Move PW message handler logic to components

components/physical_web/webui/physical_web_base_message_handler.cc

+// Copyright 2016 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 "components/physical_web/webui/physical_web_base_message_handler.h"
+
+#include "base/bind.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/metrics/user_metrics.h"
+#include "components/physical_web/data_source/physical_web_data_source.h"
+#include "components/physical_web/webui/physical_web_ui_constants.h"
+
+namespace {
+
+// Maximum value for the "selected position" histogram.
+const int kSelectedPositionMaxValue = 50;
+
+}  // namespace
+
+namespace physical_web_ui {
+
+PhysicalWebBaseMessageHandler::PhysicalWebBaseMessageHandler() {}
+
+PhysicalWebBaseMessageHandler::~PhysicalWebBaseMessageHandler() = default;
+
+void PhysicalWebBaseMessageHandler::RegisterMessagesImpl() {
+  RegisterMessageCallback(
+      kRequestNearbyUrls,
+      base::Bind(&PhysicalWebBaseMessageHandler::HandleRequestNearbyURLs,

[mattreynolds, 2016/12/13 22:40:13]

src/docs/callback.md suggests we should use base::BindRepeating since base::Bind
is due to be deprecated.

[cco3, 2016/12/21 18:06:58]

Done.

+                 base::Unretained(this)));
+  RegisterMessageCallback(kPhysicalWebItemClicked,
+      base::Bind(&PhysicalWebBaseMessageHandler::HandlePhysicalWebItemClicked,
+                 base::Unretained(this)));
+}
+
+void PhysicalWebBaseMessageHandler::HandleRequestNearbyURLs(
+    const base::ListValue* args) {
+  base::DictionaryValue results;
+
+  std::unique_ptr<base::ListValue> metadata =
+      GetPhysicalWebDataSource()->GetMetadata();
+
+  // Add item indices. When an item is selected, the index of the selected item
+  // is recorded in a UMA histogram.
+  for (size_t i = 0; i < metadata->GetSize(); i++) {
+    base::DictionaryValue* metadata_item = NULL;
+    metadata->GetDictionary(i, &metadata_item);
+    metadata_item->SetInteger(physical_web_ui::kIndex, i);
+  }
+
+  results.Set(physical_web_ui::kMetadata, metadata.release());
+
+  // Pass the list of Physical Web URL metadata to the WebUI. A jstemplate will
+  // create a list view with an item for each URL.
+  CallJavaScriptFunction(physical_web_ui::kReturnNearbyUrls, results);
+}
+
+void PhysicalWebBaseMessageHandler::HandlePhysicalWebItemClicked(
+    const base::ListValue* args) {
+  int index;
+  if (!args->GetInteger(0, &index)) {
+    DLOG(ERROR) << "Invalid selection index";
+    return;
+  }
+
+  // Record the index of the selected item. The index must be strictly less than
+  // the maximum enumeration value.
+  if (index > kSelectedPositionMaxValue) {

[mattreynolds, 2016/12/13 22:40:13]

Turns out this is incorrect, UMA_HISTOGRAM_EXACT_LINEAR does have overflow and
underflow buckets so this check is unnecessary. Let's remove it.

[cco3, 2016/12/21 18:06:58]

Done.

+    index = kSelectedPositionMaxValue;
+  }
+  UMA_HISTOGRAM_EXACT_LINEAR("PhysicalWeb.WebUI.ListViewUrlPosition", index,
+                             kSelectedPositionMaxValue);

[mattreynolds, 2016/12/13 22:40:13]

Let's remove the kSelectedPositionMaxValue constant and just put the max value
inline.

[cco3, 2016/12/21 18:06:58]

Done.

+
+  // Count the number of selections.
+  base::RecordAction(
+      base::UserMetricsAction("PhysicalWeb.WebUI.ListViewUrlSelected"));
+}
+
+} //  namespace physical_web_ui