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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

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 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

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package com.sun.xml.internal.ws.policy;

import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;

import com.sun.xml.internal.ws.policy.sourcemodel.wspolicy.NamespaceVersion;

import java.util.ArrayList;

import java.util.Collection;

import java.util.LinkedList;

/**

 * Merge policies and return the effective policy.

 *

 * WS-PolicyAttachment defines a merge algorithm for WSDL 1.1 policy attachments.

 */

public final class PolicyMerger {

    private static final PolicyMerger merger = new PolicyMerger();

    /**

     * This private constructor is to avoid direct class instantiation from outsied of the package

     */

    private PolicyMerger() {

        // nothing to instantiate

    }

    /**

     * Factory method for obtaining thread-safe policy merger instance.

     *

     * @return policy merger instance.

     */

    public static PolicyMerger getMerger() {

        return merger;

    }

    /**

     * Takes collection of policies and merges them into a single policy using algorithm described in

     * WS-PolicyAttachment specification. None of the original policies in the collection are modified in

     * any way.

     *

     * The newly created policy has an ID that is a concatentation of all merged policy IDs.

     *

     * @param policies collection of policies to be merged. The collection must not contain '{@code null}' elements!

     * @return merged policy containing combination of policy alternatives stored in all input policies.

     *         If provided collection of policies is {@code null} or empty, returns {@code null}. If provided

     *         collection of policies contains only single policy, the policy is returned.

     */

    public Policy merge(final Collection<Policy> policies) {

        if (policies == null || policies.isEmpty()) {

            return null;

        } else if (policies.size() == 1) {

            return policies.iterator().next();

        }

        final Collection<Collection<AssertionSet>> alternativeSets = new LinkedList<Collection<AssertionSet>>();

        final StringBuilder id = new StringBuilder();

        NamespaceVersion mergedVersion = policies.iterator().next().getNamespaceVersion();

        for (Policy policy : policies) {

            alternativeSets.add(policy.getContent());

            if (mergedVersion.compareTo(policy.getNamespaceVersion()) < 0) {

                mergedVersion = policy.getNamespaceVersion();

            }

            final String policyId = policy.getId();

            if (policyId != null) {

                if (id.length() > 0) {

                    id.append('-');

                }

                id.append(policyId);

            }

        }

        final Collection<Collection<AssertionSet>> combinedAlternatives = PolicyUtils.Collections.combine(null, alternativeSets, false);

        if (combinedAlternatives == null || combinedAlternatives.isEmpty()) {

            return Policy.createNullPolicy(mergedVersion, null, id.length() == 0 ? null : id.toString());

        } else {

            final Collection<AssertionSet> mergedSetList = new ArrayList<AssertionSet>(combinedAlternatives.size());

            for (Collection<AssertionSet> toBeMerged : combinedAlternatives) {

                mergedSetList.add(AssertionSet.createMergedAssertionSet(toBeMerged));

            }

            return Policy.createPolicy(mergedVersion, null, id.length() == 0 ? null : id.toString(), mergedSetList);

        }

    }

}