gistfile1.scala

  // This character generator is similar to the default one from ScalaCheck, but it filters out:
  // 1. Unprintable control characters.  These cause problems in Mongo queries, and should not able
  //    to get into our database since they will not be present in inputs parsed from HTTP text.
  // 2. Characters that do not exist in the default platform encoding.  We can exclude a big range
  //    of these right away (which ScalaCheck does) because they're in the range used for two-
  //    character UTF-16 sequences, but others are only detected by checking Character.isDefined(_).
  //    The symptom of using a bad character in a string is that when you encode it to UTF-8 and
  //    back again, you get a different string, so any of our web and database tests that check the
  //    input against the output may fail-- and you'll see a question mark somewhere in the data,
  //    since that's how bad characters are displayed.
  // This involves building a humungous list of characters, but it only gets built once, and since
  // it's an array the random strings will be a bit faster than ScalaCheck's usual.
  lazy val validUnicodeChars: Array[Char] = (9.toChar :: 10.toChar :: 13.toChar ::
    ((0x20.toChar to 0xD7FF.toChar) ++ (0xE000.toChar to Char.MaxValue)).filter(Character.isDefined).toList
    ).toArray

  def genUnicodeChar: Gen[Char] = Gen.oneOf(validUnicodeChars)
  def genUnicodeString: Gen[String] = Gen.listOf(genUnicodeChar).map(_.mkString)