esri2sf <- function(url, outFields=c("*"), where="1=1", token='') {
  library(httr)
  library(jsonlite)
  library(sf)
  library(dplyr)
  layerInfo <- jsonlite::fromJSON(
    httr::content(
      httr::POST(
        url,
        query=list(f="json", token=token),
        encode="form",
        config = httr::config(ssl_verifypeer = FALSE)
      ),
      as="text"
    )
  )
  print(layerInfo$type)
  geomType <- layerInfo$geometryType
  print(geomType)
  queryUrl <- paste(url, "query", sep="/")
  esriFeatures <- getEsriFeatures(queryUrl, outFields, where, token)
  simpleFeatures <- st_read(esriFeatures)
  return(simpleFeatures)
}

getEsriFeatures <- function(queryUrl, fields, where, token='') {
  ids <- getObjectIds(queryUrl, where, token)
  if(is.null(ids)){
    warning("No records match the search critera")
    return()
  }
  idSplits <- split(ids, ceiling(seq_along(ids)/500))
  results <- lapply(idSplits, getEsriFeaturesByIds, queryUrl, fields, token)
  merged <- unlist(results, recursive=FALSE)
  return(merged)
}

getObjectIds <- function(queryUrl, where, token=''){
  # create Simple Features from ArcGIS servers json response
  query <- list(
    where=where,
    returnIdsOnly="true",
    token=token,
    f="json"
  )
  responseRaw <- httr::content(
    httr::POST(
      queryUrl,
      body=query,
      encode="form",
      config = httr::config(ssl_verifypeer = FALSE)),
    as="text"
  )
  response <- jsonlite::fromJSON(responseRaw)
  return(response$objectIds)
}

getEsriFeaturesByIds <- function(ids, queryUrl, fields, token=''){
  # create Simple Features from ArcGIS servers json response
  query <- list(
    objectIds = paste(ids, collapse=","),
    outFields = paste(fields, collapse=","),
    token = token,
    outSR = '4326',
    f = "geojson"
  )
  responseRaw <- httr::content(
    httr::POST(
      queryUrl,
      body=query,
      encode="form",
      config = httr::config(ssl_verifypeer = FALSE)
    ))
return(responseRaw)
}

generateToken <- function(server, uid, pwd='', expiration=5000){
  # generate auth token from GIS server
  if (pwd=='') {
    pwd <- rstudioapi::askForPassword("pwd")
  }
  query <- list(
    username=uid,
    password=pwd,
    expiration=expiration,
    client="requestip",
    f="json"
  )
  url <- paste(server, "arcgis/admin/generateToken", sep="/")
  r <- httr::POST(url, body=query, encode="form")
  token <- jsonlite::fromJSON(httr::content(r, "parsed"))$token
  return(token)
}