package fr.mieuxvoter.mj;

import java.math.BigInteger;
import java.security.InvalidParameterException;

public class NormalizedTally extends Tally implements TallyInterface {

	public NormalizedTally(ProposalTallyInterface[] proposalsTallies) {
		super(proposalsTallies);
		Integer amountOfProposals = getAmountOfProposals();
		
		// Compute the Least Common Multiple
		BigInteger amountOfJudges = BigInteger.ONE;
		for (ProposalTallyInterface proposalTally : proposalsTallies) {
			amountOfJudges = lcm(amountOfJudges, proposalTally.getAmountOfJudgments());
		}
		
		if (0 == amountOfJudges.compareTo(BigInteger.ZERO)) {
			throw new InvalidParameterException("Cannot normalize: one or more proposals have no judgments.");
		}
		
		// Normalize proposals to the LCM
		ProposalTally[] normalizedTallies = new ProposalTally[amountOfProposals];
		for (int i = 0 ; i < amountOfProposals ; i++) {
			ProposalTallyInterface proposalTally = proposalsTallies[i];
			ProposalTally normalizedTally = new ProposalTally(proposalTally);
			BigInteger factor = amountOfJudges.divide(proposalTally.getAmountOfJudgments());
			Integer amountOfGrades = proposalTally.getTally().length;
			BigInteger[] gradesTallies = normalizedTally.getTally();
			for (int j = 0 ; j < amountOfGrades; j++) {
				gradesTallies[j] = gradesTallies[j].multiply(factor);
			}
			normalizedTallies[i] = normalizedTally;
		}
		
		setProposalsTallies(normalizedTallies);
		setAmountOfJudges(amountOfJudges);
	}

	/**
	 * Least Common Multiple
	 * 
	 * http://en.wikipedia.org/wiki/Least_common_multiple
	 * 
	 * lcm( 6, 9 ) = 18
	 * lcm( 4, 9 ) = 36
	 * lcm( 0, 9 ) = 0
	 * lcm( 0, 0 ) = 0
	 * 
	 * @author www.java2s.com
	 * @param a first integer
	 * @param b second integer
	 * @return least common multiple of a and b
	 */
	public static BigInteger lcm(BigInteger a, BigInteger b) {
		if (a.signum() == 0 || b.signum() == 0)
			return BigInteger.ZERO;
		return a.divide(a.gcd(b)).multiply(b).abs();
	}

}