#! /usr/bin/env python



"""Read/write support for Maildir, mbox, MH, Babyl, and MMDF mailboxes."""



# Notes for authors of new mailbox subclasses:

#

# Remember to fsync() changes to disk before closing a modified file

# or returning from a flush() method.  See functions _sync_flush() and

# _sync_close().



import sys

import os

import time

import calendar

import socket

import errno

import copy

import email

import email.message

import email.generator

import rfc822

import StringIO

try:

    if sys.platform == 'os2emx':

        # OS/2 EMX fcntl() not adequate

        raise ImportError

    import fcntl

except ImportError:

    fcntl = None



__all__ = [ 'Mailbox', 'Maildir', 'mbox', 'MH', 'Babyl', 'MMDF',

            'Message', 'MaildirMessage', 'mboxMessage', 'MHMessage',

            'BabylMessage', 'MMDFMessage', 'UnixMailbox',

            'PortableUnixMailbox', 'MmdfMailbox', 'MHMailbox', 'BabylMailbox' ]



class Mailbox:

    """A group of messages in a particular place."""



    def __init__(self, path, factory=None, create=True):

        """Initialize a Mailbox instance."""

        self._path = os.path.abspath(os.path.expanduser(path))

        self._factory = factory



    def add(self, message):

        """Add message and return assigned key."""

        raise NotImplementedError('Method must be implemented by subclass')



    def remove(self, key):

        """Remove the keyed message; raise KeyError if it doesn't exist."""

        raise NotImplementedError('Method must be implemented by subclass')



    def __delitem__(self, key):

        self.remove(key)



    def discard(self, key):

        """If the keyed message exists, remove it."""

        try:

            self.remove(key)

        except KeyError:

            pass



    def __setitem__(self, key, message):

        """Replace the keyed message; raise KeyError if it doesn't exist."""

        raise NotImplementedError('Method must be implemented by subclass')



    def get(self, key, default=None):

        """Return the keyed message, or default if it doesn't exist."""

        try:

            return self.__getitem__(key)

        except KeyError:

            return default



    def __getitem__(self, key):

        """Return the keyed message; raise KeyError if it doesn't exist."""

        if not self._factory:

            return self.get_message(key)

        else:

            return self._factory(self.get_file(key))



    def get_message(self, key):

        """Return a Message representation or raise a KeyError."""

        raise NotImplementedError('Method must be implemented by subclass')



    def get_string(self, key):

        """Return a string representation or raise a KeyError."""

        raise NotImplementedError('Method must be implemented by subclass')



    def get_file(self, key):

        """Return a file-like representation or raise a KeyError."""

        raise NotImplementedError('Method must be implemented by subclass')



    def iterkeys(self):

        """Return an iterator over keys."""

        raise NotImplementedError('Method must be implemented by subclass')



    def keys(self):

        """Return a list of keys."""

        return list(self.iterkeys())



    def itervalues(self):

        """Return an iterator over all messages."""

        for key in self.iterkeys():

            try:

                value = self[key]

            except KeyError:

                continue

            yield value



    def __iter__(self):

        return self.itervalues()



    def values(self):

        """Return a list of messages. Memory intensive."""

        return list(self.itervalues())



    def iteritems(self):

        """Return an iterator over (key, message) tuples."""

        for key in self.iterkeys():

            try:

                value = self[key]

            except KeyError:

                continue

            yield (key, value)



    def items(self):

        """Return a list of (key, message) tuples. Memory intensive."""

        return list(self.iteritems())



    def has_key(self, key):

        """Return True if the keyed message exists, False otherwise."""

        raise NotImplementedError('Method must be implemented by subclass')



    def __contains__(self, key):

        return self.has_key(key)



    def __len__(self):

        """Return a count of messages in the mailbox."""

        raise NotImplementedError('Method must be implemented by subclass')



    def clear(self):

        """Delete all messages."""

        for key in self.iterkeys():

            self.discard(key)



    def pop(self, key, default=None):

        """Delete the keyed message and return it, or default."""

        try:

            result = self[key]

        except KeyError:

            return default

        self.discard(key)

        return result



    def popitem(self):

        """Delete an arbitrary (key, message) pair and return it."""

        for key in self.iterkeys():

            return (key, self.pop(key))     # This is only run once.

        else:

            raise KeyError('No messages in mailbox')



    def update(self, arg=None):

        """Change the messages that correspond to certain keys."""

        if hasattr(arg, 'iteritems'):

            source = arg.iteritems()

        elif hasattr(arg, 'items'):

            source = arg.items()

        else:

            source = arg

        bad_key = False

        for key, message in source:

            try:

                self[key] = message

            except KeyError:

                bad_key = True

        if bad_key:

            raise KeyError('No message with key(s)')



    def flush(self):

        """Write any pending changes to the disk."""

        raise NotImplementedError('Method must be implemented by subclass')



    def lock(self):

        """Lock the mailbox."""

        raise NotImplementedError('Method must be implemented by subclass')



    def unlock(self):

        """Unlock the mailbox if it is locked."""

        raise NotImplementedError('Method must be implemented by subclass')



    def close(self):

        """Flush and close the mailbox."""

        raise NotImplementedError('Method must be implemented by subclass')



    def _dump_message(self, message, target, mangle_from_=False):

        # Most files are opened in binary mode to allow predictable seeking.

        # To get native line endings on disk, the user-friendly \n line endings

        # used in strings and by email.Message are translated here.

        """Dump message contents to target file."""

        if isinstance(message, email.message.Message):

            buffer = StringIO.StringIO()

            gen = email.generator.Generator(buffer, mangle_from_, 0)

            gen.flatten(message)

            buffer.seek(0)

            target.write(buffer.read().replace('\n', os.linesep))

        elif isinstance(message, str):

            if mangle_from_:

                message = message.replace('\nFrom ', '\n>From ')

            message = message.replace('\n', os.linesep)

            target.write(message)

        elif hasattr(message, 'read'):

            while True:

                line = message.readline()

                if line == '':

                    break

                if mangle_from_ and line.startswith('From '):

                    line = '>From ' + line[5:]

                line = line.replace('\n', os.linesep)

                target.write(line)

        else:

            raise TypeError('Invalid message type: %s' % type(message))





class Maildir(Mailbox):

    """A qmail-style Maildir mailbox."""



    colon = ':'



    def __init__(self, dirname, factory=rfc822.Message, create=True):

        """Initialize a Maildir instance."""

        Mailbox.__init__(self, dirname, factory, create)

        if not os.path.exists(self._path):

            if create:

                os.mkdir(self._path, 0700)

                os.mkdir(os.path.join(self._path, 'tmp'), 0700)

                os.mkdir(os.path.join(self._path, 'new'), 0700)

                os.mkdir(os.path.join(self._path, 'cur'), 0700)

            else:

                raise NoSuchMailboxError(self._path)

        self._toc = {}



    def add(self, message):

        """Add message and return assigned key."""

        tmp_file = self._create_tmp()

        try:

            self._dump_message(message, tmp_file)

        finally:

            _sync_close(tmp_file)

        if isinstance(message, MaildirMessage):

            subdir = message.get_subdir()

            suffix = self.colon + message.get_info()

            if suffix == self.colon:

                suffix = ''

        else:

            subdir = 'new'

            suffix = ''

        uniq = os.path.basename(tmp_file.name).split(self.colon)[0]

        dest = os.path.join(self._path, subdir, uniq + suffix)

        try:

            if hasattr(os, 'link'):

                os.link(tmp_file.name, dest)

                os.remove(tmp_file.name)

            else:

                os.rename(tmp_file.name, dest)

        except OSError, e:

            os.remove(tmp_file.name)

            if e.errno == errno.EEXIST:

                raise ExternalClashError('Name clash with existing message: %s'

                                         % dest)

            else:

                raise

        if isinstance(message, MaildirMessage):

            os.utime(dest, (os.path.getatime(dest), message.get_date()))

        return uniq



    def remove(self, key):

        """Remove the keyed message; raise KeyError if it doesn't exist."""

        os.remove(os.path.join(self._path, self._lookup(key)))



    def discard(self, key):

        """If the keyed message exists, remove it."""

