Rework undocumented listjoin to create UID sequences

This function was badly named and completely undocumented. Rework it to
avoid copying the full UID list using an iterator. Make it possible to
hand it a list of UIDs as strings rather than implicitely relying on the
fact that they are numeric already. Document the code.

The behavior off the function itself remained otherwise unchanged.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/folder/Gmail.py

@@ -54,7 +54,7 @@ class GmailFolder(IMAPFolder):
             try:
                 imapobj.select(self.getfullname())
                 result = imapobj.uid('copy',
-                                     imaputil.listjoin(uidlist),
+                                     imaputil.uid_sequence(uidlist),
                                      self.trash_folder)
                 assert result[0] == 'OK', \
                        "Bad IMAPlib result: %s" % result[0]

offlineimap/folder/IMAP.py

@@ -638,7 +638,7 @@ class IMAPFolder(BaseFolder):
                 self.ui.flagstoreadonly(self, uidlist, flags)
                 return
             r = imapobj.uid('store',
-                            imaputil.listjoin(uidlist),
+                            imaputil.uid_sequence(uidlist),
                             operation + 'FLAGS',
                             imaputil.flagsmaildir2imap(flags))
             assert r[0] == 'OK', 'Error with store: ' + '. '.join(r[1])

offlineimap/imaputil.py

@@ -188,33 +188,31 @@ def flagsmaildir2imap(maildirflaglist):
     retval.sort()
     return '(' + ' '.join(retval) + ')'
 
-def listjoin(list):
-    start = None
-    end = None
-    retval = []
+def uid_sequence(uidlist):
+    """Collapse UID lists into shorter sequence sets
 
-    def getlist(start, end):
+    [1,2,3,4,5,10,12,13] will return "1:5,10,12:13".  This function does
+    not sort the list, and only collapses if subsequent entries form a
+    range.
+    :returns: The collapsed UID list as string"""
+    def getrange(start, end):
         if start == end:
             return(str(start))
-        else:
-            return(str(start) + ":" + str(end))
-        
+        return "%s:%s" % (start, end)
 
-    for item in list:
-        if start == None:
-            # First item.
-            start = item
-            end = item
-        elif item == end + 1:
-            # An addition to the list.
-            end = item
-        else:
-            # Here on: starting a new list.
-            retval.append(getlist(start, end))
-            start = item
-            end = item
+    if not len(uidlist): return '' # Empty list, return
+    start, end = None, None
+    retval = []
 
-    if start != None:
-        retval.append(getlist(start, end))
+    for item in iter(uidlist):
+        item = int(item)
+        if start == None:     # First item
+            start, end = item, item
+        elif item == end + 1: # Next item in a range
+            end = item
+        else:                 # Starting a new range
+            retval.append(getrange(start, end))
+            start, end = item, item
 
+    retval.append(getrange(start, end)) # Add final range/item
     return ",".join(retval)