/* 
   Unix SMB/CIFS implementation.

   Generic, persistent and shared between processes cache mechanism for use
   by various parts of the Samba code

   Copyright (C) Rafal Szczesniak    2002

   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/>.
*/

#include "includes.h"

#undef  DBGC_CLASS
#define DBGC_CLASS DBGC_TDB

#define TIMEOUT_LEN 12
#define CACHE_DATA_FMT	"%12u/"
#define READ_CACHE_DATA_FMT_TEMPLATE "%%12u/%%%us"
#define BLOB_TYPE "DATA_BLOB"
#define BLOB_TYPE_LEN 9

static struct tdb_context *cache;
static struct tdb_context *cache_notrans;

/**
 * @file gencache.c
 * @brief Generic, persistent and shared between processes cache mechanism
 *        for use by various parts of the Samba code
 *
 **/


/**
 * Cache initialisation function. Opens cache tdb file or creates
 * it if does not exist.
 *
 * @return true on successful initialisation of the cache or
 *         false on failure
 **/

static bool gencache_init(void)
{
	char* cache_fname = NULL;
	int open_flags = O_RDWR|O_CREAT;

	/* skip file open if it's already opened */
	if (cache) return True;

	cache_fname = lock_path("gencache.tdb");

	DEBUG(5, ("Opening cache file at %s\n", cache_fname));

	cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT, open_flags, 0644);

	if (!cache && (errno == EACCES)) {
		open_flags = O_RDONLY;
		cache = tdb_open_log(cache_fname, 0, TDB_DEFAULT, open_flags,
				     0644);
		if (cache) {
			DEBUG(5, ("gencache_init: Opening cache file %s read-only.\n", cache_fname));
		}
	}

	if (!cache) {
		DEBUG(5, ("Attempt to open gencache.tdb has failed.\n"));
		return False;
	}

	cache_fname = lock_path("gencache_notrans.tdb");

	DEBUG(5, ("Opening cache file at %s\n", cache_fname));

	cache_notrans = tdb_open_log(cache_fname, 0, TDB_CLEAR_IF_FIRST,
				     open_flags, 0644);
	if (cache_notrans == NULL) {
		DEBUG(5, ("Opening %s failed: %s\n", cache_fname,
			  strerror(errno)));
		tdb_close(cache);
		return false;
	}

	return True;
}

static TDB_DATA last_stabilize_key(void)
{
	TDB_DATA result;
	result.dptr = (uint8_t *)"@LAST_STABILIZED";
	result.dsize = 17;
	return result;
}

/**
 * Set an entry in the cache file. If there's no such
 * one, then add it.
 *
 * @param keystr string that represents a key of this entry
 * @param blob DATA_BLOB value being cached
 * @param timeout time when the value is expired
 *
 * @retval true when entry is successfuly stored
 * @retval false on failure
 **/

bool gencache_set_data_blob(const char *keystr, const DATA_BLOB *blob,
			    time_t timeout)
{
	int ret;
	TDB_DATA databuf;
	char* val;
	time_t last_stabilize;
	static int writecount;

	if (tdb_data_cmp(string_term_tdb_data(keystr),
			 last_stabilize_key()) == 0) {
		DEBUG(10, ("Can't store %s as a key\n", keystr));
		return false;
	}

	if ((keystr == NULL) || (blob == NULL)) {
		return false;
	}

	if (!gencache_init()) return False;

	val = talloc_asprintf(talloc_tos(), CACHE_DATA_FMT, (int)timeout);
	if (val == NULL) {
		return False;
	}
	val = talloc_realloc(NULL, val, char, talloc_array_length(val)-1);
	if (val == NULL) {
		return false;
	}
	val = (char *)talloc_append_blob(NULL, val, *blob);
	if (val == NULL) {
		return false;
	}

	DEBUG(10, ("Adding cache entry with key = %s and timeout ="
	           " %s (%d seconds %s)\n", keystr, ctime(&timeout),
		   (int)(timeout - time(NULL)), 
		   timeout > time(NULL) ? "ahead" : "in the past"));

	ret = tdb_store_bystring(
		cache_notrans, keystr,
		make_tdb_data((uint8_t *)val, talloc_array_length(val)),
		0);
	TALLOC_FREE(val);

	if (ret != 0) {
		return false;
	}

	/*
	 * Every 100 writes within a single process, stabilize the cache with
	 * a transaction. This is done to prevent a single transaction to
	 * become huge and chew lots of memory.
	 */
	writecount += 1;
	if (writecount > lp_parm_int(-1, "gencache", "stabilize_count", 100)) {
		gencache_stabilize();
		writecount = 0;
		goto done;
	}

