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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_ITERATORS_CHARACTER_ITERATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_ITERATORS_CHARACTER_ITERATOR_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/dom/range.h"
#include "third_party/blink/renderer/core/editing/forward.h"
#include "third_party/blink/renderer/core/editing/iterators/text_iterator.h"
#include "third_party/blink/renderer/core/editing/iterators/text_iterator_behavior.h"
#include "third_party/blink/renderer/platform/heap/heap.h"

namespace blink {

// Builds on the text iterator, adding a character position so we can walk one
// character at a time, or faster, as needed. Useful for searching.
template <typename Strategy>
class CharacterIteratorAlgorithm {
  STACK_ALLOCATED();

 public:
  CharacterIteratorAlgorithm(
      const PositionTemplate<Strategy>& start,
      const PositionTemplate<Strategy>& end,
      const TextIteratorBehavior& = TextIteratorBehavior());
  explicit CharacterIteratorAlgorithm(
      const EphemeralRangeTemplate<Strategy>&,
      const TextIteratorBehavior& = TextIteratorBehavior());

  void Advance(int num_characters);

  bool AtBreak() const { return at_break_; }
  bool AtEnd() const { return text_iterator_.AtEnd(); }

  int length() const { return text_iterator_.length() - run_offset_; }
  UChar CharacterAt(unsigned index) const {
    return text_iterator_.CharacterAt(run_offset_ + index);
  }

  int CharacterOffset() const { return offset_; }

  const Document& OwnerDocument() const;
  const Node& CurrentContainer() const;
  int StartOffset() const;
  int EndOffset() const;

  PositionTemplate<Strategy> GetPositionBefore() const;
  PositionTemplate<Strategy> GetPositionAfter() const;

  // TDOO(editing-dev): We should rename |StartPosition()| to
  // |GetPositionBeforeDeprecated()| and use |GetPositionBefore()| to
  // avoid using |EditingPositionOf()|.
  // Note: Following two tests are failed when using |GetPositionBefore()|
  // instead of |StartPosition()|:
  //  1. extend-by-sentence-002.html
  //  2. move_forward_sentence_empty_line_break.html
  PositionTemplate<Strategy> StartPosition() const;
  // TDOO(editing-dev): We should rename |EndPosition()| to
  // |GetPositionAfterDeprecated()| and use |GetPositionAfter()| to
  // avoid using |EditingPositionOf()|.
  PositionTemplate<Strategy> EndPosition() const;

  EphemeralRangeTemplate<Strategy> CalculateCharacterSubrange(int offset,
                                                              int length);

 private:
  void Initialize();

  int offset_;
  int run_offset_;
  bool at_break_;

  TextIteratorAlgorithm<Strategy> text_iterator_;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    CharacterIteratorAlgorithm<EditingStrategy>;
using CharacterIterator = CharacterIteratorAlgorithm<EditingStrategy>;

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    CharacterIteratorAlgorithm<EditingInFlatTreeStrategy>;
using CharacterIteratorInFlatTree =
    CharacterIteratorAlgorithm<EditingInFlatTreeStrategy>;

CORE_EXPORT EphemeralRange CalculateCharacterSubrange(const EphemeralRange&,
                                                      int character_offset,
                                                      int character_count);

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_ITERATORS_CHARACTER_ITERATOR_H_