#ifndef _EVENTXX_HPP_
#define _EVENTXX_HPP_

#include <sys/types.h> // timeval
#include <stdexcept>   // std::exception, std::invalid_argument,
                       // std::runtime_error, std::bad_alloc

/**
 * Namespace for all symbols libevent C++ wrapper defines.
 */
namespace eventxx
{


// All libevent C API symbols and other internal stuff goes here.
namespace internal
{
#include <event.h>
}


/** @defgroup exceptions Exceptions
 *
 * eventxx makes a heavy use of exceptions. Each function has it's exceptions
 * specified, so it's very easy to find out what exceptions to expect.
 *
 * Exceptions are mostly thrown when there is a programming error. So if you get
 * an exception check your code.
 */
//@{


/**
 * Base class for all libevent exceptions.
 */
struct exception: public std::exception
{
};


/**
 * Invalid event exception.
 *
 * This exception is thrown when passing an invalid event to a function, the
 * reason is given in the what() description but it usually means that the you
 * are making some restricted operation with an active event.
 *
 * If you hit this exception, you probably got a programming error.
 */
struct invalid_event: public std::invalid_argument, public exception
{

	/**
	 * Creates an invalid event exception with a reason.
	 *
	 * @param what Reason why the event is invalid).
	 */
	explicit invalid_event(const std::string& what) throw():
		std::invalid_argument(what)
	{
	}

}; // struct invalid_event


/**
 * Invalid priority exception.
 *
 * This exception is thrown when passing an invalid priority to a function. This
 * usually means you don't have enough priority queues in your dispatcher, so
 * you should have allocated more in the constructor.
 *
 * If you hit this exception, you probably got a programming error.
 *
 * @see dispatcher::dispatcher(int) to allocate more priority queues.
 */
struct invalid_priority: public std::invalid_argument, public exception
{

	/**
	 * Creates an invalid priority exception with a reason.
	 *
	 * @param what Reason why the priority is invalid).
	 */
	explicit invalid_priority(const std::string& what
			= "invalid priority value") throw():
		std::invalid_argument(what)
	{
	}

}; // struct invalid_priority

//@}


/// Miscellaneous constants
enum
{
	DEFAULT_PRIORITY = -1,      ///< Default priority (the middle value).
	ONCE = EVLOOP_ONCE,         ///< Loop just once.
	NONBLOCK = EVLOOP_NONBLOCK  ///< Don't block the event loop.
};


/**
 * Time used for timeout values.
 *
 * This timeout is compose of seconds and microseconds.
 */
struct time: ::timeval
{

	/**
	 * Creates a new time with @p sec seconds and @p usec microseconds.
	 *
	 * @param sec Number of seconds.
	 * @param usec Number of microseconds.
	 */
	time(long sec = 0l, long usec = 0l) throw()
		{ tv_sec = sec; tv_usec = usec; }

	/**
	 * Gets the number of seconds.
	 *
	 * @return Number of seconds.
	 */
	long sec() const throw() { return tv_sec; };

	/**
	 * Gets the number of microseconds.
	 *
	 * @return Number of microseconds.
	 */
	long usec() const throw() { return tv_usec; };

	/**
	 * Sets the number of seconds.
	 *
	 * @param s Number of seconds.
	 */
	void sec(long s) throw() { tv_sec = s; };

	/**
	 * Sets the number of microseconds.
	 *
	 * @param u Number of microseconds.
	 */
	void usec(long u) throw() { tv_usec = u; };

}; // struct time


/** @defgroup events Events
 *
 * There are many ways to specify how to handle an event. You can use use the
 * same plain functions callbacks (see eventxx::cevent, eventxx::ctimer and
 * eventxx::csignal) like in C or the other kind of more advanced, stateful
 * function objects (see eventxx::event, eventxx::timer and eventxx::signal
 * templates). The former are just typedef'ed specialization of the later.
 *
 * A member function wrapper functor (eventxx::mem_cb) is also included,
 * so you can use any member function (method) as an event handler.
 *
 * Please note that C-like function callback take a short as the type of event,
 * while functors (or member functions) use eventxx::type.
 *
 * All events derive from a plain class (not template) eventxx::basic_event, one
 * of the main utilities of it (besides containing common code ;) is to be used
 * in STL containers.
 *
 * Please see each class documentation for details and examples.
 */
//@{


