/**
 * Licensed to Apereo under one or more contributor license
 * agreements. See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Apereo licenses this file to you 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 the following location:
 *
 *   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 org.apereo.portal.portlets.dynamicskin;

import java.util.Iterator;
import java.util.Map;
import java.util.TreeSet;

import javax.portlet.PortletPreferences;

/**
 * {@link DynamicSkinUniqueTokenGenerator} implementation that generates a token by computing a hashcode using the 
 * values for the Dynamic Skin configurable portlet preferences.  To ensure that when using the same 
 * {@link PortletPreferences} that multiple calls to generate the token will return identical result, the portlet 
 * preferences are ordered by name prior to hashcode calculation.
 */
public class ConfigurablePreferencesBasedTokenGenerator implements DynamicSkinUniqueTokenGenerator {

    /**
     * Returns a String hashcode of the values for the portlet preferences that are configurable by the Dynamic Skin
     * portlet.  The hashcode is generated in a repeatable fashion by calculating it based on sorted portlet preference
     * names.  Though hashcode does not guarantee uniqueness, from a practical perspective we'll have so few different 
     * values we can reasonably assume preference value combinations will be unique.
     *
     * @see DynamicSkinUniqueTokenGenerator#generateToken(DynamicSkinInstanceData)
     */
    public String generateToken(final DynamicSkinInstanceData data) {
        final PortletPreferences preferences = data.getPortletRequest().getPreferences();
        int hash = 0;
        // Add the list of preference names to an ordered list so we can get reliable hashcode calculations.
        final Map<String, String[]> prefs = preferences.getMap();
        final TreeSet<String> orderedNames = new TreeSet<String>(prefs.keySet());
        final Iterator<String> iterator = orderedNames.iterator();
        while (iterator.hasNext()) {
            final String preferenceName = iterator.next();
            if (preferenceName.startsWith(DynamicRespondrSkinConstants.CONFIGURABLE_PREFIX)) {
                hash = hash * 31 + preferences.getValue(preferenceName, "").trim().hashCode();
            }
        }
        return Integer.toString(hash);
    }

}