/*
  This file is part of TALER
  Copyright (C) 2014, 2015 Christian Grothoff (and other contributing authors)

  TALER 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.

  TALER 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
  TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file pq/db_pq.c
 * @brief helper functions for libpq (PostGres) interactions
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 * @author Florian Dold
 * @author Christian Grothoff
 */
#include "platform.h"
#include <gnunet/gnunet_util_lib.h>
#include "taler_pq_lib.h"


/**
 * Execute a prepared statement.
 */
PGresult *
TALER_PQ_exec_prepared (PGconn *db_conn,
                        const char *name,
                        const struct TALER_PQ_QueryParam *params)
{
  unsigned int len;
  unsigned int i;

  /* count the number of parameters */
  {
    const struct TALER_PQ_QueryParam *x;
    for (len = 0, x = params;
         x->more;
         len++, x++);
  }

  /* new scope to allow stack allocation without alloca */
  {
    void *param_values[len];
    int param_lengths[len];
    int param_formats[len];

    for (i = 0; i < len; i += 1)
    {
      param_values[i] = (void *) params[i].data;
      param_lengths[i] = params[i].size;
      param_formats[i] = 1;
    }
    return PQexecPrepared (db_conn,
			   name,
			   len,
                           (const char **) param_values,
                           param_lengths,
                           param_formats,
			   1);
  }
}


/**
 * Extract results from a query result according to the given specification.
 * If colums are NULL, the destination is not modified, and #GNUNET_NO
 * is returned.
 *
 * @param result result to process
 * @param[in|out] rs result specification to extract for
 * @param row row from the result to extract
 * @return
 *   #GNUNET_YES if all results could be extracted
 *   #GNUNET_NO if at least one result was NULL
 *   #GNUNET_SYSERR if a result was invalid (non-existing field)
 */
int
TALER_PQ_extract_result (PGresult *result,
                         struct TALER_PQ_ResultSpec *rs,
                         int row)
{
  int had_null = GNUNET_NO;
  size_t len;
  unsigned int i;
  unsigned int j;
  const char *res;
  int fnum;

  for (i=0; NULL != rs[i].fname; i++)
  {
    fnum = PQfnumber (result,
		      rs[i].fname);
    if (fnum < 0)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Field `%s' does not exist in result\n",
                  rs[i].fname);
      return GNUNET_SYSERR;
    }

    /* if a field is null, continue but
     * remember that we now return a different result */
    if (PQgetisnull (result,
		     row,
		     fnum))
    {
      had_null = GNUNET_YES;
      continue;
    }
    len = PQgetlength (result,
		       row,
		       fnum);
    if ( (0 != rs[i].dst_size) &&
         (rs[i].dst_size != len) )
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Field `%s' has wrong size (got %u, expected %u)\n",
                  rs[i].fname,
                  (unsigned int) len,
                  (unsigned int) rs[i].dst_size);
      for (j=0; j<i; j++)
      {
        if (0 == rs[j].dst_size)
        {
          GNUNET_free (rs[j].dst);
          rs[j].dst = NULL;
          if (NULL != rs[j].result_size)
	    *rs[j].result_size = 0;
        }
      }
      return GNUNET_SYSERR;
    }
    res = PQgetvalue (result,
		      row,
		      fnum);
    GNUNET_assert (NULL != res);
    if (0 == rs[i].dst_size)
    {
      if (NULL != rs[i].result_size)
	*rs[i].result_size = len;
      rs[i].dst_size = len;
      *((void **) rs[i].dst) = GNUNET_malloc (len);
      rs[i].dst = * ((void **) rs[i].dst);
    }
    memcpy (rs[i].dst,
	    res,
	    len);
  }
  if (GNUNET_YES == had_null)
    return GNUNET_NO;
  return GNUNET_YES;
}


