/*

 * Copyright (c) 2015, 2017, 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.nio.zipfs;

import java.io.IOException;

import java.io.InputStream;

import java.lang.Runtime.Version;

import java.nio.file.NoSuchFileException;

import java.nio.file.Path;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Map;

import java.util.TreeMap;

import java.util.function.Consumer;

import java.util.function.Function;

import java.util.jar.Attributes;

import java.util.jar.Manifest;

/**

 * Adds aliasing to ZipFileSystem to support multi-release jar files.  An alias map

 * is created by {@link JarFileSystem#createVersionedLinks(int)}.  The map is then

 * consulted when an entry is looked up in {@link JarFileSystem#getEntry(byte[])}

 * to determine if the entry has a corresponding versioned entry.  If so, the

 * versioned entry is returned.

 *

 * @author Steve Drach

 */

class JarFileSystem extends ZipFileSystem {

    private Function<byte[],byte[]> lookup;

    @Override

    IndexNode getInode(byte[] path) {

        // check for an alias to a versioned entry

        byte[] versionedPath = lookup.apply(path);

        return versionedPath == null ? super.getInode(path) : super.getInode(versionedPath);

    }

    JarFileSystem(ZipFileSystemProvider provider, Path zfpath, Map<String,?> env)

            throws IOException {

        super(provider, zfpath, env);

        lookup = path -> path;  // lookup needs to be set before isMultiReleaseJar is called

                                // because it eventually calls getEntry

        if (isMultiReleaseJar()) {

            int version;

            Object o = env.get("multi-release");

            if (o instanceof String) {

                String s = (String)o;

                if (s.equals("runtime")) {

                    version = Runtime.version().major();

                } else {

                    version = Integer.parseInt(s);

                }

            } else if (o instanceof Integer) {

                version = (Integer)o;

            } else if (o instanceof Version) {

                version = ((Version)o).major();

            } else {

                throw new IllegalArgumentException("env parameter must be String, Integer, "

                        + "or Version");

            }

            lookup = createVersionedLinks(version < 0 ? 0 : version);

            setReadOnly();

        }

    }

    private boolean isMultiReleaseJar() throws IOException {

        try (InputStream is = newInputStream(getBytes("/META-INF/MANIFEST.MF"))) {

            String multiRelease = new Manifest(is).getMainAttributes()

                    .getValue(Attributes.Name.MULTI_RELEASE);

            return "true".equalsIgnoreCase(multiRelease);

        } catch (NoSuchFileException x) {

            return false;

        }

    }

    /**

     * create a map of aliases for versioned entries, for example:

     *   version/PackagePrivate.class -> META-INF/versions/9/version/PackagePrivate.class

     *   version/PackagePrivate.java -> META-INF/versions/9/version/PackagePrivate.java

     *   version/Version.class -> META-INF/versions/10/version/Version.class

     *   version/Version.java -> META-INF/versions/10/version/Version.java

     *

     * then wrap the map in a function that getEntry can use to override root

     * entry lookup for entries that have corresponding versioned entries

     */

    private Function<byte[],byte[]> createVersionedLinks(int version) {

        HashMap<IndexNode,byte[]> aliasMap = new HashMap<>();

        getVersionMap(version, getInode(getBytes("/META-INF/versions"))).values()

                .forEach(versionNode -> {   // for each META-INF/versions/{n} directory

                    // put all the leaf inodes, i.e. entries, into the alias map

                    // possibly shadowing lower versioned entries

                    walk(versionNode, entryNode -> {

                        byte[] rootName = getRootName(versionNode, entryNode);

                        if (rootName != null) {

                            IndexNode rootNode = getInode(rootName);

                            if (rootNode == null) { // no matching root node, make a virtual one

                                rootNode = IndexNode.keyOf(rootName);

                            }

                            aliasMap.put(rootNode, entryNode.name);

                        }

                    });

                });

        return path -> aliasMap.get(IndexNode.keyOf(path));

    }

    /**

     * create a sorted version map of version -> inode, for inodes <= max version

     *   9 -> META-INF/versions/9

     *  10 -> META-INF/versions/10

     */

    private TreeMap<Integer, IndexNode> getVersionMap(int version, IndexNode metaInfVersions) {

        TreeMap<Integer,IndexNode> map = new TreeMap<>();

        IndexNode child = metaInfVersions.child;

        while (child != null) {

            Integer key = getVersion(child.name, metaInfVersions.name.length + 1);

            if (key != null && key <= version) {

                map.put(key, child);

            }

            child = child.sibling;

        }

        return map;

    }

    /**

     * extract the integer version number -- META-INF/versions/9 returns 9

     */

    private Integer getVersion(byte[] name, int offset) {

        try {

            return Integer.parseInt(getString(Arrays.copyOfRange(name, offset, name.length)));

        } catch (NumberFormatException x) {

            // ignore this even though it might indicate issues with the JAR structure

            return null;

        }

    }

    /**

     * walk the IndexNode tree processing all leaf nodes

     */

    private void walk(IndexNode inode, Consumer<IndexNode> process) {

        if (inode == null) return;

        if (inode.isDir()) {

            walk(inode.child, process);

        } else {

            process.accept(inode);

        }

        walk(inode.sibling, process);

    }

    /**

     * extract the root name from a versioned entry name

     *   given inode for META-INF/versions/9/foo/bar.class

     *   and prefix META-INF/versions/9/

     *   returns foo/bar.class

     */

    private byte[] getRootName(IndexNode prefix, IndexNode inode) {

        int offset = prefix.name.length;

        byte[] fullName = inode.name;

        return Arrays.copyOfRange(fullName, offset, fullName.length);

    }

}