// Example of sum types
// Models a landing craft leaving orbit and landing on a world
import rand
import time

struct Moon {
}

struct Mars {
}

fn (m Mars) dust_storm() bool {
    return rand.int() >= 0
}

struct Venus {
}

type World = Mars | Moon | Venus

struct Lander {
}

fn (l Lander) deorbit() {
    println('leaving orbit')
}

fn (l Lander) open_parachutes(n int) {
    println('opening ${n} parachutes')
}

fn wait() {
    println('waiting...')
    time.sleep(1 * time.second)
}

fn (l Lander) land(w World) {
    if w is Mars {
        for w.dust_storm() {
            wait()
        }
    }
    l.deorbit()
    match w {
        Moon {} // no atmosphere
        Mars {
            // light atmosphere
            l.open_parachutes(3)
        }
        Venus {
            // heavy atmosphere
            l.open_parachutes(1)
        }
    }
    println('landed')
}

fn main() {
    l := Lander{}
    l.land(Venus{})
    l.land(Mars{})
}