/*

 * Copyright (c) 2017, 2018, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.internal.module;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleFinder;

import java.lang.module.ModuleReference;

import java.util.Set;

import java.util.stream.Collectors;

/**

 * Defines methods to compute the default set of root modules for the unnamed

 * module.

 */

public final class DefaultRoots {

    private DefaultRoots() { }

    /**

     * Returns the default set of root modules for the unnamed module from the

     * modules observable with the intersection of two module finders.

     *

     * The first module finder should be the module finder that finds modules on

     * the upgrade module path or among the system modules. The second module

     * finder should be the module finder that finds all modules on the module

     * path, or a subset of when using --limit-modules.

     */

    static Set<String> compute(ModuleFinder finder1, ModuleFinder finder2) {

        return finder1.findAll().stream()

                .filter(mref -> !ModuleResolution.doNotResolveByDefault(mref))

                .map(ModuleReference::descriptor)

                .filter(descriptor -> finder2.find(descriptor.name()).isPresent()

                                      && exportsAPI(descriptor))

                .map(ModuleDescriptor::name)

                .collect(Collectors.toSet());

    }

    /**

     * Returns the default set of root modules for the unnamed module from the

     * modules observable with the given module finder.

     *

     * This method is used by the jlink system modules plugin.

     */

    public static Set<String> compute(ModuleFinder finder) {

        return compute(finder, finder);

    }

    /**

     * Returns true if the given module exports a package to all modules

     */

    private static boolean exportsAPI(ModuleDescriptor descriptor) {

        return descriptor.exports()

                .stream()

                .filter(e -> !e.isQualified())

                .findAny()

                .isPresent();

    }

}