/*
  * This file is part of GNUnet
  * (C) 2009-2013 Christian Grothoff (and other contributing authors)
  *
  * GNUnet 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, or (at your
  * option) any later version.
  *
  * GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */

/**
 * @file namecache/plugin_namecache_postgres.c
 * @brief postgres-based namecache backend
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_namecache_plugin.h"
#include "gnunet_namecache_service.h"
#include "gnunet_gnsrecord_lib.h"
#include "gnunet_postgres_lib.h"
#include "namecache.h"


/**
 * After how many ms "busy" should a DB operation fail for good?
 * A low value makes sure that we are more responsive to requests
 * (especially PUTs).  A high value guarantees a higher success
 * rate (SELECTs in iterate can take several seconds despite LIMIT=1).
 *
 * The default value of 1s should ensure that users do not experience
 * huge latencies while at the same time allowing operations to succeed
 * with reasonable probability.
 */
#define BUSY_TIMEOUT_MS 1000


/**
 * Log an error message at log-level 'level' that indicates
 * a failure of the command 'cmd' on file 'filename'
 * with the message given by strerror(errno).
 */
#define LOG_POSTGRES(db, level, cmd) do { GNUNET_log_from (level, "namecache-postgres", _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, sqlite3_errmsg(db->dbh)); } while(0)

#define LOG(kind,...) GNUNET_log_from (kind, "namecache-postgres", __VA_ARGS__)


/**
 * Context for all functions in this plugin.
 */
struct Plugin
{

  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Native Postgres database handle.
   */
  PGconn *dbh;

};


/**
 * Create our database indices.
 *
 * @param dbh handle to the database
 */
static void
create_indices (PGconn * dbh)
{
  /* create indices */
  if ( (GNUNET_OK !=
	GNUNET_POSTGRES_exec (dbh,
                              "CREATE INDEX ir_query_hash ON ns096blocks (query,expiration_time)")) ||
       (GNUNET_OK !=
	GNUNET_POSTGRES_exec (dbh,
                              "CREATE INDEX ir_block_expiration ON ns096blocks (expiration_time)")) )
    LOG (GNUNET_ERROR_TYPE_ERROR,
	 _("Failed to create indices\n"));
}


/**
 * Initialize the database connections and associated
 * data structures (create tables and indices
 * as needed as well).
 *
 * @param plugin the plugin context (state for this module)
 * @return GNUNET_OK on success
 */
static int
database_setup (struct Plugin *plugin)
{
  PGresult *res;

  plugin->dbh = GNUNET_POSTGRES_connect (plugin->cfg,
					 "namecache-postgres");
  if (NULL == plugin->dbh)
    return GNUNET_SYSERR;
  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_get_value_yesno (plugin->cfg,
					    "namecache-postgres",
					    "TEMPORARY_TABLE"))
  {
    res =
      PQexec (plugin->dbh,
              "CREATE TEMPORARY TABLE ns096blocks ("
	      " query BYTEA NOT NULL DEFAULT '',"
	      " block BYTEA NOT NULL DEFAULT '',"
	      " expiration_time BIGINT NOT NULL DEFAULT 0"
	      ")" "WITH OIDS");
  }
  else
  {
    res =
      PQexec (plugin->dbh,
              "CREATE TABLE ns096blocks ("
	      " query BYTEA NOT NULL DEFAULT '',"
	      " block BYTEA NOT NULL DEFAULT '',"
	      " expiration_time BIGINT NOT NULL DEFAULT 0"
	      ")" "WITH OIDS");
  }
  if ( (NULL == res) ||
       ((PQresultStatus (res) != PGRES_COMMAND_OK) &&
        (0 != strcmp ("42P07",    /* duplicate table */
                      PQresultErrorField
                      (res,
                       PG_DIAG_SQLSTATE)))))
  {
    (void) GNUNET_POSTGRES_check_result (plugin->dbh, res,
                                         PGRES_COMMAND_OK, "CREATE TABLE",
					 "ns096blocks");
    PQfinish (plugin->dbh);
    plugin->dbh = NULL;
    return GNUNET_SYSERR;
  }
  if (PQresultStatus (res) == PGRES_COMMAND_OK)
    create_indices (plugin->dbh);
  PQclear (res);

