implemented har feature

packages/devtools_app/lib/src/screens/network/constants.dart

@@ -0,0 +1,88 @@
+// Copyright 2024 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.
+
+enum NetworkEventKeys {
+  log,
+  version,
+  creator,
+  name,
+  pages,
+  startedDateTime,
+  id,
+  title,
+  pageTimings,
+  onContentLoad,
+  onLoad,
+  entries,
+  pageref,
+  time,
+  request,
+  method,
+  url,
+  httpVersion,
+  cookies,
+  headers,
+  queryString,
+  postData,
+  mimeType,
+  text,
+  headersSize,
+  bodySize,
+  response,
+  status,
+  statusText,
+  content,
+  size,
+  redirectURL,
+  cache,
+  timings,
+  blocked,
+  dns,
+  connect,
+  send,
+  wait,
+  receive,
+  ssl,
+  serverIPAddress,
+  connection,
+  comment,
+  value,
+  uri,
+  redirects,
+  path,
+  domain,
+  expires,
+  httpOnly,
+  secure,
+  reasonPhrase,
+}
+
+class NetworkEventDefaults {
+  static const logVersion = '1.2';
+  static const creatorName = 'devtools';
+  static const onContentLoad = -1;
+  static const onLoad = -1;
+  static const httpVersion = 'HTTP/1.1';
+  static const responseHttpVersion = 'http/2.0';
+  static const blocked = -1;
+  static const dns = -1;
+  static const connect = -1;
+  static const send = 1;
+  static const receive = 1;
+  static const ssl = -1;
+}
+
+class NetworkEventCustomFieldKeys {
+  static const isolateId = '_isolateId';
+  static const id = '_id';
+  static const startTime = '_startTime';
+  static const events = '_events';
+}
+
+enum NetworkEventCustomFieldRemappedKeys {
+  isolateId,
+  id,
+  startTime,
+  events,
+}

packages/devtools_app/lib/src/screens/network/har_builder.dart

@@ -0,0 +1,42 @@
+// Copyright 2024 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.
+
+import '../../shared/http/http_request_data.dart';
+import '../../shared/utils.dart';
+import 'constants.dart';
+import 'har_data_entry.dart';
+
+/// Builds a HAR (HTTP Archive) object from a list of HTTP requests.
+///
+/// The HAR format is a JSON-based format used for logging a web browser's
+/// interaction with a site. It is useful for performance analysis and
+/// debugging. This function constructs the HAR object based on the 1.2
+/// specification.
+///
+/// For more details on the HAR format, see the [HAR 1.2 Specification](https://github.com/ahmadnassri/har-spec/blob/master/versions/1.2.md).
+///
+/// Parameters:
+/// - [httpRequests]: A list of [DartIOHttpRequestData] data.
+///
+/// Returns:
+/// - A Map representing the HAR object.
+Map<String, Object?> buildHar(List<DartIOHttpRequestData> httpRequests) {
+  // Build the creator
+  final creator = <String, Object?>{
+    NetworkEventKeys.name.name: NetworkEventDefaults.creatorName,
+    NetworkEventKeys.version.name: devToolsVersion,
+  };
+
+  // Build the entries
+  final entries = httpRequests.map((e) => HarDataEntry.toJson(e)).toList();
+
+  // Assemble the final HAR object
+  return <String, Object?>{
+    NetworkEventKeys.log.name: <String, Object?>{
+      NetworkEventKeys.version.name: NetworkEventDefaults.logVersion,
+      NetworkEventKeys.creator.name: creator,
+      NetworkEventKeys.entries.name: entries,
+    },
+  };
+}