/*
 * testlibpq.c
 *
 *      Test the C version of libpq, the PostgreSQL frontend library.
 */

#include <stdio.h>
#include <stdlib.h>
#include <libpq-fe.h>

static void exit_nicely(PGconn *conn) {
    PQfinish(conn);
    exit(1);
}

int main(int argc, char **argv) {

    const char *conninfo;
    PGconn     *conn;
    PGresult   *res;
    int         nFields;
    int         i, j;

    /*
     * If the user supplies a parameter on the command line, use it as the
     * conninfo string; otherwise default to setting dbname=postgres and using
     * environment variables or defaults for all other connection parameters.
     */

    if (argc > 1)
        conninfo = argv[1];
    else
        conninfo = "dbname = postgres";

    /* Make a connection to the database */

    conn = PQconnectdb(conninfo);

    /* Check to see that the backend connection was successfully made */

    if (PQstatus(conn) != CONNECTION_OK) {
        fprintf(stderr, "Connection to database failed: %s", PQerrorMessage(conn));
        exit_nicely(conn);
    }

    /*
     * Our test case here involves using a cursor, for which we must be inside
     * a transaction block.  We could do the whole thing with a single
     * PQexec() of "select * from pg_database", but that's too trivial to make
     * a good example.
     */

    /* Start a transaction block */

    res = PQexec(conn, "BEGIN");
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {
        fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
        PQclear(res);
        exit_nicely(conn);
    }

    /*
     * Should PQclear PGresult whenever it is no longer needed to avoid memory
     * leaks
     */

    PQclear(res);

    /*
     * Fetch rows from pg_database, the system catalog of databases
     */

    res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
    if (PQresultStatus(res) != PGRES_COMMAND_OK) {
        fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
        PQclear(res);
        exit_nicely(conn);
    }
    PQclear(res);

    res = PQexec(conn, "FETCH ALL in myportal");
    if (PQresultStatus(res) != PGRES_TUPLES_OK) {
        fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
        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 portal ... we don't bother to check for errors ... */
 
    res = PQexec(conn, "CLOSE myportal");
    PQclear(res);

    /* end the transaction */
 
    res = PQexec(conn, "END");
    PQclear(res);

    /* close the connection to the database and cleanup */
 
    PQfinish(conn);

    return 0;
}
