// 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
let db = null;
try {
  if (FIREBASE_CREDENTIALS) {
    const serviceAccount = JSON.parse(FIREBASE_CREDENTIALS);
    admin.initializeApp({
      credential: admin.credential.cert(serviceAccount),
    });
    db = admin.firestore();
    console.log('Firebase admin initialized from FIREBASE_CREDENTIALS env var.');
  } else {
    // If admin was already initialized in the environment (e.g. GCP), this will succeed
    if (!admin.apps.length) {
      console.warn('FIREBASE_CREDENTIALS not provided. Firebase admin not initialized. Some operations will error if they require Firestore.');
    } else {
      db = admin.firestore();
    }
  }
} catch (err) {
  console.error('Failed to initialize Firebase admin:', err);
  // keep running — code paths that need db will guard and log appropriately
}

// -------------------------------------------------
// Utility: verify x-paystack-signature
// -------------------------------------------------
function verifyPaystackSignature(rawBodyBuffer, signatureHeader) {
  if (!PAYSTACK_SECRET) return false;
  if (!rawBodyBuffer) return false;
  try {
    const hmac = crypto.createHmac('sha512', PAYSTACK_SECRET);
    hmac.update(rawBodyBuffer);
    const expected = hmac.digest('hex');
    // signatureHeader may be undefined - handle gracefully
    if (!signatureHeader) return false;
    return crypto.timingSafeEqual(Buffer.from(expected, 'utf8'), Buffer.from(String(signatureHeader), 'utf8'));
  } catch (e) {
    console.error('Error while verifying signature:', e);
    return false;
  }
}

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

// ------------------------------
// Expiry helper: getExpiryFromPlan
// ------------------------------
const EXTRA_FREE_MS = 2 * 60 * 60 * 1000; // 2 hours in ms

const WEEKLY_PLAN_IDS = new Set([
  3311892,
  3305738,
  'PLN_ngz4l76whecrpkv',
  'PLN_f7a3oagrpt47d5f',
]);

const MONTHLY_PLAN_IDS = new Set([
  3305739,
  'PLN_584ck56g65xhkum',
]);

function getExpiryFromPlan(planInput) {
  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') {
    planCode = planInput;
    const asNum = Number(planInput);
    if (!Number.isNaN(asNum)) planId = asNum;
  }

  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 (interval.includes('hour')) {
      // treat hour interval as a week by default (matching original logic)
      const expires = Date.now() + 7 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
      return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
    }
  }

  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() };
  }

  const expires = Date.now() + 30 * 24 * 60 * 60 * 1000 + EXTRA_FREE_MS;
  return { expiresAtMs: expires, expiresAtIso: new Date(expires).toISOString() };
}

// ------------------------------
// Helper: get userId from stored slug mapping
//   - try doc id == slug
//   - fallback: query where pageId == slug
// ------------------------------
async function getUserIdFromSlug(dbInstance, slugOrPageId) {
  if (!slugOrPageId || !dbInstance) return null;
  try {
    // try doc id first (we store mapping under doc id === slug)
    const doc = await dbInstance.collection('paystack-page-mappings').doc(String(slugOrPageId)).get();
    if (doc.exists) {
      const data = doc.data();
      if (data?.userId) return data.userId;
    }

    // fallback: maybe caller passed pageId; search by pageId field
    const q = await dbInstance.collection('paystack-page-mappings').where('pageId', '==', String(slugOrPageId)).limit(1).get();
    if (!q.empty) {
      const d = q.docs[0].data();
      if (d?.userId) return d.userId;
    }

    return null;
  } catch (e) {
    console.error('Failed to read page mapping for slug/pageId:', slugOrPageId, e);
    return null;
  }
}

// ------------------------------
// Robust extractor for userId (tries metadata, custom_fields, customer metadata, slug mapping, email fallback)
// ------------------------------
async function extractUserIdFromPayload(data = {}, dbInstance) {
  // 1) direct metadata on data
  const metadata = data.metadata || {};
  if (metadata.userId || metadata.user_id) return { userId: metadata.userId || metadata.user_id, source: 'metadata' };

