/*-
 * Copyright 2016 Vsevolod Stakhov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "config.h"
#include <event.h>
#include "aio_event.h"
#include "rspamd.h"
#include "unix-std.h"

#ifdef HAVE_SYS_EVENTFD_H
#include <sys/eventfd.h>
#endif

#ifdef HAVE_AIO_H
#include <aio.h>
#endif

/* Linux syscall numbers */
#if defined(__i386__)
# define SYS_io_setup      245
# define SYS_io_destroy    246
# define SYS_io_getevents  247
# define SYS_io_submit     248
# define SYS_io_cancel     249
#elif defined(__x86_64__)
# define SYS_io_setup       206
# define SYS_io_destroy     207
# define SYS_io_getevents   208
# define SYS_io_submit      209
# define SYS_io_cancel      210
#else
# warning \
	"aio is not supported on this platform, please contact author for details"
# define SYS_io_setup       0
# define SYS_io_destroy     0
# define SYS_io_getevents   0
# define SYS_io_submit      0
# define SYS_io_cancel      0
#endif

#define SYS_eventfd       323
#define MAX_AIO_EV        64

struct io_cbdata {
	gint fd;
	rspamd_aio_cb cb;
	guint64 len;
	gpointer buf;
	gpointer io_buf;
	gpointer ud;
};

#ifdef LINUX

/* Linux specific mappings and utilities to avoid using of libaio */

typedef unsigned long aio_context_t;

typedef enum io_iocb_cmd {
	IO_CMD_PREAD = 0,
	IO_CMD_PWRITE = 1,

	IO_CMD_FSYNC = 2,
	IO_CMD_FDSYNC = 3,

	IO_CMD_POLL = 5,
	IO_CMD_NOOP = 6,
} io_iocb_cmd_t;

#if defined(__LITTLE_ENDIAN)
#define PADDED(x,y)     x, y
#elif defined(__BIG_ENDIAN)
#define PADDED(x,y)     y, x
#else
#error edit for your odd byteorder.
#endif

/*
 * we always use a 64bit off_t when communicating
 * with userland.  its up to libraries to do the
 * proper padding and aio_error abstraction
 */

struct iocb {
	/* these are internal to the kernel/libc. */
	guint64 aio_data; /* data to be returned in event's data */
	guint32 PADDED (aio_key, aio_reserved1);
	/* the kernel sets aio_key to the req # */

	/* common fields */
	guint16 aio_lio_opcode; /* see IOCB_CMD_ above */
	gint16 aio_reqprio;
	guint32 aio_fildes;

	guint64 aio_buf;
	guint64 aio_nbytes;
	gint64 aio_offset;

	/* extra parameters */
	guint64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */

	/* flags for the "struct iocb" */
	guint32 aio_flags;

	/*
	 * if the IOCB_FLAG_RESFD flag of "aio_flags" is set, this is an
	 * eventfd to signal AIO readiness to
	 */
	guint32 aio_resfd;
};

struct io_event {
	guint64 data;   /* the data field from the iocb */
	guint64 obj;    /* what iocb this event came from */
	gint64 res;     /* result code for this event */
	gint64 res2;    /* secondary result */
};

/* Linux specific io calls */
static int
io_setup (guint nr_reqs, aio_context_t *ctx)
{
	return syscall (SYS_io_setup, nr_reqs, ctx);
}

static int
io_destroy (aio_context_t ctx)
{
	return syscall (SYS_io_destroy, ctx);
}

static int
io_getevents (aio_context_t ctx,
	long min_nr,
	long nr,
	struct io_event *events,
	struct timespec *tmo)
{
	return syscall (SYS_io_getevents, ctx, min_nr, nr, events, tmo);
}

static int
io_submit (aio_context_t ctx, long n, struct iocb **paiocb)
{
	return syscall (SYS_io_submit, ctx, n, paiocb);
}

static int
io_cancel (aio_context_t ctx, struct iocb *iocb, struct io_event *result)
{
	return syscall (SYS_io_cancel, ctx, iocb, result);
}

# ifndef HAVE_SYS_EVENTFD_H
static int
eventfd (guint initval, guint flags)
{
	return syscall (SYS_eventfd, initval);
}
# endif

#endif

/**
 * AIO context
 */
struct aio_context {
	struct event_base *base;
	gboolean has_aio;       /**< Whether we have aio support on a system */
#ifdef LINUX
	/* Eventfd variant */
	gint event_fd;
	struct event eventfd_ev;
	aio_context_t io_ctx;
#elif defined(HAVE_AIO_H)
	/* POSIX aio */
	struct event rtsigs[128];
#endif
};

