Rework instrumentation API

pkg/analyzer/lib/instrumentation/instrumentation.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library instrumentation;
 
 /**
  * The interface used by client code to communicate with an instrumentation
  * server.
  */
 abstract class InstrumentationServer {
   /**
    * Pass the given [message] to the instrumentation server so that it will be
    * logged with other messages.
+   *
+   * This method should be used for most logging.
    */
   void log(String message);
 
   /**
+   * Pass the given [message] to the instrumentation server so that it will be
+   * logged with other messages.
+   *
+   * This method should only be used for logging high priority messages, such as
+   * exceptions that cause the server to shutdown.
+   */
+  void logWithPriority(String message);
+
+  /**
    * Signal that the client is done communicating with the instrumentation
    * server. This method should be invoked exactly one time and no other methods
    * should be invoked on this instance after this method has been invoked.
    */
   void shutdown();
 }
 
 /**
- * An [InstrumentationServer] that ignores all instrumentation requests sent to
- * it. It can be used when no instrumentation data is to be collected as a way
- * to avoid needing to check for null values.
+ * The interface used by client code to communicate with an instrumentation
+ * server by wrapping an [InstrumentationServer].
  */
-class NullInstrumentationServer implements InstrumentationServer {
+class InstrumentationService {
   /**
-   * Initialize a newly created instance of this class.
+   * An instrumentation service that will not log any instrumentation data.
    */
-  const NullInstrumentationServer();
+  static const InstrumentationService NULL_SERVICE =
+      const InstrumentationService(null);
 
-  @override
-  void log(String message) {
+  static const String TAG_NOTIFICATION = 'Noti';
+  static const String TAG_REQUEST = 'Req';
+  static const String TAG_RESPONSE = 'Res';
+  static const String TAG_VERSION = 'Ver';
+  /**
+   * The instrumentation server used to communicate with the server, or `null`
+   * if instrumentation data should not be logged.
+   */
+  final InstrumentationServer instrumentationServer;
+
+  /**
+   * Initialize a newly created instrumentation service to comunicate with the
+   * given instrumentation server.
+   */
+  const InstrumentationService(this.instrumentationServer);
+
+  /**
+   * The current time, expressed as a decimal encoded number of milliseconds.
+   */
+  String get _timestamp => new DateTime.now().millisecond.toString();
+
+  /**
+   * Log that a notification has been sent to the client.
+   */
+  void logNotification(String notification) {
+    _log(TAG_NOTIFICATION, notification);
   }
 
-  @override
+  /**
+   * Log that a request has been sent to the client.
+   */
+  void logRequest(String request) {
+    _log(TAG_REQUEST, request);
+  }
+
+  /**
+   * Log that a response has been sent to the client.
+   */
+  void logResponse(String response) {
+    _log(TAG_RESPONSE, response);
+  }
+
+  /**
+   * Signal that the client is done communicating with the instrumentation
+   * server. This method should be invoked exactly one time and no other methods
+   * should be invoked on this instance after this method has been invoked.
+   */
   void shutdown() {
+    if (instrumentationServer != null) {
+      instrumentationServer.shutdown();
+    }
+  }
+
+  /**
+   * Log the given message with the given tag.
+   */
+  void _log(String tag, String message) {
+    if (instrumentationServer != null) {
+      instrumentationServer.log('$_timestamp:$tag:$message');
+    }
   }
 }