        # This overrides an inapplicable implementation in the superclass.

        try:

            self.remove(key)

        except KeyError:

            pass

        except OSError, e:

            if e.errno != errno.ENOENT:

                raise



    def __setitem__(self, key, message):

        """Replace the keyed message; raise KeyError if it doesn't exist."""

        old_subpath = self._lookup(key)

        temp_key = self.add(message)

        temp_subpath = self._lookup(temp_key)

        if isinstance(message, MaildirMessage):

            # temp's subdir and suffix were specified by message.

            dominant_subpath = temp_subpath

        else:

            # temp's subdir and suffix were defaults from add().

            dominant_subpath = old_subpath

        subdir = os.path.dirname(dominant_subpath)

        if self.colon in dominant_subpath:

            suffix = self.colon + dominant_subpath.split(self.colon)[-1]

        else:

            suffix = ''

        self.discard(key)

        new_path = os.path.join(self._path, subdir, key + suffix)

        os.rename(os.path.join(self._path, temp_subpath), new_path)

        if isinstance(message, MaildirMessage):

            os.utime(new_path, (os.path.getatime(new_path),

                                message.get_date()))



    def get_message(self, key):

        """Return a Message representation or raise a KeyError."""

        subpath = self._lookup(key)

        f = open(os.path.join(self._path, subpath), 'r')

        try:

            if self._factory:

                msg = self._factory(f)

            else:

                msg = MaildirMessage(f)

        finally:

            f.close()

        subdir, name = os.path.split(subpath)

        msg.set_subdir(subdir)

        if self.colon in name:

            msg.set_info(name.split(self.colon)[-1])

        msg.set_date(os.path.getmtime(os.path.join(self._path, subpath)))

        return msg



    def get_string(self, key):

        """Return a string representation or raise a KeyError."""

        f = open(os.path.join(self._path, self._lookup(key)), 'r')

        try:

            return f.read()

        finally:

            f.close()



    def get_file(self, key):

        """Return a file-like representation or raise a KeyError."""

        f = open(os.path.join(self._path, self._lookup(key)), 'rb')

        return _ProxyFile(f)



    def iterkeys(self):

        """Return an iterator over keys."""

        self._refresh()

        for key in self._toc:

            try:

                self._lookup(key)

            except KeyError:

                continue

            yield key



    def has_key(self, key):

        """Return True if the keyed message exists, False otherwise."""

        self._refresh()

        return key in self._toc



    def __len__(self):

        """Return a count of messages in the mailbox."""

        self._refresh()

        return len(self._toc)



    def flush(self):

        """Write any pending changes to disk."""

        return  # Maildir changes are always written immediately.



    def lock(self):

        """Lock the mailbox."""

        return



    def unlock(self):

        """Unlock the mailbox if it is locked."""

        return



    def close(self):

        """Flush and close the mailbox."""

        return



    def list_folders(self):

        """Return a list of folder names."""

        result = []

        for entry in os.listdir(self._path):

            if len(entry) > 1 and entry[0] == '.' and \

               os.path.isdir(os.path.join(self._path, entry)):

                result.append(entry[1:])

        return result



    def get_folder(self, folder):

        """Return a Maildir instance for the named folder."""

        return Maildir(os.path.join(self._path, '.' + folder),

                       factory=self._factory,

                       create=False)



    def add_folder(self, folder):

        """Create a folder and return a Maildir instance representing it."""

        path = os.path.join(self._path, '.' + folder)

        result = Maildir(path, factory=self._factory)

        maildirfolder_path = os.path.join(path, 'maildirfolder')

        if not os.path.exists(maildirfolder_path):

            os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY,

                0666))

        return result



    def remove_folder(self, folder):

        """Delete the named folder, which must be empty."""

        path = os.path.join(self._path, '.' + folder)

        for entry in os.listdir(os.path.join(path, 'new')) + \

                     os.listdir(os.path.join(path, 'cur')):

            if len(entry) < 1 or entry[0] != '.':

                raise NotEmptyError('Folder contains message(s): %s' % folder)

        for entry in os.listdir(path):

            if entry != 'new' and entry != 'cur' and entry != 'tmp' and \

               os.path.isdir(os.path.join(path, entry)):

                raise NotEmptyError("Folder contains subdirectory '%s': %s" %

                                    (folder, entry))

        for root, dirs, files in os.walk(path, topdown=False):

            for entry in files:

                os.remove(os.path.join(root, entry))

            for entry in dirs:

                os.rmdir(os.path.join(root, entry))

        os.rmdir(path)



    def clean(self):

        """Delete old files in "tmp"."""

        now = time.time()

        for entry in os.listdir(os.path.join(self._path, 'tmp')):

            path = os.path.join(self._path, 'tmp', entry)

            if now - os.path.getatime(path) > 129600:   # 60 * 60 * 36

                os.remove(path)



    _count = 1  # This is used to generate unique file names.



    def _create_tmp(self):

        """Create a file in the tmp subdirectory and open and return it."""

        now = time.time()

        hostname = socket.gethostname()

        if '/' in hostname:

            hostname = hostname.replace('/', r'\057')

        if ':' in hostname:

            hostname = hostname.replace(':', r'\072')

        uniq = "%s.M%sP%sQ%s.%s" % (int(now), int(now % 1 * 1e6), os.getpid(),

                                    Maildir._count, hostname)

        path = os.path.join(self._path, 'tmp', uniq)

        try:

            os.stat(path)

        except OSError, e:

            if e.errno == errno.ENOENT:

                Maildir._count += 1

                try:

                    return _create_carefully(path)

                except OSError, e:

                    if e.errno != errno.EEXIST:

                        raise

            else:

                raise



        # Fall through to here if stat succeeded or open raised EEXIST.

        raise ExternalClashError('Name clash prevented file creation: %s' %

                                 path)



    def _refresh(self):

        """Update table of contents mapping."""

        self._toc = {}

        for subdir in ('new', 'cur'):

            subdir_path = os.path.join(self._path, subdir)

            for entry in os.listdir(subdir_path):

                p = os.path.join(subdir_path, entry)

                if os.path.isdir(p):

                    continue

                uniq = entry.split(self.colon)[0]

                self._toc[uniq] = os.path.join(subdir, entry)



    def _lookup(self, key):

        """Use TOC to return subpath for given key, or raise a KeyError."""

        try:

            if os.path.exists(os.path.join(self._path, self._toc[key])):

                return self._toc[key]

        except KeyError:

            pass

        self._refresh()

        try:

            return self._toc[key]

        except KeyError:

            raise KeyError('No message with key: %s' % key)



    # This method is for backward compatibility only.

    def next(self):

        """Return the next message in a one-time iteration."""

        if not hasattr(self, '_onetime_keys'):

            self._onetime_keys = self.iterkeys()

        while True:

            try:

                return self[self._onetime_keys.next()]

            except StopIteration:

                return None

            except KeyError:

                continue





class _singlefileMailbox(Mailbox):

    """A single-file mailbox."""



    def __init__(self, path, factory=None, create=True):

        """Initialize a single-file mailbox."""

