R/icos_dobj_info.R

In bluegreen-labs/icoscp: Interface to the 'ICOS' Carbon Portal

#' Grab digital object info
#'
#' Get additional information on a digital object.
#'
#' @param dobj digital object URI or PID
#' @importFrom memoise memoise
#'
#' @return a data frame with digital object information
#' @export
#'
#' @examples
#' \dontrun{
#' dobj <- "https://meta.icos-cp.eu/objects/lNJPHqvsMuTAh-3DOvJejgYc"
#' print(icos_dobj_info(dobj))
#' }

icos_dobj_info <- memoise::memoise(
  function(dobj) {

    # trap parameter exception
    if (missing(dobj)){
      message("Digital object persistent identifier is missing, returning NULL!")
      return(invisible(NULL))
    }

    # define endpoint
    endpoint <- server()

    # format string whatever way
    # you cut it
    dobj <- gsub("<||>", "", as.character(dobj))
    dobj <- basename(dobj)
    dobj <- sprintf("<https://meta.icos-cp.eu/objects/%s>", dobj)

    query <- sprintf("
              prefix cpmeta: <http://meta.icos-cp.eu/ontologies/cpmeta/>
              select * where {
                  values ?dobj { %s }
                  ?dobj cpmeta:hasObjectSpec ?objSpec ;
                  cpmeta:hasNumberOfRows ?nRows ;
                  cpmeta:hasName ?fileName .
                  ?objSpec rdfs:label ?specLabel .
                  OPTIONAL{?dobj cpmeta:hasActualColumnNames ?columnNames }
              }
              ", dobj)

    # runs sparql query
    df <- try(
      SPARQL(
        endpoint,
        query,
        format = "xml"
      )$results
    )

    # check results
    if(inherits(df, "try-error") || nrow(df) == 0 ) {
      message("No info found for the digital object")
      return(invisible(NULL))
    } else {
      return(df)
    }
})