[WIP] Federated cloud firestore platform interface

packages/cloud_firestore/cloud_firestore/example/.flutter-plugins-dependencies

@@ -0,0 +1 @@
+{"_info":"// This is a generated file; do not edit or check into version control.","dependencyGraph":[{"name":"cloud_firestore","dependencies":["firebase_core"]},{"name":"firebase_core","dependencies":[]}]}

packages/cloud_firestore/cloud_firestore/lib/cloud_firestore.dart

@@ -9,6 +9,8 @@ import 'dart:convert';
 import 'dart:typed_data';
 import 'dart:ui' show hashValues, hashList;
 
+import 'package:cloud_firestore_platform_interface/cloud_firestore_platform_interface.dart';
+
 import 'package:collection/collection.dart';
 import 'package:firebase_core/firebase_core.dart';
 import 'package:flutter/foundation.dart' show ReadBuffer, WriteBuffer;

packages/cloud_firestore/cloud_firestore/lib/src/document_reference.dart

@@ -48,14 +48,11 @@ class DocumentReference {
   /// If [merge] is true, the provided data will be merged into an
   /// existing document instead of overwriting.
   Future<void> setData(Map<String, dynamic> data, {bool merge = false}) {
-    return Firestore.channel.invokeMethod<void>(
-      'DocumentReference#setData',
-      <String, dynamic>{
-        'app': firestore.app.name,
-        'path': path,
-        'data': data,
-        'options': <String, bool>{'merge': merge},
-      },
+    return Firestore.platform.setDocumentReferenceData(
+      firestore.app.name,
+      path: path,
+      data: data,
+      options: <String, bool>{'merge': merge},
     );
   }
 
@@ -66,13 +63,10 @@ class DocumentReference {
   ///
   /// If no document exists yet, the update will fail.
   Future<void> updateData(Map<String, dynamic> data) {
-    return Firestore.channel.invokeMethod<void>(
-      'DocumentReference#updateData',
-      <String, dynamic>{
-        'app': firestore.app.name,
-        'path': path,
-        'data': data,
-      },
+    return Firestore.platform.updateDocumentReferenceData(
+      firestore.app.name,
+      path: path,
+      data: data,
     );
   }
 
@@ -81,14 +75,12 @@ class DocumentReference {
   /// If no document exists, the read will return null.
   Future<DocumentSnapshot> get({Source source = Source.serverAndCache}) async {
     final Map<String, dynamic> data =
-        await Firestore.channel.invokeMapMethod<String, dynamic>(
-      'DocumentReference#get',
-      <String, dynamic>{
-        'app': firestore.app.name,
-        'path': path,
-        'source': _getSourceString(source),
-      },
+        await Firestore.platform.getDocumentReference(
+      firestore.app.name,
+      path: path,
+      source: _getSourceString(source),
     );
+
     return DocumentSnapshot._(
       data['path'],
       _asStringKeyedMap(data['data']),
@@ -100,9 +92,9 @@ class DocumentReference {
 
   /// Deletes the document referred to by this [DocumentReference].
   Future<void> delete() {
-    return Firestore.channel.invokeMethod<void>(
-      'DocumentReference#delete',
-      <String, dynamic>{'app': firestore.app.name, 'path': path},
+    return Firestore.platform.deleteDocumentReference(
+      firestore.app.name,
+      path: path,
     );
   }
 
@@ -118,34 +110,19 @@ class DocumentReference {
   // TODO(jackson): Reduce code duplication with [Query]
   Stream<DocumentSnapshot> snapshots({bool includeMetadataChanges = false}) {
     assert(includeMetadataChanges != null);
-    Future<int> _handle;
-    // It's fine to let the StreamController be garbage collected once all the
-    // subscribers have cancelled; this analyzer warning is safe to ignore.
-    StreamController<DocumentSnapshot> controller; // ignore: close_sinks
-    controller = StreamController<DocumentSnapshot>.broadcast(
-      onListen: () {
-        _handle = Firestore.channel.invokeMethod<int>(
-          'DocumentReference#addSnapshotListener',
-          <String, dynamic>{
-            'app': firestore.app.name,
-            'path': path,
-            'includeMetadataChanges': includeMetadataChanges,
-          },
-        ).then<int>((dynamic result) => result);
-        _handle.then((int handle) {
-          Firestore._documentObservers[handle] = controller;
-        });
-      },
-      onCancel: () {
-        _handle.then((int handle) async {
-          await Firestore.channel.invokeMethod<void>(
-            'removeListener',
-            <String, dynamic>{'handle': handle},
-          );
-          Firestore._documentObservers.remove(handle);
-        });
-      },
-    );
-    return controller.stream;
+
+    return Firestore.platform
+        .getDocumentReferenceSnapshots(
+          firestore.app.name,
+          path: path,
+          includeMetadataChanges: includeMetadataChanges,
+        )
+        .map((dynamic data) => DocumentSnapshot._(
+              data['path'],
+              _asStringKeyedMap(data['data']),
+              SnapshotMetadata._(data['metadata']['hasPendingWrites'],
+                  data['metadata']['isFromCache']),
+              firestore,
+            ));
   }
 }

