#include "kgio.h"
static VALUE sym_wait_readable, sym_wait_writable;
static VALUE eErrno_EPIPE, eErrno_ECONNRESET;
static ID id_set_backtrace;

/*
 * we know MSG_DONTWAIT works properly on all stream sockets under Linux
 * we can define this macro for other platforms as people care and
 * notice.
 */
#if defined(__linux__) && ! defined(USE_MSG_DONTWAIT)
#  define USE_MSG_DONTWAIT
#endif

NORETURN(static void raise_empty_bt(VALUE, const char *));
NORETURN(static void my_eof_error(void));
NORETURN(static void wr_sys_fail(const char *));
NORETURN(static void rd_sys_fail(const char *));

static void raise_empty_bt(VALUE err, const char *msg)
{
	VALUE exc = rb_exc_new2(err, msg);
	VALUE bt = rb_ary_new();

	rb_funcall(exc, id_set_backtrace, 1, bt);
	rb_exc_raise(exc);
}

static void my_eof_error(void)
{
	raise_empty_bt(rb_eEOFError, "end of file reached");
}

static void wr_sys_fail(const char *msg)
{
	switch (errno) {
	case EPIPE:
		errno = 0;
		raise_empty_bt(eErrno_EPIPE, msg);
	case ECONNRESET:
		errno = 0;
		raise_empty_bt(eErrno_ECONNRESET, msg);
	}
	rb_sys_fail(msg);
}

static void rd_sys_fail(const char *msg)
{
	if (errno == ECONNRESET) {
		errno = 0;
		raise_empty_bt(eErrno_ECONNRESET, msg);
	}
	rb_sys_fail(msg);
}

static void prepare_read(struct io_args *a, int argc, VALUE *argv, VALUE io)
{
	VALUE length;

	a->io = io;
	a->fd = my_fileno(io);
	rb_scan_args(argc, argv, "11", &length, &a->buf);
	a->len = NUM2LONG(length);
	if (NIL_P(a->buf)) {
		a->buf = rb_str_new(NULL, a->len);
	} else {
		StringValue(a->buf);
		rb_str_resize(a->buf, a->len);
	}
	a->ptr = RSTRING_PTR(a->buf);
}

static int read_check(struct io_args *a, long n, const char *msg, int io_wait)
{
	if (n == -1) {
		if (errno == EINTR)
			return -1;
		rb_str_set_len(a->buf, 0);
		if (errno == EAGAIN) {
			if (io_wait) {
				(void)kgio_call_wait_readable(a->io);

				/* buf may be modified in other thread/fiber */
				rb_str_resize(a->buf, a->len);
				a->ptr = RSTRING_PTR(a->buf);
				return -1;
			} else {
				a->buf = sym_wait_readable;
				return 0;
			}
		}
		rd_sys_fail(msg);
	}
	rb_str_set_len(a->buf, n);
	if (n == 0)
		a->buf = Qnil;
	return 0;
}

static VALUE my_read(int io_wait, int argc, VALUE *argv, VALUE io)
{
	struct io_args a;
	long n;

	prepare_read(&a, argc, argv, io);

	if (a.len > 0) {
		set_nonblocking(a.fd);
retry:
		n = (long)read(a.fd, a.ptr, a.len);
		if (read_check(&a, n, "read", io_wait) != 0)
			goto retry;
	}
	return a.buf;
}

/*
 * call-seq:
 *
 *	io.kgio_read(maxlen)           ->  buffer
 *	io.kgio_read(maxlen, buffer)   ->  buffer
 *
 * Reads at most maxlen bytes from the stream socket.  Returns with a
 * newly allocated buffer, or may reuse an existing buffer if supplied.
 *
 * Calls whatever is is defined to be the kgio_wait_readable method
 * for the class.
 *
 * Returns nil on EOF.
 *
 * This behaves like read(2) and IO#readpartial, NOT fread(3) or
 * IO#read which possess read-in-full behavior.
 */
static VALUE kgio_read(int argc, VALUE *argv, VALUE io)
{
	return my_read(1, argc, argv, io);
}

/*
 * Same as Kgio::PipeMethods#kgio_read, except EOFError is raised
 * on EOF without a backtrace.  This method is intended as a
 * drop-in replacement for places where IO#readpartial is used, and
 * may be aliased as such.
 */
static VALUE kgio_read_bang(int argc, VALUE *argv, VALUE io)
{
	VALUE rv = my_read(1, argc, argv, io);

	if (NIL_P(rv)) my_eof_error();
	return rv;
}

/*
 * call-seq:
 *
 *	io.kgio_tryread(maxlen)           ->  buffer
 *	io.kgio_tryread(maxlen, buffer)   ->  buffer
 *
 * Reads at most maxlen bytes from the stream socket.  Returns with a
 * newly allocated buffer, or may reuse an existing buffer if supplied.
 *
 * Returns nil on EOF.
 *
 * Returns :wait_readable if EAGAIN is encountered.
 */
static VALUE kgio_tryread(int argc, VALUE *argv, VALUE io)
{
	return my_read(0, argc, argv, io);
}

