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

#ifndef	LFJAIL_PROCESS_HH
#define	LFJAIL_PROCESS_HH

#include <sys/wait.h>

namespace lfjail {

/*
 * wait_result: the exit status of a process.
 */
struct wait_result final {
	// Return true if the process exited normally with an exit code of
	// zero, otherwise false.
	auto okay(this wait_result const &) -> bool;
	explicit operator bool(this wait_result const &);

	// Return the exit status, if any.
	auto status(this wait_result const &) -> std::optional<int>;

	// Return the exit signal, if any.
	auto signal(this wait_result const &) -> std::optional<int>;

private:
	friend struct process;

	int _status;

	// Construct a new wait_result from the output of waitpid().
	wait_result(int status);
};

/*
 * process: represents a process we created, which can be waited for.
 */
struct process final {
	process() = delete;

	process(::pid_t pid);

	// When destroyed, we automatically wait for the process to
	// avoid creating zombie processes.
	~process();

	// Movable.
	process(process &&) noexcept = default;
	auto operator=(process &&) noexcept -> process& = default;

	// Not copyable.
	process(process const &) = delete;
	auto operator=(process const &) -> process& = delete;

	// Get the child's process id.
	auto pid(this process const &self) noexcept -> ::pid_t;

	// Wait for this process to exit (by calling waitpid()) and return
	// its exit status.  This destroys the process state, leaving this
	// object in a moved-from state.
	auto wait(this process &&) -> wait_result;

	// Release this process so we won't try to wait for it when
	// destroying this object.
	auto release(this process &&) -> ::pid_t;

private:
	::pid_t _pid;
};

}

#endif	// !LFJAIL_PROCESS_HH