majority-judgment-library-java/src/main/java/fr/mieuxvoter/mj/ProposalTallyAnalysis.java

package fr.mieuxvoter.mj;

import java.math.BigInteger;

/**
 * Collect useful data on a proposal tally.
 * Does NOT compute the rank, but provides all we need.
 * 
 * This uses BigInteger because in a normalization scenario we use the
 * smallest common multiple of the amounts of judges of proposals.
 * It makes the code harder to read and understand, but it allows us
 * to bypass the floating-point nightmare of the normalization of merit profiles,
 * which is one way to handle default grades on some polls.
 */
public class ProposalTallyAnalysis {

	protected ProposalTallyInterface tally;

	protected BigInteger totalSize = BigInteger.ZERO;  // amount of judges

	protected Integer medianGrade = 0;

	protected BigInteger medianGroupSize = BigInteger.ZERO;  // amount of judges in the median group

	protected Integer contestationGrade = 0;  // "best" grade of the contestation group 

	protected BigInteger contestationGroupSize = BigInteger.ZERO;  // of lower grades than median

	protected Integer adhesionGrade = 0;  // "worst" grade of the adhesion group

	protected BigInteger adhesionGroupSize = BigInteger.ZERO;  // of higher grades than median

	protected Integer secondMedianGrade = 0;  // grade of the biggest group out of the median

	protected BigInteger secondMedianGroupSize = BigInteger.ZERO;  // either contestation or adhesion

	protected Integer secondMedianGroupSign = 0;  // -1 for contestation, +1 for adhesion, 0 for empty group size


	public ProposalTallyAnalysis() {}
	
	public ProposalTallyAnalysis(ProposalTallyInterface tally) {
		reanalyze(tally);
	}

	public void reanalyze(ProposalTallyInterface tally) {
		reanalyze(tally, true);
	}
	
	public void reanalyze(ProposalTallyInterface tally, Boolean favorContestation) {
		this.tally = tally;
		this.totalSize = BigInteger.ZERO;
		this.medianGrade = 0;
		this.medianGroupSize = BigInteger.ZERO;
		this.contestationGrade = 0;
		this.contestationGroupSize = BigInteger.ZERO;
		this.adhesionGrade = 0;
		this.adhesionGroupSize = BigInteger.ZERO;
		this.secondMedianGrade = 0;
		this.secondMedianGroupSize = BigInteger.ZERO;
		this.secondMedianGroupSign = 0;
		
		BigInteger[] gradesTallies = this.tally.getTally();
		int amountOfGrades = gradesTallies.length;

		for (int grade = 0; grade < amountOfGrades; grade++) {
			BigInteger gradeTally = gradesTallies[grade];
			//assert(0 <= gradeTally);  // Negative tallies are not allowed.
			this.totalSize = this.totalSize.add(gradeTally);
		}
		
		Integer medianOffset = 1;
		if ( ! favorContestation) {
			medianOffset = 2;
		}
		BigInteger medianCursor = this.totalSize.add(BigInteger.valueOf(medianOffset)).divide(BigInteger.valueOf(2));
//		Long medianCursor = (long) Math.floor((this.totalSize + medianOffset) / 2.0);
		
		BigInteger tallyBeforeCursor = BigInteger.ZERO;
		BigInteger tallyCursor = BigInteger.ZERO;
		Boolean foundMedian = false;
		Integer contestationGrade = 0;
		Integer adhesionGrade = 0;
		for (int grade = 0; grade < amountOfGrades; grade++) {
			BigInteger gradeTally = gradesTallies[grade];
			tallyBeforeCursor = tallyCursor;
			tallyCursor = tallyCursor.add(gradeTally);
			
