Show personalisation in individual letters

Adds a new endpoint that works like view template/view preview of
letter, so that this page works the same way it does for emails/text
messages (ie showing the full content of the message, including
personalisation).

We’re not worrying about redaction in letters for now.

app/main/views/notifications.py

@@ -14,6 +14,7 @@ from app import (
     current_service
 )
 from app.main import main
+from app.template_previews import TemplatePreview
 from app.utils import (
     user_has_permissions,
     get_help_argument,
@@ -41,20 +42,18 @@ def get_status_arg(filter_args):
         return REQUESTED_STATUSES
 
 
-@main.route("/services/<service_id>/notification/<notification_id>")
+@main.route("/services/<service_id>/notification/<uuid:notification_id>")
 @login_required
 @user_has_permissions('view_activity', admin_override=True)
 def view_notification(service_id, notification_id):
-    notification = notification_api_client.get_notification(service_id, notification_id)
+    notification = notification_api_client.get_notification(service_id, str(notification_id))
     template = get_template(
         notification['template'],
         current_service,
         letter_preview_url=url_for(
-            '.view_template_version_preview',
+            '.view_letter_notification_as_image',
             service_id=service_id,
-            template_id=notification['template']['id'],
-            version=notification['template_version'],
-            filetype='png',
+            notification_id=notification_id,
         ),
         show_recipient=True,
         redact_missing_personalisation=True,
@@ -86,6 +85,28 @@ def view_notification(service_id, notification_id):
     )
 
 
+@main.route("/services/<service_id>/notification/<uuid:notification_id>.png")
+@login_required
+@user_has_permissions('view_activity', admin_override=True)
+def view_letter_notification_as_image(service_id, notification_id):
+
+    notification = notification_api_client.get_notification(service_id, notification_id)
+
+    template = get_template(
+        notification['template'],
+        current_service,
+        letter_preview_url=url_for(
+            '.view_letter_notification_as_image',
+            service_id=service_id,
+            notification_id=notification_id,
+        ),
+    )
+
+    template.values = notification['personalisation']
+
+    return TemplatePreview.from_utils_template(template, 'png', page=request.args.get('page'))
+
+
 @main.route("/services/<service_id>/notification/<notification_id>.json")
 @user_has_permissions('view_activity', admin_override=True)
 def view_notification_updates(service_id, notification_id):

tests/app/main/views/test_notifications.py

@@ -1,4 +1,5 @@
 from freezegun import freeze_time
+from flask import url_for
 import pytest
 
 from app.utils import (
@@ -8,6 +9,7 @@ from app.utils import (
     DELIVERED_STATUSES,
 )
 
+from notifications_utils.template import LetterImageTemplate
 from tests.conftest import mock_get_notification, SERVICE_ONE_ID, normalize_spaces
 
 
@@ -134,3 +136,28 @@ def test_notification_page_shows_status_of_letter_notification(
         'Estimated delivery date: 6 January'
     )
     assert page.select('p.notification-status') == []
+
+
+def test_should_show_image_of_letter_notification(
+    logged_in_client,
+    fake_uuid,
+    mocker
+):
+
+    mock_get_notification(mocker, fake_uuid, template_type='letter')
+
+    mocked_preview = mocker.patch(
+        'app.main.views.templates.TemplatePreview.from_utils_template',
+        return_value='foo'
+    )
+
+    response = logged_in_client.get(url_for(
+        'main.view_letter_notification_as_image',
+        service_id=SERVICE_ONE_ID,
+        notification_id=fake_uuid,
+    ))
+
+    assert response.status_code == 200
+    assert response.get_data(as_text=True) == 'foo'
+    assert isinstance(mocked_preview.call_args[0][0], LetterImageTemplate)
+    assert mocked_preview.call_args[0][1] == 'png'

tests/conftest.py

@@ -1703,6 +1703,7 @@ def mock_get_notification(
             service_id,
             '5407f4db-51c7-4150-8758-35412d42186a',
             content='hello ((name))',
+            subject='blah',
             redact_personalisation=redact_personalisation,
             type_=template_type,
         )