Restructured folder/IMAP code

In preparation for GMail label sync, we had split our some functionality
that will be needed further into their own functions.  This also permitted
the code to look more compact and concise.

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/folder/Base.py

@@ -66,6 +66,10 @@ class BaseFolder(object):
             self.ui.debug('', "Filtering out '%s'[%s] due to folderfilter" \
                           % (self.ffilter_name, repository))
 
+        # Passes for syncmessagesto
+        self.syncmessagesto_passes = [('copying messages'       , self.__syncmessagesto_copy),
+                                      ('deleting messages'      , self.__syncmessagesto_delete),
+                                      ('syncing flags'          , self.__syncmessagesto_flags)]
 
     def getname(self):
         """Returns name"""
@@ -319,6 +323,103 @@ class BaseFolder(object):
         for uid in uidlist:
             self.deletemessageflags(uid, flags)
 
+
+    def addmessageheader(self, content, headername, headervalue):
+        self.ui.debug('',
+                 'addmessageheader: called to add %s: %s' % (headername,
+                                                             headervalue))
+        insertionpoint = content.find('\n\n')
+        self.ui.debug('', 'addmessageheader: insertionpoint = %d' % insertionpoint)
+        leader = content[0:insertionpoint]
+        self.ui.debug('', 'addmessageheader: leader = %s' % repr(leader))
+        if insertionpoint == 0 or insertionpoint == -1:
+            newline = ''
+            insertionpoint = 0
+        else:
+            newline = '\n'
+        newline += "%s: %s" % (headername, headervalue)
+        self.ui.debug('', 'addmessageheader: newline = ' + repr(newline))
+        trailer = content[insertionpoint:]
+        self.ui.debug('', 'addmessageheader: trailer = ' + repr(trailer))
+        return leader + newline + trailer
+
+
+    def __find_eoh(self, content):
+        """
+        Searches for the point where mail headers end.
+        Either double '\n', or end of string.
+
+        Arguments:
+        - content: contents of the message to search in
+        Returns: position of the first non-header byte.
+
+        """
+        eoh_cr = content.find('\n\n')
+        if eoh_cr == -1:
+            eoh_cr = len(content)
+
+        return eoh_cr
+
+
+    def getmessageheader(self, content, name):
+        """
+        Searches for the given header and returns its value.
+        Arguments:
+        - contents: message itself
+        - name: name of the header to be searched
+
+        Returns: header value or None if no such header was found
+
+        """
+        self.ui.debug('', 'getmessageheader: called to get %s' % name)
+        eoh = self.__find_eoh(content)
+        self.ui.debug('', 'getmessageheader: eoh = %d' % eoh)
+        headers = content[0:eoh]
+        self.ui.debug('', 'getmessageheader: headers = %s' % repr(headers))
+
+        m = re.search('^%s:(.*)$' % name, headers, flags = re.MULTILINE)
+        if m:
+            return m.group(1).strip()
+        else:
+            return None
+
+
+    def deletemessageheaders(self, content, header_list):
+        """
+        Deletes headers in the given list from the message content.
+
+        Arguments:
+        - content: message itself
+        - header_list: list of headers to be deleted or just the header name
+
+        We expect our message to have '\n' as line endings.
+
+        """
+        if type(header_list) != type([]):
+            header_list = [header_list]
+        self.ui.debug('', 'deletemessageheaders: called to delete %s' % (header_list))
+
+        if not len(header_list): return content
+
+        eoh = self.__find_eoh(content)
+        self.ui.debug('', 'deletemessageheaders: end of headers = %d' % eoh)
+        headers = content[0:eoh]
+        rest = content[eoh:]
+        self.ui.debug('', 'deletemessageheaders: headers = %s' % repr(headers))
+        new_headers = []
+        for h in headers.split('\n'):
+            keep_it = True
+            for trim_h in self.filterheaders:
+                if len(h) > len(trim_h) and h[0:len(trim_h)+1] == (trim_h + ":"):
+                    keep_it = False
+                    break
+            if keep_it: new_headers.append(h)
+
+        return ('\n'.join(new_headers) + rest)
+
+
+
+
     def change_message_uid(self, uid, new_uid):
         """Change the message from existing uid to new_uid
 
@@ -564,14 +665,16 @@ class BaseFolder(object):
          deleted there), sync the flag change to both dstfolder and
          statusfolder.
 
+        Pass4: Synchronize label changes (Gmail only)
+         Compares label mismatches in self with those in statusfolder.
+         If msg has a valid UID and exists on dstfolder, syncs the labels
+         to both dstfolder and statusfolder.
+
         :param dstfolder: Folderinstance to sync the msgs to.
         :param statusfolder: LocalStatus instance to sync against.
-        """
-        passes = [('copying messages'       , self.__syncmessagesto_copy),
-                  ('deleting messages'      , self.__syncmessagesto_delete),
-                  ('syncing flags'          , self.__syncmessagesto_flags)]
 
-        for (passdesc, action) in passes:
+        """
+        for (passdesc, action) in self.syncmessagesto_passes:
             # bail out on CTRL-C or SIGTERM
             if offlineimap.accounts.Account.abort_NOW_signal.is_set():
                 break