Implement newsletter double opt-in email flow and CSP nonce headers

apps/newsletter/services.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
 import logging
+import os
+
+import requests
 
 logger = logging.getLogger(__name__)
 
@@ -15,9 +18,26 @@ class ProviderSyncService:
 
 
 class ButtondownSyncService(ProviderSyncService):
+    endpoint = "https://api.buttondown.email/v1/subscribers"
+
     def sync(self, subscription):
-        logger.info("Synced subscription %s", subscription.email)
+        api_key = os.getenv("BUTTONDOWN_API_KEY", "")
+        if not api_key:
+            raise ProviderSyncError("BUTTONDOWN_API_KEY is not configured")
+
+        response = requests.post(
+            self.endpoint,
+            headers={"Authorization": f"Token {api_key}", "Content-Type": "application/json"},
+            json={"email": subscription.email},
+            timeout=10,
+        )
+        if response.status_code >= 400:
+            raise ProviderSyncError(f"Buttondown sync failed: {response.status_code}")
+        logger.info("Synced subscription %s to Buttondown", subscription.email)
 
 
 def get_provider_service() -> ProviderSyncService:
+    provider = os.getenv("NEWSLETTER_PROVIDER", "buttondown").lower().strip()
+    if provider != "buttondown":
+        raise ProviderSyncError(f"Unsupported newsletter provider: {provider}")
     return ButtondownSyncService()

apps/newsletter/tests/test_views.py

@@ -12,6 +12,24 @@ def test_subscribe_ok(client):
     assert NewsletterSubscription.objects.filter(email="a@example.com").exists()
 
 
+@pytest.mark.django_db
+def test_subscribe_sends_confirmation_email(client, mailoutbox):
+    resp = client.post("/newsletter/subscribe/", {"email": "new@example.com", "source": "nav"})
+    assert resp.status_code == 200
+    assert len(mailoutbox) == 1
+    assert "Confirm your No Hype AI newsletter subscription" in mailoutbox[0].subject
+
+
+@pytest.mark.django_db
+def test_duplicate_subscribe_returns_ok_without_extra_email(client, mailoutbox):
+    client.post("/newsletter/subscribe/", {"email": "dupe@example.com", "source": "nav"})
+    assert len(mailoutbox) == 1
+    resp = client.post("/newsletter/subscribe/", {"email": "dupe@example.com", "source": "footer"})
+    assert resp.status_code == 200
+    assert resp.json()["status"] == "ok"
+    assert len(mailoutbox) == 1
+
+
 @pytest.mark.django_db
 def test_subscribe_invalid(client):
     resp = client.post("/newsletter/subscribe/", {"email": "bad"})

apps/newsletter/views.py

@@ -1,8 +1,13 @@
 from __future__ import annotations
 
+import logging
+
 from django.core import signing
+from django.core.mail import EmailMultiAlternatives
 from django.http import Http404, JsonResponse
 from django.shortcuts import get_object_or_404, redirect
+from django.template.loader import render_to_string
+from django.urls import reverse
 from django.views import View
 
 from apps.newsletter.forms import SubscriptionForm
@@ -10,6 +15,27 @@ from apps.newsletter.models import NewsletterSubscription
 from apps.newsletter.services import ProviderSyncError, get_provider_service
 
 CONFIRMATION_TOKEN_MAX_AGE_SECONDS = 60 * 60 * 24 * 2
+logger = logging.getLogger(__name__)
+
+
+def confirmation_token(email: str) -> str:
+    return signing.dumps(email, salt="newsletter-confirm")
+
+
+def send_confirmation_email(request, subscription: NewsletterSubscription) -> None:
+    token = confirmation_token(subscription.email)
+    confirm_url = request.build_absolute_uri(reverse("newsletter_confirm", args=[token]))
+    context = {"confirmation_url": confirm_url, "subscription": subscription}
+    subject = render_to_string("newsletter/email/confirmation_subject.txt", context).strip()
+    text_body = render_to_string("newsletter/email/confirmation_body.txt", context)
+    html_body = render_to_string("newsletter/email/confirmation_body.html", context)
+    message = EmailMultiAlternatives(
+        subject=subject,
+        body=text_body,
+        to=[subscription.email],
+    )
+    message.attach_alternative(html_body, "text/html")
+    message.send()
 
 
 class SubscribeView(View):
@@ -20,9 +46,14 @@ class SubscribeView(View):
         if form.cleaned_data.get("honeypot"):
             return JsonResponse({"status": "ok"})
 
-        email = form.cleaned_data["email"]
+        email = form.cleaned_data["email"].lower().strip()
         source = form.cleaned_data.get("source") or "unknown"
-        NewsletterSubscription.objects.get_or_create(email=email, defaults={"source": source})
+        subscription, created = NewsletterSubscription.objects.get_or_create(
+            email=email,
+            defaults={"source": source},
+        )
+        if created and not subscription.confirmed:
+            send_confirmation_email(request, subscription)
         return JsonResponse({"status": "ok"})
 
 
@@ -42,10 +73,6 @@ class ConfirmView(View):
         service = get_provider_service()
         try:
             service.sync(subscription)
-        except ProviderSyncError:
-            pass
+        except ProviderSyncError as exc:
+            logger.exception("Newsletter provider sync failed: %s", exc)
         return redirect("/")
-
-
-def confirmation_token(email: str) -> str:
-    return signing.dumps(email, salt="newsletter-confirm")