ChallengeLookBehind.java

/* ========================================================================
 * PlantUML : a free UML diagram generator
 * ========================================================================
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 * (C) Copyright 2009-2024, Arnaud Roques
 *
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 * Original Author:  Arnaud Roques
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package com.plantuml.ubrex;

public class ChallengeLookBehind implements Challenge {

	private final Challenge origin;
	private final LookAround ahead;

	public ChallengeLookBehind(Challenge origin, LookAround ahead) {
		this.origin = origin;
		this.ahead = ahead;
	}

	@Override
	public ChallengeResult runChallenge(TextNavigator string, int position) {
		final TextNavigator stringReversed = string.reverse(position);
		final int tmp = origin.runChallenge(stringReversed, 0).getFullCaptureLength();
		switch (ahead) {
		case LOOK_BEHIND_POSITIVE:
			if (tmp < 0)
				return new ChallengeResult(NO_MATCH);
			return new ChallengeResult(0);

		case LOOK_BEHIND_NEGATIVE:
			if (tmp < 0)
				return new ChallengeResult(0);
			return new ChallengeResult(NO_MATCH);
		}
		throw new IllegalStateException();
	}

}