Rock Paper Scissors

import * as readline from "readline/promises";
import { stdin, stdout } from "process";

// ── Game rules as a lookup table ─────────────────────────────────────────────
// Each choice knows what it beats — no nested if/else needed
const RULES = {
  rock:     { beats: "scissors", emoji: "🪨" },
  paper:    { beats: "rock",     emoji: "📄" },
  scissors: { beats: "paper",   emoji: "✂️"  },
};
const CHOICES = Object.keys(RULES);  // ["rock", "paper", "scissors"]

// ── Pure game logic ───────────────────────────────────────────────────────────
export function cpuChoice() {
  return CHOICES[Math.floor(Math.random() * CHOICES.length)];
}

export function play(player, cpu) {
  // validate
  if (!CHOICES.includes(player)) throw new Error(`Unknown choice: "${player}"`);
  if (player === cpu)              return "draw";
  return RULES[player].beats === cpu ? "win" : "lose";
}

// ── CLI game loop ─────────────────────────────────────────────────────────────
const rl = readline.createInterface({ input: stdin, output: stdout });
const score = { win: 0, lose: 0, draw: 0 };
const shortcuts = { r: "rock", p: "paper", s: "scissors" };

console.log("
🪨 📄 ✂️  Rock Paper Scissors");
console.log("Type rock/paper/scissors (or r/p/s). Press Ctrl+C or type 'quit' to exit.
");

while (true) {
  const raw = (await rl.question("Your choice: ")).trim().toLowerCase();

  if (raw === "quit" || raw === "q") break;

  const player = shortcuts[raw] ?? raw;   // expand shortcut if used
  if (!CHOICES.includes(player)) {
    console.log(`  Please enter rock, paper, or scissors (or r/p/s).
`);
    continue;
  }

  const cpu    = cpuChoice();
  const result = play(player, cpu);
  score[result]++;

  const icon = { win: "✓", lose: "✗", draw: "=" }[result];
  const msg  = { win: "You win!", lose: "Computer wins!", draw: "Draw!" }[result];
  console.log(`  ${RULES[player].emoji} vs ${RULES[cpu].emoji}  →  ${msg}`);
  console.log(`  Score: ${score.win}W ${score.lose}L ${score.draw}D
`);
}

rl.close();

const total = score.win + score.lose + score.draw;
if (total > 0) {
  const winPct = Math.round(score.win / total * 100);
  console.log(`
Final score: ${score.win}W ${score.lose}L ${score.draw}D (${winPct}% wins)`);
}

import { play, cpuChoice } from "./rps.mjs";

let pass=0,fail=0;
function test(desc,fn){try{fn();console.log("  ✓",desc);pass++;}catch(e){console.log("  ✗",desc,"—",e.message);fail++;}}

// Deterministic outcome tests
test("rock beats scissors",     () => { if(play("rock","scissors")!=="win")  throw new Error(); });
test("scissors beats paper",    () => { if(play("scissors","paper")!=="win") throw new Error(); });
test("paper beats rock",        () => { if(play("paper","rock")!=="win")     throw new Error(); });
test("rock loses to paper",     () => { if(play("rock","paper")!=="lose")    throw new Error(); });
test("paper loses to scissors", () => { if(play("paper","scissors")!=="lose")throw new Error(); });
test("same choice = draw",      () => { if(play("rock","rock")!=="draw")     throw new Error(); });
test("invalid throws",          () => { try{play("gun","rock");throw new Error("no throw");}catch(e){if(e.message==="no throw")throw e;} });

// Statistical: cpuChoice always in valid set
test("cpuChoice always valid", () => {
  const valid=new Set(["rock","paper","scissors"]);
  for(let i=0;i<500;i++){if(!valid.has(cpuChoice()))throw new Error();}
});

// Statistical: results cover all outcomes over many rounds
test("play produces all three outcomes", () => {
  const outcomes=new Set();
  for(let i=0;i<500;i++) outcomes.add(play("rock",["rock","paper","scissors"][Math.floor(Math.random()*3)]));
  if(outcomes.size!==3) throw new Error("Only got: "+[...outcomes]);
});

console.log(\`
\${pass} passed, \${fail} failed\`);

node rps.mjs          # play the game
node rps.test.mjs     # run tests