// This source code is released into the public domain.
module;

#include <expected>
#include <string>

#include "nihil.hh"

export module nihil.posix:fexecv;

import nihil.error;
import :argv;
import :executor;
import :fd;

namespace nihil {

#ifdef NIHIL_HAVE_FEXECVE

/*
 * fexecv: use a file descriptor and an argument vector to call ::fexecve().
 * This is the lowest-level executor which all others are implemented
 * in terms of (if it's available).
 *
 * TODO: Should have a way to pass the environment (envp).
 */
export struct fexecv final
{
	using tag = exec_tag;

	fexecv(fd &&execfd, argv &&args) noexcept
		: m_execfd(std::move(execfd))
		, m_args(std::move(args))
	{
	}

	[[nodiscard]] auto exec(this fexecv &self) -> std::expected<void, error>
	{
		::fexecve(self.m_execfd.get(), self.m_args.data(), environ);
		return std::unexpected(error("fexecve failed", error(std::errc(errno))));
	}

	// Movable
	fexecv(fexecv &&) noexcept = default;
	auto operator=(this fexecv &, fexecv &&) noexcept -> fexecv & = default;

	// Not copyable (because we hold the open fd object)
	fexecv(fexecv const &) = delete;
	auto operator=(this fexecv &, fexecv const &) -> fexecv & = delete;

private:
	fd m_execfd;
	argv m_args;
};

#endif // NIHIL_HAVE_FEXECVE

} // namespace nihil