R/list_sites.r

In khufkens/phenocamr: Facilitates 'PhenoCam' Data Access and Time Series Post-Processing

#' List all site meta-data
#' 
#' The site list can be helpful in determining which time series to download
#' using `download_phenocam()`. The site list also includes meta-data 
#' concerning plant functional types, general climatological
#' conditions such as mean annual temperature or geographic location.
#' 
#' @param out_dir output directory (default = tempdir())
#' @param internal TRUE or FALSE (default = TRUE)
#' @return A data frame with meta-data for all available sites.
#' @export
#' @examples
#'
#' \dontrun{
#' # download the site meta-data
#' df <- list_sites()
#' }

list_sites <- memoise::memoise(
  function(
    out_dir = tempdir(),
    internal = TRUE){
  
  # download json data using httr
  error <- try(httr::content(httr::GET(url = server_lists(),
                                      httr::timeout(30)),
                            "text",
                            encoding = "UTF-8"))
  
  if (inherits(error, "try-error")){
    stop("Download of ROI list failed, timeout or server error...")
  }
  
  # row bind the json list and replace
  # NULL values with NA
  meta_data <- jsonlite::fromJSON(error)
  
  # output according to parameters
  if(internal){
    return(meta_data)
  } else {
    utils::write.table(meta_data,
                       file.path(out_dir, "site_meta_data.csv"),
                       col.names = TRUE,
                       row.names = FALSE,
                       quote = FALSE) 
  }
})