/// C function used as callback in the C API.
typedef void (*ccallback_type)(int, short, void*);


/**
 * Type of events.
 *
 * There are 4 kind of events: eventxx::TIMEOUT, eventxx::READ, eventxx::WRITE
 * or eventxx::SIGNAL. eventxx::PERSIST is not an event, is an event modifier
 * flag, that tells eventxx that this event should live until dispatcher::del()
 * is called. You can use, for example:
 * @code
 * eventxx::event(fd, eventxx::READ | eventxx::PERSIST, ...);
 * @endcode
 */
enum type
{
	TIMEOUT = EV_TIMEOUT, ///< Timeout event.
	READ = EV_READ,       ///< Read event.
	WRITE = EV_WRITE,     ///< Write event.
	SIGNAL = EV_SIGNAL,   ///< Signal event.
	PERSIST = EV_PERSIST  ///< Not really an event, is an event modifier.
};

inline
type operator| (const type& t1, const type& t2)
{
	int r = static_cast< int >(t1) | static_cast< int >(t2);
	return *reinterpret_cast< type* >(&r);
}


/**
 * Basic event from which all events derive.
 *
 * All events derive from this class, so it's useful for use in containers,
 * like:
 * @code
 * std::list< eventxx::basic_event* > events;
 * @endcode
 */
struct basic_event: internal::event
{

	/**
	 * Checks if there is an event pending.
	 *
	 * @param ev Type of event to check.
	 *
	 * @return true if there is a pending event, false if not.
	 */
	bool pending(type ev) const throw()
	{
		// HACK libevent don't use const
		return event_pending(const_cast< basic_event* >(this), ev, 0);
	}

	/**
	 * Timeout of the event.
	 *
	 * @return Timeout of the event.
	 */
	time timeout() const throw()
	{
		time tv;
		// HACK libevent don't use const
		event_pending(const_cast< basic_event* >(this), EV_TIMEOUT, &tv);
		return tv;
	}

	/**
	 * Sets the event's priority.
	 *
	 * @param priority New event priority.
	 *
	 * @pre The event must be added to some dispatcher.
	 *
	 * @see dispatcher::dispatcher(int)
	 */
	void priority(int priority) const throw(invalid_event, invalid_priority)
	{
		if (ev_flags & EVLIST_ACTIVE)
			throw invalid_event("can't change the priority of an "
					"active event");
		// HACK libevent don't use const
		if (event_priority_set(const_cast< basic_event* >(this),
					priority))
			throw invalid_priority();
	}

	/**
	 * Event's file descriptor.
	 *
	 * @return Event's file descriptor.
	 */
	int fd() const throw()
	{
		return EVENT_FD(this);
	}

	/// @note This is an abstract class, you can't instantiate it.
	protected:
		basic_event() throw() {}
		basic_event(const basic_event&);
		basic_event& operator= (const basic_event&);

}; // struct basic_event


/**
 * Generic event object.
 *
 * This object stores all the information about an event, including a callback
 * functor, which is called when the event is fired. The template parameter
 * must be a functor (callable object or function) that can take 2 parameters:
 * an integer (the file descriptor of the fired event) and an event::type (the
 * type of event being fired).
 * There is a specialized version of this class which takes as the template
 * parameter a C function with the eventxx::ccallback_type signature, just like
 * C @libevent API does.
 *
 * @see eventxx::event< ccallback_type >
 */
template < typename F >
struct event: basic_event
{

	/**
	 * Creates a new event.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor (see eventxx::type).
	 * @param handler Callback functor.
	 */
	event(int fd, type ev, F& handler) throw()
	{
		event_set(this, fd, static_cast< short >(ev), &wrapper,
				reinterpret_cast< void* >(&handler));
	}

	protected:
		event() {}
		static void wrapper(int fd, short ev, void* h)
		{
			F& handler = *reinterpret_cast< F* >(h);
			// Hackish, but this way the handler can get a clean
			// event type
			handler(fd, *reinterpret_cast< type* >(&ev));
		}