        Mailbox.__init__(self, path, factory, create)

        try:

            f = open(self._path, 'rb+')

        except IOError, e:

            if e.errno == errno.ENOENT:

                if create:

                    f = open(self._path, 'wb+')

                else:

                    raise NoSuchMailboxError(self._path)

            elif e.errno == errno.EACCES:

                f = open(self._path, 'rb')

            else:

                raise

        self._file = f

        self._toc = None

        self._next_key = 0

        self._pending = False   # No changes require rewriting the file.

        self._locked = False

        self._file_length = None        # Used to record mailbox size



    def add(self, message):

        """Add message and return assigned key."""

        self._lookup()

        self._toc[self._next_key] = self._append_message(message)

        self._next_key += 1

        self._pending = True

        return self._next_key - 1



    def remove(self, key):

        """Remove the keyed message; raise KeyError if it doesn't exist."""

        self._lookup(key)

        del self._toc[key]

        self._pending = True



    def __setitem__(self, key, message):

        """Replace the keyed message; raise KeyError if it doesn't exist."""

        self._lookup(key)

        self._toc[key] = self._append_message(message)

        self._pending = True



    def iterkeys(self):

        """Return an iterator over keys."""

        self._lookup()

        for key in self._toc.keys():

            yield key



    def has_key(self, key):

        """Return True if the keyed message exists, False otherwise."""

        self._lookup()

        return key in self._toc



    def __len__(self):

        """Return a count of messages in the mailbox."""

        self._lookup()

        return len(self._toc)



    def lock(self):

        """Lock the mailbox."""

        if not self._locked:

            _lock_file(self._file)

            self._locked = True



    def unlock(self):

        """Unlock the mailbox if it is locked."""

        if self._locked:

            _unlock_file(self._file)

            self._locked = False



    def flush(self):

        """Write any pending changes to disk."""

        if not self._pending:

            return



        # In order to be writing anything out at all, self._toc must

        # already have been generated (and presumably has been modified

        # by adding or deleting an item).

        assert self._toc is not None



        # Check length of self._file; if it's changed, some other process

        # has modified the mailbox since we scanned it.

        self._file.seek(0, 2)

        cur_len = self._file.tell()

        if cur_len != self._file_length:

            raise ExternalClashError('Size of mailbox file changed '

                                     '(expected %i, found %i)' %

                                     (self._file_length, cur_len))



        new_file = _create_temporary(self._path)

        try:

            new_toc = {}

            self._pre_mailbox_hook(new_file)

            for key in sorted(self._toc.keys()):

                start, stop = self._toc[key]

                self._file.seek(start)

                self._pre_message_hook(new_file)

                new_start = new_file.tell()

                while True:

                    buffer = self._file.read(min(4096,

                                                 stop - self._file.tell()))

                    if buffer == '':

                        break

                    new_file.write(buffer)

                new_toc[key] = (new_start, new_file.tell())

                self._post_message_hook(new_file)

        except:

            new_file.close()

            os.remove(new_file.name)

            raise

        _sync_close(new_file)

        # self._file is about to get replaced, so no need to sync.

        self._file.close()

        try:

            os.rename(new_file.name, self._path)

        except OSError, e:

            if e.errno == errno.EEXIST or \

              (os.name == 'os2' and e.errno == errno.EACCES):

                os.remove(self._path)

                os.rename(new_file.name, self._path)

            else:

                raise

        self._file = open(self._path, 'rb+')

        self._toc = new_toc

        self._pending = False

        if self._locked:

            _lock_file(self._file, dotlock=False)



    def _pre_mailbox_hook(self, f):

        """Called before writing the mailbox to file f."""

        return



    def _pre_message_hook(self, f):

        """Called before writing each message to file f."""

        return



    def _post_message_hook(self, f):

        """Called after writing each message to file f."""

        return



    def close(self):

        """Flush and close the mailbox."""

        self.flush()

        if self._locked:

            self.unlock()

        self._file.close()  # Sync has been done by self.flush() above.



    def _lookup(self, key=None):

        """Return (start, stop) or raise KeyError."""

        if self._toc is None:

            self._generate_toc()

        if key is not None:

            try:

                return self._toc[key]

            except KeyError:

                raise KeyError('No message with key: %s' % key)



    def _append_message(self, message):

        """Append message to mailbox and return (start, stop) offsets."""

        self._file.seek(0, 2)

        self._pre_message_hook(self._file)

        offsets = self._install_message(message)

        self._post_message_hook(self._file)

        self._file.flush()

        self._file_length = self._file.tell()  # Record current length of mailbox

        return offsets







class _mboxMMDF(_singlefileMailbox):

    """An mbox or MMDF mailbox."""



    _mangle_from_ = True



    def get_message(self, key):

        """Return a Message representation or raise a KeyError."""

        start, stop = self._lookup(key)

        self._file.seek(start)

        from_line = self._file.readline().replace(os.linesep, '')

        string = self._file.read(stop - self._file.tell())

        msg = self._message_factory(string.replace(os.linesep, '\n'))

        msg.set_from(from_line[5:])

        return msg



    def get_string(self, key, from_=False):

        """Return a string representation or raise a KeyError."""

        start, stop = self._lookup(key)

        self._file.seek(start)

        if not from_:

            self._file.readline()

        string = self._file.read(stop - self._file.tell())

        return string.replace(os.linesep, '\n')



    def get_file(self, key, from_=False):

        """Return a file-like representation or raise a KeyError."""

        start, stop = self._lookup(key)

        self._file.seek(start)

        if not from_:

            self._file.readline()

        return _PartialFile(self._file, self._file.tell(), stop)



    def _install_message(self, message):

        """Format a message and blindly write to self._file."""

        from_line = None

        if isinstance(message, str) and message.startswith('From '):

            newline = message.find('\n')

            if newline != -1:

                from_line = message[:newline]

                message = message[newline + 1:]

            else:

                from_line = message

                message = ''

        elif isinstance(message, _mboxMMDFMessage):

            from_line = 'From ' + message.get_from()

        elif isinstance(message, email.message.Message):

            from_line = message.get_unixfrom()  # May be None.

        if from_line is None:

            from_line = 'From MAILER-DAEMON %s' % time.asctime(time.gmtime())

        start = self._file.tell()

        self._file.write(from_line + os.linesep)

        self._dump_message(message, self._file, self._mangle_from_)

        stop = self._file.tell()

        return (start, stop)





class mbox(_mboxMMDF):

    """A classic mbox mailbox."""



    _mangle_from_ = True



    def __init__(self, path, factory=None, create=True):

        """Initialize an mbox mailbox."""

        self._message_factory = mboxMessage

        _mboxMMDF.__init__(self, path, factory, create)



    def _pre_message_hook(self, f):

        """Called before writing each message to file f."""

        if f.tell() != 0:

            f.write(os.linesep)



    def _generate_toc(self):

        """Generate key-to-(start, stop) table of contents."""

        starts, stops = [], []

        self._file.seek(0)

        while True:

            line_pos = self._file.tell()

            line = self._file.readline()

            if line.startswith('From '):

                if len(stops) < len(starts):

                    stops.append(line_pos - len(os.linesep))

                starts.append(line_pos)

            elif line == '':

                stops.append(line_pos)

                break

        self._toc = dict(enumerate(zip(starts, stops)))

        self._next_key = len(self._toc)

        self._file_length = self._file.tell()





class MMDF(_mboxMMDF):

    """An MMDF mailbox."""



    def __init__(self, path, factory=None, create=True):

        """Initialize an MMDF mailbox."""

        self._message_factory = MMDFMessage

        _mboxMMDF.__init__(self, path, factory, create)



    def _pre_message_hook(self, f):

        """Called before writing each message to file f."""

        f.write('\001\001\001\001' + os.linesep)



    def _post_message_hook(self, f):

        """Called after writing each message to file f."""

        f.write(os.linesep + '\001\001\001\001' + os.linesep)



    def _generate_toc(self):

        """Generate key-to-(start, stop) table of contents."""

        starts, stops = [], []

        self._file.seek(0)

        next_pos = 0

        while True:

            line_pos = next_pos

            line = self._file.readline()

            next_pos = self._file.tell()

            if line.startswith('\001\001\001\001' + os.linesep):

                starts.append(next_pos)

                while True:

                    line_pos = next_pos

                    line = self._file.readline()

                    next_pos = self._file.tell()

                    if line == '\001\001\001\001' + os.linesep:

                        stops.append(line_pos - len(os.linesep))

                        break

                    elif line == '':

                        stops.append(line_pos)

                        break

            elif line == '':

                break

        self._toc = dict(enumerate(zip(starts, stops)))

        self._next_key = len(self._toc)

        self._file.seek(0, 2)

        self._file_length = self._file.tell()





class MH(Mailbox):

    """An MH mailbox."""



    def __init__(self, path, factory=None, create=True):

        """Initialize an MH instance."""

