# -*- test-case-name: twisted.conch.test.test_filetransfer -*-
#
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

from __future__ import division, absolute_import

import errno
import struct

from zope.interface import implementer

from twisted.conch.interfaces import ISFTPServer, ISFTPFile
from twisted.conch.ssh.common import NS, getNS
from twisted.internet import defer, protocol
from twisted.python import failure, log
from twisted.python.compat import (
    _PY3, range, itervalues, nativeString, networkString)



class FileTransferBase(protocol.Protocol):

    versions = (3, )

    packetTypes = {}

    def __init__(self):
        self.buf = b''
        self.otherVersion = None  # This gets set


    def sendPacket(self, kind, data):
        self.transport.write(struct.pack('!LB', len(data)+1, kind) + data)


    def dataReceived(self, data):
        self.buf += data
        while len(self.buf) > 5:
            length, kind = struct.unpack('!LB', self.buf[:5])
            if len(self.buf) < 4 + length:
                return
            data, self.buf = self.buf[5:4+length], self.buf[4+length:]
            packetType = self.packetTypes.get(kind, None)
            if not packetType:
                log.msg('no packet type for', kind)
                continue
            f = getattr(self, 'packet_{}'.format(packetType), None)
            if not f:
                log.msg('not implemented: {}'.format(packetType))
                log.msg(repr(data[4:]))
                reqId, = struct.unpack('!L', data[:4])
                self._sendStatus(reqId, FX_OP_UNSUPPORTED,
                                 "don't understand {}".format(packetType))
                # XXX not implemented
                continue
            try:
                f(data)
            except Exception:
                log.err()
                continue


    def _parseAttributes(self, data):
        (flags,) = struct.unpack('!L', data[:4])
        attrs = {}
        data = data[4:]
        if flags & FILEXFER_ATTR_SIZE == FILEXFER_ATTR_SIZE:
            (size,) = struct.unpack('!Q', data[:8])
            attrs['size'] = size
            data = data[8:]
        if flags & FILEXFER_ATTR_OWNERGROUP == FILEXFER_ATTR_OWNERGROUP:
            uid, gid = struct.unpack('!2L', data[:8])
            attrs['uid'] = uid
            attrs['gid'] = gid
            data = data[8:]
        if flags & FILEXFER_ATTR_PERMISSIONS == FILEXFER_ATTR_PERMISSIONS:
            (perms,) = struct.unpack('!L', data[:4])
            attrs['permissions'] = perms
            data = data[4:]
        if flags & FILEXFER_ATTR_ACMODTIME == FILEXFER_ATTR_ACMODTIME:
            atime, mtime = struct.unpack('!2L', data[:8])
            attrs['atime'] = atime
            attrs['mtime'] = mtime
            data = data[8:]
        if flags & FILEXFER_ATTR_EXTENDED == FILEXFER_ATTR_EXTENDED:
            (extendedCount,) = struct.unpack('!L', data[:4])
            data = data[4:]
            for i in range(extendedCount):
                (extendedType, data) = getNS(data)
                (extendedData, data) = getNS(data)
                attrs['ext_{}'.format(nativeString(extendedType))] = \
                    extendedData
        return attrs, data


    def _packAttributes(self, attrs):
        flags = 0
        data = b''
        if 'size' in attrs:
            data += struct.pack('!Q', attrs['size'])
            flags |= FILEXFER_ATTR_SIZE
        if 'uid' in attrs and 'gid' in attrs:
            data += struct.pack('!2L', attrs['uid'], attrs['gid'])
            flags |= FILEXFER_ATTR_OWNERGROUP
        if 'permissions' in attrs:
            data += struct.pack('!L', attrs['permissions'])
            flags |= FILEXFER_ATTR_PERMISSIONS
        if 'atime' in attrs and 'mtime' in attrs:
            data += struct.pack('!2L', attrs['atime'], attrs['mtime'])
            flags |= FILEXFER_ATTR_ACMODTIME
        extended = []
        for k in attrs:
            if k.startswith('ext_'):
                extType = NS(networkString(k[4:]))
                extData = NS(attrs[k])
                extended.append(extType + extData)
        if extended:
            data += struct.pack('!L', len(extended))
            data += b''.join(extended)
            flags |= FILEXFER_ATTR_EXTENDED
        return struct.pack('!L', flags) + data



