Implement Thread() and Threads()

[notmuch] / cnotmuch / database.py

import ctypes, os
from ctypes import c_int, c_char_p, c_void_p, c_uint, c_uint64, c_bool, byref
from cnotmuch.globals import nmlib, STATUS, NotmuchError, Enum
from cnotmuch.thread import Thread, Threads
from cnotmuch.tags import Tags
import logging
from datetime import date

class Database(object):
    """Represents a notmuch database (wraps notmuch_database_t)

    .. note:: Do remember that as soon as we tear down this object,
           all underlying derived objects such as queries, threads,
           messages, tags etc will be freed by the underlying library
           as well. Accessing these objects will lead to segfaults and
           other unexpected behavior. See above for more details.
    """
    _std_db_path = None
    """Class attribute to cache user's default database"""

    MODE = Enum(['READ_ONLY','READ_WRITE'])
    """Constants: Mode in which to open the database"""

    """notmuch_database_get_path (notmuch_database_t *database)"""
    _get_path = nmlib.notmuch_database_get_path
    _get_path.restype = c_char_p

    """notmuch_database_get_version"""
    _get_version = nmlib.notmuch_database_get_version
    _get_version.restype = c_uint

    """notmuch_database_open (const char *path, notmuch_database_mode_t mode)"""
    _open = nmlib.notmuch_database_open 
    _open.restype = c_void_p

    """ notmuch_database_find_message """
    _find_message = nmlib.notmuch_database_find_message
    _find_message.restype = c_void_p

    """notmuch_database_get_all_tags (notmuch_database_t *database)"""
    _get_all_tags = nmlib.notmuch_database_get_all_tags
    _get_all_tags.restype = c_void_p

    """ notmuch_database_create(const char *path):"""
    _create = nmlib.notmuch_database_create
    _create.restype = c_void_p

    def __init__(self, path=None, create=False, mode= 0):
        """If *path* is *None*, we will try to read a users notmuch 
        configuration and use his configured database. The location of the 
        configuration file can be specified through the environment variable
        *NOTMUCH_CONFIG*, falling back to the default `~/.notmuch-config`.

        If *create* is `True`, the database will always be created in
        :attr:`MODE`.READ_WRITE mode. Default mode for opening is READ_ONLY.

        :param path:   Directory to open/create the database in (see
                       above for behavior if `None`)
        :type path:    `str` or `None`
        :param create: Pass `False` to open an existing, `True` to create a new
                       database.  
        :type create:  bool
        :param mode:   Mode to open a database in. Is always 
                       :attr:`MODE`.READ_WRITE when creating a new one.
        :type mode:    :attr:`MODE`
        :returns:      Nothing
        :exception:    :exc:`NotmuchError` in case of failure.
        """
        self._db = None
        if path is None:
            # no path specified. use a user's default database
            if Database._std_db_path is None:
                #the following line throws a NotmuchError if it fails
                Database._std_db_path = self._get_user_default_db()
            path = Database._std_db_path

        if create == False:
            self.open(path, mode)
        else:
            self.create(path)

    def _verify_initialized_db(self):
        """Raises a NotmuchError in case self._db is still None"""
        if self._db is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)            

    def create(self, path):
        """Creates a new notmuch database

        This function is used by __init__() and usually does not need
        to be called directly. It wraps the underlying
        *notmuch_database_create* function and creates a new notmuch
        database at *path*. It will always return a database in
        :attr:`MODE`.READ_WRITE mode as creating an empty database for
        reading only does not make a great deal of sense.

        :param path: A directory in which we should create the database.
        :type path: str
        :returns: Nothing
        :exception: :exc:`NotmuchError` in case of any failure
                    (after printing an error message on stderr).
        """
        if self._db is not None:
            raise NotmuchError(
            message="Cannot create db, this Database() already has an open one.")

        res = Database._create(path, Database.MODE.READ_WRITE)

        if res is None:
            raise NotmuchError(
                message="Could not create the specified database")
        self._db = res

    def open(self, path, mode= 0): 
        """Opens an existing database

        This function is used by __init__() and usually does not need
        to be called directly. It wraps the underlying
        *notmuch_database_open* function.

