Solution

src/app.js

@@ -1,3 +1,34 @@
 'use strict';
 
-// Write your code here
+const readline = require('node:readline');
+const { stdin, stdout, exit } = require('node:process');
+
+const { generateRandomNumber } = require('./modules/generateRandomNumber');
+const { checkIsValidUserInput } = require('./modules/checkIsValidUserInput');
+const { getBullsAndCows } = require('./modules/getBullsAndCows');
+
+const PROMPT_MESSAGE = 'Write 4 digits: \n';
+const INVALID_INPUT_MESSAGE = 'The input must be 4 uniq digits: \n';
+const TRY_AGAIN_MESSAGE = 'Need to try one more time: \n';
+const WIN_MESSAGE = 'You win! The correct answer is';
+
+const input = readline.createInterface({ input: stdin, output: stdout });
+const answer = generateRandomNumber();
+
+stdout.write(PROMPT_MESSAGE);
+
+input.on('line', (text) => {
+  if (!checkIsValidUserInput(text)) {
+    stdout.write(INVALID_INPUT_MESSAGE + PROMPT_MESSAGE);
+  }
+
+  const { bulls, cows } = getBullsAndCows(text, answer);
+
+  if (bulls === 4) {
+    stdout.write(`${WIN_MESSAGE} ${text}`);
+    input.close();
+    exit();
+  }
+
+  stdout.write(`{bulls: ${bulls}, cows: ${cows}} \n${TRY_AGAIN_MESSAGE}`);
+});

src/modules/checkIsValidUserInput.js

@@ -9,7 +9,19 @@
  * @return {boolean} - True if the user input is valid, false otherwise
  */
 function checkIsValidUserInput(userInput) {
-  /* Write your code here */
+  switch (true) {
+    case userInput[0] === '0':
+      return false;
+
+    case isNaN(+userInput):
+      return false;
+
+    case new Set(userInput.split('')).size !== 4:
+      return false;
+
+    default:
+      return true;
+  }
 }
 
 module.exports = {

src/modules/generateRandomNumber.js

@@ -6,8 +6,21 @@
  *
  * @return {number} A random 4-digit number
  */
+
 function generateRandomNumber() {
-  /* Write your code here */
+  const digits = new Set();
+
+  const firstDigit = Math.floor(1 + Math.random() * 9);
+
+  digits.add(firstDigit);
+
+  while (digits.size < 4) {
+    const randomDigit = Math.floor(Math.random() * 10);
+
+    digits.add(randomDigit);
+  }
+
+  return Number(Array.from(digits).join(''));
 }
 
 module.exports = {

src/modules/getBullsAndCows.js

@@ -13,7 +13,27 @@
  * Example: { bulls: 1, cows: 2 }
  */
 function getBullsAndCows(userInput, numberToGuess) {
-  /* Write your code here */
+  let bulls = 0;
+  let cows = 0;
+
+  const userInputStr = String(userInput);
+  const numberToGuessStr = String(numberToGuess);
+
+  for (let i = 0; i < userInputStr.length; i++) {
+    const guessNumber = userInputStr[i];
+    const rightNumber = numberToGuessStr[i];
+
+    if (guessNumber === rightNumber) {
+      bulls += 1;
+    } else if (
+      numberToGuessStr.includes(guessNumber) &&
+      guessNumber !== rightNumber
+    ) {
+      cows += 1;
+    }
+  }
+
+  return { bulls, cows };
 }
 
 module.exports = {