class FileTransferServer(FileTransferBase):

    def __init__(self, data=None, avatar=None):
        FileTransferBase.__init__(self)
        self.client = ISFTPServer(avatar) # yay interfaces
        self.openFiles = {}
        self.openDirs = {}


    def packet_INIT(self, data):
        (version,) = struct.unpack('!L', data[:4])
        self.version = min(list(self.versions) + [version])
        data = data[4:]
        ext = {}
        while data:
            extName, data = getNS(data)
            extData, data = getNS(data)
            ext[extName] = extData
        ourExt = self.client.gotVersion(version, ext)
        ourExtData = b""
        for (k, v) in ourExt.items():
            ourExtData += NS(k) + NS(v)
        self.sendPacket(FXP_VERSION, struct.pack('!L', self.version) +
                        ourExtData)


    def packet_OPEN(self, data):
        requestId = data[:4]
        data = data[4:]
        filename, data = getNS(data)
        (flags,) = struct.unpack('!L', data[:4])
        data = data[4:]
        attrs, data = self._parseAttributes(data)
        assert data == b'', 'still have data in OPEN: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.openFile, filename, flags, attrs)
        d.addCallback(self._cbOpenFile, requestId)
        d.addErrback(self._ebStatus, requestId, b"open failed")


    def _cbOpenFile(self, fileObj, requestId):
        fileId = networkString(str(hash(fileObj)))
        if fileId in self.openFiles:
            raise KeyError('id already open')
        self.openFiles[fileId] = fileObj
        self.sendPacket(FXP_HANDLE, requestId + NS(fileId))


    def packet_CLOSE(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        assert data == b'', 'still have data in CLOSE: {!r}'.format(data)
        if handle in self.openFiles:
            fileObj = self.openFiles[handle]
            d = defer.maybeDeferred(fileObj.close)
            d.addCallback(self._cbClose, handle, requestId)
            d.addErrback(self._ebStatus, requestId, b"close failed")
        elif handle in self.openDirs:
            dirObj = self.openDirs[handle][0]
            d = defer.maybeDeferred(dirObj.close)
            d.addCallback(self._cbClose, handle, requestId, 1)
            d.addErrback(self._ebStatus, requestId, b"close failed")
        else:
            self._ebClose(failure.Failure(KeyError()), requestId)


    def _cbClose(self, result, handle, requestId, isDir=0):
        if isDir:
            del self.openDirs[handle]
        else:
            del self.openFiles[handle]
        self._sendStatus(requestId, FX_OK, b'file closed')


    def packet_READ(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        (offset, length), data = struct.unpack('!QL', data[:12]), data[12:]
        assert data == b'', 'still have data in READ: {!r}'.format(data)
        if handle not in self.openFiles:
            self._ebRead(failure.Failure(KeyError()), requestId)
        else:
            fileObj = self.openFiles[handle]
            d = defer.maybeDeferred(fileObj.readChunk, offset, length)
            d.addCallback(self._cbRead, requestId)
            d.addErrback(self._ebStatus, requestId, b"read failed")


    def _cbRead(self, result, requestId):
        if result == b'':  # Python's read will return this for EOF
            raise EOFError()
        self.sendPacket(FXP_DATA, requestId + NS(result))


    def packet_WRITE(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        offset, = struct.unpack('!Q', data[:8])
        data = data[8:]
        writeData, data = getNS(data)
        assert data == b'', 'still have data in WRITE: {!r}'.format(data)
        if handle not in self.openFiles:
            self._ebWrite(failure.Failure(KeyError()), requestId)
        else:
            fileObj = self.openFiles[handle]
            d = defer.maybeDeferred(fileObj.writeChunk, offset, writeData)
            d.addCallback(self._cbStatus, requestId, b"write succeeded")
            d.addErrback(self._ebStatus, requestId, b"write failed")


