const fs = require("fs");

function finalizeInvoice(filePath, invoiceId, customerType) {
  const raw = fs.readFileSync(filePath, "utf8");
  const state = JSON.parse(raw);
  const invoice = state.invoices.find((item) => item.id === invoiceId);

  if (!invoice) {
    throw new Error("Invoice not found");
  }

  let subtotal = 0;

  for (const line of invoice.lines) {
    subtotal = subtotal + line.quantity * line.unitPrice;
  }

  let discount = 0;

  if (customerType === "vip") {
    discount = subtotal * 0.15;
  }

  if (subtotal > 200) {
    discount = discount + 10;
  }

  const taxed = (subtotal - discount) * 1.1;
  invoice.status = "finalized";
  invoice.total = Math.round(taxed * 100) / 100;
  invoice.finalizedAt = new Date().toISOString();

  fs.writeFileSync(filePath, JSON.stringify(state, null, 2));
  console.log("Invoice finalized", invoiceId);

  return invoice;
}

module.exports = { finalizeInvoice };