/*

 * 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

 * particular file as subject to the "Classpath" exception as provided

 *

 * 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.

 *

 */

package sun.nio.fs;

import java.nio.file.*;

import java.io.IOException;

import java.util.*;

import com.sun.nio.file.ExtendedWatchEventModifier;

import sun.misc.Unsafe;

import static sun.nio.fs.WindowsNativeDispatcher.*;

import static sun.nio.fs.WindowsConstants.*;

/*

 * Win32 implementation of WatchService based on ReadDirectoryChangesW.

 */

class WindowsWatchService

    extends AbstractWatchService

{

    private final Unsafe unsafe = Unsafe.getUnsafe();

    // background thread to service I/O completion port

    private final Poller poller;

    /**

     * Creates an I/O completion port and a daemon thread to service it

     */

    WindowsWatchService(WindowsFileSystem fs) throws IOException {

        // create I/O completion port

        long port = 0L;

        try {

            port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0);

        } catch (WindowsException x) {

            throw new IOException(x.getMessage());

        }

        this.poller = new Poller(fs, this, port);

        this.poller.start();

    }

    @Override

    WatchKey register(Path path,

                      WatchEvent.Kind<?>[] events,

                      WatchEvent.Modifier... modifiers)

         throws IOException

    {

        // delegate to poller

        return poller.register(path, events, modifiers);

    }

    @Override

    void implClose() throws IOException {

        // delegate to poller

        poller.close();

    }

    /**

     * Windows implementation of WatchKey.

     */

    private class WindowsWatchKey extends AbstractWatchKey {

        // file key (used to detect existing registrations)

        private FileKey fileKey;

        // handle to directory

        private volatile long handle = INVALID_HANDLE_VALUE;

        // interest events

        private Set<? extends WatchEvent.Kind<?>> events;

        // subtree

        private boolean watchSubtree;

        // buffer for change events

        private NativeBuffer buffer;

        // pointer to bytes returned (in buffer)

        private long countAddress;

        // pointer to overlapped structure (in buffer)

        private long overlappedAddress;

        // completion key (used to map I/O completion to WatchKey)

        private int completionKey;

        WindowsWatchKey(AbstractWatchService watcher, FileKey fileKey) {

            super(watcher);

            this.fileKey = fileKey;

        }

        WindowsWatchKey init(long handle,

                             Set<? extends WatchEvent.Kind<?>> events,

                             boolean watchSubtree,

                             NativeBuffer buffer,

                             long countAddress,

                             long overlappedAddress,

                             int completionKey)

        {

            this.handle = handle;

            this.events = events;

            this.watchSubtree = watchSubtree;

            this.buffer = buffer;

            this.countAddress = countAddress;

            this.overlappedAddress = overlappedAddress;

            this.completionKey = completionKey;

            return this;

        }

        long handle() {

            return handle;

        }

        Set<? extends WatchEvent.Kind<?>> events() {

            return events;

        }

        void setEvents(Set<? extends WatchEvent.Kind<?>> events) {

            this.events = events;

        }

        boolean watchSubtree() {

            return watchSubtree;

        }

        NativeBuffer buffer() {

            return buffer;

        }

        long countAddress() {

            return countAddress;

        }

        long overlappedAddress() {

            return overlappedAddress;

        }

        FileKey fileKey() {

            return fileKey;

        }

        int completionKey() {

            return completionKey;

        }

        // close directory and release buffer

        void releaseResources() {

            CloseHandle(handle);

            buffer.cleaner().clean();

        }

        // Invalidate key by closing directory and releasing buffer

        void invalidate() {

            releaseResources();

            handle = INVALID_HANDLE_VALUE;

            buffer = null;

            countAddress = 0;

            overlappedAddress = 0;

        }

        @Override

        public boolean isValid() {

            return handle != INVALID_HANDLE_VALUE;

        }

        @Override

        public void cancel() {

            if (isValid()) {

                // delegate to poller

                poller.cancel(this);

            }

        }

    }

    // file key to unique identify (open) directory

    private static class FileKey {

        private final int volSerialNumber;

        private final int fileIndexHigh;

        private final int fileIndexLow;

        FileKey(int volSerialNumber, int fileIndexHigh, int fileIndexLow) {

            this.volSerialNumber = volSerialNumber;

            this.fileIndexHigh = fileIndexHigh;

            this.fileIndexLow = fileIndexLow;

        }

        @Override

        public int hashCode() {

            return volSerialNumber ^ fileIndexHigh ^ fileIndexLow;

        }

        @Override

        public boolean equals(Object obj) {

            if (obj == this)

                return true;

            if (!(obj instanceof FileKey))

                return false;

            FileKey other = (FileKey)obj;

            if (this.volSerialNumber != other.volSerialNumber) return false;

            if (this.fileIndexHigh != other.fileIndexHigh) return false;

            if (this.fileIndexLow != other.fileIndexLow) return false;

            return true;

        }

    }

    // all change events

    private static final int ALL_FILE_NOTIFY_EVENTS =

        FILE_NOTIFY_CHANGE_FILE_NAME |

        FILE_NOTIFY_CHANGE_DIR_NAME |

        FILE_NOTIFY_CHANGE_ATTRIBUTES  |

        FILE_NOTIFY_CHANGE_SIZE |

        FILE_NOTIFY_CHANGE_LAST_WRITE |

        FILE_NOTIFY_CHANGE_CREATION |

        FILE_NOTIFY_CHANGE_SECURITY;

    /**

     * Background thread to service I/O completion port.

