R/otp-connect.R

In marcusyoung/opentripplanner: Open Trip Planner for R

#' Set up and confirm a connection to an OTP instance.
#'
#' Defines the parameters required to connect to a router on an OTP instance and,
#' if required, confirms that the instance and router are queryable.
#'
#' @param hostname A string, e.g. "ec2-34-217-73-26.us-west-2.compute.amazonaws.com".
#'     Optional, default is "localhost".
#' @param router A string, e.g. "UK2018". Optional, default is "default".
#' @param port A positive integer. Optional, default is 8080.
#' @param ssl Logical, indicates whether to use https. Optional, default is FALSE.
#' @param check Logical. If TRUE connection object is only returned if OTP
#'     instance and router are confirmed reachable. Optional, default is TRUE.
#' @return Returns an S3 object of class otpconnect. If \code{check} is TRUE
#'     and the router is not reachable the object is not returned.
#' @examples \dontrun{
#' otpcon <- otp_connect()
#' otpcon <- otp_connect(router = "UK2018",
#'                       ssl = TRUE)
#' otpcon <- otp_connect(hostname = "ec2.us-west-2.compute.amazonaws.com",
#'                       router = "UK2018",
#'                       port = 8888,
#'                       ssl = TRUE)
#' }
#' @export
otp_connect <- function(hostname = "localhost",
                        router = "default",
                        port = 8080,
                        ssl = FALSE,
                        check = TRUE)
{
  # argument checks

  coll <- checkmate::makeAssertCollection()
  checkmate::assert_string(hostname, add = coll)
  checkmate::assert_string(router, add = coll)
  checkmate::assert_int(port, lower = 1, add = coll)
  checkmate::assert_logical(ssl, add = coll)
  checkmate::assert_logical(check, add = coll)
  checkmate::reportAssertions(coll)

  otpcon <- list(
    hostname = hostname,
    router = router,
    port = port,
    ssl = ssl
  )

  # Set the name for the class
  class(otpcon) <- append(class(otpcon), "otpconnect")


  # If check then confirm router is queryable

  if (isTRUE(check)) {
    if (check_router(otpcon) == 200) {
      message("Router ", make_url(otpcon), " exists")
      return(otpcon)
    } else {
      stop("Router ", make_url(otpcon),  " does not exist")
    }
  } else {
    return(otpcon)
  }
}

# otpconnect class method to generate baseurl

make_url <- function(x)
{
  UseMethod("make_url", x)
}

make_url.default <- function(x)
{
  warning(
    "make_url does not know how to handle objects of class ",
    class(x),
    ", and can only be used on the class otpconnect"
  )
  return(NULL)
}

make_url.otpconnect <- function(x)
{
  url <- paste0(
    ifelse(isTRUE(x$ssl), 'https://', 'http://'),
    x$hostname,
    ':',
    x$port,
    '/otp/routers/',
    x$router
  )
  return(url)
}

# otpconnect method to check if router exists

check_router <- function(x)
{
  UseMethod("check_router", x)
}

check_router.default <- function(x)
{
  warning(
    "check_router does not know how to handle objects of class ",
    class(x),
    ", and can only be used on the class otpconnect"
  )
  return(NULL)
}

check_router.otpconnect <- function(x)
{
  check <- try(httr::GET(make_url(x)), silent = T)
  if (class(check) == "try-error") {
    return(check[1])
  } else{
    return(check$status_code)
  }

}