    def packet_REMOVE(self, data):
        requestId = data[:4]
        data = data[4:]
        filename, data = getNS(data)
        assert data == b'', 'still have data in REMOVE: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.removeFile, filename)
        d.addCallback(self._cbStatus, requestId, b"remove succeeded")
        d.addErrback(self._ebStatus, requestId, b"remove failed")


    def packet_RENAME(self, data):
        requestId = data[:4]
        data = data[4:]
        oldPath, data = getNS(data)
        newPath, data = getNS(data)
        assert data == b'', 'still have data in RENAME: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.renameFile, oldPath, newPath)
        d.addCallback(self._cbStatus, requestId, b"rename succeeded")
        d.addErrback(self._ebStatus, requestId, b"rename failed")


    def packet_MKDIR(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        attrs, data = self._parseAttributes(data)
        assert data == b'', 'still have data in MKDIR: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.makeDirectory, path, attrs)
        d.addCallback(self._cbStatus, requestId, b"mkdir succeeded")
        d.addErrback(self._ebStatus, requestId, b"mkdir failed")


    def packet_RMDIR(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        assert data == b'', 'still have data in RMDIR: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.removeDirectory, path)
        d.addCallback(self._cbStatus, requestId, b"rmdir succeeded")
        d.addErrback(self._ebStatus, requestId, b"rmdir failed")


    def packet_OPENDIR(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        assert data == b'', 'still have data in OPENDIR: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.openDirectory, path)
        d.addCallback(self._cbOpenDirectory, requestId)
        d.addErrback(self._ebStatus, requestId, b"opendir failed")


    def _cbOpenDirectory(self, dirObj, requestId):
        handle = networkString((str(hash(dirObj))))
        if handle in self.openDirs:
            raise KeyError("already opened this directory")
        self.openDirs[handle] = [dirObj, iter(dirObj)]
        self.sendPacket(FXP_HANDLE, requestId + NS(handle))


    def packet_READDIR(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        assert data == b'', 'still have data in READDIR: {!r}'.format(data)
        if handle not in self.openDirs:
            self._ebStatus(failure.Failure(KeyError()), requestId)
        else:
            dirObj, dirIter = self.openDirs[handle]
            d = defer.maybeDeferred(self._scanDirectory, dirIter, [])
            d.addCallback(self._cbSendDirectory, requestId)
            d.addErrback(self._ebStatus, requestId, b"scan directory failed")


    def _scanDirectory(self, dirIter, f):
        while len(f) < 250:
            try:
                info = next(dirIter)
            except StopIteration:
                if not f:
                    raise EOFError
                return f
            if isinstance(info, defer.Deferred):
                info.addCallback(self._cbScanDirectory, dirIter, f)
                return
            else:
                f.append(info)
        return f


    def _cbScanDirectory(self, result, dirIter, f):
        f.append(result)
        return self._scanDirectory(dirIter, f)


    def _cbSendDirectory(self, result, requestId):
        data = b''
        for (filename, longname, attrs) in result:
            data += NS(filename)
            data += NS(longname)
            data += self._packAttributes(attrs)
        self.sendPacket(FXP_NAME, requestId +
                        struct.pack('!L', len(result))+data)


    def packet_STAT(self, data, followLinks=1):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        assert data == b'', 'still have data in STAT/LSTAT: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.getAttrs, path, followLinks)
        d.addCallback(self._cbStat, requestId)
        d.addErrback(self._ebStatus, requestId, b'stat/lstat failed')


    def packet_LSTAT(self, data):
        self.packet_STAT(data, 0)


    def packet_FSTAT(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        assert data == b'', 'still have data in FSTAT: {!r}'.format(data)
        if handle not in self.openFiles:
            self._ebStatus(failure.Failure(KeyError(
                '{} not in self.openFiles'.format(handle))), requestId)
        else:
            fileObj = self.openFiles[handle]
            d = defer.maybeDeferred(fileObj.getAttrs)
            d.addCallback(self._cbStat, requestId)
            d.addErrback(self._ebStatus, requestId, b'fstat failed')


