=head1 NAME

dbfp_query_departure - get a list of departures at a given station from the
DB timetable API

=head1 SYNOPSIS

    #include <dbfp.h>

    int dbfp_query_departure(struct dbfp *dbfp, char *location_id, time_t time,
                    size_t *n, struct dbfp_departure **departures);

=head1 DESCRIPTION

B<dbfp_query_departure> queries a list of departures at a the station with the
given I<location_id> at the given I<time> using the connection metadata stored
in I<dbfp>.  The number of results is stored in I<n>.  The results are stored
in I<departures>.  The memory for the I<departures> is allocated by the
function.  The stored array contains exactly I<n> elements, and is not NULL
terminated.

Possible values for I<location_id> can be retrieved using
I<dbfp_query_location>.  If I<time> is zero, the current time is used.
I<dbfp>, I<location_id>, I<n> and I<departures> must not be NULL. I<dbfp> must
have been initialized with I<dbfp_init>.  The elements in I<departures> should
be closed with I<dbfp_departure_close>.  I<departures> should be freed by the
caller.

If the query fails, the values of I<n> and I<departures> are set to 0 and NULL
respectively.

The B<dbfp_departure> structure is defined as:

    struct dbfp_departure {
            char *name;
            char *type;
            char *stopid;
            char *stop;
            time_t time;
            char *direction;
            char *track;
    };

I<name> is the name of the departing train, I<type> is the type of the train.
I<stopid> is the ID of the stop the train departs from, and I<stop> is its
name.  I<time> is the departure time, I<direction> the direction of the train,
and I<track> the departure track.

=head1 RETURN VALUE

B<dbfp_query_departure> returns zero if successful, or a non-zero error code.
Positive error codes are from I<errno.h>, negative error codes are specific
to dbfp.

=head1 ERRORS

=over

=item EINVAL

if I<dbfp>, I<location_id>, I<n> or I<departures> is NULL

=item ENOMEM

if there is not enough memory to store the results of the query

=item DBFP_ERROR_CURL

if an error occured during the preparation or execution of the network request

=item DBFP_ERROR_FORMAT

if an error occurs during the formatting of the URL

=item DBFP_ERROR_PARSE

if an error occurs during the parsing of the XML response

=item DBFP_ERROR_STRUCTURE

if the API response has not the expected structure

=back

=head1 BUGS

Due to a typo in the DB timetable API, the I<type> field of one or more of the
I<departures> elements might be NULL.

The time zone handling has to be checked and documented.

=head1 EXAMPLE

    #include <dbfp.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    int main(int argc, char **argv)
    {
            int err = 0;
            struct dbfp dbfp;
            struct dbfp_departure *departures = NULL;
            size_t n = 0;
            size_t i;

            err = dbfp_init(&dbfp, "API key");
            if (err)
                    goto cleanup;
            err = dbfp_query_departure(&dbfp, "8000105", 0, &n, &departures);
            if (err)
                    goto cleanup;

            printf("Number of matches: %zu\n", n);
            if (n > 0)
                    printf("Departures from %s:\n", departures[0].stop);
            for (i = 0; i < n; i++)
                    printf("%s to %s from track %s\n", departures[i].name,
                                    departures[i].direction, departures[i].track);

    cleanup:
            if (err)
                    printf("An error occured: %s\n", strerror(err));
            for (i = 0; i < n; i++)
                    dbfp_departure_close(&departures[i]);
            free(departures);
            dbfp_close(&dbfp);

            return err ? EXIT_FAILURE : EXIT_SUCCESS;
    }

=head1 SEE ALSO

L<dbfp_init(3)>, L<dbfp_departure_close(3)>