index.js

// 1.Deposit some money
// 2.Determine number of lines to bet on
// 3.Collect a bet amount
// 4.Spin the slot machine
// 5.Check if the user won
// 6.Give the user their winnings
// 7.Play again

const prompt = require("prompt-sync")(); //Imports a package called prompt-sync to get user input from the terminal

const ROWS = 3;
const COLS = 3;

const SYMBOLS_COUNT = {
    A : 2,
    B : 4, 
    C : 6,
    D : 8
}

const SYMBOL_VALUES = {
    A : 5,
    B : 4, 
    C : 3,
    D : 2
}
// 1.Deposit some money
const deposit = () => {
    while (true){
        const depositAmount = prompt("Enter a deposit amount: ");
        const numberDepositAmount = parseFloat(depositAmount);
        if (isNaN(numberDepositAmount) || numberDepositAmount <= 0) {
            console.log("Invalid deposit amount, try again.");
        } else {
            return numberDepositAmount;
        }
    }
};

// 2.Determine number of lines to bet on
const getNumberOfLines = () => {
    while (true){
        const lines = prompt("Enter the number of lines to bet on (1-3): ");
        const numberOfLines = parseFloat(lines);
        if (isNaN(numberOfLines) || numberOfLines <= 0 || numberOfLines > 3) {
            console.log("Invalid number of lines, try again.");
        } else {
            return numberOfLines;
        }
    }
};

// 3.Collect a bet amount
// maximum bet is the balance divided by the number of lines that you are going to bet on
const getBet = (balance, lines) => {
    while (true){
        const bet = prompt("Enter the bet amount per line: ");
        const numberBet = parseFloat(bet);
        if (isNaN(numberBet) || numberBet <= 0 || numberBet > balance / lines) {
            console.log("Invalid bet amount, try again.");
        } else {
            return numberBet;
        }
    }
};

// 4.Spin the Slot Machine
// Generate a random 3×3 slot machine grid using the symbol probabilities.
const spin = () => {
    const symbols = [];
    for (const [symbol, count] of Object.entries(SYMBOLS_COUNT)){
        for (let i=0; i<count; i++){
            symbols.push(symbol);
        }
    }

    const reels = []; // reels = [[],[],[]] -> each one of the arrays represents a column inside the slot machine
    for (let i=0; i<COLS; i++){
        reels.push([]); 
        const reelSymbols = [...symbols];
        for (let j=0; j<ROWS; j++){
            const randomIndex = Math.floor(Math.random() * reelSymbols.length);
            const selectedSymbol = reelSymbols[randomIndex];
            reels[i].push(selectedSymbol);
            reelSymbols.splice(randomIndex, 1);
        }
    }

    return reels;
};

const transpose = (reels) => { 
    const rows = [];

    for (let i=0; i<ROWS; i++){ 
        rows.push([]);
        for(let j=0; j<COLS; j++){ 
            rows[i].push(reels[j][i]);
        }
    }

    return rows;
};

const printRows = (rows) => { 
    for (const row of rows) {
        let rowString = "";
        for (const [i, symbol] of row.entries()) {
            rowString += symbol;
            if (i != row.length-1) {
                rowString += " | ";
            }
        }
        console.log(rowString);
    }
}

// 5.Check if the user won
// It checks the selected rows, If all symbols in a row are the same -> you win money
const getWinnings = (rows, bet, lines) => { 
    let winnings = 0;

    for (let row=0; row<lines; row++) {
        const symbols = rows[row];
        let allSame = true;

        for (const symbol of symbols) {
            if (symbol != symbols[0]){
                allSame = false;
                break;
            }
        }

        if (allSame) { 
            winnings += bet * SYMBOL_VALUES[symbols[0]];
        }
    }

    return winnings;
}

const game = () => { 
    let balance = deposit();
    
    while (true) {
        console.log("You have a balance of $" + balance);
        const numberOfLines = getNumberOfLines();
        const bet = getBet(balance, numberOfLines);
        balance -= bet * numberOfLines;
        const reels = spin();
        const rows = transpose(reels);
        printRows(rows);
        const winnings = getWinnings(rows, bet, numberOfLines);
        balance += winnings;
        console.log("You won, $" + winnings.toString());

        if (balance <= 0) {
            console.log("You ran out of money!");
            break;
        }

        const playAgain = prompt("Do you want to play again (y/n)? ");
        if (playAgain != "y") break;
    }
}

game();