}; // struct event< F >


/**
 * This is the specialization of eventxx::event for C-style callbacks.
 *
 * @see eventxx::event
 */
template <>
struct event< ccallback_type >: basic_event
{

	/**
	 * Creates a new event.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor (see eventxx::type).
	 * @param handler C-style callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 */
	event(int fd, type ev, ccallback_type handler, void* arg = 0) throw()
	{
		event_set(this, fd, static_cast< short >(ev), handler, arg);
	}

	protected:
		event() {}

}; // struct event< ccallback_type >


/**
 * Timer event object.
 *
 * This is just a special case of event that is fired only when a timeout is
 * reached. It's just a shortcut to:
 * @code
 * event(-1, 0, handler);
 * @endcode
 *
 * @note This event can't eventxx::PERSIST.
 * @see timer< ccallback_type >
 */
template < typename F >
struct timer: event< F >
{

	/**
	 * Creates a new timer event.
	 *
	 * @param handler Callback functor.
	 */
	timer(F& handler) throw()
	{
		evtimer_set(this, &event< F >::wrapper,
			reinterpret_cast< void* >(&handler));
	}

}; // struct timer< F >


/**
 * This is the specialization of eventxx::timer for C-style callbacks.
 *
 * @note This event can't eventxx::PERSIST.
 * @see timer
 */
template <>
struct timer< ccallback_type >: event< ccallback_type >
{

	/**
	 * Creates a new timer event.
	 *
	 * @param handler C-style callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 */
	timer(ccallback_type handler, void* arg = 0) throw()
	{
		evtimer_set(this, handler, arg);
	}

}; // struct timer< ccallback_type >


/**
 * Signal event object.
 *
 * This is just a special case of event that is fired when a signal is raised
 * (instead of a file descriptor being active). It's just a shortcut to:
 * @code
 * event(signum, eventxx::SIGNAL, handler);
 * @endcode
 *
 * @note This event always eventxx::PERSIST.
 * @see signal< ccallback_type >
 */
template < typename F >
struct signal: event< F >
{

	/**
	 * Creates a new signal event.
	 *
	 * @param signum Signal number to monitor.
	 * @param handler Callback functor.
	 */
	signal(int signum, F& handler) throw()
	{
		signal_set(this, signum, &event< F >::wrapper,
			reinterpret_cast< void* >(&handler));
	}

	/**
	 * Event's signal number.
	 *
	 * @return Event's signal number.
	 */
	int signum() const
	{
		return EVENT_SIGNAL(this);
	}

}; // struct signal<F>


/**
 * This is the specialization of eventxx::signal for C-style callbacks.
 *
 * @note This event always eventxx::PERSIST.
 * @see signal
 */
template <>
struct signal< ccallback_type >: event< ccallback_type >
{

	/**
	 * Creates a new signal event.
	 *
	 * @param signum Signal number to monitor.
	 * @param handler C-style callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 */
	signal(int signum, ccallback_type handler, void* arg = 0) throw()
	{
		signal_set(this, signum, handler, arg);
	}

	/**
	 * Event's signal number.
	 *
	 * @return Event's signal number.
	 */
	int signum() const
	{
		return EVENT_SIGNAL(this);
	}

}; // struct signal< ccallback_type >


/// Shortcut to C-style event.
typedef eventxx::event< ccallback_type > cevent;

/// Shortcut to C-style timer.
typedef eventxx::timer< ccallback_type > ctimer;

/// Shortcut to C-style signal handler.
typedef eventxx::signal< ccallback_type > csignal;

/**
 * Helper functor to use an arbitrary member function as an event handler.
 *
 * With this wrapper, you can use any object method, which accepts the right
 * parameters (int, short) and returns void, as an event handler. This way you
 * don't have to overload the operator() which can be confusing depending on the
 * context.
 *
 * You can see an usage example in the Examples Section.
 */
template < typename O, typename M >
struct mem_cb
{

