// paystack-webhook.js
// Node >= 14, install dependencies:
// npm install express firebase-admin axios

const express = require('express');
const crypto = require('crypto');
const admin = require('firebase-admin');
const axios = require('axios');

const app = express();

// -------------------------------------------------
// Environment variables (set these in your env/secrets)
// -------------------------------------------------
// - FIREBASE_CREDENTIALS: stringified JSON service account
// - PAYSTACK_DEMO_SECRET
// - PAYSTACK_LIVE_SECRET
// - PORT (optional)
// -------------------------------------------------

const {
  FIREBASE_CREDENTIALS,
  PAYSTACK_DEMO_SECRET,
  PAYSTACK_LIVE_SECRET,
  PORT,
} = process.env;

// choose which secret to use (dev/demo by default)
const PAYSTACK_SECRET = PAYSTACK_DEMO_SECRET; // PAYSTACK_LIVE_SECRET

if (!PAYSTACK_SECRET) {
  console.warn('WARNING: PAYSTACK_SECRET is not set. Outgoing Paystack calls and webhook verification will fail.');
}

// Initialize Firebase Admin using credentials read from env
if (FIREBASE_CREDENTIALS) {
  try {
    const serviceAccount = JSON.parse(FIREBASE_CREDENTIALS);
    admin.initializeApp({
      credential: admin.credential.cert(serviceAccount),
    });
    console.log('Firebase admin initialized from FIREBASE_CREDENTIALS env var.');
  } catch (err) {
    console.error('Failed to parse FIREBASE_CREDENTIALS JSON:', err);
    process.exit(1);
  }
} else {
  console.warn('FIREBASE_CREDENTIALS not provided. Firebase admin not initialized.');
}

// -------------------------------------------------
// Webhook raw parser (required to verify Paystack signature)
// -------------------------------------------------
app.use(
  express.raw({
    type: 'application/json',
    limit: '1mb',
  })
);

// Utility: verify x-paystack-signature
function verifyPaystackSignature(rawBodyBuffer, signatureHeader) {
  if (!PAYSTACK_SECRET) return false;
  const hmac = crypto.createHmac('sha512', PAYSTACK_SECRET);
  hmac.update(rawBodyBuffer);
  const expected = hmac.digest('hex');
  try {
    return crypto.timingSafeEqual(Buffer.from(expected, 'utf8'), Buffer.from(signatureHeader || '', 'utf8'));
  } catch (e) {
    return false;
  }
}

// Helper: safe JSON parse
function safeParseJSON(raw) {
  try {
    return JSON.parse(raw);
  } catch (err) {
    return null;
  }
}

// ------------------------------
// Expiry helper: getExpiryFromPlan
// ------------------------------
// Returns an object:
// { expiresAtMs: <Number>, expiresAtIso: <String> }
// Rules:
// - If planObj.interval exists use that (weekly -> +7 days, monthly -> +30 days)
// - Else fallback to matching plan id or code against WEEKLY_PLAN_IDS / MONTHLY_PLAN_IDS
// - Always add EXTRA_FREE_MS (2 hours) to the computed expiry
// - If no match, default to 30 days + 2 hours
const EXTRA_FREE_MS = 2 * 60 * 60 * 1000; // 2 hours in ms

// EDIT THESE SETS to include any numeric plan ids or plan codes you consider weekly/monthly
const WEEKLY_PLAN_IDS = new Set([
  // numeric ids
  3311892, // demo, remove in prod
  3305738,
  // string plan codes (if your API sometimes returns the PLN_xxx code)
  
  'PLN_ngz4l76whecrpkv,

  'PLN_f7a3oagrpt47d5f', // demo, remove in prod
]);

const MONTHLY_PLAN_IDS = new Set([
  3305739,
    'PLN_584ck56g65xhkum', // replace/extend as needed
]);

function getExpiryFromPlan(planInput) {
  // planInput may be: undefined | number | string | object { id, plan_code, interval }
  let interval = null;
  let planId = null;
  let planCode = null;

  if (!planInput) {
    interval = null;
  } else if (typeof planInput === 'object') {
    planId = planInput.id ?? planInput.plan_id ?? null;
    planCode = planInput.plan_code ?? planInput.planCode ?? null;
    interval = (planInput.interval || planInput.billing_interval || null);
  } else if (typeof planInput === 'number') {
    planId = planInput;
  } else if (typeof planInput === 'string') {
    // could be "PLN_xxx" or numeric string
    planCode = planInput;
    const asNum = Number(planInput);
    if (!Number.isNaN(asNum)) planId = asNum;
  }

