// 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/assist.dart';
import 'package:analysis_server/src/services/correction/dart/abstract_producer.dart';
import 'package:analysis_server/src/services/correction/util.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer_plugin/utilities/assist/assist.dart';
import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
import 'package:analyzer_plugin/utilities/range_factory.dart';

class JoinIfWithOuter extends CorrectionProducer {
  @override
  AssistKind get assistKind => DartAssistKind.JOIN_IF_WITH_OUTER;

  @override
  Future<void> compute(ChangeBuilder builder) async {
    // climb up condition to the (supposedly) "if" statement
    var node = this.node;
    while (node is Expression) {
      node = node.parent;
    }
    // prepare target "if" statement
    if (node is! IfStatement) {
      return;
    }
    var targetIfStatement = node as IfStatement;
    if (targetIfStatement.elseStatement != null) {
      return;
    }
    // prepare outer "if" statement
    var parent = targetIfStatement.parent;
    if (parent is Block) {
      if ((parent as Block).statements.length != 1) {
        return;
      }
      parent = parent.parent;
    }
    if (parent is! IfStatement) {
      return;
    }
    var outerIfStatement = parent as IfStatement;
    if (outerIfStatement.elseStatement != null) {
      return;
    }
    // prepare environment
    var prefix = utils.getNodePrefix(outerIfStatement);
    // merge conditions
    var targetCondition = targetIfStatement.condition;
    var outerCondition = outerIfStatement.condition;
    var targetConditionSource = utils.getNodeText(targetCondition);
    var outerConditionSource = utils.getNodeText(outerCondition);
    if (shouldWrapParenthesisBeforeAnd(targetCondition)) {
      targetConditionSource = '($targetConditionSource)';
    }
    if (shouldWrapParenthesisBeforeAnd(outerCondition)) {
      outerConditionSource = '($outerConditionSource)';
    }
    var condition = '$outerConditionSource && $targetConditionSource';
    // replace outer "if" statement
    var targetThenStatement = targetIfStatement.thenStatement;
    var targetThenStatements = getStatements(targetThenStatement);
    var lineRanges = utils.getLinesRangeStatements(targetThenStatements);
    var oldSource = utils.getRangeText(lineRanges);
    var newSource = utils.indentSourceLeftRight(oldSource);

    await builder.addDartFileEdit(file, (builder) {
      builder.addSimpleReplacement(range.node(outerIfStatement),
          'if ($condition) {$eol$newSource$prefix}');
    });
  }

  /// Return an instance of this class. Used as a tear-off in `AssistProcessor`.
  static JoinIfWithOuter newInstance() => JoinIfWithOuter();
}