calcurse-caldav: Split object addition and removal

Instead of performing two synchronization steps (push/pull), split the
synchronization protocol into four steps:

1. Retrieve new objects from the server.
2. Delete local objects that no longer exist on the server.
3. Push new objects to the server.
4. Delete remote objects that no longer exist locally.

Each of the steps is performed by a separate function.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

contrib/caldav/calcurse-caldav.py

@@ -230,19 +230,12 @@ def push_object(conn, objhash):
     return (href, etag)
 
 
-def remove_remote_object(conn, etag, href):
-    headers = {'If-Match': '"' + etag + '"'}
-    remote_query(conn, "DELETE", href, headers, None)
-
-
 def push_objects(conn, syncdb, etagdict):
     objhashes = calcurse_hashset()
     new = objhashes - set([entry[1] for entry in syncdb.values()])
-    gone = set([entry[1] for entry in syncdb.values()]) - objhashes
-
-    added = deleted = 0
 
     # Copy new objects to the server.
+    added = 0
     for objhash in new:
         if verbose:
             print("Pushing new object {} to the server.".format(objhash))
@@ -253,7 +246,20 @@ def push_objects(conn, syncdb, etagdict):
         syncdb[href] = (etag, objhash)
         added += 1
 
+    return added
+
+
+def remove_remote_object(conn, etag, href):
+    headers = {'If-Match': '"' + etag + '"'}
+    remote_query(conn, "DELETE", href, headers, None)
+
+
+def remove_remote_objects(conn, syncdb, etagdict):
+    objhashes = calcurse_hashset()
+    gone = set([entry[1] for entry in syncdb.values()]) - objhashes
+
     # Remove locally deleted objects from the server.
+    deleted = 0
     for objhash in gone:
         queue = []
         for href, entry in syncdb.items():
@@ -280,7 +286,7 @@ def push_objects(conn, syncdb, etagdict):
             syncdb.pop(href, None)
             deleted += 1
 
-    return (added, deleted)
+    return deleted
 
 
 def pull_objects(conn, syncdb, etagdict):
@@ -291,7 +297,6 @@ def pull_objects(conn, syncdb, etagdict):
             missing.add(href)
         elif etagdict[href] != syncdb[href][0]:
             modified.add(href)
-    orphan = set(syncdb.keys()) - set(etagdict.keys())
 
     # Download and import new objects from the server.
     body = ('<?xml version="1.0" encoding="utf-8" ?>'
@@ -305,7 +310,7 @@ def pull_objects(conn, syncdb, etagdict):
 
     root = etree.fromstring(body)
 
-    added = deleted = 0
+    added = 0
 
     for node in root.findall(".//D:response", namespaces=nsmap):
         hrefnode = node.find("./D:href", namespaces=nsmap)
@@ -341,7 +346,14 @@ def pull_objects(conn, syncdb, etagdict):
         syncdb[href] = (etag, objhash)
         added += 1
 
+    return added
+
+
+def remove_local_objects(conn, syncdb, etagdict):
+    orphan = set(syncdb.keys()) - set(etagdict.keys())
+
     # Delete objects that no longer exist on the server.
+    deleted = 0
     for href in orphan:
         etag, objhash = syncdb[href]
 
@@ -354,7 +366,7 @@ def pull_objects(conn, syncdb, etagdict):
         syncdb.pop(href, None)
         deleted += 1
 
-    return (added, deleted)
+    return deleted
 
 
 def run_hook(name):
@@ -517,13 +529,17 @@ try:
     # server.
     etagdict = get_etags(conn)
 
-    # Retrieve new objects from the server, delete local items that no longer
-    # exist on the server.
-    local_new, local_del = pull_objects(conn, syncdb, etagdict)
+    # Retrieve new objects from the server
+    local_new = pull_objects(conn, syncdb, etagdict)
 
-    # Push new objects to the server, remove items from the server if they no
-    # longer exist locally.
-    remote_new, remote_del = push_objects(conn, syncdb, etagdict)
+    # Delete local items that no longer exist on the server.
+    local_del = remove_local_objects(conn, syncdb, etagdict)
+
+    # Push new objects to the server.
+    remote_new = push_objects(conn, syncdb, etagdict)
+
+    # Remove items from the server if they no longer exist locally.
+    remote_del = remove_remote_objects(conn, syncdb, etagdict)
 
     # Write the synchronization database.
     save_syncdb(syncdbfn, syncdb)