[macos] Add BasicMessageChannel

library/macos/FLEBasicMessageChannel.h

@@ -0,0 +1,70 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "FLEBinaryMessenger.h"
+#import "FLEMessageCodec.h"
+
+/**
+ * A message response callback. Used for sending a message's reply back to the Flutter engine.
+ * The reply must be serializable by the codec used to encode the message.
+ */
+typedef void (^FLEMessageReply)(id _Nullable reply);
+
+/**
+ * A handler for receiving a message. Implementations should asynchronously call |callback|
+ * exactly once with the reply to the message (or nil if there is none).
+ */
+typedef void (^FLEMessageHandler)(id _Nullable message, FLEMessageReply _Nonnull callback);
+
+/**
+ * A channel for communicating with the Flutter engine by sending asynchronous messages.
+ */
+@interface FLEBasicMessageChannel : NSObject
+
+// TODO: support +messageChannelWithName:binaryMessenger: once the standard codec is supported
+// (Issue #67).
+
+/**
+ * Returns a new channel that sends and receives messages on the channel named |name|, encoded
+ * with |codec| and dispatched via |messenger|.
+ */
++ (nonnull instancetype)messageChannelWithName:(nonnull NSString *)name
+                               binaryMessenger:(nonnull NSObject<FLEBinaryMessenger> *)messenger
+                                         codec:(nonnull NSObject<FLEMessageCodec> *)codec;
+
+/**
+ * Initializes a channel to send and receive messages on the channel named |name|, encoded
+ * with |codec| and dispatched via |messenger|.
+ */
+- (nonnull instancetype)initWithName:(nonnull NSString *)name
+                     binaryMessenger:(nonnull NSObject<FLEBinaryMessenger> *)messenger
+                               codec:(nonnull NSObject<FLEMessageCodec> *)codec;
+
+/**
+ * Sends a message to the Flutter engine on this channel.
+ *
+ * The message must be encodable using this channel's codec.
+ */
+- (void)sendMessage:(nullable id)message;
+
+// TODO: Support sendMessage:result: once
+// https://github.com/flutter/flutter/issues/18852 is resolved
+
+/**
+ * Registers a handler that should be called any time a message is received on this channel.
+ */
+- (void)setMessageHandler:(nullable FLEMessageHandler)handler;
+@end

library/macos/FLEBasicMessageChannel.m

@@ -0,0 +1,62 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "FLEBasicMessageChannel.h"
+
+@implementation FLEBasicMessageChannel {
+  NSString *_name;
+  __weak id<FLEBinaryMessenger> _messenger;
+  id<FLEMessageCodec> _codec;
+}
++ (instancetype)messageChannelWithName:(NSString *)name
+                       binaryMessenger:(NSObject<FLEBinaryMessenger> *)messenger
+                                 codec:(NSObject<FLEMessageCodec> *)codec {
+  return [[[self class] alloc] initWithName:name binaryMessenger:messenger codec:codec];
+}
+
+- (instancetype)initWithName:(NSString *)name
+             binaryMessenger:(NSObject<FLEBinaryMessenger> *)messenger
+                       codec:(NSObject<FLEMessageCodec> *)codec {
+  self = [super init];
+  if (self) {
+    _name = [name copy];
+    _messenger = messenger;
+    _codec = codec;
+  }
+  return self;
+}
+
+- (void)sendMessage:(id)message {
+  [_messenger sendOnChannel:_name message:[_codec encode:message]];
+}
+
+- (void)setMessageHandler:(FLEMessageHandler)handler {
+  if (!handler) {
+    [_messenger setMessageHandlerOnChannel:_name binaryMessageHandler:nil];
+    return;
+  }
+
+  // Don't capture the channel in the callback, since that makes lifetimes harder to reason about.
+  id<FLEMessageCodec> codec = _codec;
+
+  FLEBinaryMessageHandler messageHandler = ^(NSData *message, FLEBinaryReply callback) {
+    handler([codec decode:message], ^(id reply) {
+      callback([codec encode:reply]);
+    });
+  };
+
+  [_messenger setMessageHandlerOnChannel:_name binaryMessageHandler:messageHandler];
+}
+
+@end

library/macos/FLEJSONMessageCodec.h

@@ -0,0 +1,24 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "FLEMessageCodec.h"
+
+/**
+ * A codec that uses JSON as the encoding format. Messages using this codec must be serializable
+ * to JSON.
+ */
+@interface FLEJSONMessageCodec : NSObject <FLEMessageCodec>
+@end