        Mailbox.__init__(self, path, factory, create)

        if not os.path.exists(self._path):

            if create:

                os.mkdir(self._path, 0700)

                os.close(os.open(os.path.join(self._path, '.mh_sequences'),

                                 os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0600))

            else:

                raise NoSuchMailboxError(self._path)

        self._locked = False



    def add(self, message):

        """Add message and return assigned key."""

        keys = self.keys()

        if len(keys) == 0:

            new_key = 1

        else:

            new_key = max(keys) + 1

        new_path = os.path.join(self._path, str(new_key))

        f = _create_carefully(new_path)

        try:

            if self._locked:

                _lock_file(f)

            try:

                self._dump_message(message, f)

                if isinstance(message, MHMessage):

                    self._dump_sequences(message, new_key)

            finally:

                if self._locked:

                    _unlock_file(f)

        finally:

            _sync_close(f)

        return new_key



    def remove(self, key):

        """Remove the keyed message; raise KeyError if it doesn't exist."""

        path = os.path.join(self._path, str(key))

        try:

            f = open(path, 'rb+')

        except IOError, e:

            if e.errno == errno.ENOENT:

                raise KeyError('No message with key: %s' % key)

            else:

                raise

        try:

            if self._locked:

                _lock_file(f)

            try:

                f.close()

                os.remove(os.path.join(self._path, str(key)))

            finally:

                if self._locked:

                    _unlock_file(f)

        finally:

            f.close()



    def __setitem__(self, key, message):

        """Replace the keyed message; raise KeyError if it doesn't exist."""

        path = os.path.join(self._path, str(key))

        try:

            f = open(path, 'rb+')

        except IOError, e:

            if e.errno == errno.ENOENT:

                raise KeyError('No message with key: %s' % key)

            else:

                raise

        try:

            if self._locked:

                _lock_file(f)

            try:

                os.close(os.open(path, os.O_WRONLY | os.O_TRUNC))

                self._dump_message(message, f)

                if isinstance(message, MHMessage):

                    self._dump_sequences(message, key)

            finally:

                if self._locked:

                    _unlock_file(f)

        finally:

            _sync_close(f)



    def get_message(self, key):

        """Return a Message representation or raise a KeyError."""

        try:

            if self._locked:

                f = open(os.path.join(self._path, str(key)), 'r+')

            else:

                f = open(os.path.join(self._path, str(key)), 'r')

        except IOError, e:

            if e.errno == errno.ENOENT:

                raise KeyError('No message with key: %s' % key)

            else:

                raise

        try:

            if self._locked:

                _lock_file(f)

            try:

                msg = MHMessage(f)

            finally:

                if self._locked:

                    _unlock_file(f)

        finally:

            f.close()

        for name, key_list in self.get_sequences().iteritems():

            if key in key_list:

                msg.add_sequence(name)

        return msg



    def get_string(self, key):

        """Return a string representation or raise a KeyError."""

        try:

            if self._locked:

                f = open(os.path.join(self._path, str(key)), 'r+')

            else:

                f = open(os.path.join(self._path, str(key)), 'r')

        except IOError, e:

            if e.errno == errno.ENOENT:

                raise KeyError('No message with key: %s' % key)

            else:

                raise

        try:

            if self._locked:

                _lock_file(f)

            try:

                return f.read()

            finally:

                if self._locked:

                    _unlock_file(f)

        finally:

            f.close()



    def get_file(self, key):

        """Return a file-like representation or raise a KeyError."""

        try:

            f = open(os.path.join(self._path, str(key)), 'rb')

        except IOError, e:

            if e.errno == errno.ENOENT:

                raise KeyError('No message with key: %s' % key)

            else:

                raise

        return _ProxyFile(f)



    def iterkeys(self):

        """Return an iterator over keys."""

        return iter(sorted(int(entry) for entry in os.listdir(self._path)

                                      if entry.isdigit()))



    def has_key(self, key):

        """Return True if the keyed message exists, False otherwise."""

        return os.path.exists(os.path.join(self._path, str(key)))



    def __len__(self):

        """Return a count of messages in the mailbox."""

        return len(list(self.iterkeys()))



    def lock(self):

        """Lock the mailbox."""

        if not self._locked:

            self._file = open(os.path.join(self._path, '.mh_sequences'), 'rb+')

            _lock_file(self._file)

            self._locked = True



    def unlock(self):

        """Unlock the mailbox if it is locked."""

        if self._locked:

            _unlock_file(self._file)

            _sync_close(self._file)

            del self._file

            self._locked = False



    def flush(self):

        """Write any pending changes to the disk."""

        return



    def close(self):

        """Flush and close the mailbox."""

        if self._locked:

            self.unlock()



    def list_folders(self):

        """Return a list of folder names."""

        result = []

        for entry in os.listdir(self._path):

            if os.path.isdir(os.path.join(self._path, entry)):

                result.append(entry)

        return result



    def get_folder(self, folder):

        """Return an MH instance for the named folder."""

        return MH(os.path.join(self._path, folder),

                  factory=self._factory, create=False)



    def add_folder(self, folder):

        """Create a folder and return an MH instance representing it."""

        return MH(os.path.join(self._path, folder),

                  factory=self._factory)



    def remove_folder(self, folder):

        """Delete the named folder, which must be empty."""

        path = os.path.join(self._path, folder)

        entries = os.listdir(path)

        if entries == ['.mh_sequences']:

            os.remove(os.path.join(path, '.mh_sequences'))

        elif entries == []:

            pass

        else:

            raise NotEmptyError('Folder not empty: %s' % self._path)

        os.rmdir(path)



    def get_sequences(self):

        """Return a name-to-key-list dictionary to define each sequence."""

        results = {}

        f = open(os.path.join(self._path, '.mh_sequences'), 'r')

        try:

            all_keys = set(self.keys())

            for line in f:

                try:

                    name, contents = line.split(':')

                    keys = set()

                    for spec in contents.split():

                        if spec.isdigit():

                            keys.add(int(spec))

                        else:

                            start, stop = (int(x) for x in spec.split('-'))

                            keys.update(range(start, stop + 1))

                    results[name] = [key for key in sorted(keys) \

                                         if key in all_keys]

                    if len(results[name]) == 0:

                        del results[name]

                except ValueError:

                    raise FormatError('Invalid sequence specification: %s' %

                                      line.rstrip())

        finally:

            f.close()

        return results



    def set_sequences(self, sequences):

        """Set sequences using the given name-to-key-list dictionary."""

        f = open(os.path.join(self._path, '.mh_sequences'), 'r+')

        try:

            os.close(os.open(f.name, os.O_WRONLY | os.O_TRUNC))

            for name, keys in sequences.iteritems():

                if len(keys) == 0:

                    continue

                f.write('%s:' % name)

                prev = None

                completing = False

                for key in sorted(set(keys)):

                    if key - 1 == prev:

                        if not completing:

                            completing = True

                            f.write('-')

                    elif completing:

                        completing = False

                        f.write('%s %s' % (prev, key))

                    else:

                        f.write(' %s' % key)

                    prev = key

                if completing:

                    f.write(str(prev) + '\n')

                else:

                    f.write('\n')

        finally:

            _sync_close(f)



    def pack(self):

        """Re-name messages to eliminate numbering gaps. Invalidates keys."""