	/**
	 * Member function callback constructor.
	 *
	 * It expects to receive a class as the first parameter (O), and a
	 * member function (of that class O) as the second parameter.
	 *
	 * When this instance is called with fd and ev as function arguments,
	 * object.method(fd, ev) will be called.
	 *
	 * @param object Object to be used.
	 * @param method Method to be called.
	 */
	mem_cb(O& object, M method) throw():
		_object(object), _method(method) {}

	void operator() (int fd, type ev) { (_object.*_method)(fd, ev); }
	protected:
		O& _object;
		M _method;

}; // struct mem_cb

//@}


/**
 * Event dispatcher.
 *
 * This class is the responsible for looping and dispatching events. Every time
 * you need an event loop you should create an instance of this class.
 *
 * You can @link dispatcher::add add @endlink events to the dispatcher, and you
 * can @link dispatcher::del remove @endlink them later or you can @link
 * dispatcher::add_once add events to be processed just once @endlink. You can
 * @link dispatcher::dispatch loop once or forever @endlink (well, of course you
 * can break that forever removing all the events or by @link dispatcher::exit
 * exiting the loop @endlink).
 */
struct dispatcher
{

	/**
	 * Creates a default dispatcher (with just 1 priority).
	 *
	 * @see dispatcher(int) if you want to create a dispatcher with more
	 *      priorities.
	 */
	dispatcher() throw()
	{
		_event_base = static_cast< internal::event_base* >(
				internal::event_init());
	}

	/**
	 * Creates a dispatcher with npriorities priorities.
	 *
	 * @param npriorities Number of priority queues to use.
	 */
	dispatcher(int npriorities) throw(std::bad_alloc)
	{
		_event_base = static_cast< internal::event_base* >(
				internal::event_init());
		if (!_event_base) throw std::bad_alloc();
		// Can't fail because there is no way that it has active events
		internal::event_base_priority_init(_event_base, npriorities);
	}

#ifndef EVENTXX_NO_EVENT_BASE_FREE
	/// Free dispatcher resources, see @ref Status section for details.
	~dispatcher() throw() { event_base_free(_event_base); }
#endif

	/**
	 * Adds an event to the dispatcher.
	 *
	 * @param e Event to add.
	 * @param priority Priority of the event.
	 */
	void add(basic_event& e, int priority = DEFAULT_PRIORITY)
		throw(invalid_priority)
	{
		internal::event_base_set(_event_base, &e);
		if (priority != DEFAULT_PRIORITY
				&& internal::event_priority_set(&e, priority))
			throw invalid_priority();
		internal::event_add(&e, 0);
	}

	/**
	 * Adds an event to the dispatcher with a timeout.
	 *
	 * The event is fired when there is activity on e or when to has elapsed,
	 * whatever come first.
	 *
	 * @param e Event to add.
	 * @param to Timeout.
	 * @param priority Priority of the event.
	 */
	void add(basic_event& e, const time& to,
			int priority = DEFAULT_PRIORITY)
		throw(invalid_priority)
	{
		internal::event_base_set(_event_base, &e);
		if (priority != DEFAULT_PRIORITY
				&& internal::event_priority_set(&e, priority))
			throw invalid_priority();
		// XXX HACK libevent don't use const
		internal::event_add(&e, const_cast< time* >(&to));
	}

	/**
	 * Adds a temporary event.
	 *
	 * Adds a temporary event, without the need of instantiating a new event
	 * object. Events added this way can't eventxx::PERSIST.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor.
	 * @param handler Callback function.
	 */
	template < typename F >
	void add_once(int fd, type ev, F& handler)
	{
		internal::event_once(fd, static_cast< short>(ev),
			&dispatcher::wrapper< F >,
			reinterpret_cast< void* >(&handler), 0);
	}

	/**
	 * Adds a temporary event to with a C-style callback.
	 *
	 * Adds a temporary event, without the need of instantiating a new event
	 * object. Events added this way can't eventxx::PERSIST.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor.
	 * @param handler Callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 */
	void add_once(int fd, type ev, ccallback_type handler, void* arg)
	{
		internal::event_once(fd, static_cast< short >(ev), handler,
			arg, 0);
	}

