Generate email ids for oneplus registration based on an amazon review (http://www.amazon.in/review/REA7WFX7PV3KO)

oneplus.scala

object OnePlus {
  def main(args: Array[String]) {
    generate_aliases("typeyouremailhere@gmail.com").foreach(println)
  }

  def generate_aliases(email:String) = {
    val email_pattern = """(\w+)@([\w\.]+)""".r
    email match {
      case email_pattern(address, domain) => {
        interleave_all_with(address, '.').map {case address => s"$address@$domain"}
      }
    }
  }

  private def interleave_all_with(address:String, char:Char):Array[String] = interleave_all(address, char, address.length-1)

  private def interleave_all(address:String, char:Char, times:Int):Array[String] = times match {
    case 1 => interleave(address, char, 1, address.length, Array.empty[String])
    case n => {
      val aliases = interleave_all(address, char, times-1)
      val results = aliases ++ aliases.flatMap {case (alias:String) => interleave_with(alias, char)}
      results.map(result => result.replaceAll("\\.\\.", ".")).filterNot(_.endsWith(".")).distinct
    }
  }

  private def interleave_with(address:String, char: Char):Array[String] = interleave(address, char, 1, address.length, Array.empty[String])

  private def interleave(address:String, char: Char, from: Int, to: Int, results: Array[String]): Array[String] = if (from < to)
    interleave(address, char, from + 1, to, results ++ Array(alias(address, char, from, to)))
  else
    results

  private def alias(address:String, char:Char, from:Int, to:Int) = address.slice(0, from) + char + address.slice(from, to)
}