        sequences = self.get_sequences()

        prev = 0

        changes = []

        for key in self.iterkeys():

            if key - 1 != prev:

                changes.append((key, prev + 1))

                if hasattr(os, 'link'):

                    os.link(os.path.join(self._path, str(key)),

                            os.path.join(self._path, str(prev + 1)))

                    os.unlink(os.path.join(self._path, str(key)))

                else:

                    os.rename(os.path.join(self._path, str(key)),

                              os.path.join(self._path, str(prev + 1)))

            prev += 1

        self._next_key = prev + 1

        if len(changes) == 0:

            return

        for name, key_list in sequences.items():

            for old, new in changes:

                if old in key_list:

                    key_list[key_list.index(old)] = new

        self.set_sequences(sequences)



    def _dump_sequences(self, message, key):

        """Inspect a new MHMessage and update sequences appropriately."""

        pending_sequences = message.get_sequences()

        all_sequences = self.get_sequences()

        for name, key_list in all_sequences.iteritems():

            if name in pending_sequences:

                key_list.append(key)

            elif key in key_list:

                del key_list[key_list.index(key)]

        for sequence in pending_sequences:

            if sequence not in all_sequences:

                all_sequences[sequence] = [key]

        self.set_sequences(all_sequences)





class Babyl(_singlefileMailbox):

    """An Rmail-style Babyl mailbox."""



    _special_labels = frozenset(('unseen', 'deleted', 'filed', 'answered',

                                 'forwarded', 'edited', 'resent'))



    def __init__(self, path, factory=None, create=True):

        """Initialize a Babyl mailbox."""

        _singlefileMailbox.__init__(self, path, factory, create)

        self._labels = {}



    def add(self, message):

        """Add message and return assigned key."""

        key = _singlefileMailbox.add(self, message)

        if isinstance(message, BabylMessage):

            self._labels[key] = message.get_labels()

        return key



    def remove(self, key):

        """Remove the keyed message; raise KeyError if it doesn't exist."""

        _singlefileMailbox.remove(self, key)

        if key in self._labels:

            del self._labels[key]



    def __setitem__(self, key, message):

        """Replace the keyed message; raise KeyError if it doesn't exist."""

        _singlefileMailbox.__setitem__(self, key, message)

        if isinstance(message, BabylMessage):

            self._labels[key] = message.get_labels()



    def get_message(self, key):

        """Return a Message representation or raise a KeyError."""

        start, stop = self._lookup(key)

        self._file.seek(start)

        self._file.readline()   # Skip '1,' line specifying labels.

        original_headers = StringIO.StringIO()

        while True:

            line = self._file.readline()

            if line == '*** EOOH ***' + os.linesep or line == '':

                break

            original_headers.write(line.replace(os.linesep, '\n'))

        visible_headers = StringIO.StringIO()

        while True:

            line = self._file.readline()

            if line == os.linesep or line == '':

                break

            visible_headers.write(line.replace(os.linesep, '\n'))

        body = self._file.read(stop - self._file.tell()).replace(os.linesep,

                                                                 '\n')

        msg = BabylMessage(original_headers.getvalue() + body)

        msg.set_visible(visible_headers.getvalue())

        if key in self._labels:

            msg.set_labels(self._labels[key])

        return msg



    def get_string(self, key):

        """Return a string representation or raise a KeyError."""

        start, stop = self._lookup(key)

        self._file.seek(start)

        self._file.readline()   # Skip '1,' line specifying labels.

        original_headers = StringIO.StringIO()

        while True:

            line = self._file.readline()

            if line == '*** EOOH ***' + os.linesep or line == '':

                break

            original_headers.write(line.replace(os.linesep, '\n'))

        while True:

            line = self._file.readline()

            if line == os.linesep or line == '':

                break

        return original_headers.getvalue() + \

               self._file.read(stop - self._file.tell()).replace(os.linesep,

                                                                 '\n')



    def get_file(self, key):

        """Return a file-like representation or raise a KeyError."""

        return StringIO.StringIO(self.get_string(key).replace('\n',

                                                              os.linesep))



    def get_labels(self):

        """Return a list of user-defined labels in the mailbox."""

        self._lookup()

        labels = set()

        for label_list in self._labels.values():

            labels.update(label_list)

        labels.difference_update(self._special_labels)

        return list(labels)



    def _generate_toc(self):

        """Generate key-to-(start, stop) table of contents."""

        starts, stops = [], []

        self._file.seek(0)

        next_pos = 0

        label_lists = []

        while True:

            line_pos = next_pos

            line = self._file.readline()

            next_pos = self._file.tell()

            if line == '\037\014' + os.linesep:

                if len(stops) < len(starts):

                    stops.append(line_pos - len(os.linesep))

                starts.append(next_pos)

                labels = [label.strip() for label

                                        in self._file.readline()[1:].split(',')

                                        if label.strip() != '']

                label_lists.append(labels)

            elif line == '\037' or line == '\037' + os.linesep:

                if len(stops) < len(starts):

                    stops.append(line_pos - len(os.linesep))

            elif line == '':

                stops.append(line_pos - len(os.linesep))

                break

        self._toc = dict(enumerate(zip(starts, stops)))

        self._labels = dict(enumerate(label_lists))

        self._next_key = len(self._toc)

        self._file.seek(0, 2)

        self._file_length = self._file.tell()



    def _pre_mailbox_hook(self, f):

        """Called before writing the mailbox to file f."""

        f.write('BABYL OPTIONS:%sVersion: 5%sLabels:%s%s\037' %

                (os.linesep, os.linesep, ','.join(self.get_labels()),

                 os.linesep))



    def _pre_message_hook(self, f):

        """Called before writing each message to file f."""

        f.write('\014' + os.linesep)



    def _post_message_hook(self, f):

        """Called after writing each message to file f."""

        f.write(os.linesep + '\037')



    def _install_message(self, message):

        """Write message contents and return (start, stop)."""

        start = self._file.tell()

        if isinstance(message, BabylMessage):

            special_labels = []

            labels = []

            for label in message.get_labels():

                if label in self._special_labels:

                    special_labels.append(label)

                else:

                    labels.append(label)

            self._file.write('1')

            for label in special_labels:

                self._file.write(', ' + label)

            self._file.write(',,')

            for label in labels:

                self._file.write(' ' + label + ',')

            self._file.write(os.linesep)

        else:

            self._file.write('1,,' + os.linesep)

        if isinstance(message, email.message.Message):

            orig_buffer = StringIO.StringIO()

            orig_generator = email.generator.Generator(orig_buffer, False, 0)

            orig_generator.flatten(message)

            orig_buffer.seek(0)

            while True:

                line = orig_buffer.readline()

                self._file.write(line.replace('\n', os.linesep))

                if line == '\n' or line == '':

                    break

            self._file.write('*** EOOH ***' + os.linesep)

            if isinstance(message, BabylMessage):

                vis_buffer = StringIO.StringIO()

                vis_generator = email.generator.Generator(vis_buffer, False, 0)

                vis_generator.flatten(message.get_visible())

                while True:

                    line = vis_buffer.readline()

                    self._file.write(line.replace('\n', os.linesep))

                    if line == '\n' or line == '':

                        break

            else:

                orig_buffer.seek(0)

                while True:

                    line = orig_buffer.readline()

                    self._file.write(line.replace('\n', os.linesep))

                    if line == '\n' or line == '':

                        break

            while True:

                buffer = orig_buffer.read(4096) # Buffer size is arbitrary.

