Revert "Letter preview use api not template preview"

app/main/views/notifications.py

@@ -1,6 +1,4 @@
 # -*- coding: utf-8 -*-
-import base64
-import os
 from datetime import datetime
 
 from flask import (
@@ -13,7 +11,6 @@ from flask import (
     url_for,
 )
 from flask_login import login_required
-from notifications_python_client.errors import APIError
 
 from app import (
     current_service,
@@ -22,7 +19,7 @@ from app import (
     notification_api_client,
 )
 from app.main import main
-from app.template_previews import get_page_count_for_letter
+from app.template_previews import TemplatePreview, get_page_count_for_letter
 from app.utils import (
     DELIVERED_STATUSES,
     FAILURE_STATUSES,
@@ -86,12 +83,6 @@ def view_notification(service_id, notification_id):
     )
 
 
-def get_preview_error_image():
-    path = os.path.join(os.path.dirname(__file__), "..", "..", "assets", "images", "preview_error.png")
-    with open(path, "rb") as file:
-        return file.read()
-
-
 @main.route("/services/<service_id>/notification/<uuid:notification_id>.<filetype>")
 @login_required
 @user_has_permissions('view_activity')
@@ -100,19 +91,23 @@ def view_letter_notification_as_preview(service_id, notification_id, filetype):
     if filetype not in ('pdf', 'png'):
         abort(404)
 
-    try:
-        preview = notification_api_client.get_notification_letter_preview(
-            service_id,
-            notification_id,
-            filetype,
-            page=request.args.get('page')
-        )
+    notification = notification_api_client.get_notification(service_id, notification_id)
+    notification['template'].update({'reply_to_text': notification['reply_to_text']})
 
-        display_file = base64.b64decode(preview['content'])
-    except APIError:
-        display_file = get_preview_error_image()
+    template = get_template(
+        notification['template'],
+        current_service,
+        letter_preview_url=url_for(
+            '.view_letter_notification_as_preview',
+            service_id=service_id,
+            notification_id=notification_id,
+            filetype='png',
+        ),
+    )
 
-    return display_file
+    template.values = notification['personalisation']
+
+    return TemplatePreview.from_utils_template(template, filetype, page=request.args.get('page'))
 
 
 @main.route("/services/<service_id>/notification/<notification_id>.json")