        :param status: Open the database in read-only or read-write mode
        :type status:  :attr:`MODE` 
        :returns: Nothing
        :exception: Raises :exc:`NotmuchError` in case
                    of any failure (after printing an error message on stderr).
        """

        res = Database._open(path, mode)

        if res is None:
            raise NotmuchError(
                message="Could not open the specified database")
        self._db = res

    def get_path(self):
        """Returns the file path of an open database

        Wraps notmuch_database_get_path"""
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        return Database._get_path(self._db)

    def get_version(self):
        """Returns the database format version

        :returns: The database version as positive integer
        :exception: :exc:`NotmuchError` with STATUS.NOT_INITIALIZED if
                    the database was not intitialized.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        return Database._get_version (self._db)

    def needs_upgrade(self):
        """Does this database need to be upgraded before writing to it?

        If this function returns True then no functions that modify the
        database (:meth:`add_message`, :meth:`add_tag`,
        :meth:`Directory.set_mtime`, etc.) will work unless :meth:`upgrade` 
        is called successfully first.

        :returns: `True` or `False`
        :exception: :exc:`NotmuchError` with STATUS.NOT_INITIALIZED if
                    the database was not intitialized.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        return notmuch_database_needs_upgrade(self.db) 

    def add_message(self, filename):
        """Adds a new message to the database

        `filename` should be a path relative to the path of the open
        database (see :meth:`get_path`), or else should be an absolute
        filename with initial components that match the path of the
        database.

        The file should be a single mail message (not a multi-message mbox)
        that is expected to remain at its current location, since the
        notmuch database will reference the filename, and will not copy the
        entire contents of the file.

        :returns: On success, we return 

           1) a :class:`Message` object that can be used for things
              such as adding tags to the just-added message.
           2) one of the following STATUS values:

              STATUS.SUCCESS
                  Message successfully added to database.
              STATUS.DUPLICATE_MESSAGE_ID
                  Message has the same message ID as another message already
                  in the database. The new filename was successfully added
                  to the message in the database.

        :rtype:   2-tuple(:class:`Message`, STATUS)

        :exception: Raises a :exc:`NotmuchError` with the following meaning.
              If such an exception occurs, nothing was added to the database.

              STATUS.FILE_ERROR
                      An error occurred trying to open the file, (such as 
                      permission denied, or file not found, etc.).
              STATUS.FILE_NOT_EMAIL
                      The contents of filename don't look like an email message.
              STATUS.READ_ONLY_DATABASE
                      Database was opened in read-only mode so no message can
                      be added.
              STATUS.NOT_INITIALIZED
                      The database has not been initialized.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        msg_p = c_void_p()
        status = nmlib.notmuch_database_add_message(self._db,
                                                  filename,
                                                  byref(msg_p))
 
        if not status in [STATUS.SUCCESS,STATUS.DUPLICATE_MESSAGE_ID]:
            raise NotmuchError(status)

        #construct Message() and return
        msg = Message(msg_p, self)
        return (msg, status)

    def remove_message(self, filename):
        """Removes a message from the given notmuch database

        Note that only this particular filename association is removed from
        the database. If the same message (as determined by the message ID)
        is still available via other filenames, then the message will
        persist in the database for those filenames. When the last filename
        is removed for a particular message, the database content for that
        message will be entirely removed.

        :returns: A STATUS.* value with the following meaning:

             STATUS.SUCCESS
               The last filename was removed and the message was removed 
               from the database.
             STATUS.DUPLICATE_MESSAGE_ID
               This filename was removed but the message persists in the 
               database with at least one other filename.

        :exception: Raises a :exc:`NotmuchError` with the following meaning.
             If such an exception occurs, nothing was removed from the database.

