interface Speaker {
    say() string
}

struct ChatRoom {
mut:
    talkers map[string]Speaker
}

fn new_room() &ChatRoom {
    return &ChatRoom{
        talkers: map[string]Speaker{}
    }
}

fn (mut r ChatRoom) add(name string, s Speaker) {
    r.talkers[name] = s
}

fn test_using_a_map_of_speaker_interfaces() {
    mut room := new_room()
    room.add('my cat', Cat{ name: 'Tigga' })
    room.add('my dog', Dog{ name: 'Pirin' })
    room.add('stray dog', Dog{ name: 'Anoni' })
    room.add('me', Human{ name: 'Bilbo' })
    room.add('she', Human{ name: 'Maria' })
    mut text := ''
    for name, subject in room.talkers {
        line := '${name:12s}: ${subject.say()}'
        println(line)
        text += line
    }
    assert text.contains(' meows ')
    assert text.contains(' barks ')
    assert text.contains(' says ')
}

struct Cat {
    name string
}

fn (c &Cat) say() string {
    return '${c.name} meows "MEOW!"'
}

struct Dog {
    name string
}

fn (d &Dog) say() string {
    return '${d.name} barks "Bau Bau!"'
}

struct Human {
    name string
}

fn (h &Human) say() string {
    return '${h.name} says "Hello"'
}