	/*
	 * Every 5 minutes, call gencache_stabilize() to not let grow
	 * gencache_notrans.tdb too large.
	 */

	last_stabilize = 0;
	databuf = tdb_fetch(cache_notrans, last_stabilize_key());
	if ((databuf.dptr != NULL)
	    && (databuf.dptr[databuf.dsize-1] == '\0')) {
		last_stabilize = atoi((char *)databuf.dptr);
		SAFE_FREE(databuf.dptr);
	}
	if ((last_stabilize
	     + lp_parm_int(-1, "gencache", "stabilize_interval", 300))
	    < time(NULL)) {
		gencache_stabilize();
	}

done:
	return ret == 0;
}

/**
 * Delete one entry from the cache file.
 *
 * @param keystr string that represents a key of this entry
 *
 * @retval true upon successful deletion
 * @retval false in case of failure
 **/

bool gencache_del(const char *keystr)
{
	bool exists;
	bool ret = false;
	char *value;

	if (keystr == NULL) {
		return false;
	}

	if (!gencache_init()) return False;	

	DEBUG(10, ("Deleting cache entry (key = %s)\n", keystr));

	if (tdb_lock_bystring(cache_notrans, keystr) == -1) {
		DEBUG(5, ("Could not lock key for %s\n", keystr));
		return false;
	}

	/*
	 * We delete an element by setting its timeout to 0. This way we don't
	 * have to do a transaction on gencache.tdb every time we delete an
	 * element.
	 */

	exists = gencache_get(keystr, &value, NULL);
	if (exists) {
		SAFE_FREE(value);
		ret = gencache_set(keystr, "", 0);
	}
	tdb_unlock_bystring(cache_notrans, keystr);
	return ret;
}

static bool gencache_pull_timeout(char *val, time_t *pres, char **pendptr)
{
	time_t res;
	char *endptr;

	res = strtol(val, &endptr, 10);

	if ((endptr == NULL) || (*endptr != '/')) {
		DEBUG(2, ("Invalid gencache data format: %s\n", val));
		return false;
	}
	if (pres != NULL) {
		*pres = res;
	}
	if (pendptr != NULL) {
		*pendptr = endptr;
	}
	return true;
}

/**
 * Get existing entry from the cache file.
 *
 * @param keystr string that represents a key of this entry
 * @param blob DATA_BLOB that is filled with entry's blob
 * @param timeout pointer to a time_t that is filled with entry's
 *        timeout
 *
 * @retval true when entry is successfuly fetched
 * @retval False for failure
 **/

bool gencache_get_data_blob(const char *keystr, DATA_BLOB *blob,
			    time_t *timeout)
{
	TDB_DATA databuf;
	time_t t;
	char *endptr;

	if (keystr == NULL) {
		return false;
	}

	if (tdb_data_cmp(string_term_tdb_data(keystr),
			 last_stabilize_key()) == 0) {
		DEBUG(10, ("Can't get %s as a key\n", keystr));
		return false;
	}

	if (!gencache_init()) {
		return False;
	}

	databuf = tdb_fetch_bystring(cache_notrans, keystr);

	if (databuf.dptr == NULL) {
		databuf = tdb_fetch_bystring(cache, keystr);
	}

	if (databuf.dptr == NULL) {
		DEBUG(10, ("Cache entry with key = %s couldn't be found \n",
			   keystr));
		return False;
	}

	if (!gencache_pull_timeout((char *)databuf.dptr, &t, &endptr)) {
		SAFE_FREE(databuf.dptr);
		return False;
	}

	DEBUG(10, ("Returning %s cache entry: key = %s, value = %s, "
		   "timeout = %s", t > time(NULL) ? "valid" :
		   "expired", keystr, endptr+1, ctime(&t)));

	if (t == 0) {
		/* Deleted */
		SAFE_FREE(databuf.dptr);
		return False;
	}

	if (t <= time(NULL)) {

		/*
		 * We're expired, delete the entry. We can't use gencache_del
		 * here, because that uses gencache_get_data_blob for checking
		 * the existence of a record. We know the thing exists and
		 * directly store an empty value with 0 timeout.
		 */
		gencache_set(keystr, "", 0);