library/macos/FLEJSONMessageCodec.m

@@ -0,0 +1,67 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "FLEJSONMessageCodec.h"
+
+@implementation FLEJSONMessageCodec
+
++ (instancetype)sharedInstance {
+  static FLEJSONMessageCodec *sharedInstance;
+  if (!sharedInstance) {
+    sharedInstance = [[FLEJSONMessageCodec alloc] init];
+  }
+  return sharedInstance;
+}
+
+- (NSData *)encode:(id)message {
+  if (!message) {
+    return nil;
+  }
+
+  NSData *encoding;
+  NSError *error = nil;
+  if ([message isKindOfClass:[NSArray class]] || [message isKindOfClass:[NSDictionary class]]) {
+    encoding = [NSJSONSerialization dataWithJSONObject:message options:0 error:&error];
+  } else {
+    // Wrap then unwrap non-collection objects; see FlutterCodecs.mm in the Flutter engine.
+    encoding = [NSJSONSerialization dataWithJSONObject:@[ message ] options:0 error:&error];
+    const NSUInteger kJSONArrayStartLength = 1;
+    const NSUInteger kJSONArrayEndLength = 1;
+    encoding = [encoding subdataWithRange:NSMakeRange(kJSONArrayStartLength,
+                                                      encoding.length - (kJSONArrayStartLength +
+                                                                         kJSONArrayEndLength))];
+  }
+  if (error) {
+    NSLog(@"Error: Failed to create JSON message for %@: %@", message, error.debugDescription);
+  }
+  return encoding;
+}
+
+// See FlutterCodecs.mm in the Flutter engine for implementation notes.
+- (id)decode:(NSData *)messageData {
+  if (!messageData) {
+    return nil;
+  }
+
+  NSError *error = nil;
+  id message = [NSJSONSerialization JSONObjectWithData:messageData
+                                               options:NSJSONReadingAllowFragments
+                                                 error:&error];
+  if (error) {
+    NSLog(@"Error: Failed to decode JSON message: %@", error.debugDescription);
+  }
+  return message;
+}
+
+@end

library/macos/FLEJSONMethodCodec.h

@@ -0,0 +1,24 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+#import "FLEMethodCodec.h"
+
+/**
+ * A codec that uses JSON as the encoding format. Method arguments and error details for plugins
+ * using this codec must be serializable to JSON.
+ */
+@interface FLEJSONMethodCodec : NSObject <FLEMethodCodec>
+@end

library/macos/FLECodecs.m → library/macos/FLEJSONMethodCodec.m

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#import "FLECodecs.h"
+#import "FLEJSONMethodCodec.h"
 
 // Keys for JSON-encoded method calls.
 static NSString *const kMessageMethodKey = @"method";
@@ -70,7 +70,7 @@ - (FLEMethodCall *)decodeMethodCall:(NSData *)methodData {
   return [[FLEMethodCall alloc] initWithMethodName:method arguments:arguments];
 }
 
-- (NSData *)encodeSuccessEnvelope:(id _Nullable)result {
+- (NSData *)encodeSuccessEnvelope:(id)result {
   return SerializeAsJSON(@[ result ?: [NSNull null] ]);
 }
 

library/macos/FLEMessageCodec.h

@@ -0,0 +1,38 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+/**
+ * Translates between a binary message and higher-level message objects.
+ */
+@protocol FLEMessageCodec
+
+/**
+ * Returns the shared instance of the codec.
+ */
++ (nonnull instancetype)sharedInstance;
+
+/**
+ * Returns a binary encoding of the given |message|, or nil if the message cannot be
+ * serialized by this codec.
+ */
+- (nullable NSData*)encode:(nullable id)message;
+
+/**
+ * Returns the decoded mesasge, or nil if it cannot be decoded.
+ */
+- (nullable id)decode:(nullable NSData*)messageData;
+
+@end

library/macos/FLEMethodCall.h

@@ -0,0 +1,43 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+
+/**
+ * An object encapsulating a method call from Flutter.
+ */
+@interface FLEMethodCall : NSObject
+
+/**
+ * Initializes an FLEMethodCall. If |arguments| is provided, it must be serializable by the codec
+ * used to encode the call.
+ */
+- (nonnull instancetype)initWithMethodName:(nonnull NSString *)name
+                                 arguments:(nullable id)arguments NS_DESIGNATED_INITIALIZER;
+
+- (nonnull instancetype)init NS_UNAVAILABLE;
+
+/**
+ * The name of the method being called.
+ */
+@property(readonly, nonatomic, nonnull) NSString *methodName;
+
+/**
+ * The arguments to the method being called, if any.
+ *
+ * This object must be serializable by the codec used to encode the call.
+ */
+@property(readonly, nonatomic, nullable) id arguments;
+
+@end

library/macos/FLEMethodCall.m

@@ -0,0 +1,28 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "FLEMethodCall.h"
+
+@implementation FLEMethodCall
+
+- (instancetype)initWithMethodName:(NSString *)name arguments:(id)arguments {
+  self = [super init];
+  if (self) {
+    _methodName = name;
+    _arguments = arguments;
+  }
+  return self;
+}
+
+@end