// 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_generator.dart';
import 'package:analysis_server/src/services/correction/util.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer_plugin/utilities/change_builder/change_builder_dart.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)
      : assert(kind != null),
        assert(components != null);

  /// Use the [context] to validate that this template will be able to generate
  /// a value.
  bool validate(TemplateContext context) {
    for (var component in components) {
      if (!component.validate(context)) {
        return false;
      }
    }
    return true;
  }

  void writeOn(DartEditBuilder builder, TemplateContext context) {
    for (var component in components) {
      component.writeOn(builder, context);
    }
  }
}

/// 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 {
  /// Use the [context] to validate that this component will be able to generate
  /// a value.
  bool validate(TemplateContext context);

  /// Write the text contributed by this component to the given [builder], using
  /// the [context] to access needed information that isn't already known to
  /// this component.
  void writeOn(DartEditBuilder builder, 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;

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

/// 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
  bool validate(TemplateContext context) {
    return true;
  }

  @override
  void writeOn(DartEditBuilder builder, TemplateContext context) {
    builder.write(text);
  }
}

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

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

  @override
  bool validate(TemplateContext context) {
    return generator.validate(context);
  }

  @override
  void writeOn(DartEditBuilder builder, TemplateContext context) {
    generator.writeOn(builder, context);
  }
}