use errors;
use io;
use net;
use net::ip;
use rt;
use unix::signal;

export type op = enum u64 {
	NONE     = 0,
	READV    = 1 << 0,
	WRITEV   = 1 << 1,

	READABLE    = 1 << 16,
	WRITABLE    = 2 << 16,
	ACCEPT      = 3 << 16,
	CONNECT_TCP = 4 << 16,
	SIGNAL      = 5 << 16,
	TIMER       = 6 << 16,
	SENDTO      = 7 << 16,
	RECVFROM    = 8 << 16,
	SEND        = 9 << 16,
	RECV        = 10 << 16,
};

export type fflags = enum uint {
	NONE = 0,
	BLOCKING = 1 << 31,
};

export type file = struct {
	fd: io::file,
	ev: *loop,

	flags: fflags,
	op: op,
	cb: nullable *void,
	cb2: nullable *void,
	user: nullable *void,

	// Operation-specific data
	union {
		struct {
			rvbuf: rt::iovec,
			rvec: []rt::iovec,
			wvbuf: rt::iovec,
			wvec: []rt::iovec,
		},

		sockflags: net::sockflags,

		sockflag: net::sockflag,

		sigmask: signal::sigset,
		sendrecv: struct {
			sbuf: []u8,
			rbuf: []u8,
			dest: ip::addr,
			port: u16,
		},
	},
};

// Registers a file descriptor with an event loop.
export fn register(
	loop: *loop,
	fd: io::file,
) (*file | errors::error) = {
	const file = alloc(file {
		flags = fflags::NONE,
		fd = fd,
		ev = loop,
		op = op::NONE,
		...
	});

	let ev = rt::epoll_event {
		events = 0,
		...
	};
	ev.data.ptr = file;
	match (rt::epoll_ctl(loop.fd, rt::EPOLL_CTL_ADD, fd, &ev)) {
	case void =>
		yield;
	case let err: rt::errno =>
		if (err: int == rt::EPERM) {
			// epoll(2) does not support regular files, use blocking
			// I/O instead
			file.flags = fflags::BLOCKING;
			return file;
		};
		return errors::errno(err);
	};

	return file;
};

// Unregisters a file object with an event loop and frees resources associated
// with it. Does not close the underlying file descriptor.
export fn unregister(file: *file) void = {
	const loop = file.ev;
	if (file.flags & fflags::BLOCKING == 0) {
		// The only way that this could fail is in the event of a
		// use-after-free or if the user fucks around and constructs a
		// custom [[file]] which was never registered, so assert on
		// error.
		rt::epoll_ctl(loop.fd, rt::EPOLL_CTL_DEL, file.fd, null)!;
	};
	if (file.op == op::SIGNAL) {
		signal_restore(file);
	};
	free(file);
};

// Unregisters a file object with an event loop, frees resources associated with
// it, and closes the underlying file descriptor.
export fn close(file: *file) void = {
	const fd = file.fd;
	unregister(file);
	io::close(fd)!;
};

// Sets the user data field on this file object to the provided object.
export fn setuser(file: *file, user: nullable *void) void = {
	file.user = user;
};

// Returns the user data field from this file object. If the field was null, an
// assertion is raised.
export fn getuser(file: *file) *void = {
	return file.user as *void;
};

// Returns the file descriptor for a given file. Note that ev assumes that it
// will be responsible for all I/O on the file and any user modifications may
// cause the event loop to enter an invalid state.
export fn getfd(file: *file) io::file = {
	return file.fd;
};

// Returns the event loop for a given file.
export fn getloop(file: *file) *loop = {
	return file.ev;
};

// Updates epoll events for a given file. For internal use.
fn file_epoll_ctl(file: *file) void = {
	let events = rt::EPOLLONESHOT;
	if (file.op & op::READV != 0 || file.op == op::READABLE) {
		events |= rt::EPOLLIN | rt::EPOLLHUP;
	};
	if (file.op & op::WRITEV != 0 || file.op == op::WRITABLE) {
		events |= rt::EPOLLOUT | rt::EPOLLHUP;
	};
	switch (file.op) {
	case op::ACCEPT =>
		events |= rt::EPOLLIN;
	case op::CONNECT_TCP =>
		events |= rt::EPOLLOUT;
	case op::SIGNAL =>
		events |= rt::EPOLLIN;
	case op::TIMER =>
		events &= ~rt::EPOLLONESHOT;
		events |= rt::EPOLLIN;
	case op::SEND, op::SENDTO =>
		events |= rt::EPOLLOUT;
	case op::RECV, op::RECVFROM =>
		events |= rt::EPOLLIN;
	case =>
		yield;
	};

	let ev = rt::epoll_event {
		events = events,
		...
	};
	ev.data.ptr = file;
	// This can only fail under conditions associated with EPOLLEXCLUSIVE,
	// which we do not support.
	rt::epoll_ctl(file.ev.fd, rt::EPOLL_CTL_MOD, file.fd, &ev)!;
};

use errors;
use net;
use net::ip;
use net::tcp;
use net::udp;
use rt;

