//
// Mastermind game
// 

import scala.io.StdIn.readLine

val MaxNumGuesses = 10

// Create secret: four distinct letters from A-F.
def createSecret(): String = {
  var c = "ABCDEF"
  var secret = ""
  for (i <- 1 to 4) {
    val index = (math.random * c.length).toInt
    val letter = c(index)
    c = c.substring(0,index) + c.substring(index+1)
    secret = secret + letter
  }
  secret
}

// Check if guess is legal: Four distinct letters from A-F.
// Returns pair (ok: Boolean, message : String) 
def checkGuess(guess: String): (Boolean, String) = {
  if (guess.length != 4)
    return (false, "Your guess must have four letters")
  for (i <- 0 until 4) {
    val letter = guess(i)
    if (!"ABCDEF".contains(letter))
      return (false, "You can only use letters A, B, C, D, E, and F.")
    for (j <- 0 until i) {
      if (letter == guess(j))
	return (false, "All letters must be distinct.")
    }
  }
  return (true, "")
}

// read a guess from the terminal
def getGuess(): String = {
  while (true) {
    var guess = readLine("Enter your guess> ")
    guess = guess.trim.toUpperCase.replace(" ", "")
    val (ok, msg) = checkGuess(guess)
    if (ok)
      return guess
    println(msg)
  }
  "" // only necessary because compiler complains otherwise
}

// Compute (pos, let) where pos is the number of correct letters in
// the correct position, and let is the number of correct letters in
// the wrong position.
def evaluateGuess(secret: String, guess: String): (Int, Int) = {
  var pos = 0
  var let = 0
  for (i <- 0 until 4) {
    if (guess(i) == secret(i))
      pos += 1
    else if (secret.contains(guess(i)))
      let += 1
  }
  (pos, let)
}

// Show history of guessing  
def showHistory(h: Array[String], current: Int, secret: String) {
  for (count <- 0 until current) {
    val guess = h(count)
    val (pos, let) = evaluateGuess(secret, guess)
    printf("%2d: %s : %d positions, %d letters\n", count+1, guess, pos, let)
  }
}

// main game  
def main() {    
  val secret = createSecret()
  val history = new Array[String](MaxNumGuesses)
  var current = 0
  println("Welcome to Mastermind!")
  println("I have created a secret combination:")
  println("Four distinct letters from A - F.")
  printf("You have %d guesses to find it.\n", MaxNumGuesses)
  while (true) {
    showHistory(history, current, secret)
    if (current == MaxNumGuesses) {
      printf("My secret was %s, you failed to find it in %d guesses!\n",
             secret, current)
      return
    }
    val guess = getGuess()
    history(current) = guess
    current += 1
    val (pos, let) = evaluateGuess(secret, guess)
    if (pos == 4) {
      printf("My secret was %s, you guessed correctly in %d guesses!\n",
             secret, current)
      return
    }
  }
}

main()