/*

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

import java.nio.file.*;

import java.nio.file.attribute.*;

import java.nio.channels.*;

import java.util.*;

import java.io.IOException;

import java.security.AccessController;

import java.security.PrivilegedAction;

/**

 * Base implementation of FileStore for Unix/like implementations.

 */

abstract class UnixFileStore

    extends FileStore

{

    // original path of file that identified file system

    private final UnixPath file;

    // device ID

    private final long dev;

    // entry in the mount tab

    private final UnixMountEntry entry;

    // return the device ID where the given file resides

    private static long devFor(UnixPath file) throws IOException {

        try {

            return UnixFileAttributes.get(file, true).dev();

        } catch (UnixException x) {

            x.rethrowAsIOException(file);

            return 0L;  // keep compiler happy

        }

    }

    UnixFileStore(UnixPath file) throws IOException {

        this.file = file;

        this.dev = devFor(file);

        this.entry = findMountEntry();

    }

    UnixFileStore(UnixFileSystem fs, UnixMountEntry entry) throws IOException {

        this.file = new UnixPath(fs, entry.dir());

        this.dev = (entry.dev() == 0L) ? devFor(this.file) : entry.dev();

        this.entry = entry;

    }

    /**

     * Find the mount entry for the file store

     */

    abstract UnixMountEntry findMountEntry() throws IOException;

    UnixPath file() {

        return file;

    }

    long dev() {

        return dev;

    }

    UnixMountEntry entry() {

        return entry;

    }

    @Override

    public String name() {

        return entry.name();

    }

    @Override

    public String type() {

        return entry.fstype();

    }

    @Override

    public boolean isReadOnly() {

        return entry.isReadOnly();

    }

    // uses statvfs to read the file system information

    private UnixFileStoreAttributes readAttributes() throws IOException {

        try {

            return UnixFileStoreAttributes.get(file);

        } catch (UnixException x) {

            x.rethrowAsIOException(file);

            return null;    // keep compile happy

        }

    }

    @Override

    public long getTotalSpace() throws IOException {

        UnixFileStoreAttributes attrs = readAttributes();

        return attrs.blockSize() * attrs.totalBlocks();

    }

    @Override

    public long getUsableSpace() throws IOException {

       UnixFileStoreAttributes attrs = readAttributes();

       return attrs.blockSize() * attrs.availableBlocks();

    }

    @Override

    public long getBlockSize() throws IOException {

       UnixFileStoreAttributes attrs = readAttributes();

       return attrs.blockSize();

    }

    @Override

    public long getUnallocatedSpace() throws IOException {

        UnixFileStoreAttributes attrs = readAttributes();

        return attrs.blockSize() * attrs.freeBlocks();

    }

    @Override

    public <V extends FileStoreAttributeView> V getFileStoreAttributeView(Class<V> view)

    {

        if (view == null)

            throw new NullPointerException();

        return (V) null;

    }

    @Override

    public Object getAttribute(String attribute) throws IOException {

        if (attribute.equals("totalSpace"))

            return getTotalSpace();

        if (attribute.equals("usableSpace"))

            return getUsableSpace();

        if (attribute.equals("unallocatedSpace"))

            return getUnallocatedSpace();

        throw new UnsupportedOperationException("'" + attribute + "' not recognized");

    }

    @Override

    public boolean supportsFileAttributeView(Class<? extends FileAttributeView> type) {

        if (type == null)

            throw new NullPointerException();

        if (type == BasicFileAttributeView.class)

            return true;

        if (type == PosixFileAttributeView.class ||

            type == FileOwnerAttributeView.class)

        {

            // lookup fstypes.properties

            FeatureStatus status = checkIfFeaturePresent("posix");

            // assume supported if UNKNOWN

            return (status != FeatureStatus.NOT_PRESENT);

        }

        return false;

    }

    @Override

    public boolean supportsFileAttributeView(String name) {

        if (name.equals("basic") || name.equals("unix"))

            return true;

        if (name.equals("posix"))

            return supportsFileAttributeView(PosixFileAttributeView.class);

        if (name.equals("owner"))

            return supportsFileAttributeView(FileOwnerAttributeView.class);

        return false;

    }

    @Override

    public boolean equals(Object ob) {

        if (ob == this)

            return true;

        if (!(ob instanceof UnixFileStore))

            return false;

        UnixFileStore other = (UnixFileStore)ob;

        return (this.dev == other.dev) &&

               Arrays.equals(this.entry.dir(), other.entry.dir()) &&

               this.entry.name().equals(other.entry.name());

    }

    @Override

    public int hashCode() {

        return (int)(dev ^ (dev >>> 32)) ^ Arrays.hashCode(entry.dir());

    }

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder(Util.toString(entry.dir()));

        sb.append(" (");

        sb.append(entry.name());

        sb.append(")");

        return sb.toString();

    }

    // -- fstypes.properties --

    private static final Object loadLock = new Object();

    private static volatile Properties props;

    enum FeatureStatus {

        PRESENT,

        NOT_PRESENT,

        UNKNOWN;

    }

    /**

     * Returns status to indicate if file system supports a given feature

     */

    FeatureStatus checkIfFeaturePresent(String feature) {

        if (props == null) {

            synchronized (loadLock) {

                if (props == null) {

                    props = AccessController.doPrivileged(

                        new PrivilegedAction<>() {

                            @Override

                            public Properties run() {

                                return loadProperties();

                            }});

                }

            }

        }

        String value = props.getProperty(type());

        if (value != null) {

            String[] values = value.split("\\s");

            for (String s: values) {

                s = s.trim().toLowerCase();

                if (s.equals(feature)) {

                    return FeatureStatus.PRESENT;

                }

                if (s.startsWith("no")) {

                    s = s.substring(2);

                    if (s.equals(feature)) {

                        return FeatureStatus.NOT_PRESENT;

                    }

                }

            }

        }

        return FeatureStatus.UNKNOWN;

    }

    private static Properties loadProperties() {

        Properties result = new Properties();

        Path file = Path.of(fstypes);

        try {

            try (ReadableByteChannel rbc = Files.newByteChannel(file)) {

                result.load(Channels.newReader(rbc, "UTF-8"));

            }

        } catch (IOException x) {

        }

        return result;

    }

}