package main

import (
  "fmt"
  "math/rand"
)

// Possible entries
const Car = 0
const Goat = 1

// Possible results
const ChoiceWin = 1
const ChoiceLose = 2
const ChoiceInvalid = 3

/*
 * Create int[3] with two Goats and one Car
 * @returns []int
 */
func makeMonty() []int {
  monty := []int{
    Car,
    Car,
    Car,
  }

  // Attempt to randomize two indexes
  goatIdx1 := rand.Intn(len(monty))
  goatIdx2 := rand.Intn(len(monty))

  // It's possible to have two of the same so keep going until it works
  for goatIdx2 == goatIdx1 {
    goatIdx2 = rand.Intn(len(monty))
  }

  // Make ze goat
  monty[goatIdx1] = Goat
  monty[goatIdx2] = Goat

  return monty
}

/*
 * Randomly "reveal" first item of monty and return index and value
 */
func reveal(choice int, monty []int) (int, int) {
  revealIdx := choice
  for revealIdx == choice {
    revealIdx = rand.Intn(len(monty))
  }

  return revealIdx, monty[revealIdx]
}

/*
 * Make choice and stick to it (statistically wrong)
 */
func chooseWrong(monty []int) int {
  choice := rand.Intn(len(monty))
  _, revealVal := reveal(choice, monty)

  // If revealed tile is the winner we wont reach the puzzle
  if revealVal != Car {
    if monty[choice] == Car {
      return ChoiceWin
    } else {
      return ChoiceLose
    }
  }

  return ChoiceInvalid
}

/*
 * Make choice and change (statistically right)
 */
func chooseRight(monty []int) int {
  choice := rand.Intn(len(monty))
  revealIdx, revealVal := reveal(choice, monty)

  if revealVal != Car {
    choiceNew := 0
    for (choiceNew == choice || choiceNew == revealIdx) {
      choiceNew++
    }

    if monty[choiceNew] == Car {
      return ChoiceWin
    } else {
      return ChoiceLose
    }
  }

  return ChoiceInvalid
}

/*
 * Calls $fn $count times and output results as formatted string to $ch
 */
func chooseGo(ch chan string, count int, name string, fn func([]int) int) {
  winCount := 0
  lossCount := 0
  validCount := 0

  for i := 0; i < count; i++ {
    ret := fn(makeMonty())

    if (ret == ChoiceWin) {
      winCount++
      validCount++
    } else if (ret == ChoiceLose) {
      lossCount++
      validCount++
    }
  }

  // Whoa
  ch <-
    fmt.Sprintln(name) +
    fmt.Sprintln("  win%: ", float64(winCount) / float64(validCount)) +
    fmt.Sprintln("  wins: ", winCount) +
    fmt.Sprintln("  losses: ", lossCount) +
    fmt.Sprintln("  total: ", validCount)
}

func main() {
  ch := make(chan string)
  count := 5000000 // big number

  go chooseGo(ch, count, "wrong", chooseWrong)
  go chooseGo(ch, count, "right", chooseRight)

  message := <- ch
  fmt.Println(message)

  message = <- ch
  fmt.Println(message)
}