                if buffer == '':

                    break

                self._file.write(buffer.replace('\n', os.linesep))

        elif isinstance(message, str):

            body_start = message.find('\n\n') + 2

            if body_start - 2 != -1:

                self._file.write(message[:body_start].replace('\n',

                                                              os.linesep))

                self._file.write('*** EOOH ***' + os.linesep)

                self._file.write(message[:body_start].replace('\n',

                                                              os.linesep))

                self._file.write(message[body_start:].replace('\n',

                                                              os.linesep))

            else:

                self._file.write('*** EOOH ***' + os.linesep + os.linesep)

                self._file.write(message.replace('\n', os.linesep))

        elif hasattr(message, 'readline'):

            original_pos = message.tell()

            first_pass = True

            while True:

                line = message.readline()

                self._file.write(line.replace('\n', os.linesep))

                if line == '\n' or line == '':

                    self._file.write('*** EOOH ***' + os.linesep)

                    if first_pass:

                        first_pass = False

                        message.seek(original_pos)

                    else:

                        break

            while True:

                buffer = message.read(4096)     # Buffer size is arbitrary.

                if buffer == '':

                    break

                self._file.write(buffer.replace('\n', os.linesep))

        else:

            raise TypeError('Invalid message type: %s' % type(message))

        stop = self._file.tell()

        return (start, stop)





class Message(email.message.Message):

    """Message with mailbox-format-specific properties."""



    def __init__(self, message=None):

        """Initialize a Message instance."""

        if isinstance(message, email.message.Message):

            self._become_message(copy.deepcopy(message))

            if isinstance(message, Message):

                message._explain_to(self)

        elif isinstance(message, str):

            self._become_message(email.message_from_string(message))

        elif hasattr(message, "read"):

            self._become_message(email.message_from_file(message))

        elif message is None:

            email.message.Message.__init__(self)

        else:

            raise TypeError('Invalid message type: %s' % type(message))



    def _become_message(self, message):

        """Assume the non-format-specific state of message."""

        for name in ('_headers', '_unixfrom', '_payload', '_charset',

                     'preamble', 'epilogue', 'defects', '_default_type'):

            self.__dict__[name] = message.__dict__[name]



    def _explain_to(self, message):

        """Copy format-specific state to message insofar as possible."""

        if isinstance(message, Message):

            return  # There's nothing format-specific to explain.

        else:

            raise TypeError('Cannot convert to specified type')





class MaildirMessage(Message):

    """Message with Maildir-specific properties."""



    def __init__(self, message=None):

        """Initialize a MaildirMessage instance."""

        self._subdir = 'new'

        self._info = ''

        self._date = time.time()

        Message.__init__(self, message)



    def get_subdir(self):

        """Return 'new' or 'cur'."""

        return self._subdir



    def set_subdir(self, subdir):

        """Set subdir to 'new' or 'cur'."""

        if subdir == 'new' or subdir == 'cur':

            self._subdir = subdir

        else:

            raise ValueError("subdir must be 'new' or 'cur': %s" % subdir)



    def get_flags(self):

        """Return as a string the flags that are set."""

        if self._info.startswith('2,'):

            return self._info[2:]

        else:

            return ''



    def set_flags(self, flags):

        """Set the given flags and unset all others."""

        self._info = '2,' + ''.join(sorted(flags))



    def add_flag(self, flag):

        """Set the given flag(s) without changing others."""

        self.set_flags(''.join(set(self.get_flags()) | set(flag)))



    def remove_flag(self, flag):

        """Unset the given string flag(s) without changing others."""

        if self.get_flags() != '':

            self.set_flags(''.join(set(self.get_flags()) - set(flag)))



    def get_date(self):

        """Return delivery date of message, in seconds since the epoch."""

        return self._date



    def set_date(self, date):

        """Set delivery date of message, in seconds since the epoch."""

        try:

            self._date = float(date)

        except ValueError:

            raise TypeError("can't convert to float: %s" % date)



    def get_info(self):

        """Get the message's "info" as a string."""

        return self._info



    def set_info(self, info):

        """Set the message's "info" string."""

        if isinstance(info, str):

            self._info = info

        else:

            raise TypeError('info must be a string: %s' % type(info))



    def _explain_to(self, message):

        """Copy Maildir-specific state to message insofar as possible."""

        if isinstance(message, MaildirMessage):

            message.set_flags(self.get_flags())

            message.set_subdir(self.get_subdir())

            message.set_date(self.get_date())

        elif isinstance(message, _mboxMMDFMessage):

            flags = set(self.get_flags())

            if 'S' in flags:

                message.add_flag('R')

            if self.get_subdir() == 'cur':

                message.add_flag('O')

            if 'T' in flags:

                message.add_flag('D')

            if 'F' in flags:

                message.add_flag('F')

            if 'R' in flags:

                message.add_flag('A')

            message.set_from('MAILER-DAEMON', time.gmtime(self.get_date()))

        elif isinstance(message, MHMessage):

            flags = set(self.get_flags())

            if 'S' not in flags:

                message.add_sequence('unseen')

            if 'R' in flags:

                message.add_sequence('replied')

            if 'F' in flags:

                message.add_sequence('flagged')

        elif isinstance(message, BabylMessage):

            flags = set(self.get_flags())

            if 'S' not in flags:

                message.add_label('unseen')

            if 'T' in flags:

                message.add_label('deleted')

            if 'R' in flags:

                message.add_label('answered')

            if 'P' in flags:

                message.add_label('forwarded')

        elif isinstance(message, Message):

            pass

        else:

            raise TypeError('Cannot convert to specified type: %s' %

                            type(message))





class _mboxMMDFMessage(Message):

    """Message with mbox- or MMDF-specific properties."""



    def __init__(self, message=None):

        """Initialize an mboxMMDFMessage instance."""

        self.set_from('MAILER-DAEMON', True)

        if isinstance(message, email.message.Message):

            unixfrom = message.get_unixfrom()

            if unixfrom is not None and unixfrom.startswith('From '):

                self.set_from(unixfrom[5:])

        Message.__init__(self, message)



    def get_from(self):

        """Return contents of "From " line."""

        return self._from



    def set_from(self, from_, time_=None):

        """Set "From " line, formatting and appending time_ if specified."""

        if time_ is not None:

            if time_ is True:

                time_ = time.gmtime()

            from_ += ' ' + time.asctime(time_)

        self._from = from_



    def get_flags(self):

        """Return as a string the flags that are set."""

        return self.get('Status', '') + self.get('X-Status', '')



    def set_flags(self, flags):

        """Set the given flags and unset all others."""

        flags = set(flags)

        status_flags, xstatus_flags = '', ''

        for flag in ('R', 'O'):

            if flag in flags:

                status_flags += flag

                flags.remove(flag)

        for flag in ('D', 'F', 'A'):

            if flag in flags:

                xstatus_flags += flag

                flags.remove(flag)

        xstatus_flags += ''.join(sorted(flags))

        try:

            self.replace_header('Status', status_flags)

        except KeyError:

            self.add_header('Status', status_flags)

        try:

            self.replace_header('X-Status', xstatus_flags)

        except KeyError:

            self.add_header('X-Status', xstatus_flags)



    def add_flag(self, flag):

        """Set the given flag(s) without changing others."""

        self.set_flags(''.join(set(self.get_flags()) | set(flag)))



    def remove_flag(self, flag):

        """Unset the given string flag(s) without changing others."""

        if 'Status' in self or 'X-Status' in self:

            self.set_flags(''.join(set(self.get_flags()) - set(flag)))



    def _explain_to(self, message):

        """Copy mbox- or MMDF-specific state to message insofar as possible."""

