billing: Move most Stripe code to its own file.

We'll handle the error-handling in a separate commit, as it's still
entangled with the view function.

zilencer/lib/stripe.py

@@ -0,0 +1,63 @@
+
+import logging
+import os
+
+from django.conf import settings
+import stripe
+from stripe.error import CardError, RateLimitError, InvalidRequestError, \
+    AuthenticationError, APIConnectionError, StripeError
+
+from zerver.lib.logging_util import log_to_file
+from zerver.models import Realm, UserProfile
+from zilencer.models import Customer
+from zproject.settings import get_secret
+
+STRIPE_SECRET_KEY = get_secret('stripe_secret_key')
+STRIPE_PUBLISHABLE_KEY = get_secret('stripe_publishable_key')
+stripe.api_key = STRIPE_SECRET_KEY
+
+BILLING_LOG_PATH = os.path.join('/var/log/zulip'
+                                if not settings.DEVELOPMENT
+                                else settings.DEVELOPMENT_LOG_DIRECTORY,
+                                'billing.log')
+billing_logger = logging.getLogger('zilencer.stripe')
+log_to_file(billing_logger, BILLING_LOG_PATH)
+log_to_file(logging.getLogger('stripe'), BILLING_LOG_PATH)
+
+def count_stripe_cards(realm: Realm) -> int:
+    try:
+        customer_obj = Customer.objects.get(realm=realm)
+        cards = stripe.Customer.retrieve(customer_obj.stripe_customer_id).sources.all(object="card")
+        return len(cards["data"])
+    except Customer.DoesNotExist:
+        return 0
+
+def save_stripe_token(user: UserProfile, token: str) -> int:
+    """Returns total number of cards."""
+    # The card metadata doesn't show up in Dashboard but can be accessed
+    # using the API.
+    card_metadata = {"added_user_id": user.id, "added_user_email": user.email}
+    try:
+        customer_obj = Customer.objects.get(realm=user.realm)
+        customer = stripe.Customer.retrieve(customer_obj.stripe_customer_id)
+        billing_logger.info("Adding card on customer %s: source=%r, metadata=%r",
+                            customer_obj.stripe_customer_id, token, card_metadata)
+        card = customer.sources.create(source=token, metadata=card_metadata)
+        customer.default_source = card.id
+        customer.save()
+        return len(customer.sources.all(object="card")["data"])
+    except Customer.DoesNotExist:
+        customer_metadata = {"string_id": user.realm.string_id}
+        # Description makes it easier to identify customers in Stripe dashboard
+        description = "{} ({})".format(user.realm.name, user.realm.string_id)
+        billing_logger.info("Creating customer: source=%r, description=%r, metadata=%r",
+                            token, description, customer_metadata)
+        customer = stripe.Customer.create(source=token,
+                                          description=description,
+                                          metadata=customer_metadata)
+
+        card = customer.sources.all(object="card")["data"][0]
+        card.metadata = card_metadata
+        card.save()
+        Customer.objects.create(realm=user.realm, stripe_customer_id=customer.id)
+        return 1