#ifdef LINUX
/* Eventfd read callback */
static void
rspamd_eventfdcb (gint fd, gshort what, gpointer ud)
{
	struct aio_context *ctx = ud;
	guint64 ready;
	gint done, i;
	struct io_event event[32];
	struct timespec ts;
	struct io_cbdata *ev_data;

	/* Eventfd returns number of events ready got from kernel */
	if (read (fd, &ready, 8) != 8) {
		if (errno == EAGAIN) {
			return;
		}
		msg_err ("eventfd read returned error: %s", strerror (errno));
	}

	ts.tv_sec = 0;
	ts.tv_nsec = 0;

	while (ready) {
		/* Get events ready */
		done = io_getevents (ctx->io_ctx, 1, 32, event, &ts);

		if (done > 0) {
			ready -= done;

			for (i = 0; i < done; i++) {
				ev_data = (struct io_cbdata *) (uintptr_t) event[i].data;
				/* Call this callback */
				ev_data->cb (ev_data->fd,
					event[i].res,
					ev_data->len,
					ev_data->buf,
					ev_data->ud);
				if (ev_data->io_buf) {
					free (ev_data->io_buf);
				}
				g_slice_free1 (sizeof (struct io_cbdata), ev_data);
			}
		}
		else if (done == 0) {
			/* No more events are ready */
			return;
		}
		else {
			msg_err ("io_getevents failed: %s", strerror (errno));
			return;
		}
	}
}

#endif

/**
 * Initialize aio with specified event base
 */
struct aio_context *
rspamd_aio_init (struct event_base *base)
{
	struct aio_context *new;

	/* First of all we need to detect which type of aio we can try to use */
	new = g_malloc0 (sizeof (struct aio_context));
	new->base = base;

#ifdef LINUX
	/* On linux we are trying to use io (3) and eventfd for notifying */
	new->event_fd = eventfd (0, 0);
	if (new->event_fd == -1) {
		msg_err ("eventfd failed: %s", strerror (errno));
	}
	else {
		/* Set this socket non-blocking */
		if (rspamd_socket_nonblocking (new->event_fd) == -1) {
			msg_err ("non blocking for eventfd failed: %s", strerror (errno));
			close (new->event_fd);
		}
		else {
			event_set (&new->eventfd_ev,
				new->event_fd,
				EV_READ | EV_PERSIST,
				rspamd_eventfdcb,
				new);
			event_base_set (new->base, &new->eventfd_ev);
			event_add (&new->eventfd_ev, NULL);
			if (io_setup (MAX_AIO_EV, &new->io_ctx) == -1) {
				msg_err ("io_setup failed: %s", strerror (errno));
				close (new->event_fd);
			}
			else {
				new->has_aio = TRUE;
			}
		}
	}
#elif defined(HAVE_AIO_H)
	/* TODO: implement this */
#endif

	return new;
}

/**
 * Open file for aio
 */
gint
rspamd_aio_open (struct aio_context *ctx, const gchar *path, int flags)
{
	gint fd = -1;
	/* Fallback */
	if (!ctx->has_aio) {
		return open (path, flags);
	}
#ifdef LINUX

	fd = open (path, flags | O_DIRECT);

	return fd;
#elif defined(HAVE_AIO_H)
	fd = open (path, flags);
#endif

	return fd;
}

/**
 * Asynchronous read of file
 */
gint
rspamd_aio_read (gint fd,
	gpointer buf,
	guint64 len,
	guint64 offset,
	struct aio_context *ctx,
	rspamd_aio_cb cb,
	gpointer ud)
{
	gint r = -1;

	if (ctx->has_aio) {
#ifdef LINUX
		struct iocb *iocb[1];
		struct io_cbdata *cbdata;

		cbdata = g_slice_alloc (sizeof (struct io_cbdata));
		cbdata->cb = cb;
		cbdata->buf = buf;
		cbdata->len = len;
		cbdata->ud = ud;
		cbdata->fd = fd;
		cbdata->io_buf = NULL;

		iocb[0] = alloca (sizeof (struct iocb));
		memset (iocb[0], 0, sizeof (struct iocb));
		iocb[0]->aio_fildes = fd;
		iocb[0]->aio_lio_opcode = IO_CMD_PREAD;
		iocb[0]->aio_reqprio = 0;
		iocb[0]->aio_buf = (guint64)((uintptr_t)buf);
		iocb[0]->aio_nbytes = len;
		iocb[0]->aio_offset = offset;
		iocb[0]->aio_flags |= (1 << 0) /* IOCB_FLAG_RESFD */;
		iocb[0]->aio_resfd = ctx->event_fd;
		iocb[0]->aio_data = (guint64)((uintptr_t)cbdata);

