IndexedComponentList.java

/**
 * Copyright (c) 2012, Ben Fortuna
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  o Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 *  o Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 *  o Neither the name of Ben Fortuna nor the names of any other contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package net.fortuna.ical4j.model;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * $Id$
 *
 * Created on 4/02/2006
 *
 * Provides indexing of components on a specific property.
 * @author Ben Fortuna
 */
public class IndexedComponentList {

    private static final ComponentList EMPTY_LIST = new ComponentList();
    
    private Map index;
    
    /**
     * Creates a new instance indexed on properties with the specified name.
     * @param list a list of components
     * @param propertyName the name of the properties to index on
     */
    public IndexedComponentList(final ComponentList list, final String propertyName) {
        final Map indexedComponents = new HashMap();
        for (final Iterator i = list.iterator(); i.hasNext();) {
            final Component component = (Component) i.next();
            for (final Iterator j = component.getProperties(propertyName).iterator(); j.hasNext();) {
                final Property property = (Property) j.next();
                ComponentList components = (ComponentList) indexedComponents.get(property.getValue());
                if (components == null) {
                    components = new ComponentList();
                    indexedComponents.put(property.getValue(), components);
                }
                components.add(component);
            }
        }
        this.index = Collections.unmodifiableMap(indexedComponents);
    }
    
    /**
     * Returns a list of components containing a property with the
     * specified value.
     * @param propertyValue the value of the property contained in the
     * returned components
     * @return a component list
     */
    public ComponentList getComponents(final String propertyValue) {
        ComponentList components = (ComponentList) index.get(propertyValue);
        if (components == null) {
            components = EMPTY_LIST;
        }
        return components;
    }
    
    /**
     * Returns the first component containing a property with the specified
     * value.
     * @param propertyValue the value of the property identified in the returned
     * component
     * @return a component or null if no component is found containing a property
     * with the specified value
     */
    public Component getComponent(final String propertyValue) {
        final ComponentList components = getComponents(propertyValue);
        if (!components.isEmpty()) {
            return (Component) components.iterator().next();
        }
        return null;
    }
}