Uebung-TDD-Pure-function/src/main/java/de/edu/hsfulda/ccip/tdd/purefunction/BowlingCalculator.java

package de.edu.hsfulda.ccip.tdd.purefunction;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class BowlingCalculator {
	@FunctionalInterface
	interface FrameScorer {
		int score(Matcher frameMatcher);
	}

	private static final int INITIAL_SCORE = 0;
	private static final Pattern SINGLE_ROLL_PATTERN = Pattern.compile("\\d");
	private static final Pattern SPARE_PATTERN = Pattern.compile("(\\d)/ ([-\\d])");

	public int score(String rolls) {
		int score = INITIAL_SCORE;
		Matcher singleRollMatcher = SINGLE_ROLL_PATTERN.matcher(rolls);
		score = scoreFrameType(score, singleRollMatcher, matcher -> Integer.parseInt(singleRollMatcher.group()));

		Matcher spareMatcher = SPARE_PATTERN.matcher(rolls);
		score = scoreFrameType(score, spareMatcher, matcher -> scoreSpareFrame(spareMatcher));

		return score;
	}

	private int scoreSpareFrame(Matcher spareMatcher) {
		int frameScore = 10 - Integer.parseInt(spareMatcher.group(1));
		String nextRoll = spareMatcher.group(2);
		if(!"-".equalsIgnoreCase(nextRoll)) {
			frameScore += Integer.parseInt(spareMatcher.group(1));
		}
		return frameScore;
	}

	private int scoreFrameType(int score, Matcher scoreMatcher, FrameScorer frameScorer) {
		while (scoreMatcher.find()) {
			score += frameScorer.score(scoreMatcher);
		}
		return score;
	}

}