Fetch snapshot by time

README.md

@@ -269,6 +269,27 @@ Get a read-only snapshot of a document at the requested version.
   }
   ```
 
+`connection.fetchSnapshotByTimestamp(collection, id, timestamp, callback): void;`
+Get a read-only snapshot of a document at the requested version.
+
+* `collection` _(String)_
+  Collection name of the snapshot
+* `id` _(String)_
+  ID of the snapshot
+* `timestamp` _(number) [optional]_
+  The timestamp of the desired snapshot. The returned snapshot will be the latest snapshot before the provided timestamp
+* `callback` _(Function)_
+  Called with `(error, snapshot)`, where `snapshot` takes the following form:
+
+  ```javascript
+  {
+    id: string;         // ID of the snapshot
+    v: number;          // version number of the snapshot
+    type: string;       // the OT type of the snapshot, or null if it doesn't exist or is deleted
+    data: any;          // the snapshot
+  }
+  ```
+
 ### Class: `ShareDB.Doc`
 
 `doc.type` _(String_)
@@ -464,3 +485,5 @@ The `41xx` and `51xx` codes are reserved for use by ShareDB DB adapters, and the
 * 5018 - Required QueryEmitter listener not assigned
 * 5019 - getMilestoneSnapshot MilestoneDB method unimplemented
 * 5020 - saveMilestoneSnapshot MilestoneDB method unimplemented
+* 5021 - getMilestoneSnapshotAtOrBeforeTime MilestoneDB method unimplemented
+* 5022 - getMilestoneSnapshotAtOrAfterTime MilestoneDB method unimplemented

lib/agent.js

@@ -303,6 +303,8 @@ Agent.prototype._handleMessage = function(request, callback) {
         return this._submit(request.c, request.d, op, callback);
       case 'nf':
         return this._fetchSnapshot(request.c, request.d, request.v, callback);
+      case 'nt':
+        return this._fetchSnapshotByTimestamp(request.c, request.d, request.ts, callback);
       default:
         callback({code: 4000, message: 'Invalid or unknown message'});
     }
@@ -589,3 +591,7 @@ Agent.prototype._createOp = function(request) {
 Agent.prototype._fetchSnapshot = function (collection, id, version, callback) {
   this.backend.fetchSnapshot(this, collection, id, version, callback);
 };
+
+Agent.prototype._fetchSnapshotByTimestamp = function (collection, id, timestamp, callback) {
+  this.backend.fetchSnapshotByTimestamp(this, collection, id, timestamp, callback);
+};

lib/backend.js

@@ -81,7 +81,9 @@ Backend.prototype.SNAPSHOT_TYPES = {
   // The current snapshot is being fetched (eg through backend.fetch)
   current: 'current',
   // A specific snapshot is being fetched by version (eg through backend.fetchSnapshot)
-  byVersion: 'byVersion'
+  byVersion: 'byVersion',
+  // A specific snapshot is being fetch by timestamp (eg through backend.fetchSnapshotByTimestamp)
+  byTimestamp: 'byTimestamp'
 };
 
 Backend.prototype._shimDocAction = function() {
@@ -627,6 +629,8 @@ Backend.prototype.fetchSnapshot = function(agent, index, id, version, callback)
 
 Backend.prototype._fetchSnapshot = function (collection, id, version, callback) {
   var db = this.db;
+  var backend = this;
+
   this.milestoneDb.getMilestoneSnapshot(collection, id, version, function (error, milestoneSnapshot) {
     if (error) return callback(error);
 
@@ -637,49 +641,98 @@ Backend.prototype._fetchSnapshot = function (collection, id, version, callback)
     db.getOps(collection, id, from, version, null, function (error, ops) {
       if (error) return callback(error);
 
-      var type = null;
-      var data;
-      var fetchedVersion = 0;
-
-      if (milestoneSnapshot) {
-        type = types.map[milestoneSnapshot.type];
-        if (!type) return callback({ code: 4008, message: 'Unknown type' });
-        data = milestoneSnapshot.data;
-        fetchedVersion = milestoneSnapshot.v;
-      }
+      backend._buildSnapshotFromOps(id, milestoneSnapshot, ops, function (error, snapshot) {
+        if (error) return callback(error);
 
-      for (var index = 0; index < ops.length; index++) {
-        var op = ops[index];
-        fetchedVersion = op.v + 1;
-
-        if (op.create) {
-          type = types.map[op.create.type];
-          if (!type) return callback({ code: 4008, message: 'Unknown type' });
-          data = type.create(op.create.data);
-        } else if (op.del) {
-          data = undefined;
-          type = null;
-        } else {
-          data = type.apply(data, op.op);