// Creates a socket which listens for incoming TCP connections on the given
// IP address and port.
export fn listen_tcp(
	loop: *loop,
	addr: ip::addr,
	port: u16,
	opts: tcp::listen_option...
) (*file | net::error | errors::error) = {
	const sock = tcp::listen(addr, port, opts...)?;
	return register(loop, sock)?;
};

// Creates a socket which listens for incoming UDP packets on the given IP
// address and port.
export fn listen_udp(
	loop: *loop,
	addr: ip::addr,
	port: u16,
	opts: udp::listen_option...
) (*file | net::error | errors::error) = {
	const sock = udp::listen(addr, port, opts...)?;
	return register(loop, sock)?;
};

// Creates a UDP socket on this event loop and sets the default destination to
// the given address.
export fn connect_udp(
	loop: *loop,
	dest: ip::addr,
	port: u16,
	opts: udp::connect_option...
) (*file | net::error | errors::error) = {
	const sock = udp::connect(dest, port, opts...)?;
	const file = register(loop, sock)?;
	return file;
};

export type connectcb = fn(result: (*file | net::error), user: nullable *void) void;

// Creates a socket and connects to a given IP address and port over TCP.
//

// The variadic arguments accept [[net::sockflags]] and/or no more than one user

// The variadic arguments accept [[net::sockflag]] and/or no more than one user

// data pointer. If the user data pointer is provided, it will be passed to the
// callback. This allows the user to pass a state object through the connection
// process:
//
//	let user: state = // ...
// 	ev::connect_tcp(&loop, &connected, addr, port, &user);
//
// 	fn connected(result: (*ev::file | net::error), user: nullable *void) void = {
// 		let user = user: *state;
// 	};
//
// The user data object provided will be assigned to the [[file]] which is
// provided to the callback after the connection is established.
//
// If you don't need a user data object you can just omit it:
//
// 	ev::connect_tcp(&loop, &connected, addr, port, &user);
export fn connect_tcp(
	loop: *loop,
	cb: *connectcb,
	addr: ip::addr,
	port: u16,

	opts: (net::sockflags | *void)...

	opts: (net::sockflag | *void)...

) (void | net::error | errors::error) = {
	// XXX: This doesn't let us set keepalive

	let opt: net::sockflags = 0;

	let opt: net::sockflag = 0;

	let user: nullable *void = null;
	for (let i = 0z; i < len(opts); i += 1) {
		match (opts[i]) {

		case let o: net::sockflags =>

		case let o: net::sockflag =>

			opt |= o;
		case let u: *void =>
			assert(user == null);
			user = u;
		};
	};

	const sock = tcp::connect(addr, port, opt | net::sockflags::NONBLOCK)?;

	const sock = tcp::connect(addr, port, opt | net::sockflag::NONBLOCK)?;

	let file = register(loop, sock)?;
	file.user = user;
	file.cb = cb;
	file.op = op::CONNECT_TCP;
	file_epoll_ctl(file);
};

fn connect_tcp_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::CONNECT_TCP);
	assert(ev.events & rt::EPOLLOUT != 0);
	assert(sock.cb != null);
	const cb = sock.cb: *connectcb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	let errno = 0i, optsz = size(int): u32;
	rt::getsockopt(sock.fd, rt::SOL_SOCKET, rt::SO_ERROR, &errno, &optsz)!;
	if (errno != 0) {
		cb(errors::errno(errno), sock.user);
		close(sock);
	} else {
		// XXX: If the user puts NONBLOCK into the opts provided at
		// [[connect_tcp]] we could try to preserve that here
		const fl = rt::fcntl(sock.fd, rt::F_GETFL, void)!;
		rt::fcntl(sock.fd, rt::F_SETFL, fl & ~rt::O_NONBLOCK)!;
		cb(sock, sock.user);
	};
};

// A callback for an [[accept]] operation.
export type acceptcb = fn(file: *file, result: (*file | net::error)) void;

// Schedules an accept operation on a socket.
export fn accept(
	sock: *file,
	cb: *acceptcb,

	flags: net::sockflags...

	flags: net::sockflag...

