Game.kt

package chapter3

/**
 *
 */
fun main() {
    val options = arrayOf("Rock", "Paper", "Scissors")
    val gameChoice = getGameChoice(options)
    val userChoice = getUserChoice(options)
    printResult(gameChoice, userChoice)
}

fun getGameChoice(optionsParam: Array<String>) =
        optionsParam[(Math.random() * optionsParam.size).toInt()]

fun getUserChoice(optionsParam: Array<String>): String {
    var isValidChoice = false
    var userChoice = ""
    while (!isValidChoice) {
        print("Please enter one of the following:")
        for (item in optionsParam) print(" $item")
        println(".")
        val userInput = readLine()
        if (userInput != null && userInput in optionsParam) {
            isValidChoice = true
            userChoice = userInput
        }
        if (!isValidChoice) println("You must enter a valid choice.")
    }
    return userChoice
}

fun printResult(gameChoice: String, userChoice: String) {
    val result: String
    if (userChoice == gameChoice) result = "Tie!"
    else if (
            (userChoice == "Rock" && gameChoice == "Scissors") ||
            (userChoice == "Paper" && gameChoice == "Rock") ||
            (userChoice == "Scissors" && gameChoice == "Paper"))
        result = "You win!"
    else
        result = "You lose!"

    println("You chose $userChoice. I chose $gameChoice. $result")
}