+        if (version > snapshot.v) {
+          return callback({ code: 4024, message: 'Requested version exceeds latest snapshot version' });
         }
-      }
 
-      type = type ? type.uri : null;
+        callback(null, snapshot);
+      });
+    });
+  });
+};
 
-      if (version > fetchedVersion) {
-        return callback({ code: 4024, message: 'Requested version exceeds latest snapshot version' });
-      }
+Backend.prototype.fetchSnapshotByTimestamp = function (agent, index, id, timestamp, callback) {
+  var start = Date.now();
+  var backend = this;
+  var projection = this.projections[index];
+  var collection = projection ? projection.target : index;
+  var request = {
+    agent: agent,
+    index: index,
+    collection: collection,
+    id: id,
+    timestamp: timestamp
+  };
 
-      var snapshot = new Snapshot(id, fetchedVersion, type, data, null);
+  this._fetchSnapshotByTimestamp(collection, id, timestamp, function (error, snapshot) {
+    if (error) return callback(error);
+    var snapshotProjection = backend._getSnapshotProjection(backend.db, projection);
+    var snapshots = [snapshot];
+    var snapshotType = backend.SNAPSHOT_TYPES.byTimestamp;
+    backend._sanitizeSnapshots(agent, snapshotProjection, collection, snapshots, snapshotType, function (error) {
+      if (error) return callback(error);
+      backend.emit('timing', 'fetchSnapshot', Date.now() - start, request);
       callback(null, snapshot);
     });
   });
 };
 
+Backend.prototype._fetchSnapshotByTimestamp = function (collection, id, timestamp, callback) {
+  var db = this.db;
+  var milestoneDb = this.milestoneDb;
+  var backend = this;
+
+  var milestoneSnapshot;
+  var from = 0;
+  var to = null;
+
+  milestoneDb.getMilestoneSnapshotAtOrBeforeTime(collection, id, timestamp, function (error, snapshot) {
+    if (error) return callback(error);
+    milestoneSnapshot = snapshot;
+    if (snapshot) from = snapshot.v;
+
+    milestoneDb.getMilestoneSnapshotAtOrAfterTime(collection, id, timestamp, function (error, snapshot) {
+      if (error) return callback(error);
+      if (snapshot) to = snapshot.v;
+
+      var options = {metadata: true};
+      db.getOps(collection, id, from, to, options, function (error, ops) {
+        if (error) return callback(error);
+        filterOpsInPlaceBeforeTimestamp(ops, timestamp);
+        backend._buildSnapshotFromOps(id, milestoneSnapshot, ops, callback);
+      });
+    });
+  });
+};
+
+Backend.prototype._buildSnapshotFromOps = function (id, startingSnapshot, ops, callback) {
+  var snapshot = startingSnapshot || new Snapshot(id, 0, null, undefined, null);
+  var error = ot.applyOps(snapshot, ops);
+  callback(error, snapshot);
+};
+
 function pluckIds(snapshots) {
   var ids = [];
   for (var i = 0; i < snapshots.length; i++) {
     ids.push(snapshots[i].id);
   }
   return ids;
 }
+
+function filterOpsInPlaceBeforeTimestamp(ops, timestamp) {
+  if (timestamp === null) {
+    return;
+  }
+
+  for (var i = 0; i < ops.length; i++) {
+    var op = ops[i];
+    var opTimestamp = op.m && op.m.ts;
+    if (opTimestamp > timestamp) {
+      ops.length = i;
+      return;
+    }
+  }
+}

lib/client/connection.js

@@ -1,6 +1,7 @@
 var Doc = require('./doc');
 var Query = require('./query');
-var SnapshotRequest = require('./snapshot-request');
+var SnapshotVersionRequest = require('./snapshot-request/snapshot-version-request');
+var SnapshotTimestampRequest = require('./snapshot-request/snapshot-timestamp-request');
 var emitter = require('../emitter');
 var ShareDBError = require('../error');
 var types = require('../types');
@@ -233,6 +234,7 @@ Connection.prototype.handleMessage = function(message) {
       return this._handleBulkMessage(message, '_handleUnsubscribe');
 
     case 'nf':
+    case 'nt':
       return this._handleSnapshotFetch(err, message);
 
     case 'f':
@@ -634,7 +636,35 @@ Connection.prototype.fetchSnapshot = function(collection, id, version, callback)
   }
 
   var requestId = this.nextSnapshotRequestId++;
-  var snapshotRequest = new SnapshotRequest(this, requestId, collection, id, version, callback);
+  var snapshotRequest = new SnapshotVersionRequest(this, requestId, collection, id, version, callback);
+  this._snapshotRequests[snapshotRequest.requestId] = snapshotRequest;
+  snapshotRequest.send();
+};
+
+/**
