Show letter preview once file is uploaded

This shows the sanitised letter preview if the file had no validation
errors or the preview with the overlay if it failed validation.

app/main/views/uploads.py

@@ -13,16 +13,17 @@ from notifications_utils.pdf import pdf_page_count
 from PyPDF2.utils import PdfReadError
 from requests import RequestException
 
-from app import current_service
+from app import current_service, service_api_client
 from app.extensions import antivirus_client
 from app.main import main
 from app.main.forms import PDFUploadForm
 from app.s3_client.s3_letter_upload_client import (
+    get_letter_pdf_and_metadata,
     get_transient_letter_file_location,
     upload_letter_to_s3,
 )
-from app.template_previews import sanitise_letter
-from app.utils import user_has_permissions
+from app.template_previews import TemplatePreview, sanitise_letter
+from app.utils import get_template, user_has_permissions
 
 MAX_FILE_UPLOAD_SIZE = 2 * 1024 * 1024  # 2MB
 
@@ -49,7 +50,7 @@ def upload_letter(service_id):
             return invalid_upload_error('Your file must be smaller than 2MB')
 
         try:
-            pdf_page_count(BytesIO(pdf_file_bytes))
+            page_count = pdf_page_count(BytesIO(pdf_file_bytes))
         except PdfReadError:
             current_app.logger.info('Invalid PDF uploaded for service_id: {}'.format(service_id))
             return invalid_upload_error('Your file must be a valid PDF')
@@ -76,6 +77,7 @@ def upload_letter(service_id):
                 service_id=current_service.id,
                 file_id=upload_id,
                 original_filename=form.file.data.filename,
+                page_count=page_count,
                 status=status,
             )
         )
@@ -92,6 +94,39 @@ def invalid_upload_error(message):
 @user_has_permissions('send_messages')
 def uploaded_letter_preview(service_id, file_id):
     original_filename = request.args.get('original_filename')
+    page_count = request.args.get('page_count')
     status = request.args.get('status')
 
-    return render_template('views/uploads/preview.html', original_filename=original_filename, status=status)
+    template_dict = service_api_client.get_precompiled_template(service_id)
+
+    template = get_template(
+        template_dict,
+        service_id,
+        letter_preview_url=url_for(
+            '.view_letter_upload_as_preview',
+            service_id=service_id,
+            file_id=file_id
+        ),
+        page_count=page_count
+    )
+
+    return render_template(
+        'views/uploads/preview.html',
+        original_filename=original_filename,
+        template=template,
+        status=status,
+    )
+
+
+@main.route("/services/<service_id>/preview-letter-image/<file_id>")
+@user_has_permissions('send_messages')
+def view_letter_upload_as_preview(service_id, file_id):
+    file_location = get_transient_letter_file_location(service_id, file_id)
+    pdf_file, metadata = get_letter_pdf_and_metadata(file_location)
+
+    page = request.args.get('page')
+
+    if metadata['status'] == 'invalid':
+        return TemplatePreview.from_invalid_pdf_file(pdf_file, page)
+    else:
+        return TemplatePreview.from_valid_pdf_file(pdf_file, page)

app/navigation.py

@@ -314,6 +314,7 @@ class HeaderNavigation(Navigation):
         'view_jobs',
         'view_letter_notification_as_preview',
         'view_letter_template_preview',
+        'view_letter_upload_as_preview',
         'view_notification',
         'view_notification_updates',
         'view_notifications',
@@ -607,6 +608,7 @@ class MainNavigation(Navigation):
         'view_job_updates',
         'view_letter_notification_as_preview',
         'view_letter_template_preview',
+        'view_letter_upload_as_preview',
         'view_notification_updates',
         'view_notifications_csv',
         'view_provider',
@@ -887,6 +889,7 @@ class CaseworkNavigation(Navigation):
         'view_job_updates',
         'view_letter_notification_as_preview',
         'view_letter_template_preview',
+        'view_letter_upload_as_preview',
         'view_notification_updates',
         'view_notifications_csv',
         'view_provider',
@@ -1170,6 +1173,7 @@ class OrgNavigation(Navigation):
         'view_jobs',
         'view_letter_notification_as_preview',
         'view_letter_template_preview',
+        'view_letter_upload_as_preview',
         'view_notification',
         'view_notification_updates',
         'view_notifications',

app/notify_client/service_api_client.py

@@ -261,6 +261,12 @@ class ServiceAPIClient(NotifyAdminAPIClient):
         )
         return self.get(endpoint)
 
+    def get_precompiled_template(self, service_id):
+        """
+        Returns the precompiled template for a service, creating it if it doesn't already exist
+        """
+        return self.get('/service/{}/template/precompiled'.format(service_id))
+
     @cache.set('service-{service_id}-templates')
     def get_service_templates(self, service_id):
         """

app/s3_client/s3_letter_upload_client.py

@@ -1,3 +1,4 @@
+from boto3 import resource
 from flask import current_app
 from notifications_utils.s3 import s3upload as utils_s3upload
 
@@ -14,3 +15,13 @@ def upload_letter_to_s3(data, file_location, status):
         file_location=file_location,
         metadata={'status': status}
     )
+
+
+def get_letter_pdf_and_metadata(file_location):
+    s3 = resource('s3')
+    s3_object = s3.Object(current_app.config['TRANSIENT_UPLOADED_LETTERS'], file_location).get()
+
+    pdf = s3_object['Body'].read()
+    metadata = s3_object['Metadata']
+
+    return pdf, metadata

app/template_previews.py

@@ -1,5 +1,9 @@
+import base64
+from io import BytesIO
+
 import requests
 from flask import current_app, json
+from notifications_utils.pdf import extract_page_from_pdf
 
 from app import current_service
 
@@ -24,6 +28,36 @@ class TemplatePreview:
         )
         return (resp.content, resp.status_code, resp.headers.items())
 
+    @classmethod
+    def from_valid_pdf_file(cls, pdf_file, page):
+        pdf_page = extract_page_from_pdf(BytesIO(pdf_file), int(page) - 1)
+
+        response = requests.post(
+            '{}/precompiled-preview.png{}'.format(
+                current_app.config['TEMPLATE_PREVIEW_API_HOST'],
+                '?hide_notify=true' if page == '1' else ''
+            ),
+            data=base64.b64encode(pdf_page).decode('utf-8'),
+            headers={'Authorization': 'Token {}'.format(current_app.config['TEMPLATE_PREVIEW_API_KEY'])}
+        )
+
+        return (response.content, response.status_code, response.headers.items())
+
+    @classmethod
+    def from_invalid_pdf_file(cls, pdf_file, page):
+        pdf_page = extract_page_from_pdf(BytesIO(pdf_file), int(page) - 1)
+
+        response = requests.post(
+            '{}/precompiled/overlay.png{}'.format(
+                current_app.config['TEMPLATE_PREVIEW_API_HOST'],
+                '?page_number={}'.format(page)
+            ),
+            data=pdf_page,
+            headers={'Authorization': 'Token {}'.format(current_app.config['TEMPLATE_PREVIEW_API_KEY'])}
+        )
+
+        return (response.content, response.status_code, response.headers.items())
+
     @classmethod
     def from_example_template(cls, template, filename):
         data = {

app/templates/views/uploads/preview.html

@@ -16,4 +16,8 @@
       Validation failed
     </p>
     {% endif %}
+
+    <div class="letter-sent">
+      {{ template|string }}
+    </div>
 {% endblock %}