/*

 * Copyright (c) 2015, 2020, 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 jdk.internal.module;

import java.lang.module.Configuration;

import java.lang.module.ResolvedModule;

import java.util.HashMap;

import java.util.Map;

import java.util.Set;

import java.util.function.Function;

import jdk.internal.loader.ClassLoaders;

/**

 * Supports the mapping of modules to class loaders. The set of modules mapped

 * to the boot and platform class loaders is generated at build time from

 * this source file.

 */

public final class ModuleLoaderMap {

    /**

     * Maps the system modules to the built-in class loaders.

     */

    private static final class Mapper implements Function<String, ClassLoader> {

        private static final ClassLoader PLATFORM_CLASSLOADER =

                ClassLoaders.platformClassLoader();

        private static final ClassLoader APP_CLASSLOADER =

                ClassLoaders.appClassLoader();

        private static final Integer PLATFORM_LOADER_INDEX = 1;

        private static final Integer APP_LOADER_INDEX      = 2;

        /**

         * Map from module to a class loader index. The index is resolved to the

         * actual class loader in {@code apply}.

         */

        private final Map<String, Integer> map;

        /**

         * Creates a Mapper to map module names in the given Configuration to

         * built-in classloaders.

         *

         * As a proxy for the actual classloader, we store an easily archiveable

         * index value in the internal map. The index is stored as a boxed value

         * so that we can cheaply do identity comparisons during bootstrap.

         */

        Mapper(Configuration cf) {

            var map = new HashMap<String, Integer>();

            for (ResolvedModule resolvedModule : cf.modules()) {

                String mn = resolvedModule.name();

                if (!Modules.bootModules.contains(mn)) {

                    if (Modules.platformModules.contains(mn)) {

                        map.put(mn, PLATFORM_LOADER_INDEX);

                    } else {

                        map.put(mn, APP_LOADER_INDEX);

                    }

                }

            }

            this.map = map;

        }

        @Override

        public ClassLoader apply(String name) {

            Integer loader = map.get(name);

            if (loader == APP_LOADER_INDEX) {

                return APP_CLASSLOADER;

            } else if (loader == PLATFORM_LOADER_INDEX) {

                return PLATFORM_CLASSLOADER;

            } else { // BOOT_LOADER_INDEX

                return null;

            }

        }

    }

    /**

     * Returns the names of the modules defined to the boot loader.

     */

    public static Set<String> bootModules() {

        return Modules.bootModules;

    }

    /**

     * Returns the names of the modules defined to the platform loader.

     */

    public static Set<String> platformModules() {

        return Modules.platformModules;

    }

    private static class Modules {

        // list of boot modules is generated at build time.

        private static final Set<String> bootModules =

                Set.of(new String[] { "@@BOOT_MODULE_NAMES@@" });

        // list of platform modules is generated at build time.

        private static final Set<String> platformModules =

                Set.of(new String[] { "@@PLATFORM_MODULE_NAMES@@" });

    }

    /**

     * Returns a function to map modules in the given configuration to the

     * built-in class loaders.

     */

    static Function<String, ClassLoader> mappingFunction(Configuration cf) {

        return new Mapper(cf);

    }

    /**

     * When defining modules for a configuration, we only allow defining modules

     * to the boot or platform classloader if the ClassLoader mapping function

     * originate from here.

     */

    public static boolean isBuiltinMapper(Function<String, ClassLoader> clf) {

        return clf instanceof Mapper;

    }

}