/*
 * This source code is released into the public domain.
 */

module;

/*
 * tempfile: create a temporary file.
 */

#include <cstdint>
#include <expected>
#include <filesystem>
#include <string>

export module nihil.posix:tempfile;

import nihil.error;
import nihil.flagset;
import :fd;

namespace nihil {

struct tempfile_flags_tag {};
export using tempfile_flags_t = flagset<std::uint8_t, tempfile_flags_tag>;

// No flags.
export inline constexpr auto tempfile_none = tempfile_flags_t();

// Unlink the tempfile immediately after creating it
export inline constexpr auto tempfile_unlink = tempfile_flags_t::bit<0>();

export struct temporary_file final {
	/*
	 * Fetch the file's fd.
	 */
	[[nodiscard]] auto fd(this temporary_file &) -> nihil::fd &;

	/*
	 * Fetch the name of this file.  If tempfile_unlink was specified,
	 * throws std::logic_error.
	 */
	[[nodiscard]] auto path(this temporary_file const &)
		-> std::filesystem::path const &;

	/*
	 * Release this temporary file, causing it to be deleted immediately.
	 * Throws std::logic_error if the file has already been released.
	 */
	auto release(this temporary_file &) -> void;

	/*
	 * Destructor; unlink the file if we didn't already.
	 */
	~temporary_file();

	// Not copyable.
	temporary_file(temporary_file const &) = delete;
	auto operator=(this temporary_file &, temporary_file const &)
		-> temporary_file & = delete;

	// Movable.
	temporary_file(temporary_file &&other) noexcept;
	auto operator=(this temporary_file &, temporary_file &&) noexcept
		-> temporary_file &;

private:
	// The file descriptor for the file.
	nihil::fd		m_fd;
	std::filesystem::path	m_path;

	temporary_file(nihil::fd &&fd, std::filesystem::path) noexcept;
	temporary_file(nihil::fd &&fd) noexcept;

	friend auto tempfile(tempfile_flags_t flags)
		-> std::expected<temporary_file, error>;
};

/*
 * Create a temporary file and return it.
 */
export [[nodiscard]] auto tempfile(tempfile_flags_t flags = tempfile_none)
	-> std::expected<temporary_file, error>;

} // namespace nihil