move import combinator suggestions into a separate computer

pkg/analysis_server/lib/src/services/completion/combinator_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.dart.combinator;
+
+import 'dart:async';
+
+import 'package:analysis_server/src/protocol_server.dart' hide Element,
+    ElementKind;
+import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
+import 'package:analysis_server/src/services/completion/suggestion_builder.dart';
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+
+/**
+ * A computer for calculating `completion.getSuggestions` request results
+ * for the import combinators show and hide.
+ */
+
+class CombinatorComputer extends DartCompletionComputer {
+
+  @override
+  bool computeFast(DartCompletionRequest request) {
+    return false;
+  }
+
+  @override
+  Future<bool> computeFull(DartCompletionRequest request) {
+    return request.node.accept(new _CombinatorAstVisitor(request));
+  }
+}
+
+/**
+ * A visitor for determining which imported classes and top level variables
+ * should be suggested and building those suggestions.
+ */
+class _CombinatorAstVisitor extends GeneralizingAstVisitor<Future<bool>> {
+  final DartCompletionRequest request;
+
+  _CombinatorAstVisitor(this.request);
+
+  @override
+  Future<bool> visitCombinator(Combinator node) {
+    return _addCombinatorSuggestions(node);
+  }
+
+  @override
+  Future<bool> visitNode(AstNode node) {
+    return new Future.value(false);
+  }
+
+  @override
+  Future<bool> visitSimpleIdentifier(SimpleIdentifier node) {
+    return node.parent.accept(this);
+  }
+
+  Future _addCombinatorSuggestions(Combinator node) {
+    var directive = node.getAncestor((parent) => parent is NamespaceDirective);
+    if (directive is NamespaceDirective) {
+      LibraryElement library = directive.uriElement;
+      LibraryElementSuggestionBuilder.suggestionsFor(
+          request,
+          CompletionSuggestionKind.IDENTIFIER,
+          library);
+      return new Future.value(true);
+    }
+    return new Future.value(false);
+  }
+}