             STATUS.READ_ONLY_DATABASE
               Database was opened in read-only mode so no message can be 
               removed.
             STATUS.NOT_INITIALIZED
               The database has not been initialized.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        status = nmlib.notmuch_database_remove_message(self._db,
                                                       filename)

    def find_message(self, msgid):
        """Returns a :class:`Message` as identified by its message ID

        Wraps the underlying *notmuch_database_find_message* function.

        :param msgid: The message ID
        :type msgid: string
        :returns: :class:`Message` or `None` if no message is found or if an
                  out-of-memory situation occurs.
        :exception: :exc:`NotmuchError` with STATUS.NOT_INITIALIZED if
                  the database was not intitialized.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        msg_p = Database._find_message(self._db, msgid)
        if msg_p is None:
            return None
        return Message(msg_p, self)

    def get_all_tags(self):
        """Returns :class:`Tags` with a list of all tags found in the database

        :returns: :class:`Tags`
        :execption: :exc:`NotmuchError` with STATUS.NULL_POINTER on error
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        tags_p = Database._get_all_tags (self._db)
        if tags_p == None:
            raise NotmuchError(STATUS.NULL_POINTER)
        return Tags(tags_p, self)

    def create_query(self, querystring):
        """Returns a :class:`Query` derived from this database

        This is a shorthand method for doing::

          # short version
          # Automatically frees the Database() when 'q' is deleted

          q  = Database(dbpath).create_query('from:"Biene Maja"')

          # long version, which is functionally equivalent but will keep the
          # Database in the 'db' variable around after we delete 'q':

          db = Database(dbpath)
          q  = Query(db,'from:"Biene Maja"')

        This function is a python extension and not in the underlying C API.
        """
        # Raise a NotmuchError if not initialized
        self._verify_initialized_db()

        return Query(self, querystring)

    def __repr__(self):
        return "'Notmuch DB " + self.get_path() + "'"

    def __del__(self):
        """Close and free the notmuch database if needed"""
        if self._db is not None:
            logging.debug("Freeing the database now")
            nmlib.notmuch_database_close(self._db)

    def _get_user_default_db(self):
        """ Reads a user's notmuch config and returns his db location

        Throws a NotmuchError if it cannot find it"""
        from ConfigParser import SafeConfigParser
        config = SafeConfigParser()
        conf_f = os.getenv('NOTMUCH_CONFIG',
                           os.path.expanduser('~/.notmuch-config'))
        config.read(conf_f)
        if not config.has_option('database','path'):
            raise NotmuchError(message=
                               "No DB path specified and no user default found")
        return config.get('database','path')

    @property
    def db_p(self):
        """Property returning a pointer to `notmuch_database_t` or `None`

        This should normally not be needed by a user (and is not yet
        guaranteed to remain stable in future versions).
        """
        return self._db

#------------------------------------------------------------------------------
class Query(object):
    """Represents a search query on an opened :class:`Database`.

    A query selects and filters a subset of messages from the notmuch
    database we derive from.

    Query() provides an instance attribute :attr:`sort`, which
    contains the sort order (if specified via :meth:`set_sort`) or
    `None`.

    Technically, it wraps the underlying *notmuch_query_t* struct.

    .. note:: Do remember that as soon as we tear down this object,
           all underlying derived objects such as threads,
           messages, tags etc will be freed by the underlying library
           as well. Accessing these objects will lead to segfaults and
           other unexpected behavior. See above for more details.
    """
    # constants
    SORT = Enum(['OLDEST_FIRST','NEWEST_FIRST','MESSAGE_ID'])
    """Constants: Sort order in which to return results"""

    """notmuch_query_create"""
    _create = nmlib.notmuch_query_create
    _create.restype = c_void_p

    """notmuch_query_search_threads"""
    _search_threads = nmlib.notmuch_query_search_threads
    _search_threads.restype = c_void_p