    def _cbStat(self, result, requestId):
        data = requestId + self._packAttributes(result)
        self.sendPacket(FXP_ATTRS, data)


    def packet_SETSTAT(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        attrs, data = self._parseAttributes(data)
        if data != b'':
            log.msg('WARN: still have data in SETSTAT: {!r}'.format(data))
        d = defer.maybeDeferred(self.client.setAttrs, path, attrs)
        d.addCallback(self._cbStatus, requestId, b'setstat succeeded')
        d.addErrback(self._ebStatus, requestId, b'setstat failed')


    def packet_FSETSTAT(self, data):
        requestId = data[:4]
        data = data[4:]
        handle, data = getNS(data)
        attrs, data = self._parseAttributes(data)
        assert data == b'', 'still have data in FSETSTAT: {!r}'.format(data)
        if handle not in self.openFiles:
            self._ebStatus(failure.Failure(KeyError()), requestId)
        else:
            fileObj = self.openFiles[handle]
            d = defer.maybeDeferred(fileObj.setAttrs, attrs)
            d.addCallback(self._cbStatus, requestId, b'fsetstat succeeded')
            d.addErrback(self._ebStatus, requestId, b'fsetstat failed')


    def packet_READLINK(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        assert data == b'', 'still have data in READLINK: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.readLink, path)
        d.addCallback(self._cbReadLink, requestId)
        d.addErrback(self._ebStatus, requestId, b'readlink failed')


    def _cbReadLink(self, result, requestId):
        self._cbSendDirectory([(result, b'', {})], requestId)


    def packet_SYMLINK(self, data):
        requestId = data[:4]
        data = data[4:]
        linkPath, data = getNS(data)
        targetPath, data = getNS(data)
        d = defer.maybeDeferred(self.client.makeLink, linkPath, targetPath)
        d.addCallback(self._cbStatus, requestId, b'symlink succeeded')
        d.addErrback(self._ebStatus, requestId, b'symlink failed')


    def packet_REALPATH(self, data):
        requestId = data[:4]
        data = data[4:]
        path, data = getNS(data)
        assert data == b'', 'still have data in REALPATH: {!r}'.format(data)
        d = defer.maybeDeferred(self.client.realPath, path)
        d.addCallback(self._cbReadLink, requestId)  # Same return format
        d.addErrback(self._ebStatus, requestId, b'realpath failed')


    def packet_EXTENDED(self, data):
        requestId = data[:4]
        data = data[4:]
        extName, extData = getNS(data)
        d = defer.maybeDeferred(self.client.extendedRequest, extName, extData)
        d.addCallback(self._cbExtended, requestId)
        d.addErrback(self._ebStatus, requestId,
                     b'extended ' + extName + b' failed')


    def _cbExtended(self, data, requestId):
        self.sendPacket(FXP_EXTENDED_REPLY, requestId + data)


    def _cbStatus(self, result, requestId, msg=b"request succeeded"):
        self._sendStatus(requestId, FX_OK, msg)


    def _ebStatus(self, reason, requestId, msg=b"request failed"):
        code = FX_FAILURE
        message = msg
        if isinstance(reason.value, (IOError, OSError)):
            if reason.value.errno == errno.ENOENT:  # No such file
                code = FX_NO_SUCH_FILE
                message = networkString(reason.value.strerror)
            elif reason.value.errno == errno.EACCES:  # Permission denied
                code = FX_PERMISSION_DENIED
                message = networkString(reason.value.strerror)
            elif reason.value.errno == errno.EEXIST:
                code = FX_FILE_ALREADY_EXISTS
            else:
                log.err(reason)
        elif isinstance(reason.value, EOFError):  # EOF
            code = FX_EOF
            if reason.value.args:
                message = networkString(reason.value.args[0])
        elif isinstance(reason.value, NotImplementedError):
            code = FX_OP_UNSUPPORTED
            if reason.value.args:
                message = networkString(reason.value.args[0])
        elif isinstance(reason.value, SFTPError):
            code = reason.value.code
            message = networkString(reason.value.message)
        else:
            log.err(reason)
        self._sendStatus(requestId, code, message)