packages/cloud_firestore/cloud_firestore/lib/src/firestore.dart

@@ -10,28 +10,6 @@ part of cloud_firestore;
 class Firestore {
   Firestore({FirebaseApp app}) : app = app ?? FirebaseApp.instance {
     if (_initialized) return;
-    channel.setMethodCallHandler((MethodCall call) async {
-      if (call.method == 'QuerySnapshot') {
-        final QuerySnapshot snapshot = QuerySnapshot._(call.arguments, this);
-        _queryObservers[call.arguments['handle']].add(snapshot);
-      } else if (call.method == 'DocumentSnapshot') {
-        final DocumentSnapshot snapshot = DocumentSnapshot._(
-          call.arguments['path'],
-          _asStringKeyedMap(call.arguments['data']),
-          SnapshotMetadata._(call.arguments['metadata']['hasPendingWrites'],
-              call.arguments['metadata']['isFromCache']),
-          this,
-        );
-        _documentObservers[call.arguments['handle']].add(snapshot);
-      } else if (call.method == 'DoTransaction') {
-        final int transactionId = call.arguments['transactionId'];
-        final Transaction transaction = Transaction(transactionId, this);
-        final dynamic result =
-            await _transactionHandlers[transactionId](transaction);
-        await transaction._finish();
-        return result;
-      }
-    });
     _initialized = true;
   }
 
@@ -46,20 +24,7 @@ class Firestore {
   static bool _initialized = false;
 
   @visibleForTesting
-  static const MethodChannel channel = MethodChannel(
-    'plugins.flutter.io/cloud_firestore',
-    StandardMethodCodec(FirestoreMessageCodec()),
-  );
-
-  static final Map<int, StreamController<QuerySnapshot>> _queryObservers =
-      <int, StreamController<QuerySnapshot>>{};
-
-  static final Map<int, StreamController<DocumentSnapshot>> _documentObservers =
-      <int, StreamController<DocumentSnapshot>>{};
-
-  static final Map<int, TransactionHandler> _transactionHandlers =
-      <int, TransactionHandler>{};
-  static int _transactionHandlerId = 0;
+  static CloudFirestorePlatform platform = CloudFirestorePlatform.instance;
 
   @override
   bool operator ==(dynamic o) => o is Firestore && o.app == app;
@@ -123,39 +88,42 @@ class Firestore {
       {Duration timeout = const Duration(seconds: 5)}) async {
     assert(timeout.inMilliseconds > 0,
         'Transaction timeout must be more than 0 milliseconds');
-    final int transactionId = _transactionHandlerId++;
-    _transactionHandlers[transactionId] = transactionHandler;
-    final Map<String, dynamic> result = await channel
-        .invokeMapMethod<String, dynamic>(
-            'Firestore#runTransaction', <String, dynamic>{
-      'app': app.name,
-      'transactionId': transactionId,
-      'transactionTimeout': timeout.inMilliseconds
-    });
+
+    // Wrap the incoming [TransactionHandler] into something that can be passed
+    // to the Platform implementation.
+    final PlatformTransactionHandler handler = (int transactionId) async {
+      Transaction transaction = Transaction(transactionId, this);
+      final dynamic result = await transactionHandler(transaction);
+      await transaction._finish();
+      return result;
+    };
+
+    final Map<String, dynamic> result = await platform.runTransaction(
+      app.name,
+      transactionHandler: handler,
+      transactionTimeout: timeout.inMilliseconds,
+    );
     return result ?? <String, dynamic>{};
   }
 
   @deprecated
   Future<void> enablePersistence(bool enable) async {
     assert(enable != null);
-    await channel
-        .invokeMethod<void>('Firestore#enablePersistence', <String, dynamic>{
-      'app': app.name,
-      'enable': enable,
-    });
+    await platform.enablePersistence(
+      app.name,
+      enable: enable,
+    );
   }
 
   Future<void> settings(
       {bool persistenceEnabled,
       String host,
       bool sslEnabled,
       int cacheSizeBytes}) async {
-    await channel.invokeMethod<void>('Firestore#settings', <String, dynamic>{
-      'app': app.name,
-      'persistenceEnabled': persistenceEnabled,
-      'host': host,
-      'sslEnabled': sslEnabled,
-      'cacheSizeBytes': cacheSizeBytes,
-    });
+    await platform.settings(app.name,
+        persistenceEnabled: persistenceEnabled,
+        host: host,
+        sslEnabled: sslEnabled,
+        cacheSizeBytes: cacheSizeBytes);
   }
 }