  if ((GNUNET_OK !=
       GNUNET_POSTGRES_prepare (plugin->dbh,
				"cache_block",
				"INSERT INTO ns096blocks (query, block, expiration_time) VALUES "
 				"($1, $2, $3)", 3)) ||
      (GNUNET_OK !=
       GNUNET_POSTGRES_prepare (plugin->dbh,
				"expire_blocks",
				"DELETE FROM ns096blocks WHERE expiration_time<$1", 1)) ||
      (GNUNET_OK !=
       GNUNET_POSTGRES_prepare (plugin->dbh,
				"delete_block",
				"DELETE FROM ns096blocks WHERE query=$1 AND expiration_time<=$2", 2)) ||
      (GNUNET_OK !=
       GNUNET_POSTGRES_prepare (plugin->dbh,
				"lookup_block",
				"SELECT block FROM ns096blocks WHERE query=$1"
				" ORDER BY expiration_time DESC LIMIT 1", 1)))
  {
    PQfinish (plugin->dbh);
    plugin->dbh = NULL;
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Removes any expired block.
 *
 * @param plugin the plugin
 */
static void
namecache_postgres_expire_blocks (struct Plugin *plugin)
{
  struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();
  struct GNUNET_TIME_AbsoluteNBO now_be = GNUNET_TIME_absolute_hton (now);
  const char *paramValues[] = {
    (const char *) &now_be
  };
  int paramLengths[] = {
    sizeof (now_be)
  };
  const int paramFormats[] = { 1 };
  PGresult *res;

  res =
    PQexecPrepared (plugin->dbh, "expire_blocks", 1,
		    paramValues, paramLengths, paramFormats, 1);
  if (GNUNET_OK !=
      GNUNET_POSTGRES_check_result (plugin->dbh,
                                    res,
                                    PGRES_COMMAND_OK,
                                    "PQexecPrepared",
                                    "expire_blocks"))
    return;
  PQclear (res);
}


/**
 * Delete older block in the datastore.
 *
 * @param plugin the plugin
 * @param query query for the block
 * @param expiration_time how old does the block have to be for deletion
 */
static void
delete_old_block (struct Plugin *plugin,
                  const struct GNUNET_HashCode *query,
                  struct GNUNET_TIME_AbsoluteNBO expiration_time)
{
  const char *paramValues[] = {
    (const char *) query,
    (const char *) &expiration_time
  };
  int paramLengths[] = {
    sizeof (*query),
    sizeof (expiration_time)
  };
  const int paramFormats[] = { 1, 1 };
  PGresult *res;

  res =
    PQexecPrepared (plugin->dbh, "delete_block", 2,
		    paramValues, paramLengths, paramFormats, 1);
  if (GNUNET_OK !=
      GNUNET_POSTGRES_check_result (plugin->dbh,
                                    res,
                                    PGRES_COMMAND_OK,
                                    "PQexecPrepared",
                                    "delete_block"))
    return;
  PQclear (res);
}


/**
 * Cache a block in the datastore.
 *
 * @param cls closure (internal context for the plugin)
 * @param block block to cache
 * @return #GNUNET_OK on success, else #GNUNET_SYSERR
 */
static int
namecache_postgres_cache_block (void *cls,
                                const struct GNUNET_GNSRECORD_Block *block)
{
  struct Plugin *plugin = cls;
  struct GNUNET_HashCode query;
  size_t block_size = ntohl (block->purpose.size) +
    sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey) +
    sizeof (struct GNUNET_CRYPTO_EcdsaSignature);
  const char *paramValues[] = {
    (const char *) &query,
    (const char *) block,
    (const char *) &block->expiration_time
  };
  int paramLengths[] = {
    sizeof (query),
    (int) block_size,
    sizeof (block->expiration_time)
  };
  const int paramFormats[] = { 1, 1, 1 };
  PGresult *res;

  namecache_postgres_expire_blocks (plugin);
  GNUNET_CRYPTO_hash (&block->derived_key,
		      sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey),
		      &query);
  if (block_size > 64 * 65536)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  delete_old_block (plugin, &query, block->expiration_time);

  res =
    PQexecPrepared (plugin->dbh, "cache_block", 3,
		    paramValues, paramLengths, paramFormats, 1);
  if (GNUNET_OK !=
      GNUNET_POSTGRES_check_result (plugin->dbh,
                                    res,
                                    PGRES_COMMAND_OK,
                                    "PQexecPrepared",
                                    "cache_block"))
    return GNUNET_SYSERR;
  PQclear (res);
  return GNUNET_OK;
}


