/*

 * Copyright (c) 2015, 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

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

 * questions.

 */

package jdk.nashorn.tools.jjs;

import java.lang.reflect.Modifier;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Collections;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import java.util.Set;

import jdk.nashorn.internal.runtime.Context;

/**

 * Abstract helper class to compute properties of a Java package object. Properties of

 * package object are (simple) top level class names in that java package and

 * immediate subpackages of that package.

 */

abstract class PackagesHelper {

    private final Context context;

    /**

     * Construct a new PackagesHelper.

     *

     * @param context the current Nashorn Context

     */

    PackagesHelper(final Context context) throws IOException {

        this.context = context;

    }

    static PackagesHelper create(final Context context) throws IOException {

        return isJavacHelperAvailable()? new JavacPackagesHelper(context) : new JrtPackagesHelper(context);

    }

    // LRU cache for java package properties lists

    private final LinkedHashMap<String, List<String>> propsCache =

        new LinkedHashMap<String, List<String>>(32, 0.75f, true) {

            private static final int CACHE_SIZE = 100;

            private static final long serialVersionUID = 1;

            @Override

            protected boolean removeEldestEntry(final Map.Entry<String, List<String>> eldest) {

                return size() > CACHE_SIZE;

            }

        };

    /**

     * Return the list of properties of the given Java package or package prefix

     *

     * @param pkg Java package name or package prefix name

     * @return the list of properties of the given Java package or package prefix

     */

    final List<String> getPackageProperties(final String pkg) {

        // check the cache first

        if (propsCache.containsKey(pkg)) {

            return propsCache.get(pkg);

        }

        try {

            // make sorted list of properties

            final List<String> props = new ArrayList<>(listPackage(pkg));

            Collections.sort(props);

            propsCache.put(pkg, props);

            return props;

        } catch (final IOException exp) {

            if (Main.DEBUG) {

                exp.printStackTrace();

            }

            return Collections.<String>emptyList();

        }

    }

    /**

     * Close resources (like file system) used, if any.

     */

    abstract void close() throws IOException;

    /**

     * Return the set of properties of a given package object.

     *

     * @param pkg package start string

     * @return set of properties of the given Java package

     */

    abstract Set<String> listPackage(final String pkg) throws IOException;

    final boolean isClassAccessible(final String className) {

        try {

            final Class<?> clz = context.findClass(className);

            return Modifier.isPublic(clz.getModifiers());

        } catch (final ClassNotFoundException cnfe) {

        }

        return false;

    }

    final boolean isPackageAccessible(final String pkgName) {

        try {

            Context.checkPackageAccess(pkgName);

            return true;

        } catch (final SecurityException se) {

            return false;

        }

    }

    private static boolean isJavacHelperAvailable() {

        try {

            boolean result = JavacPackagesHelper.isAvailable();

            if (Main.DEBUG && !result) {

                System.err.println("javac packages helper is not available");

            }

            return result;

        } catch (final LinkageError err) {

            if (Main.DEBUG) {

                System.err.println("javac packages helper is not available");

                err.printStackTrace();

            }

            return false;

        }

    }

}