Blimp: create MessageDispatcher class.

blimp/common/net/message_dispatcher.cc

Index: blimp/common/net/message_dispatcher.cc
diff --git a/blimp/common/net/message_dispatcher.cc b/blimp/common/net/message_dispatcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5a90d510e6a34051850415cb9b932fe1959983c1
--- /dev/null
+++ b/blimp/common/net/message_dispatcher.cc
@@ -0,0 +1,53 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "blimp/common/net/message_dispatcher.h"
+
+#include <string>
+
+#include "base/strings/stringprintf.h"
+
+namespace blimp {
+namespace {
+
+std::string BlimpMessageToString(const BlimpMessage& message) {

[nyquist, 2015/09/08 17:30:12]

Nit: Could we make it clear that this is meant to be used for debugging, and not
for serialization by changing its name somewhat?

[Kevin M, 2015/09/08 20:50:19]

Done.

+  return base::StringPrintf("<message type=%d, tab=%d>", message.type(),
+                            message.target_tab_id());
+}
+
+}  // namespace
+
+MessageDispatcher::MessageDispatcher() {}
+
+MessageDispatcher::~MessageDispatcher() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void MessageDispatcher::AddHandler(BlimpMessage::Type type, Handler* handler) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (feature_handler_map_.find(type) == feature_handler_map_.end()) {

[nyquist, 2015/09/08 17:30:12]

Nit: Should we log an error if there already exists a handler? Seems like a
helpful error message should we ever do that by mistake. If you end up adding
that, following the pattern of early return like below would be handy.

[Kevin M, 2015/09/08 20:50:19]

Done.

+    feature_handler_map_.insert(std::make_pair(type, handler));
+  }
+}
+
+void MessageDispatcher::Dispatch(const BlimpMessage& message) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  auto handler_iter = feature_handler_map_.find(message.type());
+  if (handler_iter == feature_handler_map_.end()) {
+    LOG(ERROR) << "No registered handler for " << BlimpMessageToString(message)
+               << ".";
+    return;
+  }
+
+  DCHECK(handler_iter->second);
+  if (!handler_iter->second->Validate(message)) {
+    LOG(WARNING) << BlimpMessageToString(message) << " rejected by handler.";
+    return;
+  }
+
+  handler_iter->second->OnMessage(message);
+}
+
+}  // namespace blimp