feat(billing): B-2.8 Stripe webhook handler (subscription lifecycle + idempotency)
Endpoint: POST /checkout/webhooks/stripe (CSRF-exempt; signature-verified) Handles 5 Stripe events: - checkout.session.completed -> create Subscription, activate user - customer.subscription.updated -> sync status + current_period_end - customer.subscription.deleted -> mark canceled - invoice.payment_succeeded -> recover from past_due if applicable - invoice.payment_failed -> mark past_due Idempotency via WebhookEvent table (Stripe ID dedup) and Subscription unique constraint on stripe_subscription_id (defends against duplicate deliveries with distinct event IDs). User resolution prefers stripe_customer_id (server-set, anti-tamper) over event metadata.dictia_user_id over customer_email (per B-2.7 review note). New tables created via db.create_all(): - subscription (FK user.id ondelete=SET NULL for Loi 25 art. 28.1) - webhook_event (idempotency ledger) CSRF exemption wired via src/billing/exempt_webhook_csrf(csrf) called from src/app.py after billing_bp registration. Tests: 17/17 pass via tests/_run_stripe_webhook_windows.py. Existing 25 B-2.7 + 21 TOTP + 22 WebAuthn + 21 OAuth + 16 email tests unaffected. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Allison
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src/billing/webhooks.py
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320
src/billing/webhooks.py
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"""Stripe webhook handler (B-2.8) — subscription lifecycle.
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Endpoint: POST /checkout/webhooks/stripe (CSRF-exempt; signature verified)
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Handled events:
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- checkout.session.completed: create Subscription row, set User.subscription_status
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- customer.subscription.updated: update status + current_period_end
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- customer.subscription.deleted: mark status='canceled', clear User.subscription_status
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- invoice.payment_succeeded: touch updated_at (renewal confirmation)
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- invoice.payment_failed: set status='past_due'
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All other event types are acknowledged with 200 but ignored.
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Idempotency: every processed event ID is recorded in WebhookEvent.
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Duplicate deliveries return 200 immediately without re-processing.
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"""
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import logging
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import os
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from datetime import datetime, timezone
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from typing import Optional
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import stripe
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from flask import jsonify, request
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from src.billing import billing_bp
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from src.billing.plans import VALID_PERIODS, get_plan
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from src.billing.stripe_client import is_stripe_configured
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from src.database import db
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from src.models import Subscription, User, WebhookEvent
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logger = logging.getLogger(__name__)
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def get_webhook_secret() -> Optional[str]:
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"""Return STRIPE_WEBHOOK_SECRET, or None if not configured."""
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return os.environ.get('STRIPE_WEBHOOK_SECRET')
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def is_webhook_configured() -> bool:
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return bool(get_webhook_secret() and is_stripe_configured())
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def _verify_event(payload: bytes, sig_header: str):
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"""Validate Stripe signature and return the parsed event, or None on failure."""
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secret = get_webhook_secret()
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if not secret:
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logger.error('STRIPE_WEBHOOK_SECRET not set; rejecting webhook')
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return None
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try:
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return stripe.Webhook.construct_event(payload, sig_header, secret)
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except ValueError:
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logger.warning('Stripe webhook: invalid JSON payload')
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return None
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except stripe.error.SignatureVerificationError:
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logger.warning('Stripe webhook: signature verification failed')
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return None
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def _is_duplicate(event_id: str) -> bool:
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return WebhookEvent.query.filter_by(stripe_event_id=event_id).first() is not None
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def _resolve_user_for_event(event_obj: dict) -> Optional[User]:
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"""Resolve the DictIA User from a Stripe event object.
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Trust order (anti-tamper per B-2.7 review note):
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1. Look up by stripe_customer_id on the event object — this is server-set
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by Stripe at customer creation, not user-controlled.
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2. Fall back to event metadata 'dictia_user_id', re-validated against DB.
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3. Fall back to customer_email lookup (last resort, rare for subscriptions).
