Solution

src/app.js

@@ -1,3 +1,49 @@
 'use strict';
 
-// Write your code here
+const readline = require('readline');
+const { generateRandomNumber } = require('./modules/generateRandomNumber');
+const { checkIsValidUserInput } = require('./modules/checkIsValidUserInput');
+const { getBullsAndCows } = require('./modules/getBullsAndCows');
+
+const secretNumber = generateRandomNumber();
+
+const terminal = readline.createInterface({
+  input: process.stdin,
+  output: process.stdout,
+});
+
+function playGame() {
+  terminal.question('Guess the number: ', (userInput) => {
+    const userNumber = +userInput;
+
+    if (checkIsValidUserInput(userNumber)) {
+      const result = getBullsAndCows(
+        userInput.toString(), secretNumber.toString()
+      );
+
+      // eslint-disable-next-line no-console
+      console.log(`Bulls: ${result.bulls}, Cows: ${result.cows}`);
+
+      if (result.bulls === 4) {
+        // eslint-disable-next-line no-console
+        console.log('Congratulations! You guessed the correct number.');
+        terminal.close();
+      } else {
+        playGame();
+      }
+    } else {
+      // eslint-disable-next-line no-console
+      console.log(
+        'Invalid input. Please enter a 4-digit number with no duplicate digits.'
+      );
+      playGame();
+    }
+  });
+}
+
+// eslint-disable-next-line no-console
+console.log(
+  'Welcome to the Bulls and Cows game! Try to guess the 4-digit number.'
+);
+
+playGame();

src/modules/checkIsValidUserInput.js

@@ -9,7 +9,18 @@
  * @return {boolean} - True if the user input is valid, false otherwise
  */
 function checkIsValidUserInput(userInput) {
-  /* Write your code here */
+  const inputLength = userInput.length;
+  const numericInput = userInput;
+  const isNumeric = !isNaN(numericInput);
+  const isInRange = numericInput >= 1000;
+  const uniqueDigits = new Set(userInput);
+
+  const isValid = uniqueDigits.size === inputLength
+  && isNumeric
+  && isInRange
+  && inputLength === 4;
+
+  return isValid;
 }
 
 module.exports = {

src/modules/generateRandomNumber.js

@@ -7,7 +7,23 @@
  * @return {number} A random 4-digit number
  */
 function generateRandomNumber() {
-  /* Write your code here */
+  const number = [];
+
+  while (number.length < 4) {
+    let randomNumber = 0;
+
+    if (number.length === 0) {
+      randomNumber = Math.floor(Math.random() * 8) + 1;
+    } else {
+      do {
+        randomNumber = Math.floor(Math.random() * 9);
+      } while (number.includes(randomNumber));
+    }
+
+    number.push(randomNumber);
+  }
+
+  return Number([...number].join(''));
 }
 
 module.exports = {

src/modules/getBullsAndCows.js

@@ -13,7 +13,21 @@
  * Example: { bulls: 1, cows: 2 }
  */
 function getBullsAndCows(userInput, numberToGuess) {
-  /* Write your code here */
+  const input = userInput.toString();
+  const number = numberToGuess.toString();
+  const bullsAndCows = {
+    bulls: 0, cows: 0,
+  };
+
+  for (let i = 0; i < 4; i++) {
+    if (input[i] === number[i]) {
+      bullsAndCows.bulls += 1;
+    } else if (number.includes(input[i])) {
+      bullsAndCows.cows += 1;
+    }
+  }
+
+  return bullsAndCows;
 }
 
 module.exports = {