/*

 * Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.

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

 *

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

 * under the terms of the GNU General Public License version 2 only, as

 * 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

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file, and Oracle licenses the original version of this file under the BSD

 * license:

 */

/*

   Copyright 2009-2013 Attila Szegedi

*/

package jdk.dynalink.linker.support;

import java.util.LinkedList;

import java.util.List;

import java.util.Objects;

import jdk.dynalink.linker.GuardedInvocation;

import jdk.dynalink.linker.GuardingDynamicLinker;

import jdk.dynalink.linker.LinkRequest;

import jdk.dynalink.linker.LinkerServices;

/**

 * A {@link GuardingDynamicLinker} that delegates sequentially to a list of

 * other guarding dynamic linkers in its

 * {@link #getGuardedInvocation(LinkRequest, LinkerServices)}.

 */

public class CompositeGuardingDynamicLinker implements GuardingDynamicLinker {

    private final GuardingDynamicLinker[] linkers;

    /**

     * Creates a new composite linker.

     *

     * @param linkers a list of component linkers.

     * @throws NullPointerException if {@code linkers} or any of its elements

     * are null.

     */

    public CompositeGuardingDynamicLinker(final Iterable<? extends GuardingDynamicLinker> linkers) {

        final List<GuardingDynamicLinker> l = new LinkedList<>();

        for(final GuardingDynamicLinker linker: linkers) {

            l.add(Objects.requireNonNull(linker));

        }

        this.linkers = l.toArray(new GuardingDynamicLinker[0]);

    }

    /**

     * Delegates the call to its component linkers. The first non-null value

     * returned from a component linker is returned. If no component linker

     * returns a non-null invocation, null is returned.

     * @param linkRequest the object describing the request for linking a

     * particular invocation

     * @param linkerServices linker services

     * @return the first non-null return value from a component linker, or null

     * if none of the components returned a non-null.

     */

    @Override

    public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)

            throws Exception {

        for(final GuardingDynamicLinker linker: linkers) {

            final GuardedInvocation invocation = linker.getGuardedInvocation(linkRequest, linkerServices);

            if(invocation != null) {

                return invocation;

            }

        }

        return null;

    }

}