BreakCypher.scala

import java.net._
import scala.io.BufferedSource
import java.io._

object HackJune extends App {
  val addr = "10.112.145.210"
  val socket = new Socket(InetAddress.getByName(addr), 8000)
  
  lazy val source = new BufferedSource(socket.getInputStream()).getLines()
  
  val dictionary = scala.io.Source.fromFile("/usr/share/dict/words").getLines.toSet 
  
  val out = new PrintStream(socket.getOutputStream())

  while (source.hasNext) {
    val current = source.next
    print(current)
    if (current == "Language name?") {
      out.println("Scala")
    } else if (current == "Team name?") {
      out.println("Scala")
    } else if (current == "CORRECT!" || current == "INCORRECT!") {
    } else {
      val allSentences = split(current).flatMap(s => reverse(s)).flatMap(s => split(s)).flatMap(s => rotN(s)).toSet
      for (s <- allSentences) {
        if (isValidEnglish(s)) {
          print(" == " + s)
          out.println(s)
        }
      }
    }
    println()
  }

  // ROTn
  def rotN (enc: String): List[String] = {
    val lower = 'a' to 'z'
    val upper = 'A' to 'Z'

    (for (n <- 0 to 25) yield {
      enc.map(c => c match {
        case l if lower.contains(c) => lower(((l - 'a') + n) % 26)
        case u if upper.contains(c) => upper(((u - 'A') + n) % 26)
        case _ => c
      }).toString
    }).toList
  }
  
  // Reverse
  def reverse (enc: String): List[String] = {
    List(enc, enc.reverse)
  }
  
  // Split
  def split (enc: String): List[String] = {
    val (left, right) = enc.splitAt(enc.length / 2)
    val encZip = left.zip(right).foldLeft("")((acc, pair) => acc + pair._1 + pair._2)
    List(enc, encZip.mkString)
  } 

  
  def isValidWord(word: String) : Boolean = {
    val toTest = word.toLowerCase().replaceAll("""\W+$""", "")
    dictionary.contains(toTest)
  }
  
  def isValidEnglish(sentence: String) : Boolean = {
    val words = sentence.split(' ').filter(x => x.length > 3)
    words.map(isValidWord).foldLeft(0)((acc, w) => if (w) acc + 1 else acc) > (words.length / 2)
  }
  
}