1 files changed, 105 insertions, 0 deletions
diff --git a/common/src/leap/soledad/common/ddocs/syncs/updates/state.js b/common/src/leap/soledad/common/ddocs/syncs/updates/state.js
new file mode 100644
index 00000000..d62aeb40
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+++ b/common/src/leap/soledad/common/ddocs/syncs/updates/state.js
@@ -0,0 +1,105 @@
+/**
+ * This update handler stores information about ongoing synchronization
+ * attempts from distinct source replicas.
+ *
+ * Normally, u1db synchronization occurs during one POST request. In order to
+ * split that into many serial POST requests, we store the state of each sync
+ * in the server, using a document with id 'u1db_sync_state'.  To identify
+ * each sync attempt, we use a sync_id sent by the client. If we ever receive
+ * a new sync_id, we trash current data for that source replica and start
+ * over.
+ *
+ * We expect the following in the document body:
+ *
+ * {
+ *     'source_replica_uid': '<source_replica_uid>',
+ *     'sync_id': '<sync_id>',
+ *     'seen_ids': [['<doc_id>', <at_gen>], ...],     // optional
+ *     'changes_to_return': [                         // optional
+ *         'gen': <gen>,
+ *         'trans_id': '<trans_id>',
+ *         'changes_to_return': [[<doc_id>', <gen>, '<trans_id>'], ...]
+ *     ],
+ * }
+ *
+ * The format of the final document stored on server is:
+ *
+ * {
+ *     '_id': '<str>',
+ *     '_rev' '<str>',
+ *     'ongoing_syncs': {
+ *         '<source_replica_uid>': {
+ *             'sync_id': '<sync_id>',
+ *             'seen_ids': [['<doc_id>', <at_gen>[, ...],
+ *             'changes_to_return': {
+ *                  'gen': <gen>,
+ *                  'trans_id': '<trans_id>',
+ *                  'changes_to_return': [
+ *                          ['<doc_id>', <gen>, '<trans_id>'],
+ *                          ...,
+ *                  ],
+ *             },
+ *         },
+ *         ... // info about other source replicas here
+ *     }
+ * }
+ */
+function(doc, req) {
+
+    // prevent updates to alien documents
+    if (doc != null && doc['_id'] != 'u1db_sync_state')
+        return [null, 'invalid data'];
+
+    // create the document if it doesn't exist
+    if (!doc)
+        doc = {
+            '_id': 'u1db_sync_state',
+            'ongoing_syncs': {},
+        };
+
+    // parse and validate incoming data
+    var body = JSON.parse(req.body);
+    if (body['source_replica_uid'] == null)
+        return [null, 'invalid data'];
+    var source_replica_uid = body['source_replica_uid'];
+
+    if (body['sync_id'] == null)
+        return [null, 'invalid data'];
+    var sync_id = body['sync_id'];
+
+    // trash outdated sync data for that replica if that exists
+    if (doc['ongoing_syncs'][source_replica_uid] != null &&
+            doc['ongoing_syncs'][source_replica_uid]['sync_id'] != sync_id)
+        delete doc['ongoing_syncs'][source_replica_uid];
+
+    // create an entry for that source replica
+    if (doc['ongoing_syncs'][source_replica_uid] == null)
+        doc['ongoing_syncs'][source_replica_uid] = {
+            'sync_id': sync_id,
+            'seen_ids': {},
+            'changes_to_return': null,
+        };
+
+    // incoming meta-data values should be exclusive, so we count how many
+    // arrived and deny to accomplish the transaction if the count is high.
+    var incoming_values = 0;
+    var info = doc['ongoing_syncs'][source_replica_uid]
+
+    // add incoming seen id
+    if ('seen_id' in body) {
+        info['seen_ids'][body['seen_id'][0]] = body['seen_id'][1];
+        incoming_values += 1;
+    }
+
+    // add incoming changes_to_return
+    if ('changes_to_return' in body) {
+        info['changes_to_return'] = body['changes_to_return'];
+        incoming_values += 1;
+    }
+
+    if (incoming_values != 1)
+        return [null, 'invalid data'];
+
+    return [doc, 'ok'];
+}
+