#ifdef USE_MSG_DONTWAIT
static VALUE my_recv(int io_wait, int argc, VALUE *argv, VALUE io)
{
	struct io_args a;
	long n;

	prepare_read(&a, argc, argv, io);
	kgio_autopush_recv(io);

	if (a.len > 0) {
retry:
		n = (long)recv(a.fd, a.ptr, a.len, MSG_DONTWAIT);
		if (read_check(&a, n, "recv", io_wait) != 0)
			goto retry;
	}
	return a.buf;
}

/*
 * This method may be optimized on some systems (e.g. GNU/Linux) to use
 * MSG_DONTWAIT to avoid explicitly setting the O_NONBLOCK flag via fcntl.
 * Otherwise this is the same as Kgio::PipeMethods#kgio_read
 */
static VALUE kgio_recv(int argc, VALUE *argv, VALUE io)
{
	return my_recv(1, argc, argv, io);
}

/*
 * Same as Kgio::SocketMethods#kgio_read, except EOFError is raised
 * on EOF without a backtrace
 */
static VALUE kgio_recv_bang(int argc, VALUE *argv, VALUE io)
{
	VALUE rv = my_recv(1, argc, argv, io);

	if (NIL_P(rv)) my_eof_error();
	return rv;
}

/*
 * This method may be optimized on some systems (e.g. GNU/Linux) to use
 * MSG_DONTWAIT to avoid explicitly setting the O_NONBLOCK flag via fcntl.
 * Otherwise this is the same as Kgio::PipeMethods#kgio_tryread
 */
static VALUE kgio_tryrecv(int argc, VALUE *argv, VALUE io)
{
	return my_recv(0, argc, argv, io);
}
#else /* ! USE_MSG_DONTWAIT */
#  define kgio_recv kgio_read
#  define kgio_recv_bang kgio_read_bang
#  define kgio_tryrecv kgio_tryread
#endif /* USE_MSG_DONTWAIT */

static void prepare_write(struct io_args *a, VALUE io, VALUE str)
{
	a->buf = (TYPE(str) == T_STRING) ? str : rb_obj_as_string(str);
	a->ptr = RSTRING_PTR(a->buf);
	a->len = RSTRING_LEN(a->buf);
	a->io = io;
	a->fd = my_fileno(io);
}

static int write_check(struct io_args *a, long n, const char *msg, int io_wait)
{
	if (a->len == n) {
done:
		a->buf = Qnil;
	} else if (n == -1) {
		if (errno == EINTR)
			return -1;
		if (errno == EAGAIN) {
			long written = RSTRING_LEN(a->buf) - a->len;

			if (io_wait) {
				(void)kgio_call_wait_writable(a->io);

				/* buf may be modified in other thread/fiber */
				a->len = RSTRING_LEN(a->buf) - written;
				if (a->len <= 0)
					goto done;
				a->ptr = RSTRING_PTR(a->buf) + written;
				return -1;
			} else if (written > 0) {
				a->buf = rb_str_new(a->ptr, a->len);
			} else {
				a->buf = sym_wait_writable;
			}
			return 0;
		}
		wr_sys_fail(msg);
	} else {
		assert(n >= 0 && n < a->len && "write/send syscall broken?");
		a->ptr += n;
		a->len -= n;
		return -1;
	}
	return 0;
}

static VALUE my_write(VALUE io, VALUE str, int io_wait)
{
	struct io_args a;
	long n;

	prepare_write(&a, io, str);
	set_nonblocking(a.fd);
retry:
	n = (long)write(a.fd, a.ptr, a.len);
	if (write_check(&a, n, "write", io_wait) != 0)
		goto retry;
	return a.buf;
}

/*
 * call-seq:
 *
 *	io.kgio_write(str)	-> nil
 *
 * Returns nil when the write completes.
 *
 * Calls whatever is is defined to be the kgio_wait_writable method
 * for the class.
 */
static VALUE kgio_write(VALUE io, VALUE str)
{
	return my_write(io, str, 1);
}

/*
 * call-seq:
 *
 *	io.kgio_trywrite(str)	-> nil or :wait_writable
 *
 * Returns nil if the write was completed in full.
 *
 * Returns a String containing the unwritten portion if EAGAIN
 * was encountered, but some portion was successfully written.
 *
 * Returns :wait_writable if EAGAIN is encountered and nothing
 * was written.
 */
static VALUE kgio_trywrite(VALUE io, VALUE str)
{
	return my_write(io, str, 0);
}

#ifdef USE_MSG_DONTWAIT
/*
 * This method behaves like Kgio::PipeMethods#kgio_write, except
 * it will use send(2) with the MSG_DONTWAIT flag on sockets to
 * avoid unnecessary calls to fcntl(2).
 */
static VALUE my_send(VALUE io, VALUE str, int io_wait)
{
	struct io_args a;
	long n;

	prepare_write(&a, io, str);
retry:
	n = (long)send(a.fd, a.ptr, a.len, MSG_DONTWAIT);
	if (write_check(&a, n, "send", io_wait) != 0)
		goto retry;
	if (TYPE(a.buf) != T_SYMBOL)
		kgio_autopush_send(io);
	return a.buf;
}