  // Prefer explicit interval if provided
  if (interval) {
    interval = String(interval).toLowerCase();
    if (interval.includes('week')) {
      const expires = Date.now() + 7 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
      return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
    }
    if (interval.includes('month')) {
      const expires = Date.now() + 30 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
      return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
    }
    // if 'hourly' or other intervals -- you can treat hourly as 7 days for weekly test example or handle explicitly
    if (interval.includes('hour')) {
      // Treat hourly plans as weekly-like (example from your payload that used hourly). You can adjust.
      const expires = Date.now() + 7 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
      return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
    }
  }

  // Fallback: check known id/code sets
  if (planId && WEEKLY_PLAN_IDS.has(planId)) {
    const expires = Date.now() + 7 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
    return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
  }
  if (planCode && WEEKLY_PLAN_IDS.has(planCode)) {
    const expires = Date.now() + 7 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
    return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
  }
  if (planId && MONTHLY_PLAN_IDS.has(planId)) {
    const expires = Date.now() + 30 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
    return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
  }
  if (planCode && MONTHLY_PLAN_IDS.has(planCode)) {
    const expires = Date.now() + 30 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
    return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
  }

  // Final fallback: default to 30 days + extra 2 hours
  const expires = Date.now() + 30 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
  return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
}

// Helper: find user doc reference in Firestore
// Strategy:
// 1) If metadata.userId exists and matches a doc ID, use that doc
// 2) Try queries by email, uid, userId fields (most common naming)
// Returns a DocumentReference or null
async function findUserDocRef(db, { metadataUserId, email }) {
  const usersRef = db.collection('users');

  if (metadataUserId) {
    // Try doc id first
    try {
      const docRef = usersRef.doc(metadataUserId);
      const snap = await docRef.get();
      if (snap.exists) return docRef;
    } catch (e) {
      // continue to queries
    }

    // try equality queries on commonly used id fields
    const idFields = ['userId', 'uid', 'id'];
    for (const field of idFields) {
      try {
        const qSnap = await usersRef.where(field, '==', metadataUserId).limit(1).get();
        if (!qSnap.empty) return qSnap.docs[0].ref;
      } catch (e) {
        // ignore and proceed
      }
    }
  }

  if (email) {
    try {
      const qSnap = await usersRef.where('email', '==', email).limit(1).get();
      if (!qSnap.empty) return qSnap.docs[0].ref;
    } catch (e) {
      // ignore
    }
  }

  // Not found
  return null;
}

// ------------------------
// Existing webhook endpoint (modified to update subscription/entitlements)
// ------------------------
app.post('/webhook/paystack', async (req, res) => {
  const raw = req.body; // Buffer because we used express.raw
  const signature = req.get('x-paystack-signature') || req.get('X-Paystack-Signature');

  // Verify signature
  if (!signature || !verifyPaystackSignature(raw, signature)) {
    console.warn('Paystack webhook signature verification failed. Signature header:', signature);
    return res.status(400).json({ ok: false, message: 'Invalid signature' });
  }

  // Parse payload
  const bodyStr = raw.toString('utf8');
  const payload = safeParseJSON(bodyStr);

  if (!payload) {
    console.warn('Could not parse webhook JSON payload.');
    return res.status(400).json({ ok: false, message: 'Invalid JSON' });
  }

  const event = (payload.event || payload.type || '').toString();
  const isRefund = /refund/i.test(event);
  const isChargeSuccess = /charge\.success/i.test(event);
  const isInvoiceOrSubscription = /invoice\.(payment_succeeded|paid)|subscription\./i.test(event);
  // We only care about refunds and payments (charge.success) as per earlier note
  const isPayment = isChargeSuccess; // we intentionally only act on charge.success

