Add a redirect for the letter specification

This way we have a URL we can give people that always points to the
latest version of the spec.

And it makes our code more Flask-idiomatic to be using `url_for` to be
generating a URL, rather than passing around a constant.

app/main/views/index.py

@@ -17,11 +17,7 @@ from app.main import main
 from app.main.forms import FieldWithNoneOption, SearchByNameForm
 from app.main.views.feedback import QUESTION_TICKET_TYPE
 from app.main.views.sub_navigation_dictionaries import features_nav, pricing_nav
-from app.utils import (
+from app.utils import get_logo_cdn_domain, user_is_logged_in
-    LETTER_SPECIFICATION_URL,
-    get_logo_cdn_domain,
-    user_is_logged_in,
-)
 
 
 @main.route('/')
@@ -273,7 +269,6 @@ def features_sms():
 def features_letters():
     return render_template(
         'views/features/letters.html',
-        letter_specification_url=LETTER_SPECIFICATION_URL,
         navigation_links=features_nav()
     )
 
@@ -348,3 +343,11 @@ def old_page_redirects():
         'main.old_integration_testing': 'main.integration_testing',
     }
     return redirect(url_for(redirects[request.endpoint]), code=301)
+
+
+@main.route('/docs/notify-pdf-letter-spec-latest.pdf')
+def letter_spec():
+    return redirect(
+        'https://docs.notifications.service.gov.uk'
+        '/documentation/images/notify-pdf-letter-spec-v2.4.pdf'
+    )

app/main/views/uploads.py

@@ -33,7 +33,6 @@ from app.s3_client.s3_letter_upload_client import (
 )
 from app.template_previews import TemplatePreview, sanitise_letter
 from app.utils import (
-    LETTER_SPECIFICATION_URL,
     generate_next_dict,
     generate_previous_dict,
     get_letter_validation_error,
@@ -66,7 +65,6 @@ def uploads(service_id):
         prev_page=prev_page,
         next_page=next_page,
         scheduled_jobs='',
-        letter_specification_url=LETTER_SPECIFICATION_URL,
     )
 
 

app/navigation.py

@@ -208,6 +208,7 @@ class HeaderNavigation(Navigation):
         'invite_org_user',
         'invite_user',
         'no_cookie.letter_branding_preview_image',
+        'letter_spec',
         'letter_template',
         'link_service_to_organisation',
         'manage_org_users',
@@ -533,6 +534,7 @@ class MainNavigation(Navigation):
         'no_cookie.letter_branding_preview_image',
         'live_services',
         'live_services_csv',
+        'letter_spec',
         'letter_template',
         'message_status',
         'manage_org_users',
@@ -763,6 +765,7 @@ class CaseworkNavigation(Navigation):
         'invite_user',
         'no_cookie.letter_branding_preview_image',
         'letter_branding',
+        'letter_spec',
         'letter_template',
         'link_service_to_organisation',
         'live_services',
@@ -1049,6 +1052,7 @@ class OrgNavigation(Navigation):
         'invite_user',
         'letter_branding',
         'no_cookie.letter_branding_preview_image',
+        'letter_spec',
         'letter_template',
         'link_service_to_organisation',
         'live_services',

app/templates/views/features/letters.html

@@ -33,7 +33,7 @@
 
   <h3 class="heading heading-small" id="upload-letters">Upload your own letters</h3>
   <p>You can create reusable letter templates in Notify, or upload and send your own letters with the Notify API.</p>
-  <p>Use the <a href="{{ letter_specification_url }}">letter specification document</a> to help you set up your letter, save it as a PDF, then upload it to Notify.<p>
+  <p>Use the <a href="{{ url_for('.letter_spec') }}">letter specification document</a> to help you set up your letter, save it as a PDF, then upload it to Notify.<p>
   <p>Read our <a href="{{ url_for('.documentation') }}">API documentation</a> for more information.</p>
 
   <h2 class="heading heading-medium">Pricing</h2>

app/templates/views/uploads/choose-file.html

@@ -33,7 +33,7 @@
     )}}
   </p>
   <p>You can upload a single letter as a PDF.</p>
-  <p>Your file must meet our <a href="{{ letter_specification_url }}">letter specification</a>.</p>
+  <p>Your file must meet our <a href="{{ url_for('.letter_spec') }}">letter specification</a>.</p>
   <p>To help you set up your letter you can download a <a href="https://docs.notifications.service.gov.uk/documentation/images/notify-pdf-letter-word-template-v1.0.docx">Word document template</a>.</p>
 
