support Transaction api

crossfire/lib/src/crossfire_base.dart

@@ -13,6 +13,7 @@ abstract class Firebase {
   Future<FirebaseStorageRef> getStorage(String path);
   bool get isConnected;
   Stream<bool> get onConnectivityUpdated;
+  Future<void> runTransaction(TransactionRunner updateFunction);
 }
 
 abstract class FirebaseDocument {
@@ -103,3 +104,20 @@ enum FireDocumentChangeType {
   /// longer matches the query.
   removed,
 }
+
+typedef void TransactionRunner(FirebaseTransaction transaction);
+
+abstract class FirebaseTransaction {
+  Future<FirebaseTransaction> delete(FirebaseDocumentReference documentRef);
+  Future<FirebaseDocument> getDocument(FirebaseDocumentReference documentRef);
+  Future<FirebaseTransaction> setData(
+    FirebaseDocumentReference documentRef,
+    Map<String, dynamic> data, {
+    bool merge = false,
+  });
+  Future<FirebaseTransaction> update(
+    FirebaseDocumentReference documentRef, {
+    Map<String, dynamic> data,
+    List fieldsAndValues,
+  });
+}

crossfire_flutter/lib/crossfire_flutter.dart

@@ -110,6 +110,12 @@ class FlutterFirebase implements Firebase {
 
   @override
   Stream<bool> get onConnectivityUpdated => _connectionChangedSink.stream;
+
+  @override
+  Future<void> runTransaction(TransactionRunner updateFunction) =>
+      _firestore.runTransaction((t) {
+        updateFunction(FlutterFirebaseTransaction(t));
+      });
 }
 
 class FlutterFirebaseDocReference implements FirebaseDocumentReference {
@@ -307,3 +313,48 @@ class FlutterStorageMetadata implements FirebaseStorageMetadata {
   String get contentType => _metadata.contentType;
   int get size => _metadata.sizeBytes;
 }
+
+class FlutterFirebaseTransaction implements FirebaseTransaction {
+  final Transaction _transaction;
+
+  FlutterFirebaseTransaction(this._transaction);
+
+  @override
+  Future<FirebaseTransaction> delete(
+    FirebaseDocumentReference documentRef,
+  ) async {
+    final doc = documentRef as FlutterFirebaseDocReference;
+    await _transaction.delete(doc.ref);
+    return this;
+  }
+
+  @override
+  Future<FirebaseDocument> getDocument(
+      FirebaseDocumentReference documentRef) async {
+    final doc = documentRef as FlutterFirebaseDocReference;
+    final snap = await _transaction.get(doc.ref);
+    return FlutterFirebaseDoc(snap);
+  }
+
+  @override
+  Future<FirebaseTransaction> setData(
+    FirebaseDocumentReference documentRef,
+    Map<String, dynamic> data, {
+    bool merge = false,
+  }) async {
+    final doc = documentRef as FlutterFirebaseDocReference;
+    await _transaction.set(doc.ref, data);
+    return this;
+  }
+
+  @override
+  Future<FirebaseTransaction> update(
+    FirebaseDocumentReference documentRef, {
+    Map<String, dynamic> data,
+    List fieldsAndValues,
+  }) async {
+    final doc = documentRef as FlutterFirebaseDocReference;
+    await _transaction.update(doc.ref, data);
+    return this;
+  }
+}

crossfire_web/lib/crossfire_web.dart

@@ -37,13 +37,12 @@ class FirebaseWeb implements Firebase {
     if (usePersistence != null && usePersistence) {
       try {
         _store.enablePersistence();
-      } catch(e) {
+      } catch (e) {
         // Support re-initializing with a different app. Enabling persistence
         // can throw an error if it has already been enabled once on the page.
       }
     }
     _storage = fb.storage(app);
-
   }
 
   @override
@@ -82,6 +81,10 @@ class FirebaseWeb implements Firebase {
 
   @override
   Stream<bool> get onConnectivityUpdated => _connectionChangeSink.stream;
+
+  @override
+  Future<void> runTransaction(TransactionRunner updateFunction) => _store
+      .runTransaction((t) => updateFunction(BrowserFirebaseTransaction(t)));
 }
 
 class BrowserFirebaseQuerySnapshot implements FirebaseQuerySnapshot {
@@ -322,3 +325,51 @@ class BrowserFirebaseQuery extends FirebaseQuery {
     return new BrowserFirebaseQuery(q);
   }
 }
+
+class BrowserFirebaseTransaction implements FirebaseTransaction {
+  final Transaction _transaction;
+
+  BrowserFirebaseTransaction(this._transaction);
+
+  @override
+  Future<FirebaseTransaction> delete(
+      FirebaseDocumentReference documentRef) async {
+    final doc = documentRef as BrowserFirebaseDocReference;
+    final t = _transaction.delete(doc._ref);
+    return BrowserFirebaseTransaction(t);
+  }
+
+  @override
+  Future<FirebaseDocument> getDocument(
+      FirebaseDocumentReference documentRef) async {
+    final doc = documentRef as BrowserFirebaseDocReference;
+    final snap = await _transaction.get(doc._ref);
+    return BrowserDocumentSnapshot(snap);
+  }
+
+  @override
+  Future<FirebaseTransaction> setData(
+    FirebaseDocumentReference documentRef,
+    Map<String, dynamic> data, {
+    bool merge = false,
+  }) async {
+    final doc = documentRef as BrowserFirebaseDocReference;
+    final t = _transaction.set(doc._ref, data, SetOptions(merge: merge));
+    return BrowserFirebaseTransaction(t);
+  }
+
+  @override
+  Future<FirebaseTransaction> update(
+    FirebaseDocumentReference documentRef, {
+    Map<String, dynamic> data,
+    List fieldsAndValues,
+  }) async {
+    final doc = documentRef as BrowserFirebaseDocReference;
+    final t = _transaction.update(
+      doc._ref,
+      data: data,
+      fieldsAndValues: fieldsAndValues,
+    );
+    return BrowserFirebaseTransaction(t);
+  }
+}