  // Short names
  const db = admin.firestore();

  if (isRefund || isPayment || /subscription\.create/i.test(event) || /subscription\.update/i.test(event)) {
    console.log('--- PAYSTACK WEBHOOK (INTERESTING EVENT) ---');
    console.log('event:', event);
    console.log('payload:', JSON.stringify(payload, null, 2));

    // persist webhook for auditing
    try {
      await db.collection('paystack-webhooks').add({
        event,
        payload,
        receivedAt: admin.firestore.FieldValue.serverTimestamp(),
      });
    } catch (err) {
      console.error('Failed to persist webhook audit:', err);
    }

    // Common data paths
    const data = payload.data || {};
    // metadata could be on data.metadata or data.customer.metadata depending on event
    const metadata = data.metadata || data.customer?.metadata || null;
    const metadataUserId = metadata?.userId || metadata?.user_id || null;
    const customerEmail = data.customer?.email || (metadata && metadata.email) || null;

    // Try to find the user doc
    let userDocRef = null;
    try {
      userDocRef = await findUserDocRef(db, { metadataUserId, email: customerEmail });
    } catch (err) {
      console.error('Error finding user doc:', err);
      userDocRef = null;
    }

    // Handler: subscription.create - store subscription id only
    if (/subscription\.create/i.test(event) || event === 'subscription.create') {
      const subscriptionCode = data.subscription_code || data.subscription?.subscription_code || (data.id ? String(data.id) : null);
      const status = data.status || 'active';

      // compute expiry from plan if possible
      const planObj = data.plan || data.subscription?.plan || null;
      const expiry = getExpiryFromPlan(planObj);

      if (userDocRef && subscriptionCode) {
        try {
          await userDocRef.update({
            subscriptionId: subscriptionCode,
            subscription: {
              id: subscriptionCode,
              status,
              plan: planObj ? { id: planObj.id, code: planObj.plan_code, amount: planObj.amount, interval: planObj.interval } : null,
              createdAt: data.createdAt ? admin.firestore.Timestamp.fromDate(new Date(data.createdAt)) : admin.firestore.FieldValue.serverTimestamp(),
              expiresAtMs: expiry.expiresAtMs,
              expiresAtIso: expiry.expiresAtIso,
            },
            updatedAt: admin.firestore.FieldValue.serverTimestamp(),
          });
          console.log(`User doc updated with subscription ${subscriptionCode} and expiry ${expiry.expiresAtIso}`);
        } catch (err) {
          console.error('Failed to update user subscription info:', err);
        }
      } else {
        console.warn('subscription.create received but user not found or subscriptionCode missing — skipping user update.');
      }
    }

    // Handler: charge.success - add entitlement on successful subscription charge (or one-off if you want)
    if (isPayment) {
      // Determine if this is a recurring/subscription payment:
      const recurringMarker = (data.metadata && (data.metadata.custom_filters?.recurring || data.metadata.recurring)) || false;
      const hasSubscription = !!(data.subscription || data.subscriptions || data.plan); // defensive
      const isLikelySubscriptionPayment = recurringMarker || hasSubscription;

      // attempt to derive plan object for expiry calc
      const planObj = data.plan || (data.subscription ? data.subscription.plan : null) || null;
      const expiry = getExpiryFromPlan(planObj);

      // Create an entitlement object
      const entitlement = {
        id: data.reference || data.id ? String(data.reference || data.id) : null,
        source: 'paystack',
        amount: data.amount || null,
        reference: data.reference || null,
        paidAt: data.paid_at || data.paidAt || data.created_at || null,
        plan: planObj ? { id: planObj.id, code: planObj.plan_code } : null,
        // add computed expiry ms/iso if available
        expiresAtMs: expiry.expiresAtMs,
        expiresAtIso: expiry.expiresAtIso,
        createdAt: admin.firestore.FieldValue.serverTimestamp(),
      };

      if (userDocRef && isLikelySubscriptionPayment) {
        try {
          // Append entitlement
          await userDocRef.update({
            entitlements: admin.firestore.FieldValue.arrayUnion(entitlement),
            updatedAt: admin.firestore.FieldValue.serverTimestamp(),
          });
          console.log('Added entitlement to user:', entitlement.id || entitlement.reference, 'expiry:', expiry.expiresAtIso);
        } catch (err) {
          console.error('Failed to add entitlement to user:', err);
        }
      } else if (userDocRef && !isLikelySubscriptionPayment) {
        // If you want to also give entitlement for one-off payments, you can add here.
        console.log('charge.success received but not marked recurring/subscription - skipping entitlement add by default.');
      } else {
        console.warn('charge.success: user not found, skipping entitlement update.');
      }
    }

