(function () {
    'use strict';

    document.addEventListener('DOMContentLoaded', function () {
        var modal = document.getElementById('applyModal');
        if (!modal) return;

        var remainingBalance = parseFloat(modal.dataset.remainingBalance || '0');
        var invoiceSelect    = document.getElementById('applyInvoiceId');
        var amountInput      = document.getElementById('applyAmount');
        var maxHint          = document.getElementById('applyMaxHint');

        if (!invoiceSelect) return;

        invoiceSelect.addEventListener('change', function () {
            var selected = this.options[this.selectedIndex];
            if (!selected || !selected.value) {
                amountInput.value = '';
                if (maxHint) maxHint.textContent = '';
                return;
            }

            var invoiceBalance = parseFloat(selected.dataset.balance || '0');
            var max = Math.min(remainingBalance, invoiceBalance);
            amountInput.value = max.toFixed(2);
            amountInput.max   = max.toFixed(2);
            if (maxHint) maxHint.textContent = 'Max applicable: $' + max.toFixed(2);
        });
    });
})();