Encapsulate TracingAgent (#46986)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46986

# Changelog: [Internal]

Encapsulate integration with `FuseboxTracer.cpp` into `TracingAgent.cpp`, which will be responsible for handling `Tracing` domain CDP events.

Closer to the top of the stack, more changes will be added to it.

Reviewed By: huntie

Differential Revision: D64249695

fbshipit-source-id: 4adf5973299275e210e7cdf9c816efab881c9daf

packages/react-native/ReactCommon/jsinspector-modern/HostAgent.cpp

@@ -15,8 +15,6 @@
 
 #include <chrono>
 
-#include <reactperflogger/fusebox/FuseboxTracer.h>
-
 using namespace std::chrono;
 using namespace std::literals::string_view_literals;
 
@@ -36,7 +34,8 @@ HostAgent::HostAgent(
       targetController_(targetController),
       hostMetadata_(std::move(hostMetadata)),
       sessionState_(sessionState),
-      networkIOAgent_(NetworkIOAgent(frontendChannel, executor)) {}
+      networkIOAgent_(NetworkIOAgent(frontendChannel, std::move(executor))),
+      tracingAgent_(TracingAgent(frontendChannel)) {}
 
 void HostAgent::handleRequest(const cdp::PreparsedRequest& req) {
   bool shouldSendOKResponse = false;
@@ -149,43 +148,6 @@ void HostAgent::handleRequest(const cdp::PreparsedRequest& req) {
 
     shouldSendOKResponse = true;
     isFinishedHandlingRequest = true;
-  } else if (req.method == "Tracing.start") {
-    // @cdp Tracing.start support is experimental.
-    if (FuseboxTracer::getFuseboxTracer().startTracing()) {
-      shouldSendOKResponse = true;
-    } else {
-      frontendChannel_(cdp::jsonError(
-          req.id,
-          cdp::ErrorCode::InternalError,
-          "Tracing session already started"));
-      return;
-    }
-    isFinishedHandlingRequest = true;
-  } else if (req.method == "Tracing.end") {
-    // @cdp Tracing.end support is experimental.
-    bool firstChunk = true;
-    auto id = req.id;
-    bool wasStopped = FuseboxTracer::getFuseboxTracer().stopTracing(
-        [this, firstChunk, id](const folly::dynamic& eventsChunk) {
-          if (firstChunk) {
-            frontendChannel_(cdp::jsonResult(id));
-          }
-          frontendChannel_(cdp::jsonNotification(
-              "Tracing.dataCollected",
-              folly::dynamic::object("value", eventsChunk)));
-        });
-    if (!wasStopped) {
-      frontendChannel_(cdp::jsonError(
-          req.id,
-          cdp::ErrorCode::InternalError,
-          "Tracing session not started"));
-      return;
-    }
-    frontendChannel_(cdp::jsonNotification(
-        "Tracing.tracingComplete",
-        folly::dynamic::object("dataLossOccurred", false)));
-    shouldSendOKResponse = true;
-    isFinishedHandlingRequest = true;
   }
 
   if (!isFinishedHandlingRequest &&
@@ -193,6 +155,10 @@ void HostAgent::handleRequest(const cdp::PreparsedRequest& req) {
     return;
   }
 
+  if (!isFinishedHandlingRequest && tracingAgent_.handleRequest(req)) {
+    return;
+  }
+
   if (!isFinishedHandlingRequest && instanceAgent_ &&
       instanceAgent_->handleRequest(req)) {
     return;

packages/react-native/ReactCommon/jsinspector-modern/HostAgent.h

@@ -11,6 +11,7 @@
 #include "HostTarget.h"
 #include "NetworkIOAgent.h"
 #include "SessionState.h"
+#include "TracingAgent.h"
 
 #include <jsinspector-modern/InspectorInterfaces.h>
 #include <jsinspector-modern/InstanceAgent.h>
@@ -110,6 +111,8 @@ class HostAgent final {
   SessionState& sessionState_;
 
   NetworkIOAgent networkIOAgent_;
+
+  TracingAgent tracingAgent_;
 };
 
 } // namespace facebook::react::jsinspector_modern

packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "TracingAgent.h"
+
+#include <reactperflogger/fusebox/FuseboxTracer.h>
+
+namespace facebook::react::jsinspector_modern {
+
+bool TracingAgent::handleRequest(const cdp::PreparsedRequest& req) {
+  if (req.method == "Tracing.start") {
+    // @cdp Tracing.start support is experimental.
+    if (FuseboxTracer::getFuseboxTracer().startTracing()) {
+      frontendChannel_(cdp::jsonResult(req.id));
+    } else {
+      frontendChannel_(cdp::jsonError(
+          req.id,
+          cdp::ErrorCode::InternalError,
+          "Tracing session already started"));
+    }
+
+    return true;
+  } else if (req.method == "Tracing.end") {
+    // @cdp Tracing.end support is experimental.
+    bool firstChunk = true;
+    auto id = req.id;
+    bool wasStopped = FuseboxTracer::getFuseboxTracer().stopTracing(
+        [this, firstChunk, id](const folly::dynamic& eventsChunk) {
+          if (firstChunk) {
+            frontendChannel_(cdp::jsonResult(id));
+          }
+          frontendChannel_(cdp::jsonNotification(
+              "Tracing.dataCollected",
+              folly::dynamic::object("value", eventsChunk)));
+        });
+
+    if (!wasStopped) {
+      frontendChannel_(cdp::jsonError(
+          req.id,
+          cdp::ErrorCode::InternalError,
+          "Tracing session not started"));
+    } else {
+      frontendChannel_(cdp::jsonNotification(
+          "Tracing.tracingComplete",
+          folly::dynamic::object("dataLossOccurred", false)));
+    }
+
+    frontendChannel_(cdp::jsonResult(req.id));
+    return true;
+  }
+
+  return false;
+}
+
+} // namespace facebook::react::jsinspector_modern

packages/react-native/ReactCommon/jsinspector-modern/TracingAgent.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include "CdpJson.h"
+#include "InspectorInterfaces.h"
+
+namespace facebook::react::jsinspector_modern {
+
+/**
+ * Provides an agent for handling CDP's Tracing.start, Tracing.stop.
+ */
+class TracingAgent {
+ public:
+  /**
+   * \param frontendChannel A channel used to send responses to the
+   * frontend.
+   */
+  explicit TracingAgent(FrontendChannel frontendChannel)
+      : frontendChannel_(std::move(frontendChannel)) {}
+
+  /**
+   * Handle a CDP request. The response will be sent over the provided
+   * \c FrontendChannel synchronously or asynchronously.
+   * \param req The parsed request.
+   */
+  bool handleRequest(const cdp::PreparsedRequest& req);
+
+ private:
+  /**
+   * A channel used to send responses and events to the frontend.
+   */
+  FrontendChannel frontendChannel_;
+};
+
+} // namespace facebook::react::jsinspector_modern