async download of online csv file to get a two dimensional array named asArray

func csv(url: URL, callback: @escaping ([[String]])->()) {
  print("downloading \(url)")
  DispatchQueue.global(qos: .userInitiated).async {
    do {
      let csv = try String(contentsOf: url, encoding: .utf8)
      var asArray = [[String]]()
      var r = [String]()
      var data = ""
      var inQuote = false
      for c in csv {
        if inQuote {
          if c == "\"" {
            inQuote = false
          }
          data.append(c)
        } else {
          if c == "\"" {
            inQuote = true
            data.append(c)
          } else if c == "," {
            r.append(data)
            data = ""
          } else if c == "\n" {
            if data != "" {
              r.append(data)
              data = ""
            }
            if r.count > 0 {
              asArray.append(