Add DVLA callback:

* Process SNS callback, trigger the update notifications celery task
* Put autoconfirm into its own method and use in callbacks

app/notifications/notifications_letter_callback.py

@@ -1,39 +1,57 @@
-from datetime import datetime
+from functools import wraps
 
 from flask import (
     Blueprint,
     jsonify,
     request,
-    current_app,
-    json
+    current_app
 )
 
-from app import statsd_client
-from app.clients.email.aws_ses import get_aws_responses
-from app.dao import (
-    notifications_dao
-)
+from app.celery.tasks import update_letter_notifications_statuses
+from app.v2.errors import register_errors
+from app.notifications.utils import autoconfirm_subscription
+from app.schema_validation import validate
 
-from app.notifications.process_client_response import validate_callback_data
 
 letter_callback_blueprint = Blueprint('notifications_letter_callback', __name__)
-
-from app.errors import (
-    register_errors,
-    InvalidRequest
-)
-
 register_errors(letter_callback_blueprint)
 
 
+dvla_sns_callback_schema = {
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "description": "sns callback received on s3 update",
+    "type": "object",
+    "title": "dvla internal sns callback",
+    "properties": {
+        "Type": {"enum": ["Notification", "SubscriptionConfirmation"]},
+        "MessageId": {"type": "string"},
+        "Message": {"type": ["string", "object"]}
+    },
+    "required": ["Type", "MessageId", "Message"]
+}
+
+
+def validate_schema(schema):
+    def decorator(f):
+        @wraps(f)
+        def wrapper(*args, **kw):
+            validate(request.json, schema)
+            return f(*args, **kw)
+        return wrapper
+    return decorator
+
+
 @letter_callback_blueprint.route('/notifications/letter/dvla', methods=['POST'])
+@validate_schema(dvla_sns_callback_schema)
 def process_letter_response():
-    try:
-        dvla_request = json.loads(request.data)
-        current_app.logger.info(dvla_request)
-        return jsonify(
-            result="success", message="DVLA callback succeeded"
-        ), 200
-    except ValueError:
-        error = "DVLA callback failed: invalid json"
-        raise InvalidRequest(error, status_code=400)
+    req_json = request.json
+    if not autoconfirm_subscription(req_json):
+        # The callback should have one record for an S3 Put Event.
+        filename = req_json['Message']['Records'][0]['s3']['object']['key']
+        current_app.logger.info('Received file from DVLA: {}'.format(filename))
+        current_app.logger.info('DVLA callback: Calling task to update letter notifications')
+        update_letter_notifications_statuses.apply_async([filename], queue='notify')
+
+    return jsonify(
+        result="success", message="DVLA callback succeeded"
+    ), 200