     */

    private class Poller extends AbstractPoller {

        /*

         * typedef struct _OVERLAPPED {

         *     DWORD  Internal;

         *     DWORD  InternalHigh;

         *     DWORD  Offset;

         *     DWORD  OffsetHigh;

         *     HANDLE hEvent;

         * } OVERLAPPED;

         */

        private static final short SIZEOF_DWORD         = 4;

        private static final short SIZEOF_OVERLAPPED    = 32; // 20 on 32-bit

        /*

         * typedef struct _FILE_NOTIFY_INFORMATION {

         *     DWORD NextEntryOffset;

         *     DWORD Action;

         *     DWORD FileNameLength;

         *     WCHAR FileName[1];

         * } FileNameLength;

         */

        private static final short OFFSETOF_NEXTENTRYOFFSET = 0;

        private static final short OFFSETOF_ACTION          = 4;

        private static final short OFFSETOF_FILENAMELENGTH  = 8;

        private static final short OFFSETOF_FILENAME        = 12;

        // size of per-directory buffer for events (FIXME - make this configurable)

        private static final int CHANGES_BUFFER_SIZE    = 16 * 1024;

        private final WindowsFileSystem fs;

        private final WindowsWatchService watcher;

        private final long port;

        // maps completion key to WatchKey

        private final Map<Integer,WindowsWatchKey> int2key;

        // maps file key to WatchKey

        private final Map<FileKey,WindowsWatchKey> fk2key;

        // unique completion key for each directory

        private int lastCompletionKey;

        Poller(WindowsFileSystem fs, WindowsWatchService watcher, long port) {

            this.fs = fs;

            this.watcher = watcher;

            this.port = port;

            this.int2key = new HashMap<Integer,WindowsWatchKey>();

            this.fk2key = new HashMap<FileKey,WindowsWatchKey>();

            this.lastCompletionKey = 0;

        }

        @Override

        void wakeup() throws IOException {

            try {

                PostQueuedCompletionStatus(port, 0);

            } catch (WindowsException x) {

                throw new IOException(x.getMessage());

            }

        }

        /**

         * Register a directory for changes as follows:

         *

         * 1. Open directory

         * 2. Read its attributes (and check it really is a directory)

         * 3. Assign completion key and associated handle with completion port

         * 4. Call ReadDirectoryChangesW to start (async) read of changes

         * 5. Create or return existing key representing registration

         */

        @Override

        Object implRegister(Path obj,

                            Set<? extends WatchEvent.Kind<?>> events,

                            WatchEvent.Modifier... modifiers)

        {

            WindowsPath dir = (WindowsPath)obj;

            boolean watchSubtree = false;

            // FILE_TREE modifier allowed

            for (WatchEvent.Modifier modifier: modifiers) {

                if (modifier == ExtendedWatchEventModifier.FILE_TREE) {

                    watchSubtree = true;

                    continue;

                } else {

                    if (modifier == null)

                        return new NullPointerException();

                    if (modifier instanceof com.sun.nio.file.SensitivityWatchEventModifier)

                        continue; // ignore

                    return new UnsupportedOperationException("Modifier not supported");

                }

            }

            // open directory

            long handle = -1L;

            try {

                handle = CreateFile(dir.getPathForWin32Calls(),

                                    FILE_LIST_DIRECTORY,

                                    (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),

                                    OPEN_EXISTING,

                                    FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED);

            } catch (WindowsException x) {

                return x.asIOException(dir);

            }

            boolean registered = false;

            try {

                // read attributes and check file is a directory

                WindowsFileAttributes attrs = null;

                try {

                    attrs = WindowsFileAttributes.readAttributes(handle);

                } catch (WindowsException x) {

                    return x.asIOException(dir);

                }

                if (!attrs.isDirectory()) {

                    return new NotDirectoryException(dir.getPathForExceptionMessage());

                }

                // check if this directory is already registered

                FileKey fk = new FileKey(attrs.volSerialNumber(),

                                         attrs.fileIndexHigh(),

                                         attrs.fileIndexLow());

                WindowsWatchKey existing = fk2key.get(fk);

                // if already registered and we're not changing the subtree

                // modifier then simply update the event and return the key.

                if (existing != null && watchSubtree == existing.watchSubtree()) {

                    existing.setEvents(events);

                    return existing;

                }

                // unique completion key (skip 0)

                int completionKey = ++lastCompletionKey;

                if (completionKey == 0)

                    completionKey = ++lastCompletionKey;

