const { onRequest } = require("firebase-functions/v2/https");
const { initializeApp } = require("firebase-admin/app");
const { getFirestore, FieldValue } = require("firebase-admin/firestore");
const crypto = require("crypto");

initializeApp();
const db = getFirestore();

/**
 * Shopdm Pay Webhook Handler
 *
 * Receives payment.successful events from Shopdm Pay.
 * Matches the invoice_id to a pending donation and creates
 * a confirmed donor record.
 */
exports.shopdmPayWebhook = onRequest(
  { secrets: ["SHOPDM_MERCHANT_SECRET_DEV"] },
  async (req, res) => {
  // Only accept POST requests
  if (req.method !== "POST") {
    res.status(405).send("Method not allowed");
    return;
  }

  const payload = req.body;

  // Verify webhook signature
  // Supports both dev and prod secrets
  const secrets = [
    process.env.SHOPDM_MERCHANT_SECRET,
    process.env.SHOPDM_MERCHANT_SECRET_DEV,
  ].filter(Boolean);

  if (secrets.length > 0) {
    const signature = req.headers["x-shopdm-signature"];
    if (!signature) {
      console.error("Missing X-Shopdm-Signature header");
      res.status(401).send("Unauthorized");
      return;
    }

    const sortedPayload = JSON.stringify(
      payload,
      Object.keys(payload).sort()
    );

    const isValid = secrets.some((secret) => {
      const expected = crypto
        .createHmac("sha256", secret)
        .update(sortedPayload, "utf8")
        .digest("hex");
      return signature === expected;
    });

    if (!isValid) {
      console.error("Invalid webhook signature");
      res.status(401).send("Unauthorized");
      return;
    }
  }

  // Only process successful payments
  if (payload.event !== "payment.successful") {
    res.status(200).send("Event ignored");
    return;
  }

  const invoiceId = payload.metadata?.invoice_id;
  if (!invoiceId) {
    console.log("No invoice_id in webhook payload, skipping donor creation");
    res.status(200).send("OK - no invoice_id");
    return;
  }

  try {
    // Look up the pending donation
    const pendingRef = db.collection("pendingDonations").doc(invoiceId);
    const pendingDoc = await pendingRef.get();

    if (!pendingDoc.exists) {
      console.log(`No pending donation found for invoice_id: ${invoiceId}`);
      res.status(200).send("OK - no matching pending donation");
      return;
    }

    const pending = pendingDoc.data();

    // Check if already processed (idempotency)
    if (pending.status === "confirmed") {
      console.log(`Donation ${invoiceId} already confirmed, skipping`);
      res.status(200).send("OK - already processed");
      return;
    }

    // Get the actual payment amount from the webhook
    const paidAmount = payload.data?.amount_xcd || pending.amount;

    // Create the confirmed donor record
    await db.collection("donors").add({
      name: pending.name,
      amount: Number(paidAmount),
      classYear: pending.classYear || "",
      message: pending.message || "",
      anonymous: !!pending.anonymous,
      status: "confirmed",
      pendingDonationId: invoiceId,
      paymentId: payload.data?.object_id || "",
      date: FieldValue.serverTimestamp(),
    });

    // Mark the pending donation as confirmed
    await pendingRef.update({
      status: "confirmed",
      confirmedAt: FieldValue.serverTimestamp(),
      paymentId: payload.data?.object_id || "",
    });

    console.log(`Donation confirmed for invoice_id: ${invoiceId}, amount: ${paidAmount}`);
    res.status(200).send("OK");
  } catch (error) {
    console.error("Error processing webhook:", error);
    res.status(500).send("Internal server error");
  }
});