		/* Iocb is copied to kernel internally, so it is safe to put it on stack */
		if (io_submit (ctx->io_ctx, 1, iocb) == 1) {
			return len;
		}
		else {
			if (errno == EAGAIN || errno == ENOSYS) {
				/* Fall back to sync read */
				goto blocking;
			}
			return -1;
		}

#elif defined(HAVE_AIO_H)
#endif
	}
	else {
		/* Blocking variant */
		goto blocking;
blocking:
#ifdef _LARGEFILE64_SOURCE
		r = lseek64 (fd, offset, SEEK_SET);
#else
		r = lseek (fd, offset, SEEK_SET);
#endif
		if (r > 0) {
			r = read (fd, buf, len);
			if (r >= 0) {
				cb (fd, 0, r, buf, ud);
			}
			else {
				cb (fd, r, -1, buf, ud);
			}
		}
	}

	return r;
}

/**
 * Asynchronous write of file
 */
gint
rspamd_aio_write (gint fd,
	gpointer buf,
	guint64 len,
	guint64 offset,
	struct aio_context *ctx,
	rspamd_aio_cb cb,
	gpointer ud)
{
	gint r = -1;

	if (ctx->has_aio) {
#ifdef LINUX
		struct iocb *iocb[1];
		struct io_cbdata *cbdata;

		cbdata = g_slice_alloc (sizeof (struct io_cbdata));
		cbdata->cb = cb;
		cbdata->buf = buf;
		cbdata->len = len;
		cbdata->ud = ud;
		cbdata->fd = fd;
		/* We need to align pointer on boundary of 512 bytes here */
		if (posix_memalign (&cbdata->io_buf, 512, len) != 0) {
			return -1;
		}
		memcpy (cbdata->io_buf, buf, len);

		iocb[0] = alloca (sizeof (struct iocb));
		memset (iocb[0], 0, sizeof (struct iocb));
		iocb[0]->aio_fildes = fd;
		iocb[0]->aio_lio_opcode = IO_CMD_PWRITE;
		iocb[0]->aio_reqprio = 0;
		iocb[0]->aio_buf = (guint64)((uintptr_t)cbdata->io_buf);
		iocb[0]->aio_nbytes = len;
		iocb[0]->aio_offset = offset;
		iocb[0]->aio_flags |= (1 << 0) /* IOCB_FLAG_RESFD */;
		iocb[0]->aio_resfd = ctx->event_fd;
		iocb[0]->aio_data = (guint64)((uintptr_t)cbdata);

		/* Iocb is copied to kernel internally, so it is safe to put it on stack */
		if (io_submit (ctx->io_ctx, 1, iocb) == 1) {
			return len;
		}
		else {
			if (errno == EAGAIN || errno == ENOSYS) {
				/* Fall back to sync read */
				goto blocking;
			}
			return -1;
		}

#elif defined(HAVE_AIO_H)
#endif
	}
	else {
		/* Blocking variant */
		goto blocking;
blocking:
#ifdef _LARGEFILE64_SOURCE
		r = lseek64 (fd, offset, SEEK_SET);
#else
		r = lseek (fd, offset, SEEK_SET);
#endif
		if (r > 0) {
			r = write (fd, buf, len);
			if (r >= 0) {
				cb (fd, 0, r, buf, ud);
			}
			else {
				cb (fd, r, -1, buf, ud);
			}
		}
	}

	return r;
}

/**
 * Close of aio operations
 */
gint
rspamd_aio_close (gint fd, struct aio_context *ctx)
{
	gint r = -1;

	if (ctx->has_aio) {
#ifdef LINUX
		struct iocb iocb;
		struct io_event ev;

		memset (&iocb, 0, sizeof (struct iocb));
		iocb.aio_fildes = fd;
		iocb.aio_lio_opcode = IO_CMD_NOOP;

		/* Iocb is copied to kernel internally, so it is safe to put it on stack */
		r = io_cancel (ctx->io_ctx, &iocb, &ev);
		close (fd);
		return r;

#elif defined(HAVE_AIO_H)
#endif
	}

	r = close (fd);

	return r;
}