R/wfsBuild.R

In wstolte/nwdm:

#' Create url to be used as wfs query
#'
#' This function is used internally at Deltares to query the North Sea and Wadden sea
#' validation database. The url can then be used to download validation data.
#' @param cql_list list with cql conditions
#' @param outputformat desired format for download
#' @param maxFeatures maximum number of features to download
#' @columns character vector of columns to download
#' @example
#' cql_list = list(p35preflabel = "Water body nitrate",
#' location_code = "DOOVBWT"
#' )
#' columns = c("location_code", "date", "depth", "parameter_label", "value", "unit_preflabel", "quality_code")
#'
#' url = create_url(cql_list = cql_list)
#' read_csv(url)
#'
create_url <- function(cql_list = NULL, 
                       outputFormat = "csv", 
                       typeName = NULL, 
                       maxFeatures = 50, 
                       columns = NULL, 
                       bbox = NULL,
                       username = NULL, 
                       password = NULL) {

  require(httr)

  if(is.null(columns)) propertyName = NULL else propertyName = paste("NWDM", columns, sep = ":", collapse = ",")

  if(is.null(cql_list)) 
    cql_f = NULL 
  else 
    cql_f = paste0("(",paste(names(cql_list),paste0("'", cql_list, "'"),sep="=",collapse=" and " ),")")
  
  r <- structure(
    list(scheme = "https",
         hostname = "nwdm.openearth.eu",
         port = NULL,
         path = "geoserver/NWDM/ows",
         query = list(
           service = "WFS",
           version = "1.0.0",
           request = "GetFeature",
           typeName = typeName,
           bbox = bbox,
           cql_filter = cql_f,
           outputFormat = outputFormat,
           maxFeatures = maxFeatures,
           propertyName = propertyName
         ),
         params = NULL,
         fragment = NULL,
         username = username,
         password = password
    ),
    class = "url")

  if(!is.null(maxFeatures)) 
  {print(cat("warning: maxFeatures =", 
             maxFeatures, 
             ". Only the first", maxFeatures, "lines will be read using this url.", 
               "Change to maxFeatures = NULL if you want all data." ))
    }
  url <- httr::build_url(r)
}