getDenominator();
		int numerator1 = numerator * op2.getDenominator();
		int numerator2 = op2.getNumerator() * denominator;
		int difference = numerator1 - numerator2;

		return new RationalNumber(difference, commonDenominator);
	}

	// -----------------------------------------------------------------
	// Multiplies this rational number by the one passed as a
	// parameter.
	// -----------------------------------------------------------------
	public RationalNumber multiply(RationalNumber op2)
	{
		int numer = numerator * op2.getNumerator();
		int denom = denominator * op2.getDenominator();

		return new RationalNumber(numer, denom);
	}

	// -----------------------------------------------------------------
	// Divides this rational number by the one passed as a parameter
	// by multiplying by the reciprocal of the second rational.
	// -----------------------------------------------------------------
	public RationalNumber divide(RationalNumber op2)
	{
		return multiply(op2.reciprocal());
	}

	// -----------------------------------------------------------------
	// Determines if this rational number is equal to the one passed
	// as a parameter. Assumes they are both reduced.
	// -----------------------------------------------------------------
	public boolean equals(RationalNumber op2)
	{
		return (numerator == op2.getNumerator() && denominator == op2
				.getDenominator());
	}

	// -----------------------------------------------------------------
	// Returns this rational number as a string.
	// -----------------------------------------------------------------
	public String toString()
	{
		String result;

		if (numerator == 0)
			result = "0";
		else if (denominator == 1)
			result = numerator + "";
		else
			result = numerator + "/" + denominator;

		return result;
	}

	// -----------------------------------------------------------------
	// Reduces this rational number by dividing both the numerator
	// and the denominator by their greatest common divisor.
	// -----------------------------------------------------------------
	private void reduce()
	{
		if (numerator != 0)
		{
			int common = gcd(Math.abs(numerator), denominator);

			numerator = numerator / common;
			denominator = denominator / common;
		}
	}

	// -----------------------------------------------------------------
	// Computes and returns the greatest common divisor of the two
	// positive parameters. Uses Euclid's algorithm.
	// -----------------------------------------------------------------
	private int gcd(int num1, int num2)
	{
		while(num1 != num2)
			if (num1 > num2)
				num1 = num1 - num2;
			else
				num2 = num2 - num1;

		return num1;
	}
}