R/get_json_value.R

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

#' Extracts values from a json file
#'
#' Extracts values from a json file by locating the label and key within the json file.
#' @param file filepath; to json file
#' @param label string; which corresponds to section where the key is located
#' @param key string; name of key in which to extract the value
#' @export
#' @author
#'Tadhg Moore, Jorrit Mesman
#' @examples
#' \dontrun{
#' input_json(file = "samp.par", label = "ModelParameters", key = "f_wind", value = 1.2, out_file = NULL)
#' }

get_json_value <- function(file, label, key){
  par <- readLines(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]]
  spl2 <- strsplit(spl1[1], ": ")[[1]][2]
  val <- gsub(" ", "", spl2, fixed = TRUE)
  val <- gsub(",", "", val, fixed = TRUE)

  val2 <- NULL

  if(val == "false"){
    val2 <- FALSE
  }
  if(val == "true"){
    val2 <- TRUE
  }
  flg <- !is.na(as.numeric(val))
  if(flg){
    val2 <- as.numeric(val)
  }
  if(is.null(val2)){
    val2 <- gsub('\"', "", val)
    val2 <- as.character(val2)
  }

  return(val2)
}