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"""
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cust_id = event_obj.get('customer')
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if cust_id:
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user = User.query.filter_by(stripe_customer_id=cust_id).first()
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if user:
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return user
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metadata = event_obj.get('metadata') or {}
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raw_user_id = metadata.get('dictia_user_id')
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if raw_user_id:
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try:
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uid = int(raw_user_id)
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except (TypeError, ValueError):
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uid = None
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if uid is not None:
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user = db.session.get(User, uid)
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if user:
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# Bind stripe_customer_id if missing (defensive)
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if not user.stripe_customer_id and cust_id:
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user.stripe_customer_id = cust_id
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return user
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email = event_obj.get('customer_email')
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if email:
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user = User.query.filter_by(email=email.lower().strip()).first()
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if user and cust_id and not user.stripe_customer_id:
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user.stripe_customer_id = cust_id
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return user
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return None
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def _resolve_plan_period(event_obj: dict, default_period: str = 'monthly') -> tuple:
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"""Extract plan_slug and period from event metadata, validating both."""
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metadata = event_obj.get('metadata') or {}
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plan_slug = metadata.get('dictia_plan_slug')
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period = metadata.get('dictia_period', default_period)
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if get_plan(plan_slug) is None:
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plan_slug = None # invalid / missing — leave for handler to log
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if period not in VALID_PERIODS:
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period = default_period
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return plan_slug, period
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def _ts_to_dt(ts) -> Optional[datetime]:
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if ts is None:
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return None
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try:
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return datetime.fromtimestamp(int(ts), tz=timezone.utc).replace(tzinfo=None)
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except (TypeError, ValueError, OSError):
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return None
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def _record_event(event, sub_id: Optional[str], cust_id: Optional[str]) -> None:
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"""Insert a WebhookEvent row marking this event as processed."""
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db.session.add(WebhookEvent(
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stripe_event_id=event.id,
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event_type=event.type,
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stripe_subscription_id=sub_id,
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stripe_customer_id=cust_id,
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))
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def _handle_checkout_session_completed(event) -> None:
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obj = event.data.object # stripe.checkout.Session
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user = _resolve_user_for_event(obj)
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sub_id = obj.get('subscription')
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cust_id = obj.get('customer')
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plan_slug, period = _resolve_plan_period(obj)
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if not user:
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logger.warning('checkout.session.completed: no user for cust=%s sub=%s', cust_id, sub_id)
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_record_event(event, sub_id, cust_id)
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return
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if not sub_id:
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logger.warning('checkout.session.completed: missing subscription id for user %s', user.id)
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_record_event(event, sub_id, cust_id)
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return
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if not plan_slug:
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logger.warning('checkout.session.completed: missing/invalid plan_slug metadata for sub=%s', sub_id)
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plan_slug = 'unknown'
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# Look up the existing subscription row (defensive against duplicate webhooks)
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existing = Subscription.query.filter_by(stripe_subscription_id=sub_id).first()
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now = datetime.utcnow()
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if existing:
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existing.status = 'active'
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existing.updated_at = now
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else:
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# We need current_period_end — pull it from the subscription object
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# if the event includes it; otherwise leave None and let
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# customer.subscription.updated fill it in.
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period_end = None
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# Fetch the subscription via Stripe API for accurate period_end
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try:
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from src.billing.stripe_client import _ensure_configured
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_ensure_configured()
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sub_obj = stripe.Subscription.retrieve(sub_id)
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period_end = _ts_to_dt(sub_obj.get('current_period_end'))
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except Exception as e:
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logger.warning('Could not fetch subscription %s for period_end: %s', sub_id, e)
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db.session.add(Subscription(
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user_id=user.id,
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stripe_customer_id=cust_id,
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stripe_subscription_id=sub_id,
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plan_slug=plan_slug,
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period=period,
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status='active',
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current_period_end=period_end,
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created_at=now,
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updated_at=now,
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))
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user.subscription_status = 'active'
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if cust_id and not user.stripe_customer_id:
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user.stripe_customer_id = cust_id
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_record_event(event, sub_id, cust_id)
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def _handle_subscription_updated(event) -> None:
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obj = event.data.object # stripe.Subscription
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sub_id = obj.get('id')
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cust_id = obj.get('customer')
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new_status = obj.get('status')
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period_end = _ts_to_dt(obj.get('current_period_end'))