) req = {
	assert(sock.op == op::NONE);

	let fl: net::sockflags = 0;

	let fl: net::sockflag = 0;

	for (let i = 0z; i < len(flags); i += 1) {
		fl |= flags[i];
	};
	sock.op = op::ACCEPT;
	sock.cb = cb;

	sock.sockflags = fl;

	sock.sockflag = fl;

	file_epoll_ctl(sock);
	return req { ... };
};

fn accept_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::ACCEPT);
	assert(ev.events & rt::EPOLLIN != 0);
	assert(sock.cb != null);
	const cb = sock.cb: *acceptcb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	const r = tcp::accept(sock.fd, sock.sockflags);

	const r = tcp::accept(sock.fd, sock.sockflag);

	match (r) {
	case let fd: net::socket =>
		// TODO: Bubble up errors from here?
		const file = register(sock.ev, fd)!;
		cb(sock, file);
	case let err: net::error =>
		cb(sock, err);
	};
};

// TODO: Support recv & send in parallel

// Callback for a [[recvfrom]] operation. The second parameter is either an
// error or a tuple of the number of bytes received and the IP address and port
// of the sender.
export type recvfromcb = fn(
	file: *file,
	r: ((size, ip::addr, u16) | net::error),
) void;

// Schedules a receive operation on a socket.
export fn recvfrom(
	sock: *file,
	cb: *recvfromcb,
	buf: []u8,
) req = {
	assert(sock.op == op::NONE);
	sock.op = op::RECVFROM;
	sock.cb = cb;
	sock.sendrecv.rbuf = buf;
	file_epoll_ctl(sock);
	return req { ... };
};

fn recvfrom_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::RECVFROM);
	assert(sock.cb != null);
	const cb = sock.cb: *recvfromcb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	let src: ip::addr = ip::ANY_V4, port = 0u16;
	match (udp::recvfrom(sock.fd, sock.sendrecv.rbuf, &src, &port)) {
	case let err: net::error =>
		cb(sock, err);
	case let n: size =>
		cb(sock, (n, src, port));
	};
};

// Callback for a [[recv]] operation.
export type recvcb = fn(file: *file, r: (size | net::error)) void;

// Schedules a receive operation on a (connected) socket.
export fn recv(
	sock: *file,
	cb: *recvcb,
	buf: []u8,
) req = {
	assert(sock.op == op::NONE);
	sock.op = op::RECV;
	sock.cb = cb;
	sock.sendrecv.rbuf = buf;
	file_epoll_ctl(sock);
	return req { ... };
};

fn recv_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::RECV);
	assert(sock.cb != null);
	const cb = sock.cb: *recvcb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	const r = udp::recv(sock.fd, sock.sendrecv.rbuf);
	cb(sock, r);
};

// Callback for a [[send]] or [[sendto]] operation.
export type sendtocb = fn(file: *file, r: (size | net::error)) void;

// Schedules a send operation on a (connected) socket.
export fn send(
	sock: *file,
	cb: *sendtocb,
	buf: []u8,
) req = {
	assert(sock.op == op::NONE);
	sock.op = op::SEND;
	sock.cb = cb;
	sock.sendrecv.sbuf = buf;
	file_epoll_ctl(sock);
	return req { ... };
};

fn send_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::SEND);
	assert(sock.cb != null);
	const cb = sock.cb: *sendtocb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	const r = udp::send(sock.fd, sock.sendrecv.sbuf);
	cb(sock, r);
};

// Schedules a send operation on a socket.
export fn sendto(
	sock: *file,
	cb: *sendtocb,
	buf: []u8,
	dest: ip::addr,
	port: u16,
) req = {
	assert(sock.op == op::NONE);
	sock.op = op::SENDTO;
	sock.cb = cb;
	sock.sendrecv.sbuf = buf;
	sock.sendrecv.dest = dest;
	sock.sendrecv.port = port;
	file_epoll_ctl(sock);
	return req { ... };
};

fn sendto_ready(
	sock: *file,
	ev: *rt::epoll_event,
) void = {
	assert(sock.op == op::SENDTO);
	assert(sock.cb != null);
	const cb = sock.cb: *sendtocb;
	sock.op = op::NONE;
	file_epoll_ctl(sock);

	const r = udp::sendto(
		sock.fd,
		sock.sendrecv.sbuf,
		sock.sendrecv.dest,
		sock.sendrecv.port,
	);
	cb(sock, r);
};