R/GetBands.R

In seantuck12/MODISTools: MODIS Subsetting Tools

GetBands <-
function(Product)
{
  if(!any(Product == GetProducts())) stop("Product entered does not match any available products; see ?GetProducts.")

  getbands.xml <- paste('
    <soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
             xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:mod="', daacmodis, '/MODIS_webservice">
                         <soapenv:Header/>
                         <soapenv:Body>
                         <mod:getbands soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
                         <Product xsi:type="xsd:string">', Product, '</Product>
                         </mod:getbands>
                         </soapenv:Body>
                         </soapenv:Envelope>',
                         sep = "")

  header.fields <- c(Accept = "text/xml",
                     Accept = "multipart/*",
                     'Content-Type' = "text/xml; charset=utf-8",
                     SOAPAction = "")

  reader <- basicTextGatherer()
  header <- basicTextGatherer()

  curlPerform(url = paste0(daacmodis, wsdl_loc),
              httpheader = header.fields,
              postfields = getbands.xml,
              writefunction = reader$update,
              verbose = FALSE)

  # Check the server is not down by insepcting the XML response for internal server error message.
  if(grepl("Internal Server Error", reader$value())){
    stop("Web service failure: the ORNL DAAC server seems to be down, please try again later.
         The online subsetting tool may indicate when the server is up and running again.")
  }

  xmlres <- xmlRoot(xmlTreeParse(reader$value()))
  bandsres <- xmlSApply(xmlres[[1]],
                        function(x) xmlSApply(x,
                            function(x) xmlSApply(x,xmlValue)))

  if(colnames(bandsres) == "Fault"){
    if(length(bandsres['faultstring.text', ][[1]]) == 0){
      stop("Downloading from the web service is currently not working. Please try again later.")
    }
    stop(bandsres['faultstring.text', ])
  } else{
    return(as.vector(bandsres))
  }
}