    def _sendStatus(self, requestId, code, message, lang=b''):
        """
        Helper method to send a FXP_STATUS message.
        """
        data = requestId + struct.pack('!L', code)
        data += NS(message)
        data += NS(lang)
        self.sendPacket(FXP_STATUS, data)


    def connectionLost(self, reason):
        """
        Clean all opened files and directories.
        """
        for fileObj in self.openFiles.values():
            fileObj.close()
        self.openFiles = {}
        for (dirObj, dirIter) in self.openDirs.values():
            dirObj.close()
        self.openDirs = {}



class FileTransferClient(FileTransferBase):

    def __init__(self, extData={}):
        """
        @param extData: a dict of extended_name : extended_data items
        to be sent to the server.
        """
        FileTransferBase.__init__(self)
        self.extData = {}
        self.counter = 0
        self.openRequests = {} # id -> Deferred


    def connectionMade(self):
        data = struct.pack('!L', max(self.versions))
        for (k, v) in itervalues(self.extData):
            data += NS(k) + NS(v)
        self.sendPacket(FXP_INIT, data)


    def _sendRequest(self, msg, data):
        data = struct.pack('!L', self.counter) + data
        d = defer.Deferred()
        self.openRequests[self.counter] = d
        self.counter += 1
        self.sendPacket(msg, data)
        return d


    def _parseRequest(self, data):
        (id,) = struct.unpack('!L', data[:4])
        d = self.openRequests[id]
        del self.openRequests[id]
        return d, data[4:]


    def openFile(self, filename, flags, attrs):
        """
        Open a file.

        This method returns a L{Deferred} that is called back with an object
        that provides the L{ISFTPFile} interface.

        @type filename: L{bytes}
        @param filename: a string representing the file to open.

        @param flags: an integer of the flags to open the file with, ORed together.
        The flags and their values are listed at the bottom of this file.

        @param attrs: a list of attributes to open the file with.  It is a
        dictionary, consisting of 0 or more keys.  The possible keys are::

            size: the size of the file in bytes
            uid: the user ID of the file as an integer
            gid: the group ID of the file as an integer
            permissions: the permissions of the file with as an integer.
            the bit representation of this field is defined by POSIX.
            atime: the access time of the file as seconds since the epoch.
            mtime: the modification time of the file as seconds since the epoch.
            ext_*: extended attributes.  The server is not required to
            understand this, but it may.

        NOTE: there is no way to indicate text or binary files.  it is up
        to the SFTP client to deal with this.
        """
        data = NS(filename) + struct.pack('!L', flags) + self._packAttributes(attrs)
        d = self._sendRequest(FXP_OPEN, data)
        d.addCallback(self._cbOpenHandle, ClientFile, filename)
        return d


    def _cbOpenHandle(self, handle, handleClass, name):
        """
        Callback invoked when an OPEN or OPENDIR request succeeds.

        @param handle: The handle returned by the server
        @type handle: L{bytes}
        @param handleClass: The class that will represent the
        newly-opened file or directory to the user (either L{ClientFile} or
        L{ClientDirectory}).
        @param name: The name of the file or directory represented
        by C{handle}.
        @type name: L{bytes}
        """
        cb = handleClass(self, handle)
        cb.name = name
        return cb


    def removeFile(self, filename):
        """
        Remove the given file.

        This method returns a Deferred that is called back when it succeeds.

        @type filename: L{bytes}
        @param filename: the name of the file as a string.
        """
        return self._sendRequest(FXP_REMOVE, NS(filename))


    def renameFile(self, oldpath, newpath):
        """
        Rename the given file.

        This method returns a Deferred that is called back when it succeeds.

