Move the upload/download sqlite3 file logic to a manager

Also add a factory method so the manager can be controlled via config

ankisyncd/full_sync.py

@@ -0,0 +1,59 @@
+# -*- coding: utf-8 -*-
+
+import os
+from sqlite3 import dbapi2 as sqlite
+
+import anki.db
+
+class FullSyncManager:
+    def upload(self, col, data, session):
+        # Verify integrity of the received database file before replacing our
+        # existing db.
+        temp_db_path = session.get_collection_path() + ".tmp"
+        with open(temp_db_path, 'wb') as f:
+            f.write(data)
+
+        try:
+            with anki.db.DB(temp_db_path) as test_db:
+                if test_db.scalar("pragma integrity_check") != "ok":
+                    raise HTTPBadRequest("Integrity check failed for uploaded "
+                                         "collection database file.")
+        except sqlite.Error as e:
+            raise HTTPBadRequest("Uploaded collection database file is "
+                                 "corrupt.")
+
+        # Overwrite existing db.
+        col.close()
+        try:
+            os.rename(temp_db_path, session.get_collection_path())
+        finally:
+            col.reopen()
+            col.load()
+
+        return "OK"
+
+
+    def download(self, col, session):
+        col.close()
+        try:
+            data = open(session.get_collection_path(), 'rb').read()
+        finally:
+            col.reopen()
+            col.load()
+        return data
+
+
+def get_full_sync_manager(config):
+    if "full_sync_manager" in config and config["full_sync_manager"]:  # load from config
+        import importlib
+        import inspect
+        module_name, class_name = config['full_sync_manager'].rsplit('.', 1)
+        module = importlib.import_module(module_name.strip())
+        class_ = getattr(module, class_name.strip())
+
+        if not FullSyncManager in inspect.getmro(class_):
+            raise TypeError('''"full_sync_manager" found in the conf file but it doesn''t
+                            inherit from FullSyncManager''')
+        return class_(config)
+    else:
+        return FullSyncManager()