#include <libpq-fe.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "db.h"

#define DB_MAX_FIELDS 64
#define DB_MAX_CHAR   256

static PGconn *g_pConnection = NULL;
static PGresult *g_pResult = NULL;
static char g_pError[DB_MAX_CHAR];


static int db_clear_error(void)
{
  memset(&g_pError, 0, (size_t)(sizeof(char) * DB_MAX_CHAR));
  return DB_OK;

} // db_clear_error


static int db_set_error(const char *f_pError)
{
  db_clear_error();
  strcpy(g_pError, f_pError);
  return DB_OK;

} // db_set_error


static void db_raise_warning(void)
{
//  printf("Database exception!\n");
  printf("%s", g_pError);

} // db_raise_warning


static void db_raise_error(void)
{
  db_raise_warning();
  db_close();
  exit(1);

} // db_raise_error


static char *db_get_error(void)
{
  return g_pError;

} // db_get_error



static int db_check_connection(void)
{
  char l_pError[DB_MAX_CHAR];

  if (g_pConnection == NULL)
  {
    sprintf(l_pError, "Database connection lost!");
    db_set_error(l_pError);
    db_raise_error();

    return DB_NO_CONNECTION;
  }

  return DB_OK;

} // db_check_connection


static int db_check_result(void)
{
  char l_pError[DB_MAX_CHAR];

  if (g_pResult == NULL)
  {
    sprintf(l_pError, "Incorrect PostgreSQL result.");
    db_set_error(l_pError);
    db_raise_warning();

    return DB_INCORRECT_RESULT;
  }

  return DB_OK;

} // db_check_result


int db_init(void)
{
  char l_pError[DB_MAX_CHAR];

  g_pConnection = PQsetdbLogin(PGHOST, PGPORT, PGOPTIONS, PGTTY, DBNAME, LOGIN, PWD);

  if (PQstatus(g_pConnection) == CONNECTION_BAD)
  {
    sprintf(l_pError, "Connection to database '%s' failed.\n%s", DBNAME, PQerrorMessage(g_pConnection));
    db_set_error(l_pError);
    db_raise_error();
		return DB_NO_CONNECTION;
	}

  db_clear_error();

  return DB_OK;

} // db_init


int db_close(void)
{
  PQclear(g_pResult);
	PQfinish(g_pConnection);

  return DB_OK;

} // db_close


int db_output(void)
{
  int l_iNTuples, l_iNFields;
  char l_pText[DB_MAX_CHAR];
  int l_iColumnWidth[DB_MAX_FIELDS];
  int l_iMaxColumnWidth[DB_MAX_FIELDS];
  int i, j, k, l;

  // check the db connection
  if (db_check_connection() != DB_OK)
  {
    exit(1);
    return DB_COULD_NOT_OUTPUT;
  }

  // check the validity of the result
  if (db_check_result() != DB_OK)
  {
    return DB_COULD_NOT_OUTPUT;
  }

  l_iNTuples = PQntuples(g_pResult);
  l_iNFields = PQnfields(g_pResult);

  // copy all tuple names incl. field values
  for (i = 0; i < l_iNFields; i++)
  {
    k = 0;
    for (j = 0; j < l_iNTuples; j++)
    {
      strcpy(l_pText, PQgetvalue(g_pResult, j, i));
      l_iColumnWidth[k] = (int)strlen(l_pText);
      k++;
    }

    strcpy(l_pText, PQfname(g_pResult, i));
    l_iMaxColumnWidth[i] = (int)strlen(l_pText);
    for (j = 1; j < l_iNTuples; j++)
    {
      l_iMaxColumnWidth[i] = max(l_iMaxColumnWidth[i], l_iColumnWidth[j]);
    }
  }

  printf("\n");

  // print column names
  for (i = 0; i < l_iNFields; i++)
  {
    int len;
    if (i) printf("| ");

    strcpy(l_pText, PQfname(g_pResult, i));
    printf("%s", l_pText);
    len = (int)strlen(PQfname(g_pResult, i)) - 1;

    if (i < l_iNFields - 1)
    {
      for (k = 0; k < l_iMaxColumnWidth[i] - len; k++)
      {
        printf(" ");
      }
    }
  }

  printf("\n");

  // print horizontal line
  l = 0;
  for (k = 0; k < l_iNFields; k++) l += l_iMaxColumnWidth[k];
  l += (l_iNFields - 1) * 3;
  for (k = 0; k < l; k++) printf("-");
  printf("\n");

  // print row values
  for (i = 0; i < l_iNTuples; i++)
  {
    for (j = 0; j < l_iNFields; j++)
    {
      int len;
      if (j) printf("| ");

      strcpy(l_pText, PQgetvalue(g_pResult, i, j));
      printf("%s ", l_pText);
      len = (int)strlen(l_pText) - 1;

      if (j < l_iNFields - 1)
      {
        for (k = 1; k < l_iMaxColumnWidth[j] - len; k++)
        {
          printf(" ");
        }
      }
    }
    printf("\n");
  }

  printf("(%d rows)\n\n", l_iNTuples);

  return DB_OK;

} // db_output


int db_execute(const char* f_pQuery)
{
  char l_pError[DB_MAX_CHAR];
  char l_pCmdStatus[DB_MAX_CHAR];

  // check the db connection
  if (db_check_connection() != DB_OK)
  {
    exit(1);
    return DB_COULD_NOT_EXECUTE;
  }

  g_pResult = PQexec(g_pConnection, f_pQuery);

  if (g_pResult == NULL || (PQresultStatus(g_pResult) != PGRES_COMMAND_OK && PQresultStatus(g_pResult) != PGRES_TUPLES_OK))
  {
    sprintf(l_pError, "Unable to execute query: %s\n%s", f_pQuery, PQerrorMessage(g_pConnection));
    db_set_error(l_pError);
    db_raise_warning();

    return DB_COULD_NOT_EXECUTE;
	}

  sprintf(l_pCmdStatus, "%s", PQcmdStatus(g_pResult));

  if (!strcmp(l_pCmdStatus, "SELECT"))
  {
    db_output();
  }
  else
  {
    printf("\n%s\n\n", l_pCmdStatus);
  }

  return DB_OK;

} // db_execute