        @type oldpath: L{bytes}
        @param oldpath: the current location of the file.
        @type newpath: L{bytes}
        @param newpath: the new file name.
        """
        return self._sendRequest(FXP_RENAME, NS(oldpath)+NS(newpath))


    def makeDirectory(self, path, attrs):
        """
        Make a directory.

        This method returns a Deferred that is called back when it is
        created.

        @type path: L{bytes}
        @param path: the name of the directory to create as a string.

        @param attrs: a dictionary of attributes to create the directory
        with.  Its meaning is the same as the attrs in the openFile method.
        """
        return self._sendRequest(FXP_MKDIR, NS(path)+self._packAttributes(attrs))


    def removeDirectory(self, path):
        """
        Remove a directory (non-recursively)

        It is an error to remove a directory that has files or directories in
        it.

        This method returns a Deferred that is called back when it is removed.

        @type path: L{bytes}
        @param path: the directory to remove.
        """
        return self._sendRequest(FXP_RMDIR, NS(path))


    def openDirectory(self, path):
        """
        Open a directory for scanning.

        This method returns a Deferred that is called back with an iterable
        object that has a close() method.

        The close() method is called when the client is finished reading
        from the directory.  At this point, the iterable will no longer
        be used.

        The iterable returns triples of the form (filename, longname, attrs)
        or a Deferred that returns the same.  The sequence must support
        __getitem__, but otherwise may be any 'sequence-like' object.

        filename is the name of the file relative to the directory.
        logname is an expanded format of the filename.  The recommended format
        is:
        -rwxr-xr-x   1 mjos     staff      348911 Mar 25 14:29 t-filexfer
        1234567890 123 12345678 12345678 12345678 123456789012

        The first line is sample output, the second is the length of the field.
        The fields are: permissions, link count, user owner, group owner,
        size in bytes, modification time.

        attrs is a dictionary in the format of the attrs argument to openFile.

        @type path: L{bytes}
        @param path: the directory to open.
        """
        d = self._sendRequest(FXP_OPENDIR, NS(path))
        d.addCallback(self._cbOpenHandle, ClientDirectory, path)
        return d


    def getAttrs(self, path, followLinks=0):
        """
        Return the attributes for the given path.

        This method returns a dictionary in the same format as the attrs
        argument to openFile or a Deferred that is called back with same.

        @type path: L{bytes}
        @param path: the path to return attributes for as a string.
        @param followLinks: a boolean.  if it is True, follow symbolic links
        and return attributes for the real path at the base.  if it is False,
        return attributes for the specified path.
        """
        if followLinks: m = FXP_STAT
        else: m = FXP_LSTAT
        return self._sendRequest(m, NS(path))


    def setAttrs(self, path, attrs):
        """
        Set the attributes for the path.

        This method returns when the attributes are set or a Deferred that is
        called back when they are.

        @type path: L{bytes}
        @param path: the path to set attributes for as a string.
        @param attrs: a dictionary in the same format as the attrs argument to
        openFile.
        """
        data = NS(path) + self._packAttributes(attrs)
        return self._sendRequest(FXP_SETSTAT, data)


    def readLink(self, path):
        """
        Find the root of a set of symbolic links.

        This method returns the target of the link, or a Deferred that
        returns the same.

        @type path: L{bytes}
        @param path: the path of the symlink to read.
        """
        d = self._sendRequest(FXP_READLINK, NS(path))
        return d.addCallback(self._cbRealPath)


    def makeLink(self, linkPath, targetPath):
        """
        Create a symbolic link.

        This method returns when the link is made, or a Deferred that
        returns the same.

        @type linkPath: L{bytes}
        @param linkPath: the pathname of the symlink as a string
        @type targetPath: L{bytes}
        @param targetPath: the path of the target of the link as a string.
        """
        return self._sendRequest(FXP_SYMLINK, NS(linkPath)+NS(targetPath))


    def realPath(self, path):
        """
        Convert any path to an absolute path.

        This method returns the absolute path as a string, or a Deferred
        that returns the same.