    """notmuch_query_search_messages"""
    _search_messages = nmlib.notmuch_query_search_messages
    _search_messages.restype = c_void_p


    """notmuch_query_count_messages"""
    _count_messages = nmlib.notmuch_query_count_messages
    _count_messages.restype = c_uint

    def __init__(self, db, querystr):
        """
        :param db: An open database which we derive the Query from.
        :type db: :class:`Database`
        :param querystr: The query string for the message.
        :type querystr: str
        """
        self._db = None
        self._query = None
        self.sort = None
        self.create(db, querystr)

    def create(self, db, querystr):
        """Creates a new query derived from a Database

        This function is utilized by __init__() and usually does not need to 
        be called directly.

        :param db: Database to create the query from.
        :type db: :class:`Database`
        :param querystr: The query string
        :type querystr: str
        :returns: Nothing
        :exception: :exc:`NotmuchError`

                      * STATUS.NOT_INITIALIZED if db is not inited
                      * STATUS.NULL_POINTER if the query creation failed 
                        (too little memory)
        """
        if db.db_p is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)            
        # create reference to parent db to keep it alive
        self._db = db
        
        # create query, return None if too little mem available
        query_p = Query._create(db.db_p, querystr)
        if query_p is None:
            NotmuchError(STATUS.NULL_POINTER)
        self._query = query_p

    def set_sort(self, sort):
        """Set the sort order future results will be delivered in

        Wraps the underlying *notmuch_query_set_sort* function.

        :param sort: Sort order (see :attr:`Query.SORT`)
        :returns: Nothing
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if query has not 
                    been initialized.
        """
        if self._query is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        self.sort = sort
        nmlib.notmuch_query_set_sort(self._query, sort)

    def search_threads(self):
        """Execute a query for threads

        Execute a query for threads, returning a :class:`Threads` iterator.
        The returned threads are owned by the query and as such, will only be 
        valid until the Query is deleted.

        Technically, it wraps the underlying
        *notmuch_query_search_threads* function.

        :returns: :class:`Threads`
        :exception: :exc:`NotmuchError`

                      * STATUS.NOT_INITIALIZED if query is not inited
                      * STATUS.NULL_POINTER if search_messages failed 
        """
        if self._query is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)            

        threads_p = Query._search_threads(self._query)

        if threads_p is None:
            NotmuchError(STATUS.NULL_POINTER)

        return Threads(threads_p,self)

    def search_messages(self):
        """Filter messages according to the query and return
        :class:`Messages` in the defined sort order

        Technically, it wraps the underlying
        *notmuch_query_search_messages* function.

        :returns: :class:`Messages`
        :exception: :exc:`NotmuchError`

                      * STATUS.NOT_INITIALIZED if query is not inited
                      * STATUS.NULL_POINTER if search_messages failed 
        """
        if self._query is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)            

        msgs_p = Query._search_messages(self._query)

        if msgs_p is None:
            NotmuchError(STATUS.NULL_POINTER)

        return Messages(msgs_p,self)

    def count_messages(self):
        """Estimate the number of messages matching the query

        This function performs a search and returns Xapian's best
        guess as to the number of matching messages. It is much faster
        than performing :meth:`search_messages` and counting the
        result with `len()` (although it always returned the same
        result in my tests). Technically, it wraps the underlying
        *notmuch_query_count_messages* function.

        :returns: :class:`Messages`
        :exception: :exc:`NotmuchError`

                      * STATUS.NOT_INITIALIZED if query is not inited
        """
        if self._query is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)            

        return Query._count_messages(self._query)

    def __del__(self):
        """Close and free the Query"""
        if self._query is not None:
            logging.debug("Freeing the Query now")
            nmlib.notmuch_query_destroy (self._query)

#------------------------------------------------------------------------------
class Messages(object):
    """Represents a list of notmuch messages

