PPAP.swift

import Foundation

enum PPAP {
    case Start
    indirect case Pen(PPAP), Apple(PPAP), Pineapple(PPAP), Finish(PPAP)
    var output: String {
        switch self {
        case .Start: return "ピッピッピコ ピコ太郎〜♪"
        case .Pen(let p): return "\(p.output)\nI have a ✏️"
        case .Apple(let p): return "\(p.output)\nI have an 🍎"
        case .Pineapple(let p): return "\(p.output)\nI have a 🍍"
        case .Finish(let p): return "\(p.output)\nPen Pineapple Apple Pen! 😎"
        }
    }
    func ppap() -> PPAP {
        if case .Pen(.Apple(.Pineapple(.Pen))) = self {
            return .Finish(self)
        }
        switch (arc4random_uniform(3)) {
        case 0:  return PPAP.Pen(self).ppap()
        case 1:  return PPAP.Apple(self).ppap()
        case 2:  return PPAP.Pineapple(self).ppap()
        default: return PPAP.Finish(self)
        }
    }
}

print(PPAP.Start.ppap().output)

result

ピッピッピコ ピコ太郎〜♪
I have a 🍍
I have a ✏️
I have an 🍎
I have a ✏️
I have a 🍍
I have an 🍎
I have an 🍎
I have an 🍎
I have a ✏️
I have an 🍎
I have a 🍍
I have a ✏️
I have a ✏️
I have a ✏️
I have a 🍍
I have a 🍍
I have a ✏️
I have a ✏️
I have an 🍎
I have an 🍎
I have a 🍍
I have a 🍍
I have an 🍎
I have a 🍍
I have a 🍍
I have a ✏️
I have an 🍎
I have an 🍎
I have a ✏️
I have a 🍍
I have an 🍎
I have an 🍎
I have a ✏️
I have a ✏️
I have an 🍎
I have a ✏️
I have an 🍎
I have a ✏️
I have a 🍍
I have an 🍎
I have a ✏️
Pen Pineapple Apple Pen! 😎