/*

 * Copyright (c) 2008, 2015, 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 sun.nio.fs;

import java.nio.file.*;

import java.nio.file.attribute.*;

import java.nio.file.spi.*;

import java.io.IOException;

import java.util.*;

import java.util.regex.Pattern;

import sun.security.action.GetPropertyAction;

/**

 * Base implementation of FileSystem for Unix-like implementations.

 */

abstract class UnixFileSystem

    extends FileSystem

{

    private final UnixFileSystemProvider provider;

    private final byte[] defaultDirectory;

    private final boolean needToResolveAgainstDefaultDirectory;

    private final UnixPath rootDirectory;

    // package-private

    UnixFileSystem(UnixFileSystemProvider provider, String dir) {

        this.provider = provider;

        this.defaultDirectory = Util.toBytes(UnixPath.normalizeAndCheck(dir));

        if (this.defaultDirectory[0] != '/') {

            throw new RuntimeException("default directory must be absolute");

        }

        // if process-wide chdir is allowed or default directory is not the

        // process working directory then paths must be resolved against the

        // default directory.

        String propValue = GetPropertyAction

                .privilegedGetProperty("sun.nio.fs.chdirAllowed", "false");

        boolean chdirAllowed = (propValue.length() == 0) ?

            true : Boolean.valueOf(propValue);

        if (chdirAllowed) {

            this.needToResolveAgainstDefaultDirectory = true;

        } else {

            byte[] cwd = UnixNativeDispatcher.getcwd();

            boolean defaultIsCwd = (cwd.length == defaultDirectory.length);

            if (defaultIsCwd) {

                for (int i=0; i<cwd.length; i++) {

                    if (cwd[i] != defaultDirectory[i]) {

                        defaultIsCwd = false;

                        break;

                    }

                }

            }

            this.needToResolveAgainstDefaultDirectory = !defaultIsCwd;

        }

        // the root directory

        this.rootDirectory = new UnixPath(this, "/");

    }

    // package-private

    byte[] defaultDirectory() {

        return defaultDirectory;

    }

    boolean needToResolveAgainstDefaultDirectory() {

        return needToResolveAgainstDefaultDirectory;

    }

    UnixPath rootDirectory() {

        return rootDirectory;

    }

    boolean isSolaris() {

        return false;

    }

    static List<String> standardFileAttributeViews() {

        return Arrays.asList("basic", "posix", "unix", "owner");

    }

    @Override

    public final FileSystemProvider provider() {

        return provider;

    }

    @Override

    public final String getSeparator() {

        return "/";

    }

    @Override

    public final boolean isOpen() {

        return true;

    }

    @Override

    public final boolean isReadOnly() {

        return false;

    }

    @Override

    public final void close() throws IOException {

        throw new UnsupportedOperationException();

    }

    /**

     * Copies non-POSIX attributes from the source to target file.

     *

     * Copying a file preserving attributes, or moving a file, will preserve

     * the file owner/group/permissions/timestamps but it does not preserve

     * other non-POSIX attributes. This method is invoked by the

     * copy or move operation to preserve these attributes. It should copy

     * extended attributes, ACLs, or other attributes.

     *

     * @param   sfd

     *          Open file descriptor to source file

     * @param   tfd

     *          Open file descriptor to target file

     */

    void copyNonPosixAttributes(int sfd, int tfd) {

        // no-op by default

    }

    /**

     * Unix systems only have a single root directory (/)

     */

    @Override

    public final Iterable<Path> getRootDirectories() {

        final List<Path> allowedList =

           Collections.unmodifiableList(Arrays.asList((Path)rootDirectory));

        return new Iterable<>() {

            public Iterator<Path> iterator() {

                try {

                    SecurityManager sm = System.getSecurityManager();

                    if (sm != null)

                        sm.checkRead(rootDirectory.toString());

                    return allowedList.iterator();

                } catch (SecurityException x) {

                    List<Path> disallowed = Collections.emptyList();

                    return disallowed.iterator();

                }

            }

        };

    }

    /**

     * Returns object to iterate over entries in mounttab or equivalent

     */

    abstract Iterable<UnixMountEntry> getMountEntries();

    /**

     * Returns a FileStore to represent the file system for the given mount

     * mount.

     */

    abstract FileStore getFileStore(UnixMountEntry entry) throws IOException;

    /**

     * Iterator returned by getFileStores method.

