document.addEventListener('DOMContentLoaded', function () {
  const calcBox = document.querySelector('.nr-calc-container, .calc');
  if (!calcBox) return;

  const usdtInput = document.getElementById('c-usdt');
  const ngnInput = document.getElementById('c-ngn');
  const noteText = document.getElementById('calc-n');
  const tabBtns = document.querySelectorAll('.calc-tabs button, .nr-calc-tabs button');

  // Parse live rates safely from container attributes
  let rawBuy = parseFloat(calcBox.getAttribute('data-buy')) || 0;
  let rawSell = parseFloat(calcBox.getAttribute('data-sell')) || 0;

  // Fallback defaults if upstream API was temporarily zero or connecting
  if (rawBuy <= 0) rawBuy = 1540.0;
  if (rawSell <= 0) rawSell = 1530.0;

  let currentSide = 'buy'; // default tab

  function formatNaira(num) {
    return '₦' + Number(num).toLocaleString('en-NG', {
      minimumFractionDigits: 2,
      maximumFractionDigits: 2
    });
  }

  function getActiveRate() {
    return currentSide === 'buy' ? rawBuy : rawSell;
  }

  function recalculateFromUSDT() {
    const val = parseFloat(usdtInput.value);
    const rate = getActiveRate();
    if (isNaN(val) || val <= 0) {
      ngnInput.value = '';
      if (noteText) noteText.textContent = 'Enter an amount to see current conversion.';
      return;
    }
    const total = val * rate;
    ngnInput.value = total.toFixed(2);
    updateNote(val, total, rate);
  }

  function recalculateFromNGN() {
    const val = parseFloat(ngnInput.value);
    const rate = getActiveRate();
    if (isNaN(val) || val <= 0 || rate <= 0) {
      usdtInput.value = '';
      if (noteText) noteText.textContent = 'Enter an amount to see current conversion.';
      return;
    }
    const total = val / rate;
    usdtInput.value = total.toFixed(2);
    updateNote(total, val, rate);
  }

  function updateNote(usdt, ngn, rate) {
    if (!noteText) return;
    const action = currentSide === 'buy' ? 'buying' : 'selling';
    noteText.innerHTML = `Calculated at <strong>${formatNaira(rate)}</strong> per USDT (Best market quote for ${action}).`;
  }

  // Bind tab switching
  tabBtns.forEach(btn => {
    btn.addEventListener('click', function () {
      tabBtns.forEach(b => b.classList.remove('on'));
      this.classList.add('on');
      currentSide = this.getAttribute('data-side') || 'buy';
      recalculateFromUSDT();
    });
  });

  // Bind bidirectional live keystroke inputs
  if (usdtInput) {
    usdtInput.addEventListener('input', recalculateFromUSDT);
  }
  if (ngnInput) {
    ngnInput.addEventListener('input', recalculateFromNGN);
  }

  // Trigger initial calculation on page load
  recalculateFromUSDT();
});