incremental step moving completion into services and adding tests

pkg/analysis_services/lib/completion/top_level_computer.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 services.completion.computer.toplevel;
+
+import 'dart:async';
+
+import 'package:analysis_services/completion/completion_suggestion.dart';
+import 'package:analysis_services/search/search_engine.dart';
+import 'package:analyzer/src/generated/element.dart';
+
+/**
+ * A computer for `completion.getSuggestions` request results.
+ */
+class TopLevelComputer {
+  final SearchEngine searchEngine;
+
+  TopLevelComputer(this.searchEngine);
+
+  /**
+   * Computes [CompletionSuggestion]s for the specified position in the source.
+   */
+  Future<List<CompletionSuggestion>> compute() {
+    var future = searchEngine.searchTopLevelDeclarations('');
+    return future.then((List<SearchMatch> matches) {
+      return matches.map((SearchMatch match) {
+        Element element = match.element;
+        String completion = element.displayName;
+        return new CompletionSuggestion(
+            CompletionSuggestionKind.fromElementKind(element.kind),
+            CompletionRelevance.DEFAULT,
+            completion,
+            completion.length,
+            0,
+            element.isDeprecated,
+            false // isPotential
+            );
+      }).toList();
+    });
+  }
+}