        if isinstance(message, MaildirMessage):

            flags = set(self.get_flags())

            if 'O' in flags:

                message.set_subdir('cur')

            if 'F' in flags:

                message.add_flag('F')

            if 'A' in flags:

                message.add_flag('R')

            if 'R' in flags:

                message.add_flag('S')

            if 'D' in flags:

                message.add_flag('T')

            del message['status']

            del message['x-status']

            maybe_date = ' '.join(self.get_from().split()[-5:])

            try:

                message.set_date(calendar.timegm(time.strptime(maybe_date,

                                                      '%a %b %d %H:%M:%S %Y')))

            except (ValueError, OverflowError):

                pass

        elif isinstance(message, _mboxMMDFMessage):

            message.set_flags(self.get_flags())

            message.set_from(self.get_from())

        elif isinstance(message, MHMessage):

            flags = set(self.get_flags())

            if 'R' not in flags:

                message.add_sequence('unseen')

            if 'A' in flags:

                message.add_sequence('replied')

            if 'F' in flags:

                message.add_sequence('flagged')

            del message['status']

            del message['x-status']

        elif isinstance(message, BabylMessage):

            flags = set(self.get_flags())

            if 'R' not in flags:

                message.add_label('unseen')

            if 'D' in flags:

                message.add_label('deleted')

            if 'A' in flags:

                message.add_label('answered')

            del message['status']

            del message['x-status']

        elif isinstance(message, Message):

            pass

        else:

            raise TypeError('Cannot convert to specified type: %s' %

                            type(message))





class mboxMessage(_mboxMMDFMessage):

    """Message with mbox-specific properties."""





class MHMessage(Message):

    """Message with MH-specific properties."""



    def __init__(self, message=None):

        """Initialize an MHMessage instance."""

        self._sequences = []

        Message.__init__(self, message)



    def get_sequences(self):

        """Return a list of sequences that include the message."""

        return self._sequences[:]



    def set_sequences(self, sequences):

        """Set the list of sequences that include the message."""

        self._sequences = list(sequences)



    def add_sequence(self, sequence):

        """Add sequence to list of sequences including the message."""

        if isinstance(sequence, str):

            if not sequence in self._sequences:

                self._sequences.append(sequence)

        else:

            raise TypeError('sequence must be a string: %s' % type(sequence))



    def remove_sequence(self, sequence):

        """Remove sequence from the list of sequences including the message."""

        try:

            self._sequences.remove(sequence)

        except ValueError:

            pass



    def _explain_to(self, message):

        """Copy MH-specific state to message insofar as possible."""

        if isinstance(message, MaildirMessage):

            sequences = set(self.get_sequences())

            if 'unseen' in sequences:

                message.set_subdir('cur')

            else:

                message.set_subdir('cur')

                message.add_flag('S')

            if 'flagged' in sequences:

                message.add_flag('F')

            if 'replied' in sequences:

                message.add_flag('R')

        elif isinstance(message, _mboxMMDFMessage):

            sequences = set(self.get_sequences())

            if 'unseen' not in sequences:

                message.add_flag('RO')

            else:

                message.add_flag('O')

            if 'flagged' in sequences:

                message.add_flag('F')

            if 'replied' in sequences:

                message.add_flag('A')

        elif isinstance(message, MHMessage):

            for sequence in self.get_sequences():

                message.add_sequence(sequence)

        elif isinstance(message, BabylMessage):

            sequences = set(self.get_sequences())

            if 'unseen' in sequences:

                message.add_label('unseen')

            if 'replied' in sequences:

                message.add_label('answered')

        elif isinstance(message, Message):

            pass

        else:

            raise TypeError('Cannot convert to specified type: %s' %

                            type(message))





class BabylMessage(Message):

    """Message with Babyl-specific properties."""



    def __init__(self, message=None):

        """Initialize an BabylMessage instance."""

        self._labels = []

        self._visible = Message()

        Message.__init__(self, message)



    def get_labels(self):

        """Return a list of labels on the message."""

        return self._labels[:]



    def set_labels(self, labels):

        """Set the list of labels on the message."""

        self._labels = list(labels)



    def add_label(self, label):

        """Add label to list of labels on the message."""

        if isinstance(label, str):

            if label not in self._labels:

                self._labels.append(label)

        else:

            raise TypeError('label must be a string: %s' % type(label))



    def remove_label(self, label):

        """Remove label from the list of labels on the message."""

        try:

            self._labels.remove(label)

        except ValueError:

            pass



    def get_visible(self):

        """Return a Message representation of visible headers."""

        return Message(self._visible)



    def set_visible(self, visible):

        """Set the Message representation of visible headers."""

        self._visible = Message(visible)



    def update_visible(self):

        """Update and/or sensibly generate a set of visible headers."""

        for header in self._visible.keys():

            if header in self:

                self._visible.replace_header(header, self[header])

            else:

                del self._visible[header]

        for header in ('Date', 'From', 'Reply-To', 'To', 'CC', 'Subject'):

            if header in self and header not in self._visible:

                self._visible[header] = self[header]



    def _explain_to(self, message):

        """Copy Babyl-specific state to message insofar as possible."""

        if isinstance(message, MaildirMessage):

            labels = set(self.get_labels())

            if 'unseen' in labels:

                message.set_subdir('cur')

            else:

                message.set_subdir('cur')

                message.add_flag('S')

            if 'forwarded' in labels or 'resent' in labels:

                message.add_flag('P')

            if 'answered' in labels:

                message.add_flag('R')

            if 'deleted' in labels:

                message.add_flag('T')

        elif isinstance(message, _mboxMMDFMessage):

            labels = set(self.get_labels())

            if 'unseen' not in labels:

                message.add_flag('RO')

            else:

                message.add_flag('O')

            if 'deleted' in labels:

                message.add_flag('D')

            if 'answered' in labels:

                message.add_flag('A')

        elif isinstance(message, MHMessage):

            labels = set(self.get_labels())

            if 'unseen' in labels:

                message.add_sequence('unseen')

            if 'answered' in labels:

                message.add_sequence('replied')

        elif isinstance(message, BabylMessage):

            message.set_visible(self.get_visible())

            for label in self.get_labels():

                message.add_label(label)

        elif isinstance(message, Message):

            pass

        else:

            raise TypeError('Cannot convert to specified type: %s' %

                            type(message))





class MMDFMessage(_mboxMMDFMessage):

    """Message with MMDF-specific properties."""





class _ProxyFile:

    """A read-only wrapper of a file."""



    def __init__(self, f, pos=None):

        """Initialize a _ProxyFile."""

        self._file = f

        if pos is None:

            self._pos = f.tell()

        else:

            self._pos = pos



    def read(self, size=None):

        """Read bytes."""

        return self._read(size, self._file.read)



    def readline(self, size=None):

        """Read a line."""

        return self._read(size, self._file.readline)



    def readlines(self, sizehint=None):

        """Read multiple lines."""

        result = []

        for line in self:

            result.append(line)

            if sizehint is not None:

                sizehint -= len(line)

                if sizehint <= 0:

                    break

        return result



    def __iter__(self):

        """Iterate over lines."""

        return iter(self.readline, "")



    def tell(self):

        """Return the position."""

        return self._pos



    def seek(self, offset, whence=0):

        """Change position."""

        if whence == 1:

            self._file.seek(self._pos)

        self._file.seek(offset, whence)

        self._pos = self._file.tell()



    def close(self):

        """Close the file."""

        del self._file



    def _read(self, size, read_method):

        """Read size bytes using read_method."""

        if size is None:

            size = -1

        self._file.seek(self._pos)

        result = read_method(size)

        self._pos = self._file.tell()

        return result





class _PartialFile(_ProxyFile):

    """A read-only wrapper of part of a file."""



    def __init__(self, f, start=None, stop=None):

        """Initialize a _PartialFile."""