        @type path: L{bytes}
        @param path: the path to convert as a string.
        """
        d = self._sendRequest(FXP_REALPATH, NS(path))
        return d.addCallback(self._cbRealPath)


    def _cbRealPath(self, result):
        name, longname, attrs = result[0]
        if _PY3:
            name = name.decode("utf-8")
        return name


    def extendedRequest(self, request, data):
        """
        Make an extended request of the server.

        The method returns a Deferred that is called back with
        the result of the extended request.

        @type request: L{bytes}
        @param request: the name of the extended request to make.
        @type data: L{bytes}
        @param data: any other data that goes along with the request.
        """
        return self._sendRequest(FXP_EXTENDED, NS(request) + data)


    def packet_VERSION(self, data):
        version, = struct.unpack('!L', data[:4])
        data = data[4:]
        d = {}
        while data:
            k, data = getNS(data)
            v, data = getNS(data)
            d[k]=v
        self.version = version
        self.gotServerVersion(version, d)


    def packet_STATUS(self, data):
        d, data = self._parseRequest(data)
        code, = struct.unpack('!L', data[:4])
        data = data[4:]
        if len(data) >= 4:
            msg, data = getNS(data)
            if len(data) >= 4:
                lang, data = getNS(data)
            else:
                lang = b''
        else:
            msg = b''
            lang = b''
        if code == FX_OK:
            d.callback((msg, lang))
        elif code == FX_EOF:
            d.errback(EOFError(msg))
        elif code == FX_OP_UNSUPPORTED:
            d.errback(NotImplementedError(msg))
        else:
            d.errback(SFTPError(code, nativeString(msg), lang))


    def packet_HANDLE(self, data):
        d, data = self._parseRequest(data)
        handle, _ = getNS(data)
        d.callback(handle)


    def packet_DATA(self, data):
        d, data = self._parseRequest(data)
        d.callback(getNS(data)[0])


    def packet_NAME(self, data):
        d, data = self._parseRequest(data)
        count, = struct.unpack('!L', data[:4])
        data = data[4:]
        files = []
        for i in range(count):
            filename, data = getNS(data)
            longname, data = getNS(data)
            attrs, data = self._parseAttributes(data)
            files.append((filename, longname, attrs))
        d.callback(files)


    def packet_ATTRS(self, data):
        d, data = self._parseRequest(data)
        d.callback(self._parseAttributes(data)[0])


    def packet_EXTENDED_REPLY(self, data):
        d, data = self._parseRequest(data)
        d.callback(data)


    def gotServerVersion(self, serverVersion, extData):
        """
        Called when the client sends their version info.

        @param otherVersion: an integer representing the version of the SFTP
        protocol they are claiming.
        @param extData: a dictionary of extended_name : extended_data items.
        These items are sent by the client to indicate additional features.
        """



@implementer(ISFTPFile)
class ClientFile:
    def __init__(self, parent, handle):
        self.parent = parent
        self.handle = NS(handle)


    def close(self):
        return self.parent._sendRequest(FXP_CLOSE, self.handle)


    def readChunk(self, offset, length):
        data = self.handle + struct.pack("!QL", offset, length)
        return self.parent._sendRequest(FXP_READ, data)


    def writeChunk(self, offset, chunk):
        data = self.handle + struct.pack("!Q", offset) + NS(chunk)
        return self.parent._sendRequest(FXP_WRITE, data)


    def getAttrs(self):
        return self.parent._sendRequest(FXP_FSTAT, self.handle)


    def setAttrs(self, attrs):
        data = self.handle + self.parent._packAttributes(attrs)
        return self.parent._sendRequest(FXP_FSTAT, data)



class ClientDirectory:

    def __init__(self, parent, handle):
        self.parent = parent
        self.handle = NS(handle)
        self.filesCache = []


    def read(self):
        return self.parent._sendRequest(FXP_READDIR, self.handle)


    def close(self):
        if self.handle is None:
            return defer.succeed(None)
        d = self.parent._sendRequest(FXP_CLOSE, self.handle)
        self.handle = None
        return d


