Sanitise uploaded letters and store in S3

This sanitises uploaded letters and stores the sanitised result in S3
with if it passes validation or the original PDF in S3 if validation
fails. A metadata value of 'status' is set to either 'valid' or
'invalid'.

tests/app/main/views/test_uploads.py

@@ -1,4 +1,8 @@
+from unittest.mock import Mock
+
+import pytest
 from flask import url_for
+from requests import RequestException
 
 from app.utils import normalize_spaces
 from tests.conftest import SERVICE_ONE_ID
@@ -24,21 +28,26 @@ def test_get_upload_letter(client_request):
 def test_post_upload_letter_redirects_for_valid_file(mocker, client_request):
     mocker.patch('uuid.uuid4', return_value='fake-uuid')
     antivirus_mock = mocker.patch('app.main.views.uploads.antivirus_client.scan', return_value=True)
+    mocker.patch('app.main.views.uploads.sanitise_letter', return_value=Mock(content='The sanitised content'))
+    mock_s3 = mocker.patch('app.main.views.uploads.upload_letter_to_s3')
 
     with open('tests/test_pdf_files/one_page_pdf.pdf', 'rb') as file:
-        client_request.post(
+        page = client_request.post(
             'main.upload_letter',
             service_id=SERVICE_ONE_ID,
             _data={'file': file},
-            _expected_redirect=url_for(
-                'main.uploaded_letter_preview',
-                service_id=SERVICE_ONE_ID,
-                file_id='fake-uuid',
-                original_filename='tests/test_pdf_files/one_page_pdf.pdf',
-                _external=True
-            )
+            _follow_redirects=True,
         )
-        assert antivirus_mock.called
+    assert antivirus_mock.called
+
+    mock_s3.assert_called_once_with(
+        'The sanitised content',
+        'service-{}/fake-uuid.pdf'.format(SERVICE_ONE_ID),
+        'valid',
+    )
+
+    assert page.find('h1').text == 'tests/test_pdf_files/one_page_pdf.pdf'
+    assert not page.find(id='validation-error-message')
 
 
 def test_post_upload_letter_shows_error_when_file_is_not_a_pdf(client_request):
@@ -104,6 +113,57 @@ def test_post_choose_upload_file_when_file_is_malformed(mocker, client_request):
     assert normalize_spaces(page.select('.banner-dangerous')[0].text) == 'Your file must be a valid PDF'
 
 
+def test_post_upload_letter_with_invalid_file(mocker, client_request):
+    mocker.patch('uuid.uuid4', return_value='fake-uuid')
+    mocker.patch('app.main.views.uploads.antivirus_client.scan', return_value=True)
+    mock_s3 = mocker.patch('app.main.views.uploads.upload_letter_to_s3')
+
+    mock_sanitise_response = Mock()
+    mock_sanitise_response.raise_for_status.side_effect = RequestException(response=Mock(status_code=400))
+    mocker.patch('app.main.views.uploads.sanitise_letter', return_value=mock_sanitise_response)
+
+    with open('tests/test_pdf_files/one_page_pdf.pdf', 'rb') as file:
+        file_contents = file.read()
+        file.seek(0)
+
+        page = client_request.post(
+            'main.upload_letter',
+            service_id=SERVICE_ONE_ID,
+            _data={'file': file},
+            _follow_redirects=True
+        )
+
+        mock_s3.assert_called_once_with(
+            file_contents,
+            'service-{}/fake-uuid.pdf'.format(SERVICE_ONE_ID),
+            'invalid',
+        )
+
+    assert page.find('h1').text == 'tests/test_pdf_files/one_page_pdf.pdf'
+    assert normalize_spaces(
+        page.find(id='validation-error-message').text
+    ) == 'Validation failed'
+
+
+def test_post_upload_letter_does_not_upload_to_s3_if_template_preview_raises_unknown_error(mocker, client_request):
+    mocker.patch('uuid.uuid4', return_value='fake-uuid')
+    mocker.patch('app.main.views.uploads.antivirus_client.scan', return_value=True)
+    mock_s3 = mocker.patch('app.main.views.uploads.upload_letter_to_s3')
+
+    mocker.patch('app.main.views.uploads.sanitise_letter', side_effect=RequestException())
+
+    with pytest.raises(RequestException):
+        with open('tests/test_pdf_files/one_page_pdf.pdf', 'rb') as file:
+            client_request.post(
+                'main.upload_letter',
+                service_id=SERVICE_ONE_ID,
+                _data={'file': file},
+                _follow_redirects=True
+            )
+
+    assert not mock_s3.called
+
+
 def test_uploaded_letter_preview(client_request):
     page = client_request.get(
         'main.uploaded_letter_preview',