        _ProxyFile.__init__(self, f, start)

        self._start = start

        self._stop = stop



    def tell(self):

        """Return the position with respect to start."""

        return _ProxyFile.tell(self) - self._start



    def seek(self, offset, whence=0):

        """Change position, possibly with respect to start or stop."""

        if whence == 0:

            self._pos = self._start

            whence = 1

        elif whence == 2:

            self._pos = self._stop

            whence = 1

        _ProxyFile.seek(self, offset, whence)



    def _read(self, size, read_method):

        """Read size bytes using read_method, honoring start and stop."""

        remaining = self._stop - self._pos

        if remaining <= 0:

            return ''

        if size is None or size < 0 or size > remaining:

            size = remaining

        return _ProxyFile._read(self, size, read_method)





def _lock_file(f, dotlock=True):

    """Lock file f using lockf and dot locking."""

    dotlock_done = False

    try:

        if fcntl:

            try:

                fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)

            except IOError, e:

                if e.errno in (errno.EAGAIN, errno.EACCES):

                    raise ExternalClashError('lockf: lock unavailable: %s' %

                                             f.name)

                else:

                    raise

        if dotlock:

            try:

                pre_lock = _create_temporary(f.name + '.lock')

                pre_lock.close()

            except IOError, e:

                if e.errno == errno.EACCES:

                    return  # Without write access, just skip dotlocking.

                else:

                    raise

            try:

                if hasattr(os, 'link'):

                    os.link(pre_lock.name, f.name + '.lock')

                    dotlock_done = True

                    os.unlink(pre_lock.name)

                else:

                    os.rename(pre_lock.name, f.name + '.lock')

                    dotlock_done = True

            except OSError, e:

                if e.errno == errno.EEXIST or \

                  (os.name == 'os2' and e.errno == errno.EACCES):

                    os.remove(pre_lock.name)

                    raise ExternalClashError('dot lock unavailable: %s' %

                                             f.name)

                else:

                    raise

    except:

        if fcntl:

            fcntl.lockf(f, fcntl.LOCK_UN)

        if dotlock_done:

            os.remove(f.name + '.lock')

        raise



def _unlock_file(f):

    """Unlock file f using lockf and dot locking."""

    if fcntl:

        fcntl.lockf(f, fcntl.LOCK_UN)

    if os.path.exists(f.name + '.lock'):

        os.remove(f.name + '.lock')



def _create_carefully(path):

    """Create a file if it doesn't exist and open for reading and writing."""

    fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR, 0666)

    try:

        return open(path, 'rb+')

    finally:

        os.close(fd)



def _create_temporary(path):

    """Create a temp file based on path and open for reading and writing."""

    return _create_carefully('%s.%s.%s.%s' % (path, int(time.time()),

                                              socket.gethostname(),

                                              os.getpid()))



def _sync_flush(f):

    """Ensure changes to file f are physically on disk."""

    f.flush()

    if hasattr(os, 'fsync'):

        os.fsync(f.fileno())



def _sync_close(f):

    """Close file f, ensuring all changes are physically on disk."""

    _sync_flush(f)

    f.close()



## Start: classes from the original module (for backward compatibility).



# Note that the Maildir class, whose name is unchanged, itself offers a next()

# method for backward compatibility.



class _Mailbox:



    def __init__(self, fp, factory=rfc822.Message):

        self.fp = fp

        self.seekp = 0

        self.factory = factory



    def __iter__(self):

        return iter(self.next, None)



    def next(self):

        while 1:

            self.fp.seek(self.seekp)

            try:

                self._search_start()

            except EOFError:

                self.seekp = self.fp.tell()

                return None

            start = self.fp.tell()

            self._search_end()

            self.seekp = stop = self.fp.tell()

            if start != stop:

                break

        return self.factory(_PartialFile(self.fp, start, stop))



# Recommended to use PortableUnixMailbox instead!

class UnixMailbox(_Mailbox):



    def _search_start(self):

        while 1:

            pos = self.fp.tell()

            line = self.fp.readline()

            if not line:

                raise EOFError

            if line[:5] == 'From ' and self._isrealfromline(line):

                self.fp.seek(pos)

                return



    def _search_end(self):

        self.fp.readline()      # Throw away header line

        while 1:

            pos = self.fp.tell()

            line = self.fp.readline()

            if not line:

                return

            if line[:5] == 'From ' and self._isrealfromline(line):

                self.fp.seek(pos)

                return



    # An overridable mechanism to test for From-line-ness.  You can either

    # specify a different regular expression or define a whole new

    # _isrealfromline() method.  Note that this only gets called for lines

    # starting with the 5 characters "From ".

    #

    # BAW: According to

    #http://home.netscape.com/eng/mozilla/2.0/relnotes/demo/content-length.html

    # the only portable, reliable way to find message delimiters in a BSD (i.e

    # Unix mailbox) style folder is to search for "\n\nFrom .*\n", or at the

    # beginning of the file, "^From .*\n".  While _fromlinepattern below seems

    # like a good idea, in practice, there are too many variations for more

    # strict parsing of the line to be completely accurate.

    #

    # _strict_isrealfromline() is the old version which tries to do stricter

    # parsing of the From_ line.  _portable_isrealfromline() simply returns

    # true, since it's never called if the line doesn't already start with

    # "From ".

    #

    # This algorithm, and the way it interacts with _search_start() and

    # _search_end() may not be completely correct, because it doesn't check

    # that the two characters preceding "From " are \n\n or the beginning of

    # the file.  Fixing this would require a more extensive rewrite than is

    # necessary.  For convenience, we've added a PortableUnixMailbox class

    # which does no checking of the format of the 'From' line.



    _fromlinepattern = (r"From \s*[^\s]+\s+\w\w\w\s+\w\w\w\s+\d?\d\s+"

                        r"\d?\d:\d\d(:\d\d)?(\s+[^\s]+)?\s+\d\d\d\d\s*"

                        r"[^\s]*\s*"

                        "$")

    _regexp = None



    def _strict_isrealfromline(self, line):

        if not self._regexp:

            import re

            self._regexp = re.compile(self._fromlinepattern)

        return self._regexp.match(line)



    def _portable_isrealfromline(self, line):

        return True



    _isrealfromline = _strict_isrealfromline





class PortableUnixMailbox(UnixMailbox):

    _isrealfromline = UnixMailbox._portable_isrealfromline





class MmdfMailbox(_Mailbox):



    def _search_start(self):

        while 1:

            line = self.fp.readline()

            if not line:

                raise EOFError

            if line[:5] == '\001\001\001\001\n':

                return



    def _search_end(self):

        while 1:

            pos = self.fp.tell()

            line = self.fp.readline()

            if not line:

                return

            if line == '\001\001\001\001\n':

                self.fp.seek(pos)

                return





class MHMailbox:



    def __init__(self, dirname, factory=rfc822.Message):

        import re

        pat = re.compile('^[1-9][0-9]*$')

        self.dirname = dirname

        # the three following lines could be combined into:

        # list = map(long, filter(pat.match, os.listdir(self.dirname)))

        list = os.listdir(self.dirname)

        list = filter(pat.match, list)

        list = map(long, list)

        list.sort()

        # This only works in Python 1.6 or later;

        # before that str() added 'L':

        self.boxes = map(str, list)

        self.boxes.reverse()

        self.factory = factory



    def __iter__(self):

        return iter(self.next, None)



    def next(self):

        if not self.boxes:

            return None

        fn = self.boxes.pop()

        fp = open(os.path.join(self.dirname, fn))

        msg = self.factory(fp)

        try:

            msg._mh_msgno = fn

        except (AttributeError, TypeError):

            pass

        return msg





class BabylMailbox(_Mailbox):



    def _search_start(self):

        while 1:

            line = self.fp.readline()

            if not line:

                raise EOFError

            if line == '*** EOOH ***\n':

                return



    def _search_end(self):

        while 1:

            pos = self.fp.tell()

            line = self.fp.readline()

            if not line:

                return

            if line == '\037\014\n' or line == '\037':

                self.fp.seek(pos)

                return



## End: classes from the original module (for backward compatibility).





class Error(Exception):

    """Raised for module-specific errors."""



class NoSuchMailboxError(Error):

    """The specified mailbox does not exist and won't be created."""



class NotEmptyError(Error):

    """The specified mailbox is not empty and deletion was requested."""



class ExternalClashError(Error):

    """Another process caused an action to fail."""



class FormatError(Error):

    """A file appears to have an invalid format."""

