1 files changed, 135 insertions, 0 deletions
diff --git a/soledad/backends/objectstore.py b/soledad/backends/objectstore.py
new file mode 100644
index 00000000..7c5d1177
--- /dev/null
+++ b/soledad/backends/objectstore.py
@@ -0,0 +1,135 @@
+"""
+Abstract U1DB backend to handle storage using object stores (like CouchDB, for
+example.
+
+Right now, this is only used by CouchDatabase backend, but can also be
+extended to implement OpenStack or Amazon S3 storage, for example.
+"""
+
+from u1db.backends.inmemory import (
+    InMemoryDatabase,
+    InMemorySyncTarget,
+)
+from u1db import errors
+
+
+class ObjectStoreDatabase(InMemoryDatabase):
+    """
+    A backend for storing u1db data in an object store.
+    """
+
+    @classmethod
+    def open_database(cls, url, create, document_factory=None):
+        raise NotImplementedError(cls.open_database)
+
+    def __init__(self, replica_uid=None, document_factory=None):
+        super(ObjectStoreDatabase, self).__init__(
+            replica_uid,
+            document_factory=document_factory)
+        # sync data in memory with data in object store
+        if not self._get_doc(self.U1DB_DATA_DOC_ID):
+            self._init_u1db_data()
+        self._fetch_u1db_data()
+
+    #-------------------------------------------------------------------------
+    # methods from Database
+    #-------------------------------------------------------------------------
+
+    def _set_replica_uid(self, replica_uid):
+        super(ObjectStoreDatabase, self)._set_replica_uid(replica_uid)
+        self._store_u1db_data()
+
+    def _put_doc(self, doc):
+        raise NotImplementedError(self._put_doc)
+
+    def _get_doc(self, doc):
+        raise NotImplementedError(self._get_doc)
+
+    def get_all_docs(self, include_deleted=False):
+        raise NotImplementedError(self.get_all_docs)
+
+    def delete_doc(self, doc):
+        """Mark a document as deleted."""
+        old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
+        if old_doc is None:
+            raise errors.DocumentDoesNotExist
+        if old_doc.rev != doc.rev:
+            raise errors.RevisionConflict()
+        if old_doc.is_tombstone():
+            raise errors.DocumentAlreadyDeleted
+        if old_doc.has_conflicts:
+            raise errors.ConflictedDoc()
+        new_rev = self._allocate_doc_rev(doc.rev)
+        doc.rev = new_rev
+        doc.make_tombstone()
+        self._put_and_update_indexes(old_doc, doc)
+        return new_rev
+
+    # index-related methods
+
+    def create_index(self, index_name, *index_expressions):
+        """
+        Create an named index, which can then be queried for future lookups.
+        """
+        raise NotImplementedError(self.create_index)
+
+    def delete_index(self, index_name):
+        """Remove a named index."""
+        super(ObjectStoreDatabase, self).delete_index(index_name)
+        self._store_u1db_data()
+
+    def _replace_conflicts(self, doc, conflicts):
+        super(ObjectStoreDatabase, self)._replace_conflicts(doc, conflicts)
+        self._store_u1db_data()
+
+    def _do_set_replica_gen_and_trans_id(self, other_replica_uid,
+                                         other_generation,
+                                         other_transaction_id):
+        super(ObjectStoreDatabase, self)._do_set_replica_gen_and_trans_id(
+            other_replica_uid,
+            other_generation,
+            other_transaction_id)
+        self._store_u1db_data()
+
+    #-------------------------------------------------------------------------
+    # implemented methods from CommonBackend
+    #-------------------------------------------------------------------------
+
+    def _put_and_update_indexes(self, old_doc, doc):
+        for index in self._indexes.itervalues():
+            if old_doc is not None and not old_doc.is_tombstone():
+                index.remove_json(old_doc.doc_id, old_doc.get_json())
+            if not doc.is_tombstone():
+                index.add_json(doc.doc_id, doc.get_json())
+        trans_id = self._allocate_transaction_id()
+        self._put_doc(doc)
+        self._transaction_log.append((doc.doc_id, trans_id))
+        self._store_u1db_data()
+
+    #-------------------------------------------------------------------------
+    # methods specific for object stores
+    #-------------------------------------------------------------------------
+
+    U1DB_DATA_DOC_ID = 'u1db_data'
+
+    def _fetch_u1db_data(self):
+        """
+        Fetch u1db configuration data from backend storage.
+        """
+        NotImplementedError(self._fetch_u1db_data)
+
+    def _store_u1db_data(self):
+        """
+        Save u1db configuration data on backend storage.
+        """
+        NotImplementedError(self._store_u1db_data)
+
+    def _init_u1db_data(self):
+        """
+        Initialize u1db configuration data on backend storage.
+        """
+        NotImplementedError(self._init_u1db_data)
+
+
+class ObjectStoreSyncTarget(InMemorySyncTarget):
+    pass