RangeStringParser.java

/*******************************************************************************
 * Copyright (c) 2007, 2014 Massimiliano Ziccardi
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *******************************************************************************/
package it.jnrpe.utils.thresholds;

/**
 * The configured threshold parser.
 * 
 * @author Massimiliano Ziccardi
 * @version $Revision: 1.0 $
 */
final class RangeStringParser {

    /**
     * The root of the parsing state machine.
     */
    private static final Stage ROOT_STAGE = configureParser();

    /**
     * Private default constructor.
     */
    private RangeStringParser() {

    }

    /**
     * Configures the state machine.
     * 
    
     * @return The configured state machine. */
    private static Stage configureParser() {
        Stage startStage = new StartStage();
        Stage negativeInfinityStage = new NegativeInfinityStage();
        Stage positiveInfinityStage = new PositiveInfinityStage();
        NegateStage negateStage = new NegateStage();
        BracketStage.OpenBracketStage openBraceStage = new BracketStage.OpenBracketStage();
        NumberBoundaryStage.LeftBoundaryStage startBoundaryStage = new NumberBoundaryStage.LeftBoundaryStage();
        NumberBoundaryStage.RightBoundaryStage rightBoundaryStage = new NumberBoundaryStage.RightBoundaryStage();
        SeparatorStage separatorStage = new SeparatorStage();
        BracketStage.ClosedBracketStage closedBraketStage = new BracketStage.ClosedBracketStage();

        startStage.addTransition(negateStage);
        startStage.addTransition(openBraceStage);
        startStage.addTransition(negativeInfinityStage);
        startStage.addTransition(startBoundaryStage);

        negateStage.addTransition(negativeInfinityStage);
        negateStage.addTransition(openBraceStage);
        negateStage.addTransition(startBoundaryStage);

        openBraceStage.addTransition(startBoundaryStage);
        startBoundaryStage.addTransition(separatorStage);
        negativeInfinityStage.addTransition(separatorStage);

        separatorStage.addTransition(positiveInfinityStage);
        separatorStage.addTransition(rightBoundaryStage);

        rightBoundaryStage.addTransition(closedBraketStage);

        return startStage;
    }

    /**
     * Parses the threshold.
     * 
     * @param range
     *            The threshold to be parsed
     * @param tc
     *            The configuration
    
     * @throws RangeException
     *             - */
    public static void parse(final String range, final RangeConfig tc) throws RangeException {
        if (range == null) {
            throw new RangeException("Range can't be null");
        }
        ROOT_STAGE.parse(range, tc);
        checkBoundaries(tc);
    }

    /**
     * Checks that right boundary is greater than left boundary.
     * 
     * @param rc
     *            The range configuration
    
     * @throws RangeException
     *             If right < left */
    private static void checkBoundaries(final RangeConfig rc) throws RangeException {
        if (rc.isNegativeInfinity()) {
            // No other checks necessary. Negative infinity is less than any
            // number
            return;
        }

        if (rc.isPositiveInfinity()) {
            // No other checks necessary. Positive infinity is greater than any
            // number
            return;
        }

        if (rc.getLeftBoundary().compareTo(rc.getRightBoundary()) > 0) {
            throw new RangeException("Left boundary must be less than right boundary (left:" + rc.getLeftBoundary() + ", right:"
                    + rc.getRightBoundary() + ")");
        }
    }
}