/**
 * Extract a currency amount from a query result according to the
 * given specification.  
 *
 * @param result the result to extract the amount from
 * @param row which row of the result to extract the amount from (needed as results can have multiple rows)
 * @param val_name name of the column with the amount's "value", must include the substring "_val".
 * @param frac_name name of the column with the amount's "fractional" value, must include the substring "_frac".
 * @param curr_name name of the column with the amount's currency name, must include the substring "_curr".
 * @param[out] r_amount_nbo where to store the amount, in network byte order
 * @return
 *   #GNUNET_YES if all results could be extracted
 *   #GNUNET_NO if at least one result was NULL
 *   #GNUNET_SYSERR if a result was invalid (non-existing field)
 */
int
TALER_PQ_extract_amount_nbo (PGresult *result,
                             int row,
                             const char *val_name,
                             const char *frac_name,
                             const char *curr_name,
                             struct TALER_AmountNBO *r_amount_nbo)
{
  int val_num;
  int frac_num;
  int curr_num;
  int len;

  /* These checks are simply to check that clients obey by our naming
     conventions, and not for any functional reason */
  GNUNET_assert (NULL !=
		 strstr (val_name,
			 "_val"));
  GNUNET_assert (NULL !=
		 strstr (frac_name,
			 "_frac"));
  GNUNET_assert (NULL !=
		 strstr (curr_name,
			 "_curr"));
  /* Set return value to invalid in case we don't finish */
  memset (r_amount_nbo,
	  0,
	  sizeof (struct TALER_AmountNBO));
  val_num = PQfnumber (result,
		       val_name);
  frac_num = PQfnumber (result,
			frac_name);
  curr_num = PQfnumber (result,
			curr_name);
  if ( (val_num < 0) ||
       (frac_num < 0) ||
       (curr_num < 0) )
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  if ( (PQgetisnull (result,
		     row,
		     val_num)) ||
       (PQgetisnull (result,
		     row,
		     frac_num)) ||
       (PQgetisnull (result,
		     row,
		     curr_num)) )
  {
    GNUNET_break (0);
    return GNUNET_NO;
  }
  /* Note that Postgres stores value in NBO internally,
     so no conversion needed in this case */
  r_amount_nbo->value = *(uint64_t *) PQgetvalue (result,
						  row,
						  val_num); 
  r_amount_nbo->fraction = *(uint32_t *) PQgetvalue (result,
						     row,
						     frac_num);
  len = GNUNET_MIN (TALER_CURRENCY_LEN - 1,
                    PQgetlength (result,
				 row,
				 curr_num));
  memcpy (r_amount_nbo->currency,
	  PQgetvalue (result,
		      row,
		      curr_num),
          len);
  return GNUNET_OK;
}


/**
 * Extract a currency amount from a query result according to the
 * given specification.  
 *
 * @param result the result to extract the amount from
 * @param row which row of the result to extract the amount from (needed as results can have multiple rows)
 * @param val_name name of the column with the amount's "value", must include the substring "_val".
 * @param frac_name name of the column with the amount's "fractional" value, must include the substring "_frac".
 * @param curr_name name of the column with the amount's currency name, must include the substring "_curr".
 * @param[out] r_amount where to store the amount, in host byte order
 * @return
 *   #GNUNET_YES if all results could be extracted
 *   #GNUNET_NO if at least one result was NULL
 *   #GNUNET_SYSERR if a result was invalid (non-existing field)
 */
int
TALER_PQ_extract_amount (PGresult *result,
                         int row,
                         const char *val_name,
                         const char *frac_name,
                         const char *curr_name,
                         struct TALER_Amount *r_amount)
{
  struct TALER_AmountNBO amount_nbo;
  int ret;

  ret = TALER_PQ_extract_amount_nbo (result,
				     row,
				     val_name,
				     frac_name,
				     curr_name,
				     &amount_nbo);
  TALER_amount_ntoh (r_amount,
		     &amount_nbo);
  return ret;
}


/* end of pq/db_pq.c */