read_in_gml.R

#===== read_in_points =====


#' read_in_points
#' @description Reads points from a \code{.gml} file
#' @param xml_doc A parsed XML document (of class \code{xml2::xml_document})
#' @noRd
read_in_points <- function(xml_doc) {

    points_tibble <- tibble::tibble(x = numeric(),
                                    y = numeric(),
                                    z = numeric(),
                                    name = character())

    points_nodeset <- xml2::xml_find_all(xml_doc, "//points/*")

    for(i in seq_len(length(points_nodeset))){
        attrs <- xml2::xml_attrs(points_nodeset[[i]])

        point_name <- ""

        if(length(attrs) == 5){
            point_name <- attrs[["name"]]
        }

        points_tibble <- tibble::add_row(points_tibble,
                                        x = as.double(attrs[["x"]]),
                                        y = as.double(attrs[["y"]]),
                                        z = as.double(attrs[["z"]]),
                                        name = point_name)
    }

    return(invisible(points_tibble))
}


#===== read_in_polylines =====


#' read_in_polylines
#' @description Reads polylines from a \code{.gml} file
#' @param xml_doc A parsed XML document (of class \code{xml2::xml_document})
#' @noRd
read_in_polylines <- function(xml_doc) {

    polylines_list <- list()

    polylines_nodeset <- xml2::xml_find_all(xml_doc, "//polylines/*")

    if(length(polylines_nodeset) == 0){
        return(invisible(NULL))
    }

    for(i in seq_along(polylines_nodeset)){
        attrs <- xml2::xml_attrs(polylines_nodeset[[i]])
        pnt_nodeset <- xml2::xml_children(polylines_nodeset[[i]])
        pnt_vector <- c()

        for(j in seq_along(pnt_nodeset)){
            pnt_vector <- c(pnt_vector, xml2::xml_double(pnt_nodeset[[j]]))
            names(pnt_vector) <- rep("pnt", length(pnt_vector))
        }

        polyline <- list(name = attrs[[2]], pnt_vector)
        polylines_list <- c(polylines_list, list(polyline))
    }

    return(invisible(polylines_list))
}


#===== read_in_surfaces =====


#' read_in_surfaces
#' @description Reads surfaces from a \code{.gml} file
#' @param xml_doc A parsed XML document (of class \code{xml2::xml_document})
#' @noRd
read_in_surfaces <- function(xml_doc) {

    surfaces_list <- list()

    surfaces_nodeset <- xml2::xml_find_all(xml_doc, "//surfaces/*")

    if(length(surfaces_nodeset) == 0){
        return(invisible(NULL))
    }

    for(i in seq_len(length(surfaces_nodeset))){
        attrs <- xml2::xml_attrs(surfaces_nodeset[[i]])
        element_nodeset <- xml2::xml_children(surfaces_nodeset[[i]])

        element_1 <- as.double(xml2::xml_attrs(element_nodeset[[1]]))

        surface <- list(name = attrs[[2]],
                        element = element_1)

        if(length(element_nodeset) == 2){
            element_2 <- as.double(xml2::xml_attrs(element_nodeset[[2]]))
            surface <- c(surface, list(element = element_2))
        }

        surfaces_list <- c(surfaces_list, list(surface))
    }

    return(invisible(surfaces_list))
}