Number Guessing Game

// Import readline so we can ask the player for input
import * as readline from "readline/promises";
import { stdin, stdout } from "process";

// Create an interface that reads from the keyboard and writes to the terminal
const rl = readline.createInterface({ input: stdin, output: stdout });

// Pick a random secret number between 1 and 100
// Math.random() gives 0.0 to 0.9999
// * 100 gives 0.0 to 99.9999
// Math.floor rounds DOWN to nearest integer: 0 to 99
// + 1 shifts to: 1 to 100
const secret = Math.floor(Math.random() * 100) + 1;

// Track how many guesses the player has made
let attempts = 0;

console.log("I've picked a number between 1 and 100. Can you guess it?");

// Keep looping until the player guesses correctly
while (true) {
  // Ask for a guess — await means "wait for the player to type and press Enter"
  const input = await rl.question("Your guess: ");

  // Convert the typed string to a number
  const guess = Number(input);

  // Validate the input
  if (isNaN(guess) || guess < 1 || guess > 100) {
    console.log("Please enter a number between 1 and 100.");
    continue;  // skip the rest of this loop iteration, ask again
  }

  // Count this as a valid attempt
  attempts++;

  // Compare guess to secret
  if (guess < secret) {
    console.log("Too low! Try higher.");
  } else if (guess > secret) {
    console.log("Too high! Try lower.");
  } else {
    // Correct!
    console.log(`Correct! You found ${secret} in ${attempts} guess${attempts === 1 ? "" : "es"}!`);
    break;  // exit the while loop
  }
}

// Close the readline interface — otherwise Node.js keeps running
rl.close();

// ── logic.mjs ── (extract this from game.mjs)
export function checkGuess(secret, guess) {
  // Returns: "low", "high", or "correct"
  if (guess < secret) return "low";
  if (guess > secret) return "high";
  return "correct";
}

export function validateGuess(input) {
  // Returns the number, or null if invalid
  const n = Number(input);
  if (isNaN(n) || n < 1 || n > 100 || !Number.isInteger(n)) return null;
  return n;
}

// ── game.test.mjs ──
import { checkGuess, validateGuess } from "./logic.mjs";

let passed = 0; let failed = 0;
function test(desc, fn) {
  try { fn(); console.log("  ✓", desc); passed++; }
  catch(e) { console.log("  ✗", desc, "—", e.message); failed++; }
}
function expect(val) {
  return {
    toBe(exp) { if (val !== exp) throw new Error(`Expected ${exp}, got ${val}`); },
  };
}

console.log("Number Guessing Game — Logic Tests
");

test("guess lower than secret returns low",    () => expect(checkGuess(50, 30)).toBe("low"));
test("guess higher than secret returns high",  () => expect(checkGuess(50, 70)).toBe("high"));
test("correct guess returns correct",          () => expect(checkGuess(50, 50)).toBe("correct"));
test("works at boundaries: secret=1, guess=1", () => expect(checkGuess(1,  1)).toBe("correct"));
test("valid number string parses correctly",   () => expect(validateGuess("42")).toBe(42));
test("letters return null",                    () => expect(validateGuess("abc")).toBe(null));
test("0 is invalid (out of range)",            () => expect(validateGuess("0")).toBe(null));
test("101 is invalid (out of range)",          () => expect(validateGuess("101")).toBe(null));
test("3.5 is invalid (not integer)",           () => expect(validateGuess("3.5")).toBe(null));

console.log(\`
Results: \${passed} passed, \${failed} failed\`);

# Requires Node.js v18+ (for readline/promises and top-level await)
node game.mjs

# Run the tests:
node game.test.mjs