Diagnostic status reporting (#24932).

pkg/analysis_server/lib/src/domain_diagnostic.dart

 // Copyright (c) 2015, 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 src.domain_diagnostic;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core' hide Resource;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/analysis_server.dart';
+import 'package:analysis_server/src/utilities/average.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/generated/engine.dart'
     hide AnalysisCache, AnalysisContextImpl;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/task/model.dart';
 
@@ skipping 98 matching lines @@
   static const int maxSampleCount = 30;
 
   /// Current sample count.
   int sampleCount = 0;
 
   /// The shared timer.
   Timer timer;
 
   /// Map of contexts (tracked as folders to avoid leaks) to averages.
   /// TOOD(pq): consider adding GC to remove mappings for deleted folders
-  Map<Folder, _Average> averages = new HashMap<Folder, _Average>();
+  Map<Folder, Average> averages = new HashMap<Folder, Average>();
 
   final AnalysisServer server;
   Sampler(this.server) {
     start();
     _sample();
   }
 
   /// Get the average for the context associated with the given [folder].
   int getAverage(Folder folder) {
     resetTimerCountdown();
@@ skipping 25 matching lines @@
   /// Stop sampling.
   void stop() {
     timer.cancel();
   }
 
   /// Take a sample.
   void _sample() {
     try {
       server.folderMap.forEach((Folder folder, AnalysisContext context) {
         if (context is AnalysisContextImpl) {
-          _Average average = averages[folder];
+          Average average = averages[folder];
           if (average == null) {
-            average = new _Average();
+            average = new Average();
             averages[folder] = average;
           }
           average.addSample(_workItemCount(context));
         }
       });
     } on Exception {
       stop();
     }
   }
 }
-
-/// Simple rolling average sample counter.
-class _Average {
-  num _val;
-
-  final int sampleCount;
-  _Average([this.sampleCount = 20]);
-
-  num get value => _val ?? 0;
-
-  void addSample(num sample) {
-    if (_val == null) {
-      _val = sample;
-    } else {
-      _val =
-          _val * ((sampleCount - 1) / sampleCount) + sample * (1 / sampleCount);
-    }
-  }
-
-  @override
-  String toString() => 'average: ${value}';
-}