/*
 *  call-seq:
 *     query_parser.fields = fields -> self
 *
 *  Set the list of fields. These fields are expanded for searches on "*".
 */
static VALUE
frb_qp_set_fields(VALUE self, VALUE rfields)
{
    GET_QP;
    HashSet *fields = frb_get_fields(rfields);

    /* if def_fields == all_fields then we need to replace both */
    if (qp->def_fields == qp->all_fields) qp->def_fields = NULL;
    if (qp->tokenized_fields == qp->all_fields) qp->tokenized_fields = NULL;

    if (fields == NULL) {
        fields = hs_new_ptr(NULL);
    }

    /* make sure all the fields in tokenized fields are contained in
     * all_fields */
    if (qp->tokenized_fields) hs_safe_merge(fields, qp->tokenized_fields);

    /* delete old fields set */
    assert(qp->all_fields->free_elem_i == dummy_free);
    hs_destroy(qp->all_fields);

    /* add the new fields set and add to def_fields if necessary */
    qp->all_fields = fields;
    if (qp->def_fields == NULL) {
        qp->def_fields = fields;
        qp->fields_top->fields = fields;
    }
    if (qp->tokenized_fields == NULL) qp->tokenized_fields = fields;

    return self;
}