    This object provides an iterator over a list of notmuch messages
    (Technically, it provides a wrapper for the underlying
    *notmuch_messages_t* structure). Do note that the underlying
    library only provides a one-time iterator (it cannot reset the
    iterator to the start). Thus iterating over the function will
    "exhaust" the list of messages, and a subsequent iteration attempt
    will raise a :exc:`NotmuchError` STATUS.NOT_INITIALIZED. Also
    note, that any function that uses iteration will also
    exhaust the messages. So both::

      for msg in msgs: print msg 

    as well as::

       number_of_msgs = len(msgs)

    will "exhaust" the Messages. If you need to re-iterate over a list of
    messages you will need to retrieve a new :class:`Messages` object.

    Things are not as bad as it seems though, you can store and reuse
    the single Message objects as often as you want as long as you
    keep the parent Messages object around. (Recall that due to
    hierarchical memory allocation, all derived Message objects will
    be invalid when we delete the parent Messages() object, even if it
    was already "exhausted".) So this works::

      db   = Database()
      msgs = Query(db,'').search_messages() #get a Messages() object
      msglist = []
      for m in msgs:
         msglist.append(m)

      # msgs is "exhausted" now and even len(msgs) will raise an exception.
      # However it will be kept around until all retrieved Message() objects are
      # also deleted. If you did e.g. an explicit del(msgs) here, the 
      # following lines would fail.
      
      # You can reiterate over *msglist* however as often as you want. 
      # It is simply a list with Message objects.

      print (msglist[0].get_filename())
      print (msglist[1].get_filename())
      print (msglist[0].get_message_id())
    """

    #notmuch_tags_get
    _get = nmlib.notmuch_messages_get
    _get.restype = c_void_p

    _collect_tags = nmlib.notmuch_messages_collect_tags
    _collect_tags.restype = c_void_p

    def __init__(self, msgs_p, parent=None):
        """
        :param msgs_p:  A pointer to an underlying *notmuch_messages_t*
             structure. These are not publically exposed, so a user
             will almost never instantiate a :class:`Messages` object
             herself. They are usually handed back as a result,
             e.g. in :meth:`Query.search_messages`.  *msgs_p* must be
             valid, we will raise an :exc:`NotmuchError`
             (STATUS.NULL_POINTER) if it is `None`.
        :type msgs_p: :class:`ctypes.c_void_p`
        :param parent: The parent object
             (ie :class:`Query`) these tags are derived from. It saves
             a reference to it, so we can automatically delete the db
             object once all derived objects are dead.
        :TODO: Make the iterator work more than once and cache the tags in 
               the Python object.(?)
        """
        if msgs_p is None:
            NotmuchError(STATUS.NULL_POINTER)

        self._msgs = msgs_p
        #store parent, so we keep them alive as long as self  is alive
        self._parent = parent
        logging.debug("Inited Messages derived from %s" %(str(parent)))

    def collect_tags(self):
        """Return the unique :class:`Tags` in the contained messages

        :returns: :class:`Tags`
        :exceptions: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if not inited

        .. note:: :meth:`collect_tags` will iterate over the messages and
          therefore will not allow further iterations.
        """
        if self._msgs is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        # collect all tags (returns NULL on error)
        tags_p = Messages._collect_tags (self._msgs)
        #reset _msgs as we iterated over it and can do so only once
        self._msgs = None

        if tags_p == None:
            raise NotmuchError(STATUS.NULL_POINTER)
        return Tags(tags_p, self)

    def __iter__(self):
        """ Make Messages an iterator """
        return self

    def next(self):
        if self._msgs is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        if not nmlib.notmuch_messages_valid(self._msgs):
            self._msgs = None
            raise StopIteration

        msg = Message(Messages._get (self._msgs), self)
        nmlib.notmuch_messages_move_to_next(self._msgs)
        return msg

    def __len__(self):
        """len(:class:`Messages`) returns the number of contained messages

        .. note:: As this iterates over the messages, we will not be able to 
               iterate over them again! So this will fail::

