/*

 * Copyright (c) 2014, 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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 */

package java.lang.module;

import java.io.IOException;

import java.net.URI;

import java.util.Objects;

import java.util.Optional;

/**

 * A reference to a module's content.

 *

 * <p> A module reference is a concrete implementation of this class that

 * implements the abstract methods defined by this class. It contains the

 * module's descriptor and its location, if known.  It also has the ability to

 * create a {@link ModuleReader} in order to access the module's content, which

 * may be inside the Java run-time system itself or in an artifact such as a

 * modular JAR file.

 *

 * @see ModuleFinder

 * @see ModuleReader

 * @since 9

 */

public abstract class ModuleReference {

    private final ModuleDescriptor descriptor;

    private final URI location;

    /**

     * Constructs a new instance of this class.

     *

     * @param descriptor

     *        The module descriptor

     * @param location

     *        The module location or {@code null} if not known

     */

    protected ModuleReference(ModuleDescriptor descriptor, URI location) {

        this.descriptor = Objects.requireNonNull(descriptor);

        this.location = location;

    }

    /**

     * Returns the module descriptor.

     *

     * @return The module descriptor

     */

    public final ModuleDescriptor descriptor() {

        return descriptor;

    }

    /**

     * Returns the location of this module's content, if known.

     *

     * <p> This URI, when present, can be used as the {@linkplain

     * java.security.CodeSource#getLocation location} value of a {@link

     * java.security.CodeSource CodeSource} so that a module's classes can be

     * granted specific permissions when loaded by a {@link

     * java.security.SecureClassLoader SecureClassLoader}.

     *

     * @return The location or an empty {@code Optional} if not known

     */

    public final Optional<URI> location() {

        return Optional.ofNullable(location);

    }

    /**

     * Opens the module content for reading.

     *

     * @return A {@code ModuleReader} to read the module

     *

     * @throws IOException

     *         If an I/O error occurs

     * @throws SecurityException

     *         If denied by the security manager

     */

    public abstract ModuleReader open() throws IOException;

}