/**
 * Get the block for a particular zone and label in the
 * datastore.  Will return at most one result to the iterator.
 *
 * @param cls closure (internal context for the plugin)
 * @param query hash of public key derived from the zone and the label
 * @param iter function to call with the result
 * @param iter_cls closure for @a iter
 * @return #GNUNET_OK on success, #GNUNET_NO if there were no results, #GNUNET_SYSERR on error
 */
static int
namecache_postgres_lookup_block (void *cls,
                                 const struct GNUNET_HashCode *query,
                                 GNUNET_NAMECACHE_BlockCallback iter, void *iter_cls)
{
  struct Plugin *plugin = cls;
  const char *paramValues[] = {
    (const char *) query
  };
  int paramLengths[] = {
    sizeof (*query)
  };
  const int paramFormats[] = { 1 };
  PGresult *res;
  unsigned int cnt;
  size_t bsize;
  const struct GNUNET_GNSRECORD_Block *block;

  res = PQexecPrepared (plugin->dbh,
                        "lookup_block", 1,
                        paramValues, paramLengths, paramFormats,
                        1);
  if (GNUNET_OK !=
      GNUNET_POSTGRES_check_result (plugin->dbh, res, PGRES_TUPLES_OK,
                                    "PQexecPrepared",
				    "lookup_block"))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
	 "Failing lookup (postgres error)\n");
    return GNUNET_SYSERR;
  }
  if (0 == (cnt = PQntuples (res)))
  {
    /* no result */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
	 "Ending iteration (no more results)\n");
    PQclear (res);
    return GNUNET_NO;
  }
  GNUNET_assert (1 == cnt);
  GNUNET_assert (1 != PQnfields (res));
  bsize = PQgetlength (res, 0, 0);
  block = (const struct GNUNET_GNSRECORD_Block *) PQgetvalue (res, 0, 0);
  if ( (bsize < sizeof (*block)) ||
       (bsize != ntohl (block->purpose.size) +
        sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey) +
        sizeof (struct GNUNET_CRYPTO_EcdsaSignature)) )
  {
    GNUNET_break (0);
    LOG (GNUNET_ERROR_TYPE_DEBUG,
	 "Failing lookup (corrupt block)\n");
    PQclear (res);
    return GNUNET_SYSERR;
  }
  iter (iter_cls, block);
  PQclear (res);
  return GNUNET_OK;
}


/**
 * Shutdown database connection and associate data
 * structures.
 *
 * @param plugin the plugin context (state for this module)
 */
static void
database_shutdown (struct Plugin *plugin)
{
  PQfinish (plugin->dbh);
  plugin->dbh = NULL;
}


/**
 * Entry point for the plugin.
 *
 * @param cls the "struct GNUNET_NAMECACHE_PluginEnvironment*"
 * @return NULL on error, othrewise the plugin context
 */
void *
libgnunet_plugin_namecache_postgres_init (void *cls)
{
  static struct Plugin plugin;
  const struct GNUNET_CONFIGURATION_Handle *cfg = cls;
  struct GNUNET_NAMECACHE_PluginFunctions *api;

  if (NULL != plugin.cfg)
    return NULL;                /* can only initialize once! */
  memset (&plugin, 0, sizeof (struct Plugin));
  plugin.cfg = cfg;
  if (GNUNET_OK != database_setup (&plugin))
  {
    database_shutdown (&plugin);
    return NULL;
  }
  api = GNUNET_new (struct GNUNET_NAMECACHE_PluginFunctions);
  api->cls = &plugin;
  api->cache_block = &namecache_postgres_cache_block;
  api->lookup_block = &namecache_postgres_lookup_block;
  LOG (GNUNET_ERROR_TYPE_INFO,
       _("Postgres database running\n"));
  return api;
}


/**
 * Exit point from the plugin.
 *
 * @param cls the plugin context (as returned by "init")
 * @return always NULL
 */
void *
libgnunet_plugin_namecache_postgres_done (void *cls)
{
  struct GNUNET_NAMECACHE_PluginFunctions *api = cls;
  struct Plugin *plugin = api->cls;

  database_shutdown (plugin);
  plugin->cfg = NULL;
  GNUNET_free (api);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "postgres plugin is finished\n");
  return NULL;
}

/* end of plugin_namecache_postgres.c */