val myNum = 43

// if
// if (myNum % 2 == 1) {
//     println("odd")
// }
// println("after the if")

// if-else if
// if (myNum % 2 == 1) {
//     println("odd")
// } else if (myNum < 0) {
//     println("negative")
// }
// println("after the if")

// if-else
// if (myNum % 2 == 1) {
//     println("odd")
// } else {
//     println("even")
// }

// if-else expression
// println(if (myNum % 2 == 1) "odd" else "even")


// when
// when {
//     myNum % 2 == 1 -> println("odd")
//     myNum < 0 -> println("negative")
// }

// when expression
// val result = when {
//     myNum % 2 == 1 -> "odd"
//     myNum < 0 -> "negative"
//     else -> "even non-negative"
// }

// when with a value
// when (myNum % 2 == 1) {
//     true -> "odd"
//     false -> "even"
// }

// when with an enumeration
enum class TrafficLight {
    RED,
    YELLOW,
    GREEN,
}

// fun nextLight(current: TrafficLight): TrafficLight {
//     return when (current) {
//         TrafficLight.RED -> TrafficLight.GREEN
//         TrafficLight.YELLOW -> TrafficLight.RED
//         TrafficLight.GREEN -> TrafficLight.YELLOW
//     }
// }

// when with a sealed class
sealed class Author {
    // don't know :(
    object Unknown: Author()

    // known human
    data class FullName(
        val firstName: String, 
        val lastName: String
    ): Author()

    // tricksy!
    data class Pseudonym(
        val knownAs: FullName, 
        val realName: FullName
    ): Author()
}

// converts a full name value to the corresponding
// string with first and last name
// fun fNToString(fullName: Author.FullName): String {
//     return "${ fullName.firstName } ${ fullName.lastName }"
// }

// fun getGreeting(a: Author): String {
//     return "hi " + when (a) {
//         is Author.Unknown -> "unknown"
//         is Author.FullName -> fNToString(a)
//         is Author.Pseudonym -> "${ fNToString(a.realName) } (known as ${ fNToString(a.knownAs) })"
//     }
// }

// println(getGreeting(Author.Unknown))

// println(getGreeting(Author.FullName("hank", "green")))

// println(getGreeting(Author.Pseudonym(
//     knownAs = Author.FullName(
//         firstName = "mary", 
//         lastName = "westmacott"
//     ),
//     realName = Author.FullName(
//         firstName = "agatha", 
//         lastName = "christie"
//     ),
// )))