#ifndef FESA_APP_OUTPUT_PATHS_H_
#define FESA_APP_OUTPUT_PATHS_H_

#include <filesystem>
#include <memory>
#include <string>
#include <vector>

#include "fesa/core/status.h"

namespace fesa {

/// @brief Names the input and user-addressed output files for one invocation.
struct DerivedOutputPaths {
  std::filesystem::path input_path;
  std::filesystem::path results_path;
  std::filesystem::path log_path;
};

/// @brief Retains exclusive ownership of one derived output pair.
/// @note The lease owns a platform-private lock and must outlive output I/O.
class OutputWriteLease {
 public:
  OutputWriteLease(const OutputWriteLease&) = delete;
  OutputWriteLease& operator=(const OutputWriteLease&) = delete;
  OutputWriteLease(OutputWriteLease&&) noexcept;
  OutputWriteLease& operator=(OutputWriteLease&&) noexcept;
  ~OutputWriteLease();

 private:
  class Impl;

  friend Result<OutputWriteLease> AcquireOutputWriteLease(
      const DerivedOutputPaths& paths);

  explicit OutputWriteLease(std::unique_ptr<Impl> impl) noexcept;

  std::unique_ptr<Impl> impl_;
};

/// @brief Validates CLI operands and derives lexical sibling output paths.
/// @param arguments Arguments after argv[0].
/// @param invocation_cwd Lexical base for a relative input path.
/// @return The input/result/log path triplet or a usage failure.
/// @note This function does not resolve symlinks, junctions, or short names.
Result<DerivedOutputPaths> DeriveSingleInputOutputPaths(
    const std::vector<std::string>& arguments,
    const std::filesystem::path& invocation_cwd);

/// @brief Acquires exclusive ownership for writes to one output pair.
/// @return A move-only lease or an output-busy failure.
/// @note The lease does not create, truncate, or replace public output files.
Result<OutputWriteLease> AcquireOutputWriteLease(
    const DerivedOutputPaths& paths);

}  // namespace fesa

#endif  // FESA_APP_OUTPUT_PATHS_H_