	/**
	 * Adds a temporary event.
	 *
	 * Adds a temporary event, without the need of instantiating a new event
	 * object. Events added this way can't eventxx::PERSIST.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor.
	 * @param handler Callback function.
	 * @param to Timeout.
	 */
	template < typename F >
	void add_once(int fd, type ev, F& handler, const time& to)
	{
		internal::event_once(fd, static_cast< short >(ev),
			&dispatcher::wrapper< F >,
			reinterpret_cast< void* >(&handler),
			// XXX HACK libevent don't use const
			const_cast< time* >(&to));
	}

	/**
	 * Adds a temporary event with a C-style callback.
	 *
	 * Adds a temporary event, without the need of instantiating a new event
	 * object. Events added this way can't eventxx::PERSIST.
	 *
	 * @param fd File descriptor to monitor for events.
	 * @param ev Type of events to monitor.
	 * @param handler Callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 * @param to Timeout.
	 */
	void add_once(int fd, type ev, ccallback_type handler, void* arg,
			const time& to)
	{
		internal::event_once(fd, static_cast< short >(ev), handler, arg,
				// XXX HACK libevent don't use const
				const_cast< time* >(&to));
	}

	/**
	 * Adds a temporary timer.
	 *
	 * Adds a temporary timer, without the need of instantiating a new timer
	 * object.
	 *
	 * @param handler Callback function.
	 * @param to Timer's timeout.
	 */
	template < typename F >
	void add_once_timer(F& handler, const time& to)
	{
		internal::event_once(-1, EV_TIMEOUT, &dispatcher::wrapper< F >,
				reinterpret_cast< void* >(&handler),
				// XXX HACK libevent don't use const
				const_cast< time* >(&to));
	}

	/**
	 * Adds a temporary timer with a C-style callback.
	 *
	 * Adds a temporary timer, without the need of instantiating a new timer
	 * object.
	 *
	 * @param handler Callback function.
	 * @param arg Arbitrary pointer to pass to the handler as argument.
	 * @param to Timer's timeout.
	 */
	void add_once_timer(ccallback_type handler, void* arg, const time& to)
	{
		// XXX HACK libevent don't use const
		internal::event_once(-1, EV_TIMEOUT, handler, arg,
				const_cast< time* >(&to));
	}

	/**
	 * Removes an event.
	 *
	 * The event e will be no longer monitored by this dispatcher.
	 *
	 * @param e Event to remove.
	 */
	void del(basic_event& e) throw()
	{
		internal::event_del(&e);
	}

	/**
	 * Main dispatcher loop.
	 *
	 * This function takes the control of the program, waiting for an event
	 * and calling its callbacks when it's fired. It only returns under
	 * this conditions:
	 * - exit() was called.
	 * - All events were del()eted.
	 * - Another internal error.
	 * - eventxx::ONCE flag was set.
	 * - eventxx::NONBLOCK flag was set.
	 *
	 * @param flags If eventxx::ONCE is specified, then just one event is
	 *              processed, if eventxx::NONBLOCK is specified, then this
	 *              function returns even if there are no pending events.
	 *
	 * @return 0 if eventxx::NONBLOCK or eventxx::ONCE is set, 1 if there
	 *         are no more events registered and EINTR if you use the
	 *         @libevent's  @c event_gotsig and return -1 in your
	 *         @c event_sigcb callback.
	 */
	int dispatch(int flags = 0) throw()
	{
		return internal::event_base_loop(_event_base, flags);
	}

	/**
	 * Exit the dispatch() loop.
	 *
	 * @param to If a timeout is given, the loop exits after the specified
	 *           time is elapsed.
	 *
	 * @return Not very well specified by @libevent :-/ that's why it
	 *         doesn't throw an exception either.
	 */
	int exit(const time& to = time()) throw() // TODO  throw(exception)
	{
		// XXX HACK libevent don't use const
		return internal::event_base_loopexit(_event_base,
			const_cast< time* >(&to));
	}

	protected:
		internal::event_base* _event_base;
		template < typename F >
		static void wrapper(int fd, short ev, void* h)
		{
			F& handler = *reinterpret_cast< F* >(h);
			handler(fd, *reinterpret_cast< type* >(&ev));
		}

}; // struct dispatcher

} // namespace eventxx

#endif // _EVENTXX_HPP_

// vim: set filetype=cpp :