R/send_request.R

In MouseFM: In-silico methods for genetic finemapping in inbred mice

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#' Send HTTP request to MMUS Server
#' @param q Query string
#' @param n.tries Number of tries
#' @param method HTTP method to use
#' @return Data frame.
#' @keywords internal
#' @importFrom curl has_internet
#' @importFrom httr GET POST http_error content
backend_request = function(q, n.tries = 2, method = "GET") {
  stopifnot(is.numeric(n.tries))
  stopifnot(method == "GET" || method == "POST")
  stopifnot(nchar(q) > 0)


  # Check if there is an internet connection
  if (!has_internet()) {
    stop("No internet connection detected...")
  }


  # Send HTTP request and retrieve response
  while (n.tries > 0) {
    if (method == "GET") {
      response = GET(q)
    }
    else if (method == "POST") {
      response = POST(q)
    }

    if (!http_error(response)) {
      break
    }

    Sys.sleep(3)
    n.tries = n.tries - 1
  }


  if (n.tries == 0) {
    stop("Web server seems to be down. Try again later!")
  }


  result = content(response)
  result = unlist(strsplit(result, "\n"))


  # Display error message from server
  if (length(grep("^#", result)) == 0) {
    warning(result)
    return()
  }


  # Extract
  meta = grep("^#", result, value = TRUE)
  data = grep("^[^#]", result, value = TRUE)


  # If no results found
  if (length(data) - 1 <= 0) {
    message("No results found")
    return()
  }


  # Convert to dataframe
  header = unlist(strsplit(data[1], "\t"))
  ncols = length(header)
  data = unlist(strsplit(data[-1], "\t"))

  m = matrix(data, ncol = ncols, byrow = TRUE)
  d = as.data.frame(m, stringsAsFactors = FALSE)
  d[d == "-" | d == "." | d == "null"] = NA
  colnames(d) = header
  comment(d) = meta


  return(d)
}