Add letter upload form which redirects to blank preview page

Added a form to upload a single letter. Currently this only uses the
form to validate that a file is submitted and that the file is a PDF. If
either of these validations fail, the form will display an error.
Otherwise, we redirect to a new preview page which just has the filename
as the heading for now.

app/main/forms.py

@@ -1109,9 +1109,9 @@ class ServiceLetterBrandingDetails(StripWhitespaceForm):
 
 class PDFUploadForm(StripWhitespaceForm):
     file = FileField_wtf(
-        'Upload a letter in PDF format to check if it fits in the printable area',
+        'Upload a letter in PDF format',
         validators=[
-            FileAllowed(['pdf'], 'PDF documents only!'),
+            FileAllowed(['pdf'], 'Letters must be saved as a PDF'),
             DataRequired(message="You need to upload a file to submit")
         ]
     )

app/main/views/uploads.py

@@ -1,6 +1,10 @@
-from flask import render_template
+import uuid
 
+from flask import redirect, render_template, request, url_for
+
+from app import current_service
 from app.main import main
+from app.main.forms import PDFUploadForm
 from app.utils import user_has_permissions
 
 
@@ -8,3 +12,31 @@ from app.utils import user_has_permissions
 @user_has_permissions('send_messages')
 def uploads(service_id):
     return render_template('views/uploads/index.html')
+
+
+@main.route("/services/<service_id>/upload-letter", methods=['GET', 'POST'])
+@user_has_permissions('send_messages')
+def upload_letter(service_id):
+    form = PDFUploadForm()
+
+    if form.validate_on_submit():
+        upload_id = uuid.uuid4()
+
+        return redirect(
+            url_for(
+                'main.uploaded_letter_preview',
+                service_id=current_service.id,
+                file_id=upload_id,
+                original_filename=form.file.data.filename,
+            )
+        )
+
+    return render_template('views/uploads/choose-file.html', form=form)
+
+
+@main.route("/services/<service_id>/preview-letter/<file_id>")
+@user_has_permissions('send_messages')
+def uploaded_letter_preview(service_id, file_id):
+    original_filename = request.args.get('original_filename')
+
+    return render_template('views/uploads/preview.html', original_filename=original_filename)

app/navigation.py

@@ -304,6 +304,8 @@ class HeaderNavigation(Navigation):
         'template_history',
         'template_usage',
         'trial_mode',
+        'upload_letter',
+        'uploaded_letter_preview',
         'uploads',
         'usage',
         'view_job',
@@ -365,6 +367,8 @@ class MainNavigation(Navigation):
             'view_template_versions',
         },
         'uploads': {
+            'upload_letter',
+            'uploaded_letter_preview',
             'uploads',
         },
         'team-members': {
@@ -859,6 +863,8 @@ class CaseworkNavigation(Navigation):
         'two_factor_email_sent',
         'update_email_branding',
         'update_letter_branding',
+        'upload_letter',
+        'uploaded_letter_preview',
         'uploads',
         'usage',
         'usage_for_all_services',
@@ -1138,6 +1144,8 @@ class OrgNavigation(Navigation):
         'two_factor_email_sent',
         'update_email_branding',
         'update_letter_branding',
+        'upload_letter',
+        'uploaded_letter_preview',
         'uploads',
         'usage',
         'usage_for_all_services',

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

@@ -0,0 +1,28 @@
+{% extends "withnav_template.html" %}
+{% from "components/file-upload.html" import file_upload %}
+{% from "components/page-header.html" import page_header %}
+
+{% block service_page_title %}
+  Upload a letter
+{% endblock %}
+
+{% block maincolumn_content %}
+<div class="grid-row">
+  <div class="column-five-sixths">
+    {{ page_header(
+        'Upload a letter',
+        back_link=url_for('main.uploads', service_id=current_service.id)
+    ) }}
+
+  <p>
+    {{ file_upload(
+      form.file,
+      action = url_for('main.upload_letter', service_id=current_service.id),
+    )}}
+  </p>
+  <p>You can upload a single letter as a PDF.</p>
+  <p>Your file must meet our <a href="https://docs.notifications.service.gov.uk/documentation/images/notify-pdf-letter-spec-v2.3.pdf">letter specification</a>.</p>
+
+  </div>
+</div>
+{% endblock %}

app/templates/views/uploads/index.html

@@ -7,10 +7,12 @@
 
 {% block maincolumn_content %}
 <div class="grid-row">
-  <div class="column-two-thirds">
+  <div class="column-five-sixths">
     {{ page_header('Uploads') }}
 
     <p>Upload a letter and Notify will print, pack and post it for you.</p>
+
+    <a href="{{ url_for('.upload_letter', service_id=current_service.id) }}" class="button-secondary">Upload a letter</a>
   </div>
 </div>
 {% endblock %}

app/templates/views/uploads/preview.html

@@ -0,0 +1,14 @@
+{% extends "withnav_template.html" %}
+{% from "components/page-header.html" import page_header %}
+
+{% block service_page_title %}
+  {{ original_filename }}
+{% endblock %}
+
+{% block maincolumn_content %}
+    {{ page_header(
+        original_filename,
+        back_link=url_for('main.upload_letter', service_id=current_service.id)
+    ) }}
+
+{% endblock %}