pkg/analysis_server/lib/src/services/correction/fix/data_driven/code_template.dart

// Copyright (c) 2020, 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.

import 'package:analysis_server/src/services/correction/fix/data_driven/value_extractor.dart';
import 'package:analysis_server/src/services/correction/util.dart';
import 'package:analyzer/dart/ast/ast.dart';

/// An object used to generate code to be inserted.
class CodeTemplate {
  /// The kind of code that will be generated by this template.
  final CodeTemplateKind kind;

  /// The components of the template.
  final List<TemplateComponent> components;

  /// Initialize a newly generated code template with the given [kind] and
  /// [components].
  CodeTemplate(this.kind, this.components);

  String generate(AstNode node, CorrectionUtils utils) {
    var context = TemplateContext(node, utils);
    var buffer = StringBuffer();
    for (var component in components) {
      component.appendTo(buffer, context);
    }
    return buffer.toString();
  }
}

/// The kinds of code that can be generated by a template.
enum CodeTemplateKind {
  expression,
  statements,
}

/// An object used to compute some portion of a template.
abstract class TemplateComponent {
  /// Append the text contributed by this component to the given [sink], using
  /// the [context] to access needed information that isn't already known to
  /// this component.
  void appendTo(StringSink sink, TemplateContext context);
}

/// The context in which a template is being evaluated.
class TemplateContext {
  /// The node in the AST that is being transformed.
  final AstNode node;

  /// The utilities used to help extract the code associated with various nodes.
  final CorrectionUtils utils;

  /// A table mapping variable names to the values of those variables after they
  /// have been computed. Used to prevent computing the same value multiple
  /// times.
  final Map<ValueGenerator, String> _variableValues = {};

  /// Initialize a newly created variable support.
  TemplateContext(this.node, this.utils);

  /// Return the value of the variable with the given [name].
  String valueOf(ValueGenerator extractor) {
    return _variableValues.putIfAbsent(extractor, () {
      return extractor.from(this);
    });
  }
}

/// Literal text within a template.
class TemplateText extends TemplateComponent {
  /// The literal text to be included in the resulting code.
  final String text;

  /// Initialize a newly create template text with the given [text].
  TemplateText(this.text);

  @override
  void appendTo(StringSink sink, TemplateContext context) {
    sink.write(text);
  }
}

/// A reference to a variable within a template.
class TemplateVariable extends TemplateComponent {
  /// The extractor used to compute the value of the variable.
  final ValueGenerator extractor;

  /// Initialize a newly created template variable with the given [name].
  TemplateVariable(this.extractor);

  @override
  void appendTo(StringSink sink, TemplateContext context) {
    sink.write(context.valueOf(extractor));
  }
}