de.uniulm.omi.cloudiator.sword.util.LocationHierarchy.java Source code

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Here is the source code for de.uniulm.omi.cloudiator.sword.util.LocationHierarchy.java

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/*
 * Copyright (c) 2014-2018 University of Ulm
 *
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership.  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 de.uniulm.omi.cloudiator.sword.util;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.collect.Iterables;
import de.uniulm.omi.cloudiator.domain.LocationScope;
import de.uniulm.omi.cloudiator.sword.domain.Location;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Optional;
import javax.annotation.Nullable;

/**
 * The LocationHierarchy class.
 * <p>
 * Helper class for iterating over Locations and finding special locations of interest.
 */
public class LocationHierarchy implements Iterable<Location> {

    private final Location location;

    private LocationHierarchy(Location location) {
        checkNotNull(location, "location is null");
        this.location = location;
    }

    /**
     * Creates a LocationHierarchy using the given location as bottom.
     *
     * @param location the bottom location.
     * @return a LocationHierarchy.
     */
    public static LocationHierarchy of(Location location) {
        return new LocationHierarchy(location);
    }

    /**
     * Returns the topmost location of the hierarchy.
     *
     * @return the topmost location of the hierarchy
     */
    public Location topmostLocation() {
        return Iterables.getLast(this);
    }

    /**
     * Returns an {@link Optional} first parent location that has the given scope.
     * <p>
     * Will iterate upwards through the location hierarchy and return the first location that matches
     * the given scope.
     *
     * @param locationScope the scope to check for
     * @return an {@link Optional} first parent location or {@link Optional::empty}
     * @throws NullPointerException if the given locationScope is null.
     */
    public Optional<Location> firstParentLocationWithScope(LocationScope locationScope) {
        checkNotNull(locationScope, "locationScope is null");

        if (location.locationScope().equals(locationScope)) {
            return Optional.of(location);
        }

        for (Location iteration : this) {
            if (iteration.locationScope().equals(locationScope)) {
                return Optional.of(iteration);
            }
        }
        return Optional.empty();
    }

    @Override
    public Iterator<Location> iterator() {
        return new LocationIterator(location);
    }

    private static class LocationIterator implements Iterator<Location> {

        @Nullable
        private Location cursor;

        private LocationIterator(Location start) {
            checkNotNull(start, "start is null.");
            cursor = start;
        }

        @Override
        public boolean hasNext() {
            return cursor != null;
        }

        @Override
        public Location next() {
            if (cursor == null) {
                throw new NoSuchElementException();
            }
            Location current = cursor;
            cursor = current.parent().orElse(null);
            return current;
        }
    }
}