  // 2) customer.metadata
  const custMeta = data.customer?.metadata || {};
  if (custMeta.userId || custMeta.user_id) return { userId: custMeta.userId || custMeta.user_id, source: 'customer.metadata' };

  // 3) top-level custom_fields (array)
  if (Array.isArray(data.custom_fields)) {
    for (const f of data.custom_fields) {
      const name = (f.variable_name || f.display_name || '').toString().toLowerCase();
      if ((name.includes('user') || name.includes('user_id') || name.includes('userid')) && f.value) {
        return { userId: f.value, source: 'custom_fields' };
      }
    }
  }

  // 4) metadata.custom_fields
  if (metadata.custom_fields) {
    if (Array.isArray(metadata.custom_fields)) {
      for (const f of metadata.custom_fields) {
        const name = (f.variable_name || f.display_name || '').toString().toLowerCase();
        if (name.includes('user') && f.value) return { userId: f.value, source: 'metadata.custom_fields' };
      }
    } else if (typeof metadata.custom_fields === 'object') {
      for (const k of Object.keys(metadata.custom_fields)) {
        if (k.toLowerCase().includes('user')) return { userId: metadata.custom_fields[k], source: 'metadata.custom_fields_object' };
      }
    }
  }

  // 5) slug / page id mapping fallback - many Paystack page webhooks include data.page.slug or data.page.id
  const slugCandidate = data.slug || data.page?.slug || data.page?.id || metadata?.slug || metadata?.page_slug || null;
  if (slugCandidate && dbInstance) {
    const mappedUserId = await getUserIdFromSlug(dbInstance, slugCandidate);
    if (mappedUserId) return { userId: mappedUserId, source: 'slug_mapping' };
  }

  // 6) email fallback (return email so caller can search)
  if (data.customer?.email) return { userId: data.customer.email, source: 'email' };

  // nothing found
  return { userId: null, source: null };
}

// ------------------------------
// Helper: find user doc reference in Firestore (tries doc id and queries by fields)
// ------------------------------
async function findUserDocRef(dbInstance, { metadataUserId, email, paystackCustomerId } = {}) {
  if (!dbInstance) return null;
  const usersRef = dbInstance.collection('users');

  if (metadataUserId) {
    // if metadataUserId looks like an email, skip docId check and search by email
    if (!String(metadataUserId).includes('@')) {
      try {
        const docRef = usersRef.doc(String(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 paystack_customer_id was provided, try that too
  if (paystackCustomerId) {
    try {
      const qSnap = await usersRef.where('paystack_customer_id', '==', String(paystackCustomerId)).limit(1).get();
      if (!qSnap.empty) return qSnap.docs[0].ref;
    } catch (e) {
      // ignore
    }
  }

  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;
}

// ------------------------------
// Cleanup that should run after a successful charge for the user
// - Deletes page mapping doc if slug provided and mapping matches user
// - Removes any "pending-payments" documents for the user (optional)
// - Writes a paymentCleanup log
// Customize this per your app's needs.
// ------------------------------
async function cleanUpAfterSuccessfulCharge(dbInstance, userDocRef, { slug, pageId, reference, email } = {}) {
  if (!dbInstance || !userDocRef) return;
  try {
    // 1) delete mapping doc if exists and mapping.userId === user's id
    if (slug) {
      try {
        const mapRef = dbInstance.collection('paystack-page-mappings').doc(String(slug));
        const mapSnap = await mapRef.get();
        if (mapSnap.exists) {
          const map = mapSnap.data();
          // if mapping.userId equals user doc id or equals user's email or similar, delete.
          const userIdCandidate = userDocRef.id;
          if (String(map.userId) === String(userIdCandidate) || (email && String(map.userId) === String(email))) {
            await mapRef.delete();
            console.log('Deleted paystack-page-mappings doc for slug:', slug);
          } else {
            console.log('Skipping deletion of mapping for slug (owner mismatch):', slug);
          }
        }
      } catch (e) {
        console.error('Error deleting paystack-page-mappings doc for slug:', slug, e);
      }
    }