			if ( ! foundMedian) {
				if (-1 < tallyCursor.compareTo(medianCursor)) {  // tallyCursor >= medianCursor
					foundMedian = true;
					this.medianGrade = grade;
					this.contestationGroupSize = tallyBeforeCursor;
					this.medianGroupSize = gradeTally;
					this.adhesionGroupSize = this.totalSize.subtract(this.contestationGroupSize).subtract(this.medianGroupSize);
				} else {
					if (1 == gradeTally.compareTo(BigInteger.ZERO)) {  // 0 < gradeTally
						contestationGrade = grade;
					}
				}
			} else {
				if (1 == gradeTally.compareTo(BigInteger.ZERO) && 0 == adhesionGrade) {
					adhesionGrade = grade;
				}
			}
		}
		
		this.contestationGrade = contestationGrade;
		this.adhesionGrade = adhesionGrade;
		this.secondMedianGroupSize = this.contestationGroupSize.max(this.adhesionGroupSize);
		this.secondMedianGroupSign = 0;
//		if (this.contestationGroupSize < this.adhesionGroupSize) {
		if (1 == this.adhesionGroupSize.compareTo(this.contestationGroupSize)) {
			this.secondMedianGrade = this.adhesionGrade;
			this.secondMedianGroupSign = 1;
//		} else if (this.contestationGroupSize > this.adhesionGroupSize) {
		} else if (1 == this.contestationGroupSize.compareTo(this.adhesionGroupSize)) {
			this.secondMedianGrade = this.contestationGrade;
			this.secondMedianGroupSign = -1;
		} else {
			if (favorContestation) {
				this.secondMedianGrade = this.contestationGrade;
				this.secondMedianGroupSign = -1;
			} else {
				this.secondMedianGrade = this.adhesionGrade;
				this.secondMedianGroupSign = 1;
			}
		}
		if (0 == this.secondMedianGroupSize.compareTo(BigInteger.ZERO)) {
			this.secondMedianGroupSign = 0;
		}
	}

	public BigInteger getTotalSize() {
		return totalSize;
	}

	public void setTotalSize(BigInteger totalSize) {
		this.totalSize = totalSize;
	}

	public Integer getMedianGrade() {
		return medianGrade;
	}

	public void setMedianGrade(Integer medianGrade) {
		this.medianGrade = medianGrade;
	}

	public BigInteger getMedianGroupSize() {
		return medianGroupSize;
	}

	public void setMedianGroupSize(BigInteger medianGroupSize) {
		this.medianGroupSize = medianGroupSize;
	}
	
	public Integer getContestationGrade() {
		return contestationGrade;
	}

	public void setContestationGrade(Integer contestationGrade) {
		this.contestationGrade = contestationGrade;
	}

	public BigInteger getContestationGroupSize() {
		return contestationGroupSize;
	}

	public void setContestationGroupSize(BigInteger contestationGroupSize) {
		this.contestationGroupSize = contestationGroupSize;
	}

	public Integer getAdhesionGrade() {
		return adhesionGrade;
	}

	public void setAdhesionGrade(Integer adhesionGrade) {
		this.adhesionGrade = adhesionGrade;
	}

	public BigInteger getAdhesionGroupSize() {
		return adhesionGroupSize;
	}

	public void setAdhesionGroupSize(BigInteger adhesionGroupSize) {
		this.adhesionGroupSize = adhesionGroupSize;
	}

	public Integer getSecondMedianGrade() {
		return secondMedianGrade;
	}

	public void setSecondMedianGrade(Integer secondMedianGrade) {
		this.secondMedianGrade = secondMedianGrade;
	}

	public BigInteger getSecondMedianGroupSize() {
		return secondMedianGroupSize;
	}

	public void setSecondMedianGroupSize(BigInteger secondMedianGroupSize) {
		this.secondMedianGroupSize = secondMedianGroupSize;
	}

	public Integer getSecondMedianGroupSign() {
		return secondMedianGroupSign;
	}

	public void setSecondMedianGroupSign(Integer sign) {
		this.secondMedianGroupSign = sign;
	}

}