		SAFE_FREE(databuf.dptr);
		return False;
	}

	if (blob != NULL) {
		*blob = data_blob(
			endptr+1,
			databuf.dsize - PTR_DIFF(endptr+1, databuf.dptr));
		if (blob->data == NULL) {
			SAFE_FREE(databuf.dptr);
			DEBUG(0, ("memdup failed\n"));
			return False;
		}
	}

	SAFE_FREE(databuf.dptr);

	if (timeout) {
		*timeout = t;
	}

	return True;
} 

struct stabilize_state {
	bool written;
	bool error;
};
static int stabilize_fn(struct tdb_context *tdb, TDB_DATA key, TDB_DATA val,
			void *priv);

/**
 * Stabilize gencache
 *
 * Migrate the clear-if-first gencache data to the stable,
 * transaction-based gencache.tdb
 */

bool gencache_stabilize(void)
{
	struct stabilize_state state;
	int res;
	char *now;

	if (!gencache_init()) {
		return false;
	}

	res = tdb_transaction_start(cache);
	if (res == -1) {
		DEBUG(10, ("Could not start transaction on gencache.tdb: "
			   "%s\n", tdb_errorstr(cache)));
		return false;
	}
	res = tdb_transaction_start(cache_notrans);
	if (res == -1) {
		tdb_transaction_cancel(cache);
		DEBUG(10, ("Could not start transaction on "
			   "gencache_notrans.tdb: %s\n",
			   tdb_errorstr(cache_notrans)));
		return false;
	}

	state.error = false;
	state.written = false;

	res = tdb_traverse(cache_notrans, stabilize_fn, &state);
	if ((res == -1) || state.error) {
		if ((tdb_transaction_cancel(cache_notrans) == -1)
		    || (tdb_transaction_cancel(cache) == -1)) {
			smb_panic("tdb_transaction_cancel failed\n");
		}
		return false;
	}

	if (!state.written) {
		if ((tdb_transaction_cancel(cache_notrans) == -1)
		    || (tdb_transaction_cancel(cache) == -1)) {
			smb_panic("tdb_transaction_cancel failed\n");
		}
		return true;
	}

	res = tdb_transaction_commit(cache);
	if (res == -1) {
		DEBUG(10, ("tdb_transaction_commit on gencache.tdb failed: "
			   "%s\n", tdb_errorstr(cache)));
		if (tdb_transaction_cancel(cache_notrans) == -1) {
			smb_panic("tdb_transaction_cancel failed\n");
		}
		return false;
	}

	res = tdb_transaction_commit(cache_notrans);
	if (res == -1) {
		DEBUG(10, ("tdb_transaction_commit on gencache.tdb failed: "
			   "%s\n", tdb_errorstr(cache)));
		return false;
	}

	now = talloc_asprintf(talloc_tos(), "%d", (int)time(NULL));
	if (now != NULL) {
		tdb_store(cache_notrans, last_stabilize_key(),
			  string_term_tdb_data(now), 0);
		TALLOC_FREE(now);
	}

	return true;
}

static int stabilize_fn(struct tdb_context *tdb, TDB_DATA key, TDB_DATA val,
			void *priv)
{
	struct stabilize_state *state = (struct stabilize_state *)priv;
	int res;
	time_t timeout;

	if (tdb_data_cmp(key, last_stabilize_key()) == 0) {
		return 0;
	}

	if (!gencache_pull_timeout((char *)val.dptr, &timeout, NULL)) {
		DEBUG(10, ("Ignoring invalid entry\n"));
		return 0;
	}
	if ((timeout < time(NULL)) || (val.dsize == 0)) {
		res = tdb_delete(cache, key);
		if ((res == -1) && (tdb_error(cache) == TDB_ERR_NOEXIST)) {
			res = 0;
		} else {
			state->written = true;
		}
	} else {
		res = tdb_store(cache, key, val, 0);
		if (res == 0) {
			state->written = true;
		}
	}

	if (res == -1) {
		DEBUG(10, ("Transfer to gencache.tdb failed: %s\n",
			   tdb_errorstr(cache)));
		state->error = true;
		return -1;
	}

	if (tdb_delete(cache_notrans, key) == -1) {
		DEBUG(10, ("tdb_delete from gencache_notrans.tdb failed: "
			   "%s\n", tdb_errorstr(cache_notrans)));
		state->error = true;
		return -1;
	}
	return 0;
}