    // 2) optional: remove pending-payments documents (if your app stores them)
    try {
      const pendingRef = dbInstance.collection('pending-payments');
      const q = await pendingRef.where('userId', '==', userDocRef.id).limit(50).get();
      if (!q.empty) {
        const batch = dbInstance.batch();
        q.docs.forEach(doc => batch.delete(doc.ref));
        await batch.commit();
        console.log('Deleted pending-payments for user:', userDocRef.id);
      }
    } catch (e) {
      // not critical
      console.error('Failed to delete pending-payments (non-fatal):', e);
    }

    // 3) log the cleanup
    try {
      await dbInstance.collection('paystack-cleanups').add({
        userRef: userDocRef.path,
        slug: slug || null,
        pageId: pageId ? String(pageId) : null,
        reference: reference || null,
        email: email || null,
        cleanedAt: admin.firestore.FieldValue.serverTimestamp(),
      });
    } catch (e) {
      console.error('Failed to log cleanup:', e);
    }
  } catch (e) {
    console.error('Unexpected error during cleanup:', e);
  }
}

// ------------------------
// Webhook endpoint (only this route uses express.raw so other routes can use express.json)
// ------------------------
app.post('/webhook/paystack', express.raw({ type: 'application/json', limit: '1mb' }), async (req, res) => {
  const raw = req.body; // Buffer
  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);
  const isPayment = isChargeSuccess;

  if (!db) {
    console.error('Firestore (admin) not initialized; webhook will not persist data.');
  }

  if (isRefund || isPayment || /subscription\.create/i.test(event) || /subscription\.update/i.test(event)) {
    console.log('--- PAYSTACK WEBHOOK (INTERESTING EVENT) ---');
    console.log('event:', event);
    // persist webhook for auditing (best-effort)
    console.log(payload);
    
    try {
      if (db) {
        await db.collection('paystack-webhooks').add({
          event,
          payload,
          receivedAt: admin.firestore.FieldValue.serverTimestamp(),
        });
      }
    } catch (err) {
      console.error('Failed to persist webhook audit:', err);
    }

    const data = payload.data || {};

    // Try to extract userId robustly (metadata/custom_fields/slug/email)
    let metadataUserId = null;
    let customerEmail = null;
    let extractorSource = null;
    let maybeSlug = null;
    let maybePageId = null;
    try {
      const extracted = await extractUserIdFromPayload(data, db);
      metadataUserId = extracted.userId || null;
      extractorSource = extracted.source || null;
      // If extractor returned an email, set as customerEmail
      if (metadataUserId && String(metadataUserId).includes('@')) {
        customerEmail = String(metadataUserId);
        metadataUserId = null;
      }
    } catch (e) {
      console.error('Error extracting userId from payload:', e);
    }

    // Also set explicit customer email if present
    if (!customerEmail && data.customer?.email) customerEmail = data.customer.email;

    // Save possible slug/pageId for cleanup/connection
    maybeSlug = data.slug || data.page?.slug || data.metadata?.slug || null;
    maybePageId = data.page?.id || data.page_id || data.metadata?.page_id || null;

    // Also try to get paystack customer id from payload (helps linking)
    const paystackCustomerId = data.customer?.id ?? data.customer?.customer_code ?? null;

    // Find user doc reference
    let userDocRef = null;
    try {
      userDocRef = await findUserDocRef(db, { metadataUserId, email: customerEmail, paystackCustomerId });
      // If still null and metadataUserId is present but looks like slug, try slug mapping as last resort
      if (!userDocRef && metadataUserId && db) {
        const mapped = await getUserIdFromSlug(db, metadataUserId);
        if (mapped) {
          userDocRef = await findUserDocRef(db, { metadataUserId: mapped, email: customerEmail, paystackCustomerId });
        }
      }
    } catch (err) {
      console.error('Error finding user doc:', err);
      userDocRef = null;
    }

