document.addEventListener('DOMContentLoaded', function () {
    // DOM Elements
    const loanAmountInput = document.getElementById('loanAmount');
    const interestRateInput = document.getElementById('interestRate');
    const loanTermInput = document.getElementById('loanTerm');

    const loanAmountLabel = document.getElementById('loanAmountLabel');
    const interestRateLabel = document.getElementById('interestRateLabel');
    const loanTermLabel = document.getElementById('loanTermLabel');

    const monthlyPaymentOutput = document.getElementById('monthlyPayment');
    const totalInterestOutput = document.getElementById('totalInterest');
    const totalPaidOutput = document.getElementById('totalPaid');

    // Format number as currency
    const currencyFormatter = new Intl.NumberFormat('en-US', {
        style: 'currency',
        currency: 'USD',
    });

    function calculateLoan() {
        const principal = parseFloat(loanAmountInput.value);
        const annualInterestRate = parseFloat(interestRateInput.value);
        const years = parseInt(loanTermInput.value, 10);

        // Update labels
        loanAmountLabel.textContent = currencyFormatter.format(principal).replace('.00', '');
        interestRateLabel.textContent = `${annualInterestRate.toFixed(1)}%`;
        loanTermLabel.textContent = `${years} ${years > 1 ? 'Years' : 'Year'}`;

        // Calculation logic
        if (principal > 0 && annualInterestRate > 0 && years > 0) {
            const monthlyInterestRate = annualInterestRate / 100 / 12;
            const numberOfPayments = years * 12;

            const monthlyPayment = principal * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) - 1);
            
            if (isFinite(monthlyPayment)) {
                const totalPaid = monthlyPayment * numberOfPayments;
                const totalInterest = totalPaid - principal;

                // Update UI
                monthlyPaymentOutput.textContent = currencyFormatter.format(monthlyPayment);
                totalInterestOutput.textContent = currencyFormatter.format(totalInterest);
                totalPaidOutput.textContent = currencyFormatter.format(totalPaid);
            } else {
                // Handle case where interest is 0 or other invalid scenarios
                resetResults();
            }
        } else {
            resetResults();
        }
    }
    
    function resetResults() {
        monthlyPaymentOutput.textContent = currencyFormatter.format(0);
        totalInterestOutput.textContent = currencyFormatter.format(0);
        totalPaidOutput.textContent = currencyFormatter.format(0);
    }


    // Event Listeners
    loanAmountInput.addEventListener('input', calculateLoan);
    interestRateInput.addEventListener('input', calculateLoan);
    loanTermInput.addEventListener('input', calculateLoan);

    // Initial calculation on page load
    calculateLoan();
});