/* 
   Unix SMB/CIFS implementation.

   Copyright (C) Andrew Tridgell 2006
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
  abstract the various kernel interfaces to change notify into a
  single Samba friendly interface
*/

#include "includes.h"
#include "system/filesys.h"
#include "ntvfs/sysdep/sys_notify.h"
#include <tevent.h>
#include "../lib/util/dlinklist.h"
#include "param/param.h"
#include "lib/util/samba_module.h"

/* list of registered backends */
static struct sys_notify_backend *backends;
static uint32_t num_backends;

#define NOTIFY_BACKEND	"notify:backend"

/*
  initialise a system change notify backend
*/
_PUBLIC_ struct sys_notify_context *sys_notify_context_create(struct share_config *scfg,
							      TALLOC_CTX *mem_ctx, 
							      struct tevent_context *ev)
{
	struct sys_notify_context *ctx;
	const char *bname;
	int i;

	if (num_backends == 0) {
		return NULL;
	}

	if (ev == NULL) {
		return NULL;
	}

	ctx = talloc_zero(mem_ctx, struct sys_notify_context);
	if (ctx == NULL) {
		return NULL;
	}

	ctx->ev = ev;

	bname = share_string_option(scfg, NOTIFY_BACKEND, NULL);
	if (!bname) {
		if (num_backends) {
			bname = backends[0].name;
		} else {
			bname = "__unknown__";
		}
	}

	for (i=0;i<num_backends;i++) {
		char *enable_opt_name;
		bool enabled;
		
		enable_opt_name = talloc_asprintf(mem_ctx, "notify:%s", 
										  backends[i].name);
		enabled = share_bool_option(scfg, enable_opt_name, true);
		talloc_free(enable_opt_name);

		if (!enabled) 
			continue;

		if (strcasecmp(backends[i].name, bname) == 0) {
			bname = backends[i].name;
			break;
		}
	}

	ctx->name = bname;
	ctx->notify_watch = NULL;

	if (i < num_backends) {
		ctx->notify_watch = backends[i].notify_watch;
	}

	return ctx;
}

/*
  add a watch

  note that this call must modify the e->filter and e->subdir_filter
  bits to remove ones handled by this backend. Any remaining bits will
  be handled by the generic notify layer
*/
_PUBLIC_ NTSTATUS sys_notify_watch(struct sys_notify_context *ctx,
				   struct notify_entry *e,
				   sys_notify_callback_t callback,
				   void *private_data, void *handle)
{
	if (!ctx->notify_watch) {
		return NT_STATUS_INVALID_SYSTEM_SERVICE;
	}
	return ctx->notify_watch(ctx, e, callback, private_data, handle);
}

/*
  register a notify backend
*/
_PUBLIC_ NTSTATUS sys_notify_register(struct sys_notify_backend *backend)
{
	struct sys_notify_backend *b;
	b = talloc_realloc(talloc_autofree_context(), backends, 
			   struct sys_notify_backend, num_backends+1);
	NT_STATUS_HAVE_NO_MEMORY(b);
	backends = b;
	backends[num_backends] = *backend;
	num_backends++;
	return NT_STATUS_OK;
}

_PUBLIC_ NTSTATUS sys_notify_init(void)
{
	static bool initialized = false;
#define _MODULE_PROTO(init) extern NTSTATUS init(void);
	STATIC_sys_notify_MODULES_PROTO;
	samba_module_init_fn static_init[] = { STATIC_sys_notify_MODULES };

	if (initialized) return NT_STATUS_OK;
	initialized = true;

	samba_module_init_fns_run(static_init);
	
	return NT_STATUS_OK;
}