offsets.h

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/*
 * Copyright 2026 The A11 Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#ifndef A11_FLOW_OFFSETS_H_
#define A11_FLOW_OFFSETS_H_
 
#include <cstddef>
#include <string>
#include <string_view>
#include <utility>
#include <vector>
 
#include <nlohmann/json_fwd.hpp>
 
namespace a11::flow {
 
// A document, and the offset arithmetic every editor protocol needs over it. So
// the conversion lives here, once, and both protocol adapters use it.
class TextIndex {
 public:
  TextIndex() = default;
  explicit TextIndex(std::string text);
 
  [[nodiscard]] const std::string& Text() const { return text_; }
 
  [[nodiscard]] size_t LineCount() const { return line_starts_.size(); }
 
  [[nodiscard]] size_t Utf16Of(size_t byte_offset) const;
 
  [[nodiscard]] size_t ByteOf(size_t utf16_offset) const;
 
  [[nodiscard]] std::pair<int, int> PositionOf(size_t byte_offset) const;
 
  [[nodiscard]] size_t ByteOfPosition(int line, int character) const;
 
 private:
  [[nodiscard]] std::pair<size_t, size_t> Step(size_t offset) const;
 
  [[nodiscard]] size_t LineEnd(size_t line) const;
 
  std::string text_;
  std::vector<size_t> line_starts_;
  std::vector<size_t> line_utf16_starts_;
};
 
enum class OffsetBasis {
  kBytes,
  kUtf16,
};
 
bool OffsetBasisFromName(std::string_view name, OffsetBasis& basis);
 
std::string_view OffsetBasisName(OffsetBasis basis);
 
void RebaseToUtf16(nlohmann::json& answer, const TextIndex& index);
 
}  // namespace a11::flow
 
#endif  // A11_FLOW_OFFSETS_H_