public class Scorer {

	// the number of the frame in which the next ball
	//   will be rolled; ranges from 1 to 11
	private int rollingFrame;
	
	// 0 if firstUnscoredFrame == 1, 
	//   frameScores[firstUnscoredFrame] thereafter
	private int totalScore;
	
	// frameScores[k] == cumulative score up through frame k;
	private int [ ] frameScores;

	private int state;
	private static final int ROLLING_FIRST_BALL = 0;
	private static final int ROLLING_SECOND_BALL = 1;
	private static final int STRIKE_LAST_BALL = 2;
	private static final int TWO_CONSEC_STRIKES = 3;
	private static final int STRIKE_2_BALLS_AGO = 4;
	private static final int SPARE_LAST_BALL = 5;
	
	// the number of pins knocked down by the first ball 
	//   in frame number rollingFrame
	private int firstBallInFrame;
	
	// indicates which frame is the last in the game
	private int lastFrameNumber;

	public Scorer ( ) {
		this (10);
	}
	
	public Scorer (int frameCount) {
		lastFrameNumber = frameCount;
		rollingFrame = 1;
		totalScore = 0;
		frameScores = new int [0];
		state = ROLLING_FIRST_BALL;
	}
	
	public int frameNumber ( ) {
		if (frameScores.length == lastFrameNumber) {
			return lastFrameNumber+1;	// game is over
		} else if (rollingFrame > lastFrameNumber) {
			return lastFrameNumber;	// we're in last frame
		} else {
			return rollingFrame;
		}
	}
	
	public int scoreSoFar ( ) {
		if (frameScores.length == lastFrameNumber) {
			return frameScores[lastFrameNumber-1];
		} else {
			return totalScore;
		}
	}
	
	public boolean gameIsOver ( ) {
		return frameNumber ( ) > lastFrameNumber;
	}
	
	public int [ ] roll (int ball) {
		if (state == ROLLING_FIRST_BALL) { 
			if (ball == 10) {
				rollingFrame++;
				state = STRIKE_LAST_BALL;
			} else {
				firstBallInFrame = ball;
				state = ROLLING_SECOND_BALL;
			}
		} else if (state == ROLLING_SECOND_BALL) {
			if (firstBallInFrame + ball == 10) {
				rollingFrame++;
				state = SPARE_LAST_BALL;
			} else {
				rollingFrame++;
				addFrame (firstBallInFrame + ball);
				state = ROLLING_FIRST_BALL;
			}
		} else if (state == SPARE_LAST_BALL) {
			addFrame (10 + ball);
			if (ball == 10) {
				rollingFrame++;
				state = STRIKE_LAST_BALL;
			} else {
				firstBallInFrame = ball;
				state = ROLLING_SECOND_BALL;
			}
		} else if (state == STRIKE_LAST_BALL) {
			if (ball == 10) {
				rollingFrame++;
				state = TWO_CONSEC_STRIKES;
			} else {
				firstBallInFrame = ball;
				state = STRIKE_2_BALLS_AGO;
			}
		} else if (state == TWO_CONSEC_STRIKES) {
			addFrame (20 + ball);
			if (ball == 10) {
				rollingFrame++;
			} else {
				firstBallInFrame = ball;
				state = STRIKE_2_BALLS_AGO;
			}
		} else if (state == STRIKE_2_BALLS_AGO) {
			addFrame (10 + firstBallInFrame + ball);
			if (firstBallInFrame + ball == 10) {
				rollingFrame++;
				state = SPARE_LAST_BALL;
			} else {
				rollingFrame++;
				addFrame (firstBallInFrame + ball);
				state = ROLLING_FIRST_BALL;
			}
		} else {
			System.out.println ("Invalid state: " + state);
			System.exit (1);
		}
		return frameScores;
	}
	
	private void addFrame (int toAdd) {
		totalScore = totalScore + toAdd;
		if (frameScores.length < lastFrameNumber) {
			int [ ] temp = new int [frameScores.length+1];
			for (int k=0; k<frameScores.length; k++) {
				temp[k] = frameScores[k];
			}
			temp[frameScores.length] = totalScore;
			frameScores = temp;
		}
	}
}