Convert get_conversation_for_date to return named tuples

The get_conversation_for_date method in the logger module returns a
list of bare tuples. Knowledge of how to pack and unpack the many
individual components of the tuples is split between the caller and
the callee, making the method hard to maintain and ugly to use.
Therefore, convert the method to return named tuple instead.

src/common/logger.py

@@ -636,12 +636,22 @@ class Logger:
         start_of_day = int(time.mktime(local_time))
         return start_of_day
 
+    Message = namedtuple('Message',
+            ['contact_name', 'time', 'kind', 'show', 'message', 'subject',
+             'additional_data', 'log_line_id'])
+
     def get_conversation_for_date(self, jid, year, month, day, account):
         """
-        Return contact_name, time, kind, show, message, subject, additional_data, log_line_id
+        Load the complete conversation with a given jid on a specific date
 
-        For each row in a list of tuples, returns list with empty tuple if we
-        found nothing to meet our demands
+        The conversation contains all messages that were exchanged between
+        `account` and `jid` on the day specified by `year`, `month` and `day`,
+        where `month` and `day` are 1-based.
+
+        The conversation will be returned as a list of single messages of type
+        `Logger.Message`. Messages in the list are sorted chronologically. An
+        empty list will be returned if there are no messages in the log database
+        for the requested combination of `jid` and `account` on the given date.
         """
         try:
             self.get_jid_id(jid)
@@ -663,14 +673,11 @@ class Logger:
             ORDER BY time
             ''' % (where_sql, start_of_day, last_second_of_day), jid_tuple)
 
-        results = self.cur.fetchall()
-        messages = []
-        for entry in results:
-            additional_data = json.loads(entry[6])
-            parsed_entry = entry[:6] + (additional_data, ) + entry[7:]
-            messages.append(parsed_entry)
+        results = [self.Message(*row) for row in self.cur.fetchall()]
+        for message in results:
+            message._replace(additional_data=json.loads(message.additional_data))
 
-        return messages
+        return results
 
     SearchResult = namedtuple('SearchResult',
             ['contact_name', 'time', 'kind', 'show', 'message', 'subject',

src/history_window.py

@@ -391,20 +391,19 @@ class HistoryWindow:
         """
         Add all the lines for given date in textbuffer
         """
-        self.history_buffer.set_text('') # clear the buffer first
+        self.history_buffer.set_text('')
         self.last_time_printout = 0
         show_status = self.show_status_checkbutton.get_active()
 
-        lines = gajim.logger.get_conversation_for_date(self.jid, year, month, day, self.account)
-        for line in lines:
-            # line[0] is contact_name, line[1] is time of message
-            # line[2] is kind, line[3] is show, line[4] is message, line[5] is subject
-            # line[6] is additional_data, line[7] is log_line_id
-            if not show_status and line[2] in (KindConstant.GCSTATUS,
-            KindConstant.STATUS):
+        conversation = gajim.logger.get_conversation_for_date(
+                self.jid, year, month, day, self.account)
+        for message in conversation:
+            if not show_status and message.kind in (KindConstant.GCSTATUS,
+                                                    KindConstant.STATUS):
                 continue
-            self._add_new_line(line[0], line[1], line[2], line[3], line[4],
-                    line[5], line[6], line[7])
+            self._add_new_line(message.contact_name, message.time, message.kind,
+                    message.show, message.message, message.subject,
+                    message.additional_data, message.log_line_id)
 
     def _add_new_line(self, contact_name, tim, kind, show, message, subject,
                       additional_data, log_line_id):