/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF 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
 *
 * 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.apache.cxf.ws.policy.selector;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import org.apache.cxf.message.Message;
import org.apache.cxf.ws.policy.Assertor;
import org.apache.cxf.ws.policy.PolicyEngine;
import org.apache.neethi.Assertion;
import org.apache.neethi.Policy;

/**
 * 
 */
public class MinimalAlternativeSelector extends BaseAlternativeSelector {
    
    public Collection<Assertion> selectAlternative(
        Policy policy, PolicyEngine engine,
        Assertor assertor,
        List<List<Assertion>> request,
        Message msg) {
        
        Collection<Assertion> choice = null;
        Iterator<List<Assertion>> alternatives = policy.getAlternatives();
        while (alternatives.hasNext()) {
            List<Assertion> alternative = alternatives.next();
            
            if (engine.supportsAlternative(alternative, assertor, msg)
                && isCompatibleWithRequest(alternative, request)) {
                
                if (null == choice) {
                    choice = alternative;
                } else if (request != null) {
                    //we have a request policy, we likely want the one longest alternative that
                    //matches as any of "optional" incoming policies so that asssertions that were 
                    //asserted on the incoming will also be assertable on the outgoing. 
                    //Example: ws:addressing policy asserted on incoming should also be
                    // used to add headers for the response
                    if (alternative.size() > choice.size()) {
                        choice = alternative;
                    }
                } else if (alternative.size() < choice.size()) {
                    choice = alternative;
                }
            }
        }
        if (choice == null) {
            // didn't find one completely compatible with the incoming, just get the minimal
            alternatives = policy.getAlternatives();
            while (alternatives.hasNext()) {
                List<Assertion> alternative = alternatives.next();
                
                if (engine.supportsAlternative(alternative, assertor, msg)
                    && (null == choice || alternative.size() < choice.size())) {
                    choice = alternative;
                }
            }
        }
        return choice;
    }
}