/**
 * Get existing entry from the cache file.
 *
 * @param keystr string that represents a key of this entry
 * @param valstr buffer that is allocated and filled with the entry value
 *        buffer's disposing must be done outside
 * @param timeout pointer to a time_t that is filled with entry's
 *        timeout
 *
 * @retval true when entry is successfuly fetched
 * @retval False for failure
 **/

bool gencache_get(const char *keystr, char **value, time_t *ptimeout)
{
	DATA_BLOB blob;
	bool ret = False;

	ret = gencache_get_data_blob(keystr, &blob, ptimeout);
	if (!ret) {
		return false;
	}
	if ((blob.data == NULL) || (blob.length == 0)) {
		SAFE_FREE(blob.data);
		return false;
	}
	if (blob.data[blob.length-1] != '\0') {
		/* Not NULL terminated, can't be a string */
		SAFE_FREE(blob.data);
		return false;
	}
	*value = SMB_STRDUP((char *)blob.data);
	data_blob_free(&blob);
	if (*value == NULL) {
		return false;
	}
	return true;
}

/**
 * Set an entry in the cache file. If there's no such
 * one, then add it.
 *
 * @param keystr string that represents a key of this entry
 * @param value text representation value being cached
 * @param timeout time when the value is expired
 *
 * @retval true when entry is successfuly stored
 * @retval false on failure
 **/

bool gencache_set(const char *keystr, const char *value, time_t timeout)
{
	DATA_BLOB blob = data_blob_const(value, strlen(value)+1);
	return gencache_set_data_blob(keystr, &blob, timeout);
}

/**
 * Iterate through all entries which key matches to specified pattern
 *
 * @param fn pointer to the function that will be supplied with each single
 *        matching cache entry (key, value and timeout) as an arguments
 * @param data void pointer to an arbitrary data that is passed directly to the fn
 *        function on each call
 * @param keystr_pattern pattern the existing entries' keys are matched to
 *
 **/

struct gencache_iterate_state {
	void (*fn)(const char *key, const char *value, time_t timeout,
		   void *priv);
	const char *pattern;
	void *priv;
	bool in_persistent;
};

static int gencache_iterate_fn(struct tdb_context *tdb, TDB_DATA key,
			       TDB_DATA value, void *priv)
{
	struct gencache_iterate_state *state =
		(struct gencache_iterate_state *)priv;
	char *keystr;
	char *free_key = NULL;
	char *valstr;
	char *free_val = NULL;
	unsigned long u;
	time_t timeout;
	char *timeout_endp;

	if (tdb_data_cmp(key, last_stabilize_key()) == 0) {
		return 0;
	}

	if (state->in_persistent && tdb_exists(cache_notrans, key)) {
		return 0;
	}

	if (key.dptr[key.dsize-1] == '\0') {
		keystr = (char *)key.dptr;
	} else {
		/* ensure 0-termination */
		keystr = SMB_STRNDUP((char *)key.dptr, key.dsize);
		free_key = keystr;
	}

	if ((value.dptr == NULL) || (value.dsize <= TIMEOUT_LEN)) {
		goto done;
	}

	if (fnmatch(state->pattern, keystr, 0) != 0) {
		goto done;
	}

	if (value.dptr[value.dsize-1] == '\0') {
		valstr = (char *)value.dptr;
	} else {
		/* ensure 0-termination */
		valstr = SMB_STRNDUP((char *)value.dptr, value.dsize);
		free_val = valstr;
	}

	u = strtoul(valstr, &timeout_endp, 10);

	if ((*timeout_endp != '/') || ((timeout_endp-valstr) != TIMEOUT_LEN)) {
		goto done;
	}

	timeout = u;
	timeout_endp += 1;

	DEBUG(10, ("Calling function with arguments "
		   "(key = %s, value = %s, timeout = %s)\n",
		   keystr, timeout_endp, ctime(&timeout)));
	state->fn(keystr, timeout_endp, timeout, state->priv);

 done:
	SAFE_FREE(free_key);
	SAFE_FREE(free_val);
	return 0;
}

void gencache_iterate(void (*fn)(const char* key, const char *value, time_t timeout, void* dptr),
                      void* data, const char* keystr_pattern)
{
	struct gencache_iterate_state state;

	if ((fn == NULL) || (keystr_pattern == NULL)) {
		return;
	}

	if (!gencache_init()) return;

	DEBUG(5, ("Searching cache keys with pattern %s\n", keystr_pattern));

	state.fn = fn;
	state.pattern = keystr_pattern;
	state.priv = data;

	state.in_persistent = false;
	tdb_traverse(cache_notrans, gencache_iterate_fn, &state);

	state.in_persistent = true;
	tdb_traverse(cache, gencache_iterate_fn, &state);
}