1 files changed, 131 insertions, 0 deletions
diff --git a/__init__.py b/__init__.py
index b7082e53..7f742a89 100644
--- a/__init__.py
+++ b/__init__.py
@@ -41,3 +41,134 @@ class GPGWrapper():
 
     def import_keys(self, data):
         return self.gpg.import_keys(data)
+
+
+#----------------------------------------------------------------------------
+# u1db Transaction and Sync logs as JSON structures.
+#----------------------------------------------------------------------------
+
+class SimpleLog(object):
+    def __init__(self):
+        self._log = []
+
+    def _set_log(self, log):
+        self._log = log
+
+    def _get_log(self):
+        return self._log
+
+    log = property(
+        _get_log, _set_log, doc="Log contents.")
+
+    def append(self, msg):
+        self._log.append(msg)
+
+    def reduce(self, func, initializer=None):
+        return reduce(func, self.log, initializer)
+
+    def map(self, func):
+        return map(func, self.log)
+
+    def filter(self, func):
+        return filter(func, self.log)
+
+
+class TransactionLog(SimpleLog):
+    """
+    An ordered list of (generation, doc_id, transaction_id) tuples.
+    """
+
+    def _set_log(self, log):
+        self._log = log
+
+    def _get_log(self):
+        return sorted(self._log, reverse=True)
+
+    log = property(
+        _get_log, _set_log, doc="Log contents.")
+
+    def get_generation(self):
+        """
+        Return the current generation.
+        """
+        gens = self.map(lambda x: x[0])
+        if not gens:
+            return 0
+        return max(gens)
+
+    def get_generation_info(self):
+        """
+        Return the current generation and transaction id.
+        """
+        if not self._log:
+            return(0, '')
+        info = self.map(lambda x: (x[0], x[2]))
+        return reduce(lambda x, y: x if (x[0] > y[0]) else y, info)
+
+    def get_trans_id_for_gen(self, gen):
+        """
+        Get the transaction id corresponding to a particular generation.
+        """
+        log = self.reduce(lambda x, y: y if y[0] == gen else x)
+        if log is None:
+            return None
+        return log[2]
+
+    def whats_changed(self, old_generation):
+        """
+        Return a list of documents that have changed since old_generation.
+        """
+        results = self.filter(lambda x: x[0] > old_generation)
+        seen = set()
+        changes = []
+        newest_trans_id = ''
+        for generation, doc_id, trans_id in results:
+            if doc_id not in seen:
+                changes.append((doc_id, generation, trans_id))
+                seen.add(doc_id)
+        if changes:
+            cur_gen = changes[0][1]  # max generation
+            newest_trans_id = changes[0][2]
+            changes.reverse()
+        else:
+            results = self.log
+            if not results:
+                cur_gen = 0
+                newest_trans_id = ''
+            else:
+                cur_gen, _, newest_trans_id = results[0]
+
+        return cur_gen, newest_trans_id, changes
+        
+
+
+class SyncLog(SimpleLog):
+    """
+    A list of (replica_id, generation, transaction_id) tuples.
+    """
+
+    def find_by_replica_uid(self, replica_uid):
+        if not self.log:
+            return ()
+        return self.reduce(lambda x, y: y if y[0] == replica_uid else x)
+
+    def get_replica_gen_and_trans_id(self, other_replica_uid):
+        """
+        Return the last known generation and transaction id for the other db
+        replica.
+        """
+        info = self.find_by_replica_uid(other_replica_uid)
+        if not info:
+            return (0, '')
+        return (info[1], info[2])
+
+    def set_replica_gen_and_trans_id(self, other_replica_uid,
+                                      other_generation, other_transaction_id):
+        """
+        Set the last-known generation and transaction id for the other
+        database replica.
+        """
+        self.log = self.filter(lambda x: x[0] != other_replica_uid)
+        self.append((other_replica_uid, other_generation,
+                     other_transaction_id))
+