const Taxjar = require('taxjar');
const taxjar = new Taxjar({ apiKey: process.env.TAXJAR_API_KEY });

async function calculateTaxForOrder({ fromAddress, toAddress, lineItems, shippingCost }) {
  const response = await taxjar.taxForOrder({
    from_country: fromAddress.country,
    from_zip: fromAddress.zip,
    from_state: fromAddress.state,
    to_country: toAddress.country,
    to_zip: toAddress.zip,
    to_state: toAddress.state,
    to_city: toAddress.city,
    amount: lineItems.reduce((sum, i) => sum + i.unit_price * i.quantity, 0),
    shipping: shippingCost,
    line_items: lineItems.map(item => ({
      id: item.id,
      quantity: item.quantity,
      unit_price: item.unit_price,
      product_tax_code: item.taxCode ?? null, // e.g., '20010' for general goods
      exemption_type: item.exemptionType ?? null,
    })),
    exemption_type: customer.exemptionType ?? null, // 'wholesale', 'government', etc.
  });

  return {
    totalTax: response.tax.amount_to_collect,
    taxRate: response.tax.rate,
    hasNexus: response.tax.has_nexus,   // false = no tax to collect in this jurisdiction
    breakdown: response.tax.breakdown,
  };
}

async function commitTaxTransaction(order) {
  await taxjar.createOrder({
    transaction_id: order.id,
    transaction_date: new Date().toISOString().split('T')[0],
    from_country: WAREHOUSE_ADDRESS.country,
    from_zip: WAREHOUSE_ADDRESS.zip,
    from_state: WAREHOUSE_ADDRESS.state,
    to_country: order.shippingAddress.country,
    to_zip: order.shippingAddress.zip,
    to_state: order.shippingAddress.state,
    amount: order.subtotal,
    shipping: order.shippingCost,
    sales_tax: order.taxAmount,
    line_items: order.lineItems.map(item => ({
      id: item.id,
      quantity: item.quantity,
      unit_price: item.price,
      sales_tax: item.taxAmount,
    })),
  });
}

// On refund: void the transaction so it is excluded from filing reports
async function voidTaxTransaction(orderId) {
  await taxjar.deleteOrder(orderId);
}

async function validateEUVATNumber(vatNumber) {
  const countryCode = vatNumber.slice(0, 2);
  const number = vatNumber.slice(2);
  const res = await fetch(
    `https://ec.europa.eu/taxation_customs/vies/rest-api/ms/${countryCode}/vat/${number}`
  );
  const data = await res.json();
  return data.isValid === true;
  // If valid: apply zero-rate (reverse charge); if invalid: charge local VAT rate
}