ENH Sequence IMAP operations

Previously, we would open a new connection for each operation.
Eventually this would lead to my IMAP server complaining: "too many
simultaneous connections". This new version also reuses connections
(with a connection close timeout).

gui/resources.py

@@ -0,0 +1,40 @@
+# Copyright (C) 2013 Luis Pedro Coelho <luis@luispedro.org>
+# This file is part of rbit mail.
+from __future__ import print_function
+
+from contextlib import contextmanager
+
+class imap_manager(object):
+    def __init__(self):
+        from gevent.coros import Semaphore
+        self.client = None
+        self.sem = Semaphore(1)
+        self.count = 0
+
+    def close(self, current):
+        import gevent
+        gevent.sleep(360)
+        self.sem.acquire()
+        if self.count == current:
+            self.client.close()
+            self.client = None
+        imap_sem.release()
+
+    @contextmanager
+    def get(self):
+        import gevent
+        self.count += 1
+        self.sem.acquire()
+        self.count += 1
+        if self.client is None:
+            from rbit import config
+            from rbit import backend
+            from rbit import imap
+            cfg = config.Config('config', backend.create_session)
+            self.client = imap.IMAPClient.from_config(cfg)
+        yield self.client
+        self.sem.release()
+        gevent.spawn(lambda : self.close(self.count))
+
+
+

gui/tasks.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2012 Luis Pedro Coelho <luis@luispedro.org>
+# Copyright (C) 2012-2013 Luis Pedro Coelho <luis@luispedro.org>
 # This file is part of rbit mail.
 
 from __future__ import print_function
@@ -7,6 +7,17 @@
 
 from rbit import signals
 
+_imap_manager = None
+def get_imap():
+    # By importing only inside the function, we avoid having to import at
+    # programme start up
+    from resources import imap_manager
+    global _imap_manager
+    if _imap_manager is None:
+        _imap_manager = imap_manager()
+    return _imap_manager.get()
+
+
 def run_from_queue(group, q):
     from gevent import monkey
     # thread needs to be left alone as Qt handles those
@@ -121,15 +132,10 @@ def __init__(self, parent, message, target):
         self.target = target
 
     def _perform(self):
-        from rbit import config
-        from rbit import backend
-        from rbit import imap
-        cfg = config.Config('config', backend.create_session)
-        client = imap.IMAPClient.from_config(cfg)
-        client.select_folder(self.folder)
-        client.move_messages([self.uid], self.target)
-        client.expunge()
-        client.close()
+        with get_imap() as client:
+            client.select_folder(self.folder)
+            client.move_messages([self.uid], self.target)
+            client.expunge()
 
 class TrashMessage(MoveMessage):
     def __init__(self, parent, message):