// patterns/PaperScissorsRock.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Demonstration of multiple dispatching
import java.util.*;
import java.util.function.*;
import java.util.stream.*;
import onjava.*;
import static onjava.Tuple.*;

enum Outcome { WIN, LOSE, DRAW }

interface Item {
 Outcome compete(Item it);
 Outcome eval(Paper p);
 Outcome eval(Scissors s);
 Outcome eval(Rock r);
}

class Paper implements Item {
 @Override
 public Outcome compete(Item it) {
 return it.eval(this);
 }
 @Override
 public Outcome eval(Paper p) {
 return Outcome.DRAW;
 }
 @Override
 public Outcome eval(Scissors s) {
 return Outcome.WIN;
 }
 @Override
 public Outcome eval(Rock r) {
 return Outcome.LOSE;
 }
 @Override
 public String toString() { return "Paper"; }
}

class Scissors implements Item {
 @Override
 public Outcome compete(Item it) {
 return it.eval(this);
 }
 @Override
 public Outcome eval(Paper p) {
 return Outcome.LOSE;
 }
 @Override
 public Outcome eval(Scissors s) {
 return Outcome.DRAW;
 }
 @Override
 public Outcome eval(Rock r) {
 return Outcome.WIN;
 }
 @Override
 public String toString() { return "Scissors"; }
}

class Rock implements Item {
 @Override
 public Outcome compete(Item it) {
 return it.eval(this);
 }
 @Override
 public Outcome eval(Paper p) {
 return Outcome.WIN;
 }
 @Override
 public Outcome eval(Scissors s) {
 return Outcome.LOSE;
 }
 @Override
 public Outcome eval(Rock r) {
 return Outcome.DRAW;
 }
 @Override
 public String toString() { return "Rock"; }
}

class ItemFactory {
 static List<Supplier<Item>> items =
 Arrays.asList(
 Scissors::new, Paper::new, Rock::new);
 static final int SZ = items.size();
 private static SplittableRandom rand =
 new SplittableRandom(47);
 public static Item newItem() {
 return items.get(rand.nextInt(SZ)).get();
 }
 public static Tuple2<Item,Item> newPair() {
 return tuple(newItem(), newItem());
 }
}

class Compete {
 public static Outcome match(Tuple2<Item,Item> p) {
 System.out.print(p.a1 + " -> " + p.a2 + " : ");
 return p.a1.compete(p.a2);
 }
}

public class PaperScissorsRock {
 public static void main(String[] args) {
 Stream.generate(ItemFactory::newPair)
 .limit(20)
 .map(Compete::match)
 .forEach(System.out::println);
 }
}
/* Output:
Scissors -> Rock : LOSE
Scissors -> Paper : WIN
Rock -> Paper : LOSE
Rock -> Rock : DRAW
Rock -> Paper : LOSE
Paper -> Scissors : LOSE
Rock -> Paper : LOSE
Scissors -> Scissors : DRAW
Scissors -> Rock : LOSE
Scissors -> Paper : WIN
Scissors -> Rock : LOSE
Paper -> Scissors : LOSE
Rock -> Rock : DRAW
Scissors -> Scissors : DRAW
Paper -> Paper : DRAW
Scissors -> Paper : WIN
Scissors -> Rock : LOSE
Scissors -> Paper : WIN
Rock -> Paper : LOSE
Rock -> Scissors : WIN
*/