    // Handler: refunds - remove entitlement(s) associated with refunded transaction
    if (isRefund) {
      // Refund payload shapes vary. Try to extract refund reference or linked transaction
      const refund = data; // top-level refund object in many webhook shapes
      const refundedReference = refund.reference || refund.transaction?.reference || refund.transaction?.id || null;

      if (userDocRef && refundedReference) {
        try {
          // Read current entitlements, filter out any matching the refunded reference, and write back
          const snap = await userDocRef.get();
          if (snap.exists) {
            const userData = snap.data();
            const currentEntitlements = Array.isArray(userData.entitlements) ? userData.entitlements : [];
            const filtered = currentEntitlements.filter(e => {
              // compare by reference or id if present
              const ref = e.reference || e.id || '';
              return ref !== refundedReference && ref !== String(refundedReference);
            });

            await userDocRef.update({
              entitlements: filtered,
              updatedAt: admin.firestore.FieldValue.serverTimestamp(),
            });
            console.log('Removed entitlements matching refunded reference:', refundedReference);
          } else {
            console.warn('Refund handling: user doc disappeared between lookup and removal.');
          }
        } catch (err) {
          console.error('Failed to remove entitlement on refund:', err);
        }
      } else {
        console.warn('Refund received but user or refundedReference not found — skipping entitlement removal.');
      }
    }
  } else {
    console.log(`Received Paystack webhook for event "${event}" — ignored (not refund/payment/subscription.create).`);
  }

  return res.status(200).json({ ok: true });
});

// ------------------------
// New: Create Payment Page (link) for a plan
// ------------------------
// This endpoint expects JSON body, so we attach express.json() for this route.
// Required fields in body: planId, userId, name (friendly page name) optionally: amount, redirect_url, collect_phone, fixed_amount
app.post('/create-payment-link', express.json(), async (req, res) => {

  // If req.body was left as a Buffer (because express.raw ran), parse it:
  let body = req.body;
  if (Buffer.isBuffer(body)) {
    try {
      body = JSON.parse(body.toString('utf8'));
    } catch (err) {
      return res.status(400).json({ ok: false, message: 'Invalid JSON' });
    }
  }

  const { planId, userId, name, amount, redirect_url, collect_phone = false, fixed_amount = false } = body || {};

  if (!planId) return res.status(400).json({ ok: false, message: 'planId is required' });
  if (!userId) return res.status(400).json({ ok: false, message: 'userId is required' });
  if (!name) return res.status(400).json({ ok: false, message: 'name is required (page title)' });

  // Build the body per Paystack's Payment Pages API.
  const payload = {
    name,
    type: 'subscription',
    plan: planId,
    metadata: {
      userId,
    },
    // optional properties
    collect_phone,
    fixed_amount,
  };

  if (amount) payload.amount = amount; // amount is optional (in kobo/cents)
  if (redirect_url) payload.redirect_url = redirect_url;

  try {
    const response = await axios.post('https://api.paystack.co/page', payload, {
      headers: {
        Authorization: `Bearer ${PAYSTACK_SECRET}`,
        'Content-Type': 'application/json',
      },
      timeout: 10_000,
    });

    // Paystack returns a response with data object. Return minimal info to caller.
    const pageData = response.data && response.data.data ? response.data.data : response.data;

    return res.status(201).json({ ok: true, page: pageData });
  } catch (err) {
    console.error('Error creating Paystack payment page:', err?.response?.data || err.message || err);
    const errorDetail = err?.response?.data || { message: err.message };
    return res.status(500).json({ ok: false, error: errorDetail });
  }
});

// Simple health check
app.get('/health', (_req, res) => res.json({ ok: true }));

app.listen(PORT, () => {
  console.log(`Paystack webhook server listening on port ${PORT}`);
  console.log('POST /webhook/paystack to receive Paystack callbacks');
  console.log('POST /create-payment-link to create a subscription payment page (expects JSON body).');
});