     */

    private class FileStoreIterator implements Iterator<FileStore> {

        private final Iterator<UnixMountEntry> entries;

        private FileStore next;

        FileStoreIterator() {

            this.entries = getMountEntries().iterator();

        }

        private FileStore readNext() {

            assert Thread.holdsLock(this);

            for (;;) {

                if (!entries.hasNext())

                    return null;

                UnixMountEntry entry = entries.next();

                // skip entries with the "ignore" option

                if (entry.isIgnored())

                    continue;

                // check permission to read mount point

                SecurityManager sm = System.getSecurityManager();

                if (sm != null) {

                    try {

                        sm.checkRead(Util.toString(entry.dir()));

                    } catch (SecurityException x) {

                        continue;

                    }

                }

                try {

                    return getFileStore(entry);

                } catch (IOException ignore) {

                    // ignore as per spec

                }

            }

        }

        @Override

        public synchronized boolean hasNext() {

            if (next != null)

                return true;

            next = readNext();

            return next != null;

        }

        @Override

        public synchronized FileStore next() {

            if (next == null)

                next = readNext();

            if (next == null) {

                throw new NoSuchElementException();

            } else {

                FileStore result = next;

                next = null;

                return result;

            }

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

    @Override

    public final Iterable<FileStore> getFileStores() {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            try {

                sm.checkPermission(new RuntimePermission("getFileStoreAttributes"));

            } catch (SecurityException se) {

                return Collections.emptyList();

            }

        }

        return new Iterable<>() {

            public Iterator<FileStore> iterator() {

                return new FileStoreIterator();

            }

        };

    }

    @Override

    public final Path getPath(String first, String... more) {

        String path;

        if (more.length == 0) {

            path = first;

        } else {

            StringBuilder sb = new StringBuilder();

            sb.append(first);

            for (String segment: more) {

                if (segment.length() > 0) {

                    if (sb.length() > 0)

                        sb.append('/');

                    sb.append(segment);

                }

            }

            path = sb.toString();

        }

        return new UnixPath(this, path);

    }

    @Override

    public PathMatcher getPathMatcher(String syntaxAndInput) {

        int pos = syntaxAndInput.indexOf(':');

        if (pos <= 0 || pos == syntaxAndInput.length())

            throw new IllegalArgumentException();

        String syntax = syntaxAndInput.substring(0, pos);

        String input = syntaxAndInput.substring(pos+1);

        String expr;

        if (syntax.equalsIgnoreCase(GLOB_SYNTAX)) {

            expr = Globs.toUnixRegexPattern(input);

        } else {

            if (syntax.equalsIgnoreCase(REGEX_SYNTAX)) {

                expr = input;

            } else {

                throw new UnsupportedOperationException("Syntax '" + syntax +

                    "' not recognized");

            }

        }

        // return matcher

        final Pattern pattern = compilePathMatchPattern(expr);

        return new PathMatcher() {

            @Override

            public boolean matches(Path path) {

                return pattern.matcher(path.toString()).matches();

            }

        };

    }

    private static final String GLOB_SYNTAX = "glob";

    private static final String REGEX_SYNTAX = "regex";

    @Override

    public final UserPrincipalLookupService getUserPrincipalLookupService() {

        return LookupService.instance;

    }

    private static class LookupService {

        static final UserPrincipalLookupService instance =

            new UserPrincipalLookupService() {

                @Override

                public UserPrincipal lookupPrincipalByName(String name)

                    throws IOException

                {

                    return UnixUserPrincipals.lookupUser(name);

                }

                @Override

                public GroupPrincipal lookupPrincipalByGroupName(String group)

                    throws IOException

                {

                    return UnixUserPrincipals.lookupGroup(group);

                }

            };

    }

    // Override if the platform has different path match requirement, such as

    // case insensitive or Unicode canonical equal on MacOSX

    Pattern compilePathMatchPattern(String expr) {

        return Pattern.compile(expr);

    }

    // Override if the platform uses different Unicode normalization form

    // for native file path. For example on MacOSX, the native path is stored

    // in Unicode NFD form.

    char[] normalizeNativePath(char[] path) {

        return path;

    }

    // Override if the native file path use non-NFC form. For example on MacOSX,

    // the native path is stored in Unicode NFD form, the path need to be

    // normalized back to NFC before passed back to Java level.

    String normalizeJavaPath(String path) {

        return path;

    }

}