Kotlin Programming 2022 Spring - Midterm Project Resources
===
###### tags: `Kotlin 2022 Spring` `Kotlin` `2022 Spring`

## Random Number Generator
Use `(0..9).random()` to get a random integer in $\{0, 1, \dots, 9\}$. Use `"+-*/".random()` to get a random arithmetic operator.

## Color Text

val ANSI_BLACK_BACKGROUND = "\u001B[40m"
val ANSI_GREEN_BACKGROUND = "\u001B[42m"
val ANSI_YELLOW_BACKGROUND = "\u001B[43m"
val ANSI_RESET = "\u001B[0m"

println("${ANSI_BLACK_BACKGROUND}我會變成黑底白字${ANSI_RESET}我是正常沒有顏色的字")
println("${ANSI_GREEN_BACKGROUND}我會變成綠底白字${ANSI_RESET}我是正常沒有顏色的字")
println("${ANSI_YELLOW_BACKGROUND}我會變成黃底白字${ANSI_RESET}我是正常沒有顏色的字")

## Primel (Sample Code?)

fun blackBG(str: String): String {
    val ANSI_BLACK_BACKGROUND = "\u001B[40m"
    val ANSI_RESET = "\u001B[0m"
    return ANSI_BLACK_BACKGROUND + str + ANSI_RESET
}

fun greenBG(str: String): String {
    val ANSI_GREEN_BACKGROUND = "\u001B[42m"
    val ANSI_RESET = "\u001B[0m"
    return ANSI_GREEN_BACKGROUND + str + ANSI_RESET
}

fun yellowBG(str: String): String {
    val ANSI_YELLOW_BACKGROUND = "\u001B[43m"
    val ANSI_RESET = "\u001B[0m"
    return ANSI_YELLOW_BACKGROUND + str + ANSI_RESET
}

fun getAnswer(): String {
    while(true) {
        val cand = (10000..99999).random().toString()
        if (cand.toBigInteger().isProbablePrime(50))
            return cand
    }
}

fun valid(guess: String): Boolean {
    try {
        if (!guess.toBigInteger().isProbablePrime(50)) {
            println("$guess is not a prime.")
            return false
        }
    } catch (e: Exception) {
        println("$guess is not a valid input.")
        return false
    }
    if (guess.length != 5) {
        println("$guess is not a 5-digit prime.")
        return false
    }
    return true
}

fun main() {
    val ans = getAnswer() // step 1: generate the answer
    while (true) { // main loop
        // step 2: read the guess from user
        val guess = readLine()!!
        // step 3: check if the guess valid
        if (!valid(guess)) continue
        // step 4: if guess = ans: end game!
        if (guess == ans) {
            println("Congrats! $guess is the answer!")
            break
        }
        // step 5: print hints, then go back step 2.
        for (i in 0 until 5) {
            if (ans[i] == guess[i]) {
                print(greenBG("${guess[i]}"))
            } else if (guess[i] in ans) {
                print(yellowBG("${guess[i]}"))
            } else {
                print(blackBG(guess[i].toString()))
            }
        }
        println("")
    }
}