   </div>

app/utils.py

@@ -566,33 +566,27 @@ def get_letter_printing_statement(status, created_at):
         return 'Printed on {} at 5:30pm'.format(printed_date)
 
 
-LETTER_SPECIFICATION_URL = (
-    'https://docs.notifications.service.gov.uk'
-    '/documentation/images/notify-pdf-letter-spec-v2.4.pdf'
-)
-
-
 LETTER_VALIDATION_MESSAGES = {
     'letter-not-a4-portrait-oriented': {
         'title': 'Your letter is not A4 portrait size',
         'detail': (
             'You need to change the size or orientation of {invalid_pages}. <br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
         'summary': (
             'Validation failed because {invalid_pages} {invalid_pages_are_or_is} not A4 portrait size.<br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
     },
     'content-outside-printable-area': {
         'title': 'Your content is outside the printable area',
         'detail': (
             'You need to edit {invalid_pages}.<br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
         'summary': (
             'Validation failed because content is outside the printable area on {invalid_pages}.<br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
     },
     'letter-too-long': {
@@ -624,11 +618,11 @@ LETTER_VALIDATION_MESSAGES = {
         'title': 'The address block is empty',
         'detail': (
             'You need to add a recipient address.<br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
         'summary': (
             'Validation failed because the address block is empty.<br>'
-            f'Files must meet our <a href="{LETTER_SPECIFICATION_URL}" target="_blank">letter specification</a>.'
+            'Files must meet our <a href="{letter_spec}" target="_blank">letter specification</a>.'
         ),
     }
 }
@@ -654,11 +648,13 @@ def get_letter_validation_error(validation_message, invalid_pages=None, page_cou
             invalid_pages=invalid_pages,
             invalid_pages_are_or_is=invalid_pages_are_or_is,
             page_count=page_count,
+            letter_spec=url_for('.letter_spec'),
         ),
         'summary': LETTER_VALIDATION_MESSAGES[validation_message]['summary'].format(
             invalid_pages=invalid_pages,
             invalid_pages_are_or_is=invalid_pages_are_or_is,
             page_count=page_count,
+            letter_spec=url_for('.letter_spec'),
         ),
     }
 

tests/app/main/views/test_index.py

@@ -254,3 +254,21 @@ def test_letter_template_preview_headers(
     )
 
     assert response.headers.get('X-Frame-Options') == 'SAMEORIGIN'
+
+
+def test_letter_spec_redirect(client_request):
+    expected_url = (
+        'https://docs.notifications.service.gov.uk'
+        '/documentation/images/notify-pdf-letter-spec-v2.4.pdf'
+    )
+    client_request.get(
+        'main.letter_spec',
+        _expected_status=302,
+        _expected_redirect=expected_url,
+    )
+    client_request.logout()
+    client_request.get(
+        'main.letter_spec',
+        _expected_status=302,
+        _expected_redirect=expected_url,
+    )

tests/app/test_utils.py

@@ -5,6 +5,7 @@ from pathlib import Path
 
 import pytest
 from bs4 import BeautifulSoup
+from flask import url_for
 from freezegun import freeze_time
 
 from app import format_datetime_relative
@@ -454,15 +455,12 @@ def test_get_letter_validation_error_for_unknown_error():
     ),
 ])
 def test_get_letter_validation_error_for_known_errors(
+    client_request,
     error_message,
     expected_title,
     expected_content,
     expected_summary,
 ):
-    expected_letter_spec_url = (
-        'https://docs.notifications.service.gov.uk/'
-        'documentation/images/notify-pdf-letter-spec-v2.4.pdf'
-    )
     error = get_letter_validation_error(error_message, invalid_pages=[2], page_count=13)
     detail = BeautifulSoup(error['detail'], 'html.parser')
     summary = BeautifulSoup(error['summary'], 'html.parser')
@@ -471,10 +469,10 @@ def test_get_letter_validation_error_for_known_errors(
 
     assert detail.text == expected_content
     if detail.select_one('a'):
-        assert detail.select_one('a')['href'] == expected_letter_spec_url
+        assert detail.select_one('a')['href'] == url_for('.letter_spec')
         assert detail.select_one('a')['target'] == '_blank'
 
     assert summary.text == expected_summary
     if summary.select_one('a'):
-        assert summary.select_one('a')['href'] == expected_letter_spec_url
+        assert summary.select_one('a')['href'] == url_for('.letter_spec')
         assert summary.select_one('a')['target'] == '_blank'