/*
 * This method may be optimized on some systems (e.g. GNU/Linux) to use
 * MSG_DONTWAIT to avoid explicitly setting the O_NONBLOCK flag via fcntl.
 * Otherwise this is the same as Kgio::PipeMethods#kgio_write
 */
static VALUE kgio_send(VALUE io, VALUE str)
{
	return my_send(io, str, 1);
}

/*
 * This method may be optimized on some systems (e.g. GNU/Linux) to use
 * MSG_DONTWAIT to avoid explicitly setting the O_NONBLOCK flag via fcntl.
 * Otherwise this is the same as Kgio::PipeMethods#kgio_trywrite
 */
static VALUE kgio_trysend(VALUE io, VALUE str)
{
	return my_send(io, str, 0);
}
#else /* ! USE_MSG_DONTWAIT */
#  define kgio_send kgio_write
#  define kgio_trysend kgio_trywrite
#endif /* ! USE_MSG_DONTWAIT */

/*
 * call-seq:
 *
 *	Kgio.tryread(io, maxlen)           ->  buffer
 *	Kgio.tryread(io, maxlen, buffer)   ->  buffer
 *
 * Returns nil on EOF.
 * Returns :wait_readable if EAGAIN is encountered.
 *
 * Maybe used in place of PipeMethods#kgio_tryread for non-Kgio objects
 */
static VALUE s_tryread(int argc, VALUE *argv, VALUE mod)
{
	if (argc <= 1)
		rb_raise(rb_eArgError, "wrong number of arguments");
	return my_read(0, argc - 1, &argv[1], argv[0]);
}

/*
 * call-seq:
 *
 *	Kgio.trywrite(io, str)    -> nil or :wait_writable
 *
 * Returns nil if the write was completed in full.
 *
 * Returns a String containing the unwritten portion if EAGAIN
 * was encountered, but some portion was successfully written.
 *
 * Returns :wait_writable if EAGAIN is encountered and nothing
 * was written.
 *
 * Maybe used in place of PipeMethods#kgio_trywrite for non-Kgio objects
 */
static VALUE s_trywrite(VALUE mod, VALUE io, VALUE str)
{
	return my_write(io, str, 0);
}

void init_kgio_read_write(void)
{
	VALUE mPipeMethods, mSocketMethods;
	VALUE mKgio = rb_define_module("Kgio");
	VALUE mWaiters = rb_const_get(mKgio, rb_intern("DefaultWaiters"));

	sym_wait_readable = ID2SYM(rb_intern("wait_readable"));
	sym_wait_writable = ID2SYM(rb_intern("wait_writable"));

	rb_define_singleton_method(mKgio, "tryread", s_tryread, -1);
	rb_define_singleton_method(mKgio, "trywrite", s_trywrite, 2);

	/*
	 * Document-module: Kgio::PipeMethods
	 *
	 * This module may be used used to create classes that respond to
	 * various Kgio methods for reading and writing.  This is included
	 * in Kgio::Pipe by default.
	 */
	mPipeMethods = rb_define_module_under(mKgio, "PipeMethods");
	rb_define_method(mPipeMethods, "kgio_read", kgio_read, -1);
	rb_define_method(mPipeMethods, "kgio_read!", kgio_read_bang, -1);
	rb_define_method(mPipeMethods, "kgio_write", kgio_write, 1);
	rb_define_method(mPipeMethods, "kgio_tryread", kgio_tryread, -1);
	rb_define_method(mPipeMethods, "kgio_trywrite", kgio_trywrite, 1);

	/*
	 * Document-module: Kgio::SocketMethods
	 *
	 * This method behaves like Kgio::PipeMethods, but contains
	 * optimizations for sockets on certain operating systems
	 * (e.g. GNU/Linux).
	 */
	mSocketMethods = rb_define_module_under(mKgio, "SocketMethods");
	rb_define_method(mSocketMethods, "kgio_read", kgio_recv, -1);
	rb_define_method(mSocketMethods, "kgio_read!", kgio_recv_bang, -1);
	rb_define_method(mSocketMethods, "kgio_write", kgio_send, 1);
	rb_define_method(mSocketMethods, "kgio_tryread", kgio_tryrecv, -1);
	rb_define_method(mSocketMethods, "kgio_trywrite", kgio_trysend, 1);

	/*
	 * Returns the client IPv4 address of the socket in dotted quad
	 * form as a string.  This is always the value of the
	 * Kgio::LOCALHOST constant for UNIX domain sockets.
	 */
	rb_define_attr(mSocketMethods, "kgio_addr", 1, 1);
	id_set_backtrace = rb_intern("set_backtrace");
	eErrno_EPIPE = rb_const_get(rb_mErrno, rb_intern("EPIPE"));
	eErrno_ECONNRESET = rb_const_get(rb_mErrno, rb_intern("ECONNRESET"));
	rb_include_module(mPipeMethods, mWaiters);
	rb_include_module(mSocketMethods, mWaiters);
}