import java.util.ArrayList;
import java.util.Scanner;
import java.util.Set;
import java.util.Random;
import java.io.*;

/**
 * Runs an instant runoff election.
 * In an instant runoff election each voter submits a list of candidates,
 * in order of preference.  The first name on the list is the voter's 
 * first choice, the second the voter's second choice, etc.  The voter 
 * need not list all of the candidates.
 * 
 * The election is conducted in rounds.  Each voter's first choice is
 * tallied, and the candidate with the fewest first-place votes is 
 * eliminated.  (If there is a tie one of the lowest vote-getters is chosen 
 * at random to be eliminated.)  In each round the voter's top choice 
 * amongst the remaining candidates gets that voter's vote for that round.
 * If no current candidate is on a voter's list that voter casts no vote
 * for this round.
 * 
 * The process ends when there is a single candidate left, who is declared
 * the winner.
 * 
 * This version is written in a more object-oriented style.
 * 
 * @author Scot Drysdale, minor changes by Tom Cormen
 */
public class InstantRunoffOO {  
  private static boolean debugOn = true;          // print debugging output?
  private static Random generator = new Random(); // random number generator
  
  /**
   * Picks a random item from a list.
   * @list the list to choose from
   * @return an item chosen randomly from list
   */
  public static String pickRandomItem(ArrayList<String> list) {
    return list.get(generator.nextInt(list.size()));
  }
  
  /**
   * Runs an instant-runoff election
   * @param ballots the ballots for this election
   * @return winner of the election
   */
  public static String runInstantRunoffElection(Election ballots) {
    Set<String> candidates = ballots.getInitialCandidates();
  
    // Run rounds until down to a single candidate.
    while (candidates.size() > 1) {
      VoteTally tally = ballots.countRunoffVotes(candidates);
      String loser = pickRandomItem(tally.getLosers());
      candidates.remove(loser);
      
      if (debugOn) {
        System.out.println("Vote tally:\n" + tally);
        System.out.println("Loser: " + loser);
      }
    }
    
    if (candidates.size() > 0)
      return candidates.iterator().next();  // return the surviving candidate
    else
      return null;
  }

  /**
   * Test program
   */
  public static void main(String[] args) {
    Election ballots = new Election();
    
    Ballot ballot; 
    String ballotFileName = "/Users/scot/Documents/workspace/cs10proj/src/ballots.txt";
    Scanner ballotFile = null;
    try {
      ballotFile = new Scanner(new File(ballotFileName));
    }
    catch (FileNotFoundException e) {
      System.err.println("No such file: " + ballotFileName);
      System.exit(1);
    }
    
    while (ballotFile.hasNext()) {
      String line = ballotFile.nextLine();
      ballot = new Ballot();
      Scanner inLine = new Scanner(line);
      
      while (inLine.hasNext()) {
        String candidate = inLine.next();
        ballot.addCandidate(candidate);
      }
      ballots.addBallot(ballot);
    }
    
    String winner = runInstantRunoffElection(ballots);
    if (winner != null)
      System.out.println("The winner of the instant runoff election is: " + 
        winner);
    else
      System.out.println("No valid votes cast");
  }
}