packages/cloud_firestore/cloud_firestore/lib/src/query.dart

@@ -52,53 +52,29 @@ class Query {
   // TODO(jackson): Reduce code duplication with [DocumentReference]
   Stream<QuerySnapshot> snapshots({bool includeMetadataChanges = false}) {
     assert(includeMetadataChanges != null);
-    Future<int> _handle;
-    // It's fine to let the StreamController be garbage collected once all the
-    // subscribers have cancelled; this analyzer warning is safe to ignore.
-    StreamController<QuerySnapshot> controller; // ignore: close_sinks
-    controller = StreamController<QuerySnapshot>.broadcast(
-      onListen: () {
-        _handle = Firestore.channel.invokeMethod<int>(
-          'Query#addSnapshotListener',
-          <String, dynamic>{
-            'app': firestore.app.name,
-            'path': _path,
-            'isCollectionGroup': _isCollectionGroup,
-            'parameters': _parameters,
-            'includeMetadataChanges': includeMetadataChanges,
-          },
-        ).then<int>((dynamic result) => result);
-        _handle.then((int handle) {
-          Firestore._queryObservers[handle] = controller;
-        });
-      },
-      onCancel: () {
-        _handle.then((int handle) async {
-          await Firestore.channel.invokeMethod<void>(
-            'removeListener',
-            <String, dynamic>{'handle': handle},
-          );
-          Firestore._queryObservers.remove(handle);
-        });
-      },
-    );
-    return controller.stream;
+
+    return Firestore.platform
+        .getQuerySnapshots(
+          firestore.app.name,
+          path: _path,
+          isCollectionGroup: _isCollectionGroup,
+          parameters: _parameters,
+          includeMetadataChanges: includeMetadataChanges,
+        )
+        .map((dynamic data) => QuerySnapshot._(data, firestore));
   }
 
   /// Fetch the documents for this query
   Future<QuerySnapshot> getDocuments(
       {Source source = Source.serverAndCache}) async {
     assert(source != null);
     final Map<dynamic, dynamic> data =
-        await Firestore.channel.invokeMapMethod<String, dynamic>(
-      'Query#getDocuments',
-      <String, dynamic>{
-        'app': firestore.app.name,
-        'path': _path,
-        'isCollectionGroup': _isCollectionGroup,
-        'parameters': _parameters,
-        'source': _getSourceString(source),
-      },
+        await Firestore.platform.getQueryDocuments(
+      firestore.app.name,
+      path: _path,
+      isCollectionGroup: _isCollectionGroup,
+      parameters: _parameters,
+      source: _getSourceString(source),
     );
     return QuerySnapshot._(data, firestore);
   }

packages/cloud_firestore/cloud_firestore/lib/src/transaction.dart

@@ -23,12 +23,12 @@ class Transaction {
   }
 
   Future<DocumentSnapshot> _get(DocumentReference documentReference) async {
-    final Map<String, dynamic> result = await Firestore.channel
-        .invokeMapMethod<String, dynamic>('Transaction#get', <String, dynamic>{
-      'app': _firestore.app.name,
-      'transactionId': _transactionId,
-      'path': documentReference.path,
-    });
+    final Map<String, dynamic> result = await Firestore.platform.getTransaction(
+      _firestore.app.name,
+      transactionId: _transactionId,
+      path: documentReference.path,
+    );
+
     if (result != null) {
       return DocumentSnapshot._(
           documentReference.path,
@@ -52,12 +52,11 @@ class Transaction {
   }
 
   Future<void> _delete(DocumentReference documentReference) async {
-    return Firestore.channel
-        .invokeMethod<void>('Transaction#delete', <String, dynamic>{
-      'app': _firestore.app.name,
-      'transactionId': _transactionId,
-      'path': documentReference.path,
-    });
+    return Firestore.platform.deleteTransaction(
+      _firestore.app.name,
+      transactionId: _transactionId,
+      path: documentReference.path,
+    );
   }
 
   /// Updates fields in the document referred to by [documentReference].
@@ -74,13 +73,10 @@ class Transaction {
 
   Future<void> _update(
       DocumentReference documentReference, Map<String, dynamic> data) async {
-    return Firestore.channel
-        .invokeMethod<void>('Transaction#update', <String, dynamic>{
-      'app': _firestore.app.name,
-      'transactionId': _transactionId,
-      'path': documentReference.path,
-      'data': data,
-    });
+    return Firestore.platform.updateTransaction(_firestore.app.name,
+        transactionId: _transactionId,
+        path: documentReference.path,
+        data: data);
   }
 
   /// Writes to the document referred to by the provided [DocumentReference].
@@ -98,12 +94,11 @@ class Transaction {
 
   Future<void> _set(
       DocumentReference documentReference, Map<String, dynamic> data) async {
-    return Firestore.channel
-        .invokeMethod<void>('Transaction#set', <String, dynamic>{
-      'app': _firestore.app.name,
-      'transactionId': _transactionId,
-      'path': documentReference.path,
-      'data': data,
-    });
+    return Firestore.platform.setTransaction(
+      _firestore.app.name,
+      transactionId: _transactionId,
+      path: documentReference.path,
+      data: data,
+    );
   }
 }