Restructure the public API for server

pkg/analysis_server/lib/edit/assist/assist_core.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 analysis_server.edit.assist.assist_core;
-
-import 'package:analysis_server/src/protocol.dart' show SourceChange;
-import 'package:analyzer/src/generated/engine.dart';
-import 'package:analyzer/src/generated/source.dart';
-
-/**
- * A description of a single proposed assist.
- *
- * Clients are not expected to subtype this class.
- */
-class Assist {
-  /**
-   * An empty list of assists.
-   */
-  static const List<Assist> EMPTY_LIST = const <Assist>[];
-
-  /**
-   * A comparator that can be used to sort assists by their relevance. The most
-   * relevant assists will be sorted before assists with a lower relevance.
-   */
-  static final Comparator<Assist> SORT_BY_RELEVANCE = (Assist firstAssist,
-          Assist secondAssist) =>
-      firstAssist.kind.relevance - secondAssist.kind.relevance;
-
-  /**
-   * A description of the assist being proposed.
-   */
-  final AssistKind kind;
-
-  /**
-   * The change to be made in order to apply the assist.
-   */
-  final SourceChange change;
-
-  /**
-   * Initialize a newly created assist to have the given [kind] and [change].
-   */
-  Assist(this.kind, this.change);
-
-  @override
-  String toString() {
-    return 'Assist(kind=$kind, change=$change)';
-  }
-}
-
-/**
- * An object used to produce assists for a specific location.
- *
- * Clients are expected to subtype this class when implementing plugins.
- */
-abstract class AssistContributor {
-  /**
-   * Return a list of assists for a location in the given [source]. The location
-   * is specified by the [offset] and [length] of the selected region. The
-   * [context] can be used to get additional information that is useful for
-   * computing assists.
-   */
-  List<Assist> computeAssists(
-      AnalysisContext context, Source source, int offset, int length);
-}
-
-/**
- * A description of a class of assists. Instances are intended to hold the
- * information that is common across a number of assists and to be shared by
- * those assists.
- *
- * Clients are not expected to subtype this class.
- */
-class AssistKind {
-  /**
-   * The name of this kind of assist, used for debugging.
-   */
-  final String name;
-
-  /**
-   * The relevance of this kind of assist for the kind of error being addressed.
-   */
-  final int relevance;
-
-  /**
-   * A human-readable description of the changes that will be applied by this
-   * kind of assist.
-   */
-  final String message;
-
-  /**
-   * Initialize a newly created kind of assist to have the given [name],
-   * [relevance] and [message].
-   */
-  const AssistKind(this.name, this.relevance, this.message);
-
-  @override
-  String toString() => name;
-}