    def __iter__(self):
        return self


    def __next__(self):
        if self.filesCache:
            return self.filesCache.pop(0)
        if self.filesCache is None:
            raise StopIteration()
        d = self.read()
        d.addCallbacks(self._cbReadDir, self._ebReadDir)
        return d

    next = __next__


    def _cbReadDir(self, names):
        self.filesCache = names[1:]
        return names[0]


    def _ebReadDir(self, reason):
        reason.trap(EOFError)
        self.filesCache = None
        return failure.Failure(StopIteration())



class SFTPError(Exception):

    def __init__(self, errorCode, errorMessage, lang=''):
        Exception.__init__(self)
        self.code = errorCode
        self._message = errorMessage
        self.lang = lang


    def message(self):
        """
        A string received over the network that explains the error to a human.
        """
        # Python 2.6 deprecates assigning to the 'message' attribute of an
        # exception. We define this read-only property here in order to
        # prevent the warning about deprecation while maintaining backwards
        # compatibility with object clients that rely on the 'message'
        # attribute being set correctly. See bug #3897.
        return self._message
    message = property(message)


    def __str__(self):
        return 'SFTPError {}: {}'.format(self.code, self.message)



FXP_INIT = 1
FXP_VERSION = 2
FXP_OPEN = 3
FXP_CLOSE = 4
FXP_READ = 5
FXP_WRITE = 6
FXP_LSTAT = 7
FXP_FSTAT = 8
FXP_SETSTAT = 9
FXP_FSETSTAT = 10
FXP_OPENDIR = 11
FXP_READDIR = 12
FXP_REMOVE = 13
FXP_MKDIR = 14
FXP_RMDIR = 15
FXP_REALPATH = 16
FXP_STAT = 17
FXP_RENAME = 18
FXP_READLINK = 19
FXP_SYMLINK = 20
FXP_STATUS = 101
FXP_HANDLE = 102
FXP_DATA = 103
FXP_NAME = 104
FXP_ATTRS = 105
FXP_EXTENDED = 200
FXP_EXTENDED_REPLY = 201

FILEXFER_ATTR_SIZE = 0x00000001
FILEXFER_ATTR_UIDGID = 0x00000002
FILEXFER_ATTR_OWNERGROUP = FILEXFER_ATTR_UIDGID
FILEXFER_ATTR_PERMISSIONS = 0x00000004
FILEXFER_ATTR_ACMODTIME = 0x00000008
FILEXFER_ATTR_EXTENDED = 0x80000000

FILEXFER_TYPE_REGULAR = 1
FILEXFER_TYPE_DIRECTORY = 2
FILEXFER_TYPE_SYMLINK = 3
FILEXFER_TYPE_SPECIAL = 4
FILEXFER_TYPE_UNKNOWN = 5

FXF_READ = 0x00000001
FXF_WRITE = 0x00000002
FXF_APPEND = 0x00000004
FXF_CREAT = 0x00000008
FXF_TRUNC = 0x00000010
FXF_EXCL = 0x00000020
FXF_TEXT = 0x00000040

FX_OK = 0
FX_EOF = 1
FX_NO_SUCH_FILE = 2
FX_PERMISSION_DENIED = 3
FX_FAILURE = 4
FX_BAD_MESSAGE = 5
FX_NO_CONNECTION = 6
FX_CONNECTION_LOST = 7
FX_OP_UNSUPPORTED = 8
FX_FILE_ALREADY_EXISTS = 11
# http://tools.ietf.org/wg/secsh/draft-ietf-secsh-filexfer/ defines more
# useful error codes, but so far OpenSSH doesn't implement them. We use them
# internally for clarity, but for now define them all as FX_FAILURE to be
# compatible with existing software.
FX_NOT_A_DIRECTORY = FX_FAILURE
FX_FILE_IS_A_DIRECTORY = FX_FAILURE


# initialize FileTransferBase.packetTypes:
g = globals()
for name in list(g.keys()):
    if name.startswith('FXP_'):
        value = g[name]
        FileTransferBase.packetTypes[value] = name[4:]
del g, name, value