                 #THIS FAILS
                 msgs = Database().create_query('').search_message()
                 if len(msgs) > 0:              #this 'exhausts' msgs
                     # next line raises NotmuchError(STATUS.NOT_INITIALIZED)!!!
                     for msg in msgs: print msg

               Most of the time, using the
               :meth:`Query.count_messages` is therefore more
               appropriate (and much faster). While not guaranteeing
               that it will return the exact same number than len(),
               in my tests it effectively always did so.
        """
        if self._msgs is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        i=0
        while nmlib.notmuch_messages_valid(self._msgs):
            nmlib.notmuch_messages_move_to_next(self._msgs)
            i += 1
        self._msgs = None
        return i



    def __del__(self):
        """Close and free the notmuch Messages"""
        if self._msgs is not None:
            logging.debug("Freeing the Messages now")
            nmlib.notmuch_messages_destroy (self._msgs)


#------------------------------------------------------------------------------
class Message(object):
    """Represents a single Email message

    Technically, this wraps the underlying *notmuch_message_t* structure.
    """

    """notmuch_message_get_filename (notmuch_message_t *message)"""
    _get_filename = nmlib.notmuch_message_get_filename
    _get_filename.restype = c_char_p 

    """notmuch_message_get_message_id (notmuch_message_t *message)"""
    _get_message_id = nmlib.notmuch_message_get_message_id
    _get_message_id.restype = c_char_p 

    """notmuch_message_get_thread_id"""
    _get_thread_id = nmlib.notmuch_message_get_thread_id
    _get_thread_id.restype = c_char_p

    """notmuch_message_get_replies"""
    _get_replies = nmlib.notmuch_message_get_replies
    _get_replies.restype = c_void_p

    """notmuch_message_get_tags (notmuch_message_t *message)"""
    _get_tags = nmlib.notmuch_message_get_tags
    _get_tags.restype = c_void_p

    _get_date = nmlib.notmuch_message_get_date
    _get_date.restype = c_uint64

    _get_header = nmlib.notmuch_message_get_header
    _get_header.restype = c_char_p

    def __init__(self, msg_p, parent=None):
        """
        :param msg_p: A pointer to an internal notmuch_message_t
            Structure.  If it is `None`, we will raise an :exc:`NotmuchError`
            STATUS.NULL_POINTER.
        :param parent: A 'parent' object is passed which this message is
              derived from. We save a reference to it, so we can
              automatically delete the parent object once all derived
              objects are dead.
        """
        if msg_p is None:
            NotmuchError(STATUS.NULL_POINTER)
        self._msg = msg_p
        #keep reference to parent, so we keep it alive
        self._parent = parent
        logging.debug("Inited Message derived from %s" %(str(parent)))


    def get_message_id(self):
        """Returns the message ID
        
        :returns: String with a message ID
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if the message 
                    is not initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
        return Message._get_message_id(self._msg)

    def get_thread_id(self):
        """Returns the thread ID

        The returned string belongs to 'message' will only be valid for as 
        long as the message is valid.

        This function will not return None since Notmuch ensures that every
        message belongs to a single thread.

        :returns: String with a thread ID
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if the message 
                    is not initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        return Message._get_thread_id (self._msg);

    def get_replies(self):
        """Gets all direct replies to this message as :class:`Messages` iterator

        .. note:: This call only makes sense if 'message' was
          ultimately obtained from a :class:`Thread` object, (such as
          by coming directly from the result of calling
          :meth:`Thread.get_toplevel_messages` or by any number of
          subsequent calls to :meth:`get_replies`). If this message was
          obtained through some non-thread means, (such as by a call
          to :meth:`Query.search_messages`), then this function will
          return `None`.

        :returns: :class:`Messages` or `None` if there are no replies to 
            this message.
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if the message 
                    is not initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        msgs_p = Message._get_replies(self._msg);

        if msgs_p is None:
            return None

        return Messages(msgs_p,self)

    def get_date(self):
        """Returns time_t of the message date

        For the original textual representation of the Date header from the
        message call notmuch_message_get_header() with a header value of
        "date".

