import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

/**
 * Contains all of the ballots in an election
 * 
 * @author Scot Drysdale
 */
public class Election {
	private List<Ballot> ballots;
	
	/**
	 * Construct and empty election
	 */
	public Election() {
		ballots = new ArrayList<Ballot>();	
	}
	
	/**
	 * Add a ballot to this election
	 */
	public void addBallot(Ballot ballot) {
		ballots.add(ballot);
	}
	
	/**
	 * Creates the initial set of candidates.  We only need to include
	 * candidates who got at least one first-round vote
	 * @return the initial set of candidates
	 */
	public Set<String> getInitialCandidates() {
		Set<String> candidateSet = new TreeSet<String>();
		
		// Add all names on all ballots to the set.  Adding a candidate who
		// is already in the set does not change the set.
		for(Ballot ballot : ballots) {
			String candidate = ballot.getFirst();
			if(candidate != null)
				candidateSet.add(candidate);
		}
		return candidateSet;
	}
	
	/**
	 * Counts the number of votes that each candidate gets during a 
	 * round of an instant runoff election.  Only the top candidate
	 * on the ballot that appears in candidates is counted.
	 * 
	 * @param candidates the current list of candidates
	 * @return the vote tally for each candidate
	 */
	public VoteTally countRunoffVotes(Set<String> candidates) {
		VoteTally voteTally = new VoteTally();
	  
		// Tally up top choice on each ballot
		for(Ballot ballot : ballots) {
			String topChoice = ballot.getTopChoice(candidates);
      voteTally.recordVote(topChoice);
		}
		return voteTally;	
	}
}