                // associate handle with completion port

                try {

                    CreateIoCompletionPort(handle, port, completionKey);

                } catch (WindowsException x) {

                    return new IOException(x.getMessage());

                }

                // allocate memory for events, including space for other structures

                // needed to do overlapped I/O

                int size = CHANGES_BUFFER_SIZE + SIZEOF_DWORD + SIZEOF_OVERLAPPED;

                NativeBuffer buffer = NativeBuffers.getNativeBuffer(size);

                long bufferAddress = buffer.address();

                long overlappedAddress = bufferAddress + size - SIZEOF_OVERLAPPED;

                long countAddress = overlappedAddress - SIZEOF_DWORD;

                // start async read of changes to directory

                try {

                    ReadDirectoryChangesW(handle,

                                          bufferAddress,

                                          CHANGES_BUFFER_SIZE,

                                          watchSubtree,

                                          ALL_FILE_NOTIFY_EVENTS,

                                          countAddress,

                                          overlappedAddress);

                } catch (WindowsException x) {

                    buffer.release();

                    return new IOException(x.getMessage());

                }

                WindowsWatchKey watchKey;

                if (existing == null) {

                    // not registered so create new watch key

                    watchKey = new WindowsWatchKey(watcher, fk)

                        .init(handle, events, watchSubtree, buffer, countAddress,

                              overlappedAddress, completionKey);

                    // map file key to watch key

                    fk2key.put(fk, watchKey);

                } else {

                    // directory already registered so need to:

                    // 1. remove mapping from old completion key to existing watch key

                    // 2. release existing key's resources (handle/buffer)

                    // 3. re-initialize key with new handle/buffer

                    int2key.remove(existing.completionKey());

                    existing.releaseResources();

                    watchKey = existing.init(handle, events, watchSubtree, buffer,

                        countAddress, overlappedAddress, completionKey);

                }

                // map completion map to watch key

                int2key.put(completionKey, watchKey);

                registered = true;

                return watchKey;

            } finally {

                if (!registered) CloseHandle(handle);

            }

        }

        // cancel single key

        @Override

        void implCancelKey(WatchKey obj) {

            WindowsWatchKey key = (WindowsWatchKey)obj;

            if (key.isValid()) {

                fk2key.remove(key.fileKey());

                int2key.remove(key.completionKey());

                key.invalidate();

            }

        }

        // close watch service

        @Override

        void implCloseAll() {

            // cancel all keys

            for (Map.Entry<Integer,WindowsWatchKey> entry: int2key.entrySet()) {

                entry.getValue().invalidate();

            }

            fk2key.clear();

            int2key.clear();

            // close I/O completion port

            CloseHandle(port);

        }

        // Translate file change action into watch event

        private WatchEvent.Kind<?> translateActionToEvent(int action)

        {

            switch (action) {

                case FILE_ACTION_MODIFIED :

                    return StandardWatchEventKind.ENTRY_MODIFY;

                case FILE_ACTION_ADDED :

                case FILE_ACTION_RENAMED_NEW_NAME :

                    return StandardWatchEventKind.ENTRY_CREATE;

                case FILE_ACTION_REMOVED :

                case FILE_ACTION_RENAMED_OLD_NAME :

                    return StandardWatchEventKind.ENTRY_DELETE;

                default :

                    return null;  // action not recognized

            }

        }

        // process events (list of FILE_NOTIFY_INFORMATION structures)

        private void processEvents(WindowsWatchKey key, int size) {

            long address = key.buffer().address();

            int nextOffset;

            do {

                int action = unsafe.getInt(address + OFFSETOF_ACTION);

                // map action to event

                WatchEvent.Kind<?> kind = translateActionToEvent(action);

                if (key.events().contains(kind)) {

                    // copy the name

                    int nameLengthInBytes = unsafe.getInt(address + OFFSETOF_FILENAMELENGTH);

                    if ((nameLengthInBytes % 2) != 0) {

                        throw new AssertionError("FileNameLength.FileNameLength is not a multiple of 2");

                    }

                    char[] nameAsArray = new char[nameLengthInBytes/2];

                    unsafe.copyMemory(null, address + OFFSETOF_FILENAME, nameAsArray,

                        Unsafe.ARRAY_CHAR_BASE_OFFSET, nameLengthInBytes);

                    // create FileName and queue event

                    WindowsPath name = WindowsPath

                        .createFromNormalizedPath(fs, new String(nameAsArray));

                    key.signalEvent(kind, name);

                }

                // next event

                nextOffset = unsafe.getInt(address + OFFSETOF_NEXTENTRYOFFSET);

                address += (long)nextOffset;

            } while (nextOffset != 0);

        }

        /**

         * Poller main loop

         */

        @Override

        public void run() {

            for (;;) {

                CompletionStatus info = null;

                try {

                    info = GetQueuedCompletionStatus(port);

                } catch (WindowsException x) {

                    // this should not happen

                    x.printStackTrace();

                    return;

                }

                // wakeup

                if (info.completionKey() == 0) {

                    boolean shutdown = processRequests();