        :returns: A time_t timestamp.
        :rtype: c_unit64
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if the message 
                    is not initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
        return Message._get_date(self._msg)

    def get_header(self, header):
        """Returns a message header
        
        This returns any message header that is stored in the notmuch database.
        This is only a selected subset of headers, which is currently:

          TODO: add stored headers

        :param header: The name of the header to be retrieved.
                       It is not case-sensitive (TODO: confirm).
        :type header: str
        :returns: The header value as string
        :exception: :exc:`NotmuchError`

                    * STATUS.NOT_INITIALIZED if the message 
                      is not initialized.
                    * STATUS.NULL_POINTER, if no header was found
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        #Returns NULL if any error occurs.
        header = Message._get_header (self._msg, header)
        if header == None:
            raise NotmuchError(STATUS.NULL_POINTER)
        return header

    def get_filename(self):
        """Returns the file path of the message file

        :returns: Absolute file path & name of the message file
        :exception: :exc:`NotmuchError` STATUS.NOT_INITIALIZED if the message 
              is not initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
        return Message._get_filename(self._msg)

    def get_tags(self):
        """Returns the message tags

        :returns: A :class:`Tags` iterator.
        :exception: :exc:`NotmuchError`

                      * STATUS.NOT_INITIALIZED if the message 
                        is not initialized.
                      * STATUS.NULL_POINTER, on error
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        tags_p = Message._get_tags(self._msg)
        if tags_p == None:
            raise NotmuchError(STATUS.NULL_POINTER)
        return Tags(tags_p, self)

    def add_tag(self, tag):
        """Adds a tag to the given message

        Adds a tag to the current message. The maximal tag length is defined in
        the notmuch library and is currently 200 bytes.

        :param tag: String with a 'tag' to be added.
        :returns: STATUS.SUCCESS if the tag was successfully added.
                  Raises an exception otherwise.
        :exception: :exc:`NotmuchError`. They have the following meaning:

                  STATUS.NULL_POINTER
                    The 'tag' argument is NULL
                  STATUS.TAG_TOO_LONG
                    The length of 'tag' is too long 
                    (exceeds Message.NOTMUCH_TAG_MAX)
                  STATUS.READ_ONLY_DATABASE
                    Database was opened in read-only mode so message cannot be 
                    modified.
                  STATUS.NOT_INITIALIZED
                     The message has not been initialized.
       """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        status = nmlib.notmuch_message_add_tag (self._msg, tag)

        if STATUS.SUCCESS == status:
            # return on success
            return status

        raise NotmuchError(status)

    def remove_tag(self, tag):
        """Removes a tag from the given message

        If the message has no such tag, this is a non-operation and
        will report success anyway.

        :param tag: String with a 'tag' to be removed.
        :returns: STATUS.SUCCESS if the tag was successfully removed or if 
                  the message had no such tag.
                  Raises an exception otherwise.
        :exception: :exc:`NotmuchError`. They have the following meaning:

                   STATUS.NULL_POINTER
                     The 'tag' argument is NULL
                   STATUS.TAG_TOO_LONG
                     The length of 'tag' is too long
                     (exceeds NOTMUCH_TAG_MAX)
                   STATUS.READ_ONLY_DATABASE
                     Database was opened in read-only mode so message cannot 
                     be modified.
                   STATUS.NOT_INITIALIZED
                     The message has not been initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)

        status = nmlib.notmuch_message_remove_tag(self._msg, tag)

        if STATUS.SUCCESS == status:
            # return on success
            return status

        raise NotmuchError(status)

    def remove_all_tags(self):
        """Removes all tags from the given message.

        See :meth:`freeze` for an example showing how to safely
        replace tag values.

