refactor and cleanup code completion

pkg/analysis_services/lib/completion/completion_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;
-
-import 'dart:async';
-
-import 'package:analysis_services/completion/completion_suggestion.dart';
-import 'package:analysis_services/search/search_engine.dart';
-import 'package:analysis_services/src/completion/dart_completion_manager.dart';
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/engine.dart';
-import 'package:analyzer/src/generated/source.dart';
-
-/**
- * The base class for computing code completion suggestions.
- */
-abstract class CompletionComputer {
-  AnalysisContext context;
-  Source source;
-  int offset;
-  SearchEngine searchEngine;
-
-  /**
-   * Computes the initial set of [CompletionSuggestion]s based on
-   * the compilation [unit], the AST [node] in which the completion occurred,
-   * and information already cached in the analysis context.
-   * The supplied [unit] and [node] may not be resolved.
-   * This method should execute quickly and not block waiting for any analysis.
-   * Returns `true` if the computer's work is complete
-   * or `false` if [computeFull] should be called to complete the work.
-   */
-  bool computeFast(CompilationUnit unit, AstNode node,
-      List<CompletionSuggestion> suggestions);
-
-  /**
-   * Computes the complete set of [CompletionSuggestion]s based on
-   * the resolved compilation [unit] and the resolved AST [node] in which the
-   * completion occurred.
-   * Returns `true` if the receiver modified the list of suggestions.
-   */
-  Future<bool> computeFull(CompilationUnit unit, AstNode node,
-      List<CompletionSuggestion> suggestions);
-}
-
-/**
- * Manages `CompletionComputer`s for a given completion request.
- */
-abstract class CompletionManager {
-
-  StreamController<CompletionResult> controller;
-
-  /**
-   * Compute completion results and append them to the stream.
-   * Subclasses should override this method, append at least one result
-   * to the [controller], and close the controller stream once complete.
-   * Clients should not call this method directly as it is automatically called
-   * when a client listens to the stream returned by [results].
-   */
-  void compute();
-
-  /**
-   * Generate a stream of code completion results.
-   */
-  Stream<CompletionResult> results() {
-    controller = new StreamController<CompletionResult>(onListen: () {
-      scheduleMicrotask(compute);
-    });
-    return controller.stream;
-  }
-
-  /**
-   * Create a manager for the given request.
-   */
-  static CompletionManager create(AnalysisContext context, Source source,
-      int offset, SearchEngine searchEngine) {
-    if (context != null) {
-      if (AnalysisEngine.isDartFileName(source.shortName)) {
-        return new DartCompletionManager(context, source, offset, searchEngine);
-      }
-    }
-    return new NoOpCompletionManager(source, offset);
-  }
-}
-
-/**
- * Code completion result generated by an [CompletionManager].
- */
-class CompletionResult {
-
-  /**
-   * The length of the text to be replaced if the remainder of the identifier
-   * containing the cursor is to be replaced when the suggestion is applied
-   * (that is, the number of characters in the existing identifier).
-   */
-  final int replacementLength;
-
-  /**
-   * The offset of the start of the text to be replaced. This will be different
-   * than the offset used to request the completion suggestions if there was a
-   * portion of an identifier before the original offset. In particular, the
-   * replacementOffset will be the offset of the beginning of said identifier.
-   */
-  final int replacementOffset;
-
-  /**
-   * The suggested completions.
-   */
-  final List<CompletionSuggestion> suggestions;
-
-  /**
-   * `true` if this is that last set of results that will be returned
-   * for the indicated completion.
-   */
-  final bool last;
-
-  CompletionResult(this.replacementOffset, this.replacementLength,
-      this.suggestions, this.last);
-}
-
-
-class NoOpCompletionManager extends CompletionManager {
-  final Source source;
-  final int offset;
-
-  NoOpCompletionManager(this.source, this.offset);
-
-  @override
-  void compute() {
-    controller.add(new CompletionResult(offset, 0, [], true));
-  }
-}