+ * Fetch a read-only snapshot at a given timestamp
+ *
+ * @param collection - the collection name of the snapshot
+ * @param id - the ID of the snapshot
+ * @param timestamp (optional) - the timestamp to fetch
+ * @param callback - (error, snapshot) => void, where snapshot takes the following schema:
+ *
+ * {
+ *   id: string;         // ID of the snapshot
+ *   v: number;          // version number of the snapshot
+ *   type: string;       // the OT type of the snapshot, or null if it doesn't exist or is deleted
+ *   data: any;          // the snapshot
+ * }
+ *
+ */
+Connection.prototype.fetchSnapshotByTimestamp = function (collection, id, timestamp, callback) {
+  if (typeof timestamp === 'function') {
+    callback = timestamp;
+    timestamp = null;
+  }
+
+  var requestId = this.nextSnapshotRequestId++;
+  var snapshotRequest = new SnapshotTimestampRequest(this, requestId, collection, id, timestamp, callback);
   this._snapshotRequests[snapshotRequest.requestId] = snapshotRequest;
   snapshotRequest.send();
 };

lib/client/snapshot-request.js → lib/client/snapshot-request/snapshot-request.js

@@ -1,25 +1,19 @@
-var Snapshot = require('../snapshot');
-var util = require('../util');
-var emitter = require('../emitter');
+var Snapshot = require('../../snapshot');
+var emitter = require('../../emitter');
 
 module.exports = SnapshotRequest;
 
-function SnapshotRequest(connection, requestId, collection, id, version, callback) {
+function SnapshotRequest(connection, requestId, collection, id, callback) {
   emitter.EventEmitter.call(this);
 
   if (typeof callback !== 'function') {
     throw new Error('Callback is required for SnapshotRequest');
   }
 
-  if (!util.isValidVersion(version)) {
-    throw new Error('Snapshot version must be a positive integer or null');
-  }
-
   this.requestId = requestId;
   this.connection = connection;
   this.id = id;
   this.collection = collection;
-  this.version = version;
   this.callback = callback;
 
   this.sent = false;
@@ -31,15 +25,7 @@ SnapshotRequest.prototype.send = function () {
     return;
   }
 
-  var message = {
-    a: 'nf',
-    id: this.requestId,
-    c: this.collection,
-    d: this.id,
-    v: this.version,
-  };
-
-  this.connection.send(message);
+  this.connection.send(this._message());
   this.sent = true;
 };
 
@@ -61,6 +47,8 @@ SnapshotRequest.prototype._handleResponse = function (error, message) {
     return this.callback(error);
   }
 
-  var snapshot = new Snapshot(this.id, message.v, message.type, message.data, null);
+  var metadata = message.meta ? message.meta : null;
+  var snapshot = new Snapshot(this.id, message.v, message.type, message.data, metadata);
+
   this.callback(null, snapshot);
 };

lib/client/snapshot-request/snapshot-timestamp-request.js

@@ -0,0 +1,26 @@
+var SnapshotRequest = require('./snapshot-request');
+var util = require('../../util');
+
+module.exports = SnapshotTimestampRequest;
+
+function SnapshotTimestampRequest(connection, requestId, collection, id, timestamp, callback) {
+  SnapshotRequest.call(this, connection, requestId, collection, id, callback);
+
+  if (!util.isValidTimestamp(timestamp)) {
+    throw new Error('Snapshot timestamp must be a positive integer or null');
+  }
+
+  this.timestamp = timestamp;
+}
+
+SnapshotTimestampRequest.prototype = Object.create(SnapshotRequest.prototype);
+
+SnapshotTimestampRequest.prototype._message = function () {
+  return {
+    a: 'nt',
+    id: this.requestId,
+    c: this.collection,
+    d: this.id,
+    ts: this.timestamp,
+  };
+};

lib/client/snapshot-request/snapshot-version-request.js

@@ -0,0 +1,26 @@
+var SnapshotRequest = require('./snapshot-request');
+var util = require('../../util');
+
+module.exports = SnapshotVersionRequest;
+
+function SnapshotVersionRequest (connection, requestId, collection, id, version, callback) {
+  SnapshotRequest.call(this, connection, requestId, collection, id, callback);
+
+  if (!util.isValidVersion(version)) {
+    throw new Error('Snapshot version must be a positive integer or null');
+  }
+
+  this.version = version;
+}
+
+SnapshotVersionRequest.prototype = Object.create(SnapshotRequest.prototype);
+
+SnapshotVersionRequest.prototype._message = function () {
+  return {
+    a: 'nf',
+    id: this.requestId,
+    c: this.collection,
+    d: this.id,
+    v: this.version,
+  };
+};