        :returns: STATUS.SUCCESS if the tags were successfully removed.
                  Raises an exception otherwise.
        :exception: :exc:`NotmuchError`. They have the following meaning:

                   STATUS.READ_ONLY_DATABASE
                     Database was opened in read-only mode so message cannot 
                     be modified.
                   STATUS.NOT_INITIALIZED
                     The message has not been initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
 
        status = nmlib.notmuch_message_remove_all_tags(self._msg)

        if STATUS.SUCCESS == status:
            # return on success
            return status

        raise NotmuchError(status)

    def freeze(self):
        """Freezes the current state of 'message' within the database

        This means that changes to the message state, (via :meth:`add_tag`, 
        :meth:`remove_tag`, and :meth:`remove_all_tags`), will not be 
        committed to the database until the message is :meth:`thaw`ed.

        Multiple calls to freeze/thaw are valid and these calls will
        "stack". That is there must be as many calls to thaw as to freeze
        before a message is actually thawed.

        The ability to do freeze/thaw allows for safe transactions to
        change tag values. For example, explicitly setting a message to
        have a given set of tags might look like this::

          msg.freeze()
          msg.remove_all_tags()
          for tag in new_tags:
              msg.add_tag(tag)
          msg.thaw()

        With freeze/thaw used like this, the message in the database is
        guaranteed to have either the full set of original tag values, or
        the full set of new tag values, but nothing in between.

        Imagine the example above without freeze/thaw and the operation
        somehow getting interrupted. This could result in the message being
        left with no tags if the interruption happened after
        :meth:`remove_all_tags` but before :meth:`add_tag`.

        :returns: STATUS.SUCCESS if the message was successfully frozen.
                  Raises an exception otherwise.
        :exception: :exc:`NotmuchError`. They have the following meaning:

                   STATUS.READ_ONLY_DATABASE
                     Database was opened in read-only mode so message cannot 
                     be modified.
                   STATUS.NOT_INITIALIZED
                     The message has not been initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
 
        status = nmlib.notmuch_message_freeze(self._msg)

        if STATUS.SUCCESS == status:
            # return on success
            return status

        raise NotmuchError(status)

    def thaw(self):
        """Thaws the current 'message'

        Thaw the current 'message', synchronizing any changes that may have 
        occurred while 'message' was frozen into the notmuch database.

        See :meth:`freeze` for an example of how to use this
        function to safely provide tag changes.

        Multiple calls to freeze/thaw are valid and these calls with
        "stack". That is there must be as many calls to thaw as to freeze
        before a message is actually thawed.

        :returns: STATUS.SUCCESS if the message was successfully frozen.
                  Raises an exception otherwise.
        :exception: :exc:`NotmuchError`. They have the following meaning:

                   STATUS.UNBALANCED_FREEZE_THAW
                     An attempt was made to thaw an unfrozen message. 
                     That is, there have been an unbalanced number of calls 
                     to :meth:`freeze` and :meth:`thaw`.
                   STATUS.NOT_INITIALIZED
                     The message has not been initialized.
        """
        if self._msg is None:
            raise NotmuchError(STATUS.NOT_INITIALIZED)
 
        status = nmlib.notmuch_message_thaw(self._msg)

        if STATUS.SUCCESS == status:
            # return on success
            return status

        raise NotmuchError(status)

    
    def __str__(self):
        """A message() is represented by a 1-line summary"""
        msg = {}
        msg['from'] = self.get_header('from')
        msg['tags'] = str(self.get_tags())
        msg['date'] = date.fromtimestamp(self.get_date())
        replies = self.get_replies()
        msg['replies'] = len(replies) if replies is not None else -1
        return "%(from)s (%(date)s) (%(tags)s) (%(replies)d) replies" % (msg)

    def format_as_text(self):
        """Output like notmuch show (Not implemented)"""
        return str(self)

    def __del__(self):
        """Close and free the notmuch Message"""
        if self._msg is not None:
            logging.debug("Freeing the Message now")
            nmlib.notmuch_message_destroy (self._msg)