/*
 gcc -I/usr/include/postgresql -L/usr/lib/postgresql/12/lib -o pq-test pq-test.c -lpq
*/

#include <libpq-fe.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <sys/wait.h>
#include <sys/types.h>

/* Sample output:
** pottmi@ubuntu ~/src
** % ./pq-test
** [37095] with sslmode=require:
** [37095] Calling New()
** [37097] Calling Exec()
** [37098] Calling Exec()
** [37098] Error in results: PGRES_FATAL_ERROR
** 
** [37095] with sslmode=disable:
** [37095] Calling New()
** [37100] Calling Exec()
** [37101] Calling Exec()
** pottmi@ubuntu ~/src
** 
** pottmi@ubuntu ~/src
** % uname -a
** Linux ubuntu 5.13.0-40-generic #45~20.04.1-Ubuntu SMP Mon Apr 4 09:38:31 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
** pottmi@ubuntu ~/src
** % cat /etc/debian_version
** bullseye/sid
** pottmi@ubuntu ~/src
*/


char *connectwillfail = "postgresql://kicktest:changeme@localhost:5432/kicktest?sslmode=require";
char *connectwillsucceed = "postgresql://kicktest:changeme@localhost:5432/kicktest?sslmode=disable";
char *sql = "select count(*) from information_schema.tables where table_schema = 'public'";

PGconn *New(const char *connectstr)
{
   PGconn *con;
   printf("[%d] Calling New()\n", getpid());
   con = PQconnectdb(connectstr);
   if (PQstatus(con) != CONNECTION_OK)
   {
      printf("[%d] could not connect to %s because %s\n", getpid(),
                     connectstr, PQerrorMessage(con));
   }

   return(con);
}

void Exec(PGconn *con, char *sql)
{
   printf("[%d] Calling Exec()\n", getpid());
   PGresult *result;
   ExecStatusType status;

   result = PQexec(con, sql);
   status = PQresultStatus(result);

   if (status != PGRES_TUPLES_OK)
   {
      printf("[%d] Error in results: %s\n", getpid(), PQresStatus(status));
   }
   PQclear(result);
}

void runit(const char *connectstring)
{

   int status;
   // Allocate connection in parent, but we will not use it in the parent process.
   PGconn *con = New(connectstring);

   int pid = fork();

   if (pid == 0) // Child process
   {
      // use connection in first child.
      Exec(con, sql);
      exit(0);
   }
   else if (pid > 0) // Parent process
   {
      int pidrtn = wait(&status);
   }
   else // if (pid < 0)  // Error
   {
         printf("[%d] Failed to fork! (errno=%d)\n", pid, errno);
         exit(1);
   }

   pid = fork();
   if (pid == 0) // Child process
   {
      // use connection in a second child.
      Exec(con, sql);
      exit(0);
   }
   else if (pid > 0) // Parent process
   {
      int pidrtn = wait(&status);
   }
   else // if (pid < 0)  // Error
   {
         printf("[%d] Failed to fork! (errno=%d)\n", pid, errno);
         exit(1);
   }

   PQfinish(con);
}

void main(void)
{
   printf("[%d] with sslmode=require:\n", getpid());
   runit(connectwillfail);
   printf("\n[%d] with sslmode=disable:\n", getpid());
   runit(connectwillsucceed);
}