// Валидирует платёжные данные перед созданием заказа

exports.handler = async (ctx) => {
  const req = ctx.request;

  if (!req.body) {
    return {
      status: 400,
      body: JSON.stringify({ error: "request body required" }),
      headers: { "Content-Type": "application/json" },
    };
  }

  let data;
  try {
    data = typeof req.body === 'string' ? JSON.parse(req.body) : req.body;
  } catch {
    return {
      status: 400,
      body: JSON.stringify({ error: "invalid JSON" }),
      headers: { "Content-Type": "application/json" },
    };
  }

  const errors = [];

  // card_number: 16 цифр
  const card = String(data.card_number || "").replace(/\s/g, "");
  if (!/^\d{16}$/.test(card)) errors.push("card_number must be 16 digits");

  // cvv: 3 цифры
  const cvv = String(data.cvv || "");
  if (!/^\d{3}$/.test(cvv)) errors.push("cvv must be 3 digits");

  // expiry: MM/YY
  const expiry = String(data.expiry || "");
  if (!/^(0[1-9]|1[0-2])\/\d{2}$/.test(expiry)) errors.push("expiry must be MM/YY");
  else {
    const [mm, yy] = expiry.split("/").map(Number);
    const now = new Date();
    const exp = new Date(2000 + yy, mm - 1);
    if (exp < now) errors.push("card is expired");
  }

  // amount
  const amount = Number(data.amount);
  if (!amount || amount <= 0) errors.push("amount must be positive number");
  if (amount > 10000) errors.push("amount exceeds limit 10000");

  if (errors.length > 0) {
    return {
      status: 422,
      body: JSON.stringify({ valid: false, errors }),
      headers: { "Content-Type": "application/json" },
    };
  }

  // Маскируем карту в ответе
  const maskedCard = `****-****-****-${card.slice(-4)}`;
  return {
    body: JSON.stringify({
      valid: true,
      masked_card: maskedCard,
      amount,
      currency: data.currency || "USD",
      token: `pay_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
    }),
    headers: { "Content-Type": "application/json" },
  };
};