/*
  * testlibpq.c
  *
  * Test the C version of libpq, the PostgreSQL frontend
  * library.
  */
 #include <stdio.h>
 #include <libpq-fe.h>
 
 void
 exit_nicely(PGconn *conn)
 {
     PQfinish(conn);
     exit(1);
 }
 
 main()
 {
     char       *pghost,
                *pgport,
                *pgoptions,
                *pgtty;
     char       *dbName;
     char       *qResult;
     int        nFields;
     char       connInfo[128];  // db connection infor.
     char       userPass[128];  // user/pass infor
     int         i,
                 j;
 
     /* FILE *debug; */
 
     PGconn     *conn;
     PGresult   *res;
 
     /*
      * begin, by setting the parameters for a backend connection if the
      * parameters are null, then the system will try to use reasonable
      * defaults by looking up environment variables or, failing that,
      * using hardwired constants
      */
     pghost = "host = db.eg.bucknell.edu"; 
                                 /* host name of the backend server */
     pgport = NULL;              /* port of the backend server */
     pgoptions = NULL;           /* special options to start up the backend
                                  * server */
     pgtty = NULL;               /* debugging tty for the backend server */
     dbName = "dbname = xmeng";

     strcpy(connInfo, pghost);
     strcat(connInfo, " ");
     strcat(connInfo, dbName);
     strcat(connInfo, " ");

     scanf("%s", userPass);   // user name first
     strcat(connInfo, "user = ");
     strcat(connInfo, userPass);
     strcat(connInfo, " ");

     scanf("%s", userPass);  // now password
     strcat(connInfo, "password = ");
     strcat(connInfo, userPass);

     /* make a connection to the database */
     conn = PQconnectdb(connInfo);
     /*
     conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);
     */

     /*
      * check to see that the backend connection was successfully made
      */
     if (PQstatus(conn) == CONNECTION_BAD)
     {
         fprintf(stderr, "Connection to database '%s' failed.\n", dbName);
         fprintf(stderr, "%s", PQerrorMessage(conn));
         exit_nicely(conn);
     }
 
     /* debug = fopen("/tmp/trace.out","w"); */
     /* PQtrace(conn, debug);  */
 
     /* start a transaction block */
     res = PQexec(conn, "BEGIN");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "BEGIN command failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
 
     /*
      * should PQclear PGresult whenever it is no longer needed to avoid
      * memory leaks
      */
     PQclear(res);
 
     /*
      * fetch rows from the pg_database, the system catalog of
      * databases
      */
     res = PQexec(conn, "DECLARE mycursor CURSOR FOR SELECT * FROM  pg_database");
//     res = PQexec(conn, "SELECT * FROM xmeng");

     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "DECLARE CURSOR command failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
     PQclear(res);
     res = PQexec(conn, "FETCH ALL in mycursor");
     if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
     {
         fprintf(stderr, "FETCH ALL command didn't return tuples properly\n");
         PQclear(res);
         exit_nicely(conn);
     }
 
     /* first, print out the attribute names */
     nFields = PQnfields(res);
     for (i = 0; i < nFields; i++)
         printf("%-15s", PQfname(res, i));
     printf("\n\n");
 
     /* next, print out the rows */
     for (i = 0; i < PQntuples(res); i++)
     {
         for (j = 0; j < nFields; j++)
             printf("%-15s", PQgetvalue(res, i, j));
         printf("\n");
     }
     PQclear(res);
 
     /* close the cursor */
     res = PQexec(conn, "CLOSE mycursor");
     PQclear(res);
 
     /* commit the transaction */
     res = PQexec(conn, "COMMIT");
     PQclear(res);


     /**
      * try to create a table
      **/
/**
     res = PQexec(conn, "create table xmTestTbl (index integer, name char(10), value real)");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "create table failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
**/

     /**
      * try to drop (delete) a table
      **/
/**
     res = PQexec(conn, "drop table xmTestTbl");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "drop table failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
**/

     /**
      * try to insert a tuple into the table
      **/
/*
     res = PQexec(conn, "insert into xmTestTbl values (2, 'first_name', 3.2)");
*/

/**
     res = PQexec(conn, "insert into xmTestTbl values (3, 'second_nam', 4.2)");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "insert table 3 failed\n");
         PQclear(res);
         exit_nicely(conn);
     }

     res = PQexec(conn, "insert into xmTestTbl values (4, 'third_name', 5.2)");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "insert table 4 failed\n");
         PQclear(res);
         exit_nicely(conn);
     }

     res = PQexec(conn, "insert into xmTestTbl values (5, 'fourth_nam', 6.2)");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "insert table 5 failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
**/

/**
     res = PQexec(conn, "insert into xmTestTbl values (0, 'fifth_name', 1.2)");
     if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
     {
         fprintf(stderr, "insert table 0 failed\n");
         PQclear(res);
         exit_nicely(conn);
     }
     PQclear(res);
**/
     res = PQexec(conn, "select index from xmTestTbl where index = 3");
     qResult = PQgetvalue(res, 0, 0);
     printf("%s\n", qResult);

     fprintf(stderr, "command succeeds.\n");

     res = PQexec(conn, "select * from xmTestTbl where index >= 3");

     /* first, print out the attribute names */
     nFields = PQnfields(res);
     for (i = 0; i < nFields; i++)
         printf("%-15s", PQfname(res, i));
     printf("\n\n");
 
     /* next, print out the rows */
     for (i = 0; i < PQntuples(res); i++)
     {
         for (j = 0; j < nFields; j++)
             printf("%-15s", PQgetvalue(res, i, j));
         printf("\n");
     }

     PQclear(res);

     /* close the connection to the database and cleanup */
     PQfinish(conn);
 
     /* fclose(debug); */
     return 0;
 
 }