    // Handler: subscription.create - store subscription id and paystack_customer_id
    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';
      const planObj = data.plan || data.subscription?.plan || null;
      const expiry = getExpiryFromPlan(planObj);
      const paystackCustomerId = data.customer?.id ?? (data.customer?.customer_code ? data.customer.customer_code : null);

      if (userDocRef && subscriptionCode) {
        try {
          const updateObj = {
            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(),
          };

          // attach paystack_customer_id if present
          if (paystackCustomerId) {
            updateObj.paystack_customer_id = String(paystackCustomerId);
          }

          await userDocRef.update(updateObj);
          console.log(`User doc updated with subscription ${subscriptionCode} and expiry ${expiry.expiresAtIso} (source: ${extractorSource})`);
        } 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
    if (isPayment) {
      const recurringMarker = Boolean((data.metadata && (data.metadata.custom_filters?.recurring || data.metadata.recurring)) || false);
      const hasSubscription = !!(data.subscription || data.subscriptions || data.plan);
      const isLikelySubscriptionPayment = recurringMarker || hasSubscription;

      const planObj = data.plan || (data.subscription ? data.subscription.plan : null) || null;
      const expiry = getExpiryFromPlan(planObj);

      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,
        expiresAtMs: expiry.expiresAtMs,
        expiresAtIso: expiry.expiresAtIso,
        createdAt: admin.firestore.FieldValue.serverTimestamp(),
      };

      if (userDocRef && isLikelySubscriptionPayment) {
        try {
          await userDocRef.update({
            entitlements: admin.firestore.FieldValue.arrayUnion(entitlement),
            updatedAt: admin.firestore.FieldValue.serverTimestamp(),
            lastPaymentAt: admin.firestore.FieldValue.serverTimestamp(),
            // Save paystack_customer_id if present and not already present
            ...(paystackCustomerId ? { paystack_customer_id: String(paystackCustomerId) } : {}),
          });
          console.log('Added entitlement to user:', entitlement.id || entitlement.reference, 'expiry:', expiry.expiresAtIso);

          // Run cleanup now that the charge is successful for this user
          try {
            await cleanUpAfterSuccessfulCharge(db, userDocRef, {
              slug: maybeSlug,
              pageId: maybePageId,
              reference: entitlement.reference || entitlement.id,
              email: customerEmail,
            });
          } catch (cleanupErr) {
            console.error('Cleanup after successful charge failed:', cleanupErr);
          }

        } catch (err) {
          console.error('Failed to add entitlement to user:', err);
        }
      } else if (userDocRef && !isLikelySubscriptionPayment) {
        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) {
      const refund = data;
      const refundedReference = refund.reference || refund.transaction?.reference || refund.transaction?.id || null;

      if (userDocRef && refundedReference) {
        try {
          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 => {
              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 });
});

// ------------------------
// Create Payment Page (link) for a plan
// ------------------------
app.post('/create-payment-link', express.json(), async (req, res) => {
  const { planId, userId, name, amount, redirect_url, collect_phone = false, fixed_amount = false } = req.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: String(userId),
    },
    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,
    });

    const pageData = response.data && response.data.data ? response.data.data : response.data;

    // Persist slug -> userId mapping so webhooks can recover missing metadata later
    try {
      const slug = pageData.slug || pageData.data?.slug || null;
      const pageId = pageData.id || pageData.data?.id || null;
      if (slug && db) {
        await db.collection('paystack-page-mappings').doc(String(slug)).set({
          userId: String(userId),
          pageId: pageId ? String(pageId) : null,
          createdAt: admin.firestore.FieldValue.serverTimestamp(),
        }, { merge: true });
        console.log('Saved page slug mapping for', slug);
      } else if (pageId && db) {
        // also ensure a record exists by pageId lookup (useful if slug missing in some responses)
        await db.collection('paystack-page-mappings').doc(String(pageId)).set({
          userId: String(userId),
          pageId: String(pageId),
          createdAt: admin.firestore.FieldValue.serverTimestamp(),
        }, { merge: true });
      }
    } catch (e) {
      console.error('Failed to persist page slug mapping:', e);
    }

    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).');
});