FP to the Max on Arrow FX

FpToTheMax.kt

package es.ffgiraldez.gist.arrow

import arrow.core.Option
import arrow.core.Try
import arrow.effects.extensions.io.fx.fx
import arrow.effects.extensions.io.unsafeRun.runBlocking
import arrow.unsafe
import java.util.Random

interface Console {
    suspend fun putStrLn(s: String): Unit
    suspend fun getStrLn(): String
}

object CommandLine : Console {
    override suspend fun putStrLn(s: String) = println(s)
    override suspend fun getStrLn(): String = readLine() ?: ""
}

interface Generator {
    suspend fun nextInt(upper: Int): Int
}

object RandomGenerator : Generator {
    private val random: Random = Random()

    override suspend fun nextInt(upper: Int): Int = random.nextInt(upper) + 1
}


class FpToTheMax(
    private val console: Console,
    private val generator: Generator
) {

    fun program() = fx {
        !effect { console.putStrLn("What is your name?") }
        val name = !effect { console.getStrLn() }
        !effect { console.putStrLn("your name is $name") }
        !effect { gameLoop(name) }
    }

    private fun parseInt(s: String): Option<Int> = Try { s.toInt() }.toOption()

    private suspend fun gameLoop(name: String) {
        val num = generator.nextInt(5)
        console.putStrLn("Dear $name, please guess a number from 1 to 5:")
        val input = console.getStrLn()

        parseInt(input).fold(
            { console.putStrLn("You did not enter a number") },
            { guess ->
                if (guess == num) console.putStrLn("You guessed right, $name!")
                else console.putStrLn("You guessed wrong, $name! The number was: $num")
            }
        )

        val cont = checkContinue(name)
        return if (cont) gameLoop(name)
        else Unit
    }

    private suspend fun checkContinue(name: String): Boolean {
        console.putStrLn("Do you want to continue, $name?")
        val input = console.getStrLn().toLowerCase()
        return when (input) {
            "y" -> true
            "n" -> false
            else -> checkContinue(name)
        }
    }
}

val FPInstance = FpToTheMax(CommandLine, RandomGenerator)

fun main(args: Array<String>) {
    unsafe { runBlocking { FPInstance.program() } }
}