Add task to resanitise and replace a PDF for precompiled letter

This adds a task which is designed to be used if we want to recreate the
PDF for a precompiled letter (either one that has been created using the
API or one that has been uploaded through the website).

The task takes the `notification_id` of the letter and passes template
preview the details it needs in order to sanitise the original file and
then replace the version in the letters-pdf bucket with the freshly
sanitised version.

app/celery/letters_pdf_tasks.py

@@ -31,6 +31,7 @@ from app.letters.utils import (
     generate_letter_pdf_filename,
     get_billable_units_for_letter_page_count,
     get_file_names_from_error_bucket,
+    get_folder_name,
     get_reference_from_filename,
     move_error_pdf_to_scan_bucket,
     move_failed_pdf,
@@ -524,3 +525,37 @@ def replay_letters_in_error(filename=None):
                     [filename],
                     queue=QueueNames.LETTERS
                 )
+
+
+@notify_celery.task(name='resanitise-pdf')
+def resanitise_pdf(notification_id):
+    """
+    `notification_id` is the notification id for a PDF letter which was either uploaded or sent using the API.
+
+    This task calls the `recreate_pdf_for_precompiled_letter` template preview task which recreates the
+    PDF for a letter which is already sanitised and in the letters-pdf bucket. The new file that is generated
+    will then overwrite the existing letter in the letters-pdf bucket.
+    """
+    notification = get_notification_by_id(notification_id)
+
+    # folder_name is the folder that the letter is in the letters-pdf bucket e.g. '2021-10-10/'
+    folder_name = get_folder_name(notification.created_at)
+
+    filename = generate_letter_pdf_filename(
+            reference=notification.reference,
+            created_at=notification.created_at,
+            ignore_folder=True,
+            postage=notification.postage
+        )
+
+    notify_celery.send_task(
+        name=TaskNames.RECREATE_PDF_FOR_PRECOMPILED_LETTER,
+        kwargs={
+            'notification_id': str(notification.id),
+            'file_location': f'{folder_name}{filename}',
+            'allow_international_letters': notification.service.has_permission(
+                INTERNATIONAL_LETTERS
+            ),
+        },
+        queue=QueueNames.SANITISE_LETTERS,
+    )

app/config.py

@@ -77,6 +77,7 @@ class TaskNames(object):
     SANITISE_LETTER = 'sanitise-and-upload-letter'
     CREATE_PDF_FOR_TEMPLATED_LETTER = 'create-pdf-for-templated-letter'
     PUBLISH_GOVUK_ALERTS = 'publish-govuk-alerts'
+    RECREATE_PDF_FOR_PRECOMPILED_LETTER = 'recreate-pdf-for-precompiled-letter'
 
 
 class Config(object):

tests/app/celery/test_letters_pdf_tasks.py

@@ -23,6 +23,7 @@ from app.celery.letters_pdf_tasks import (
     process_virus_scan_error,
     process_virus_scan_failed,
     replay_letters_in_error,
+    resanitise_pdf,
     sanitise_letter,
     send_letters_volume_email_to_dvla,
     update_billable_units_for_letter,
@@ -1098,3 +1099,33 @@ def test_replay_letters_in_error_for_one_file(notify_api, mocker):
     replay_letters_in_error("file_name")
     mock_move.assert_called_once_with('file_name')
     mock_celery.assert_called_once_with(name='scan-file', kwargs={'filename': 'file_name'}, queue='antivirus-tasks')
+
+
+@pytest.mark.parametrize('permissions, expected_international_letters_allowed', (
+    ([LETTER_TYPE], False),
+    ([LETTER_TYPE, INTERNATIONAL_LETTERS], True),
+))
+def test_resanitise_pdf_calls_template_preview_with_letter_details(
+    mocker,
+    sample_letter_notification,
+    permissions,
+    expected_international_letters_allowed,
+):
+    mock_celery = mocker.patch('app.celery.letters_pdf_tasks.notify_celery.send_task')
+
+    sample_letter_notification.created_at = datetime(2021, 2, 7, 12)
+    sample_letter_notification.service = create_service(
+        service_permissions=permissions
+    )
+
+    resanitise_pdf(sample_letter_notification.id)
+
+    mock_celery.assert_called_once_with(
+        name=TaskNames.RECREATE_PDF_FOR_PRECOMPILED_LETTER,
+        kwargs={
+            'notification_id': str(sample_letter_notification.id),
+            'file_location': '2021-02-07/NOTIFY.FOO.D.2.C.20210207120000.PDF',
+            'allow_international_letters': expected_international_letters_allowed,
+        },
+        queue=QueueNames.SANITISE_LETTERS,
+    )