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sub = Subscription.query.filter_by(stripe_subscription_id=sub_id).first()
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user = _resolve_user_for_event({'customer': cust_id, 'metadata': obj.get('metadata') or {}})
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now = datetime.utcnow()
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if sub:
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if new_status:
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sub.status = new_status
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if period_end:
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sub.current_period_end = period_end
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sub.updated_at = now
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else:
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# Webhook arrived before we created the row (race) — create defensively
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plan_slug, period = _resolve_plan_period(obj)
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db.session.add(Subscription(
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user_id=user.id if user else None,
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stripe_customer_id=cust_id,
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stripe_subscription_id=sub_id,
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plan_slug=plan_slug or 'unknown',
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period=period,
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status=new_status or 'unknown',
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current_period_end=period_end,
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created_at=now,
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updated_at=now,
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))
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if user and new_status:
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user.subscription_status = new_status
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_record_event(event, sub_id, cust_id)
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def _handle_subscription_deleted(event) -> None:
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obj = event.data.object
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sub_id = obj.get('id')
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cust_id = obj.get('customer')
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sub = Subscription.query.filter_by(stripe_subscription_id=sub_id).first()
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user = _resolve_user_for_event({'customer': cust_id, 'metadata': obj.get('metadata') or {}})
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now = datetime.utcnow()
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if sub:
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sub.status = 'canceled'
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sub.updated_at = now
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if user:
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user.subscription_status = 'canceled'
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_record_event(event, sub_id, cust_id)
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def _handle_invoice_payment_succeeded(event) -> None:
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obj = event.data.object # stripe.Invoice
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sub_id = obj.get('subscription')
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cust_id = obj.get('customer')
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if sub_id:
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sub = Subscription.query.filter_by(stripe_subscription_id=sub_id).first()
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if sub:
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sub.updated_at = datetime.utcnow()
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if sub.status == 'past_due':
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sub.status = 'active'
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user = _resolve_user_for_event({'customer': cust_id, 'metadata': {}})
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if user:
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user.subscription_status = 'active'
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_record_event(event, sub_id, cust_id)
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def _handle_invoice_payment_failed(event) -> None:
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obj = event.data.object
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sub_id = obj.get('subscription')
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cust_id = obj.get('customer')
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if sub_id:
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sub = Subscription.query.filter_by(stripe_subscription_id=sub_id).first()
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user = _resolve_user_for_event({'customer': cust_id, 'metadata': {}})
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if sub:
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sub.status = 'past_due'
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sub.updated_at = datetime.utcnow()
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if user:
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user.subscription_status = 'past_due'
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_record_event(event, sub_id, cust_id)
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_HANDLERS = {
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'checkout.session.completed': _handle_checkout_session_completed,
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'customer.subscription.updated': _handle_subscription_updated,
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'customer.subscription.deleted': _handle_subscription_deleted,
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'invoice.payment_succeeded': _handle_invoice_payment_succeeded,
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'invoice.payment_failed': _handle_invoice_payment_failed,
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}
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@billing_bp.route('/webhooks/stripe', methods=['POST'])
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def stripe_webhook():
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"""Stripe webhook endpoint. Signature-verified; CSRF-exempt.
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Returns 400 on signature failure (Stripe will retry); 200 otherwise
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(even for unhandled event types, to acknowledge receipt).
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"""
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payload = request.get_data()
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sig_header = request.headers.get('Stripe-Signature', '')
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event = _verify_event(payload, sig_header)
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if event is None:
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return jsonify({'error': 'invalid_signature'}), 400
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# Idempotency check
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if _is_duplicate(event.id):
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logger.info('Stripe webhook: duplicate event %s ignored', event.id)
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return jsonify({'received': True, 'duplicate': True})
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handler = _HANDLERS.get(event.type)
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if handler is None:
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# Unhandled event type — record + ack so Stripe stops retrying
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_record_event(event, None, None)
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try:
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db.session.commit()
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except Exception:
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db.session.rollback()
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return jsonify({'received': True, 'handled': False})
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try:
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handler(event)
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db.session.commit()
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except Exception as e:
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logger.exception('Stripe webhook: handler for %s failed: %s', event.type, e)
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db.session.rollback()
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# Return 500 so Stripe retries — but only for genuine handler failures,
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# not for malformed/unhandled events
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return jsonify({'error': 'handler_failed'}), 500
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return jsonify({'received': True})
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