// Copyright (c) 2017, 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:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/syntactic_entity.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/src/generated/source.dart';

/// An instance of [RangeFactory] made available for convenience.
final RangeFactory range = RangeFactory();

/// A factory used to create instances of [SourceRange] based on various
/// syntactic and semantic entities.
class RangeFactory {
  /// Return a source range that covers all of the arguments in the
  /// [argumentList] between the [lower] and [upper] indices, inclusive. The
  /// flag [forDeletion] controls whether a comma between the given indices and
  /// the neighboring arguments should be included in the range. If the flag is
  /// `true`, then the range can be deleted to delete the covered arguments and
  /// leave a valid argument list. If the flag is `false`, then the range can be
  /// replaced with different argument values.
  ///
  /// For example, given an argument list of `(a, b, c, d)`, a lower index of
  /// `1` and an upper index of `2`, the range will cover the text `'b, c'` if
  /// [forDeletion] is `false` and the text `', b, c'` if [forDeletion] is
  /// `true`.
  ///
  /// Throws and exception if either the [lower] or [upper] bound is not a valid
  /// index into the [argumentList] or if the [upper] bound is less than the
  /// [lower] bound.
  SourceRange argumentRange(
      ArgumentList argumentList, int lower, int upper, bool forDeletion) {
    var arguments = argumentList.arguments;
    assert(lower >= 0 && lower < arguments.length);
    assert(upper >= lower && upper < arguments.length);
    if (lower == upper) {
      // Remove a single argument.
      if (forDeletion) {
        return nodeInList(arguments, arguments[lower]);
      }
      return node(arguments[lower]);
    } else if (!forDeletion) {
      return startEnd(arguments[lower], arguments[upper]);
    } else if (lower == 0) {
      if (upper == arguments.length - 1) {
        // Remove all of the arguments.
        return endStart(
            argumentList.leftParenthesis, argumentList.rightParenthesis);
      } else {
        // Remove a subset of the arguments starting with the first argument.
        return startStart(arguments[lower], arguments[upper + 1]);
      }
    } else {
      // Remove a subset of the arguments starting in the middle of the
      // arguments.
      return endEnd(arguments[lower - 1], arguments[upper]);
    }
  }

  /// Return a source range that covers the name of the given [element].
  SourceRange elementName(Element element) {
    return SourceRange(element.nameOffset, element.nameLength);
  }

  /// Return a source range that starts at the end of [leftEntity] and ends at
  /// the end of [rightEntity].
  SourceRange endEnd(SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
    var offset = leftEntity.end;
    var length = rightEntity.end - offset;
    return SourceRange(offset, length);
  }

  /// Return a source range that starts at the end of [entity] and has the given
  /// [length].
  SourceRange endLength(SyntacticEntity entity, int length) {
    return SourceRange(entity.end, length);
  }

  /// Return a source range that starts at the end of [leftEntity] and ends at
  /// the start of [rightEntity].
  SourceRange endStart(
      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
    var offset = leftEntity.end;
    var length = rightEntity.offset - offset;
    return SourceRange(offset, length);
  }

  /// Return a source range that covers the same range as the given [error].
  SourceRange error(AnalysisError error) {
    return SourceRange(error.offset, error.length);
  }

  /// Return a source range that covers the same range as the given [node].
  SourceRange node(AstNode node) {
    return SourceRange(node.offset, node.length);
  }

  /// Return a source range that covers the given [item] (including a leading or
  /// trailing comma as appropriate) in the containing [list].
  SourceRange nodeInList<T extends AstNode>(NodeList<T> list, T item) {
    if (list.length == 1) {
      var nextToken = item.endToken.next;
      if (nextToken.type == TokenType.COMMA) {
        return startEnd(item, nextToken);
      }
      return node(item);
    }
    final index = list.indexOf(item);
    if (index == 0) {
      // Remove the trailing comma.
      return startStart(item, list[1]);
    } else {
      // Remove the leading comma.
      return endEnd(list[index - 1], item);
    }
  }

  /// Return a source range that covers all of the given [nodes] (that is, from
  /// the start of the first node to the end of the last node.
  SourceRange nodes(List<AstNode> nodes) {
    if (nodes.isEmpty) {
      return SourceRange(0, 0);
    }
    return startEnd(nodes.first, nodes.last);
  }

  /// Return a source range whose length is the same as the given [range], but
  /// whose offset is the offset of the given [range] with [offset] added to it.
  SourceRange offsetBy(SourceRange range, int offset) {
    return SourceRange(range.offset + offset, range.length);
  }

  /// Return a source range that starts at the start of [leftEntity] and ends at
  /// the end of [rightEntity].
  SourceRange startEnd(
      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
    var offset = leftEntity.offset;
    var length = rightEntity.end - offset;
    return SourceRange(offset, length);
  }

  /// Return a source range that starts at the start of [entity] and has a
  /// length of [length].
  SourceRange startLength(SyntacticEntity entity, int length) {
    return SourceRange(entity.offset, length);
  }

  /// Return a source range that starts at the given [startOffset] and ends at
  /// the given [endOffset].
  SourceRange startOffsetEndOffset(int startOffset, int endOffset) {
    var length = endOffset - startOffset;
    return SourceRange(startOffset, length);
  }

  /// Return a source range that starts at the start of [leftEntity] and ends at
  /// the start of [rightEntity].
  SourceRange startStart(
      SyntacticEntity leftEntity, SyntacticEntity rightEntity) {
    var offset = leftEntity.offset;
    var length = rightEntity.offset - offset;
    return SourceRange(offset, length);
  }

  /// Return a source range that covers the same range as the given [token].
  SourceRange token(Token token) {
    return SourceRange(token.offset, token.length);
  }
}