R/input_json.R

In aemon-j/LakeEnsemblR: Run Ensemble of Lake Models

#' Input values into json file
#'
#'Inputs values into json file by locating the label and key within the json file.
#'  Preserves comments (!) if present.
#'  NOTE: this does not use a json parser so if there are json formatting errors
#'  this function will not pick them up.
#' @param file filepath; to json file which you wish to edit
#' @param label string; which corresponds to section where the key is located
#' @param key string; name of key in which to input the value
#' @param value string; to be input into the key/value pair.
#'   Note boolean values must be input as 'true'/'false' as per the json format
#' @param out_file filepath; to write the output json file (optional);
#'   defaults to overwriting file if not specified
#' @export
#' @author
#'Tadhg Moore, Jorrit Mesman
#' @examples
#' 
#' \dontrun{
#' input_json(file = "samp.par", label = "ModelParameters", key = "f_wind", value = 1.2, out_file = NULL)
#' }
input_json <- function(file, label, key, value, out_file = NULL){
  par <- readLines(file)
  if (is.null(out_file)) {
    out_file <- file
  }
  if(is.null(label)){
    ind_label <- 0
  }else{
    label_id <- paste0('"', label, '"')
    ind_label <- grep(label_id, par)
    
    if(length(ind_label) == 0){
      stop(label, " not found in ", file)
    }
  }
  key_id <- paste0('"', key, '"')
  ind_key <- grep(key_id, par)
  if (length(ind_key) == 0) {
    stop(key, " not found in ", label, " in ",
         file)
  }
  ind_key <- ind_key[ind_key > ind_label]
  ind_map <- ind_key[which.min(ind_key - ind_label)]
  if (length(ind_map) == 0) {
    stop(key, " not found in ", label, " in ",
         file)
  }
  spl1 <- strsplit(par[ind_map], c("!"))[[1]]
  if (length(spl1) == 2) {
    comment <- spl1[2]
  }
  spl2 <- strsplit(spl1[1], ": ")[[1]][2]
  sub <- paste0(value, ",")
  par[ind_map] <- gsub(pattern = paste0("\\Q", spl2, "\\E"),
                       replacement = sub,
                       x = par[ind_map])
  writeLines(par, out_file)
  old_val <- gsub(" ", "", spl2, fixed = TRUE)
  message("Replaced ", label, " ", key, " ",
          old_val, " with ", value)
}