From 70d541690f75e263806fa1c548b15c5e0a49a117 Mon Sep 17 00:00:00 2001
From: Patrick Jentsch <p.jentsch@uni-bielefeld.de>
Date: Mon, 15 Nov 2021 14:36:18 +0100
Subject: [PATCH] Add 503 error handler

---
 app/errors/handlers.py           | 10 ++++++++++
 app/templates/errors/503.html.j2 | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 app/templates/errors/503.html.j2

diff --git a/app/errors/handlers.py b/app/errors/handlers.py
index afbc543a..a5e49f90 100644
--- a/app/errors/handlers.py
+++ b/app/errors/handlers.py
@@ -40,3 +40,13 @@ def internal_server_error(e):
         response.status_code = 500
         return response
     return render_template('errors/500.html.j2', title='Internal Server Error'), 500
+
+
+@bp.app_errorhandler(503)
+def service_unavailable_error(e):
+    if (request.accept_mimetypes.accept_json
+            and not request.accept_mimetypes.accept_html):
+        response = jsonify({'error': 'service unavailable'})
+        response.status_code = 503
+        return response
+    return render_template('errors/503.html.j2', title='Service Unavailable'), 503
diff --git a/app/templates/errors/503.html.j2 b/app/templates/errors/503.html.j2
new file mode 100644
index 00000000..eb10cfb0
--- /dev/null
+++ b/app/templates/errors/503.html.j2
@@ -0,0 +1,19 @@
+{% extends "base.html.j2" %}
+
+{% block page_content %}
+<div class="container">
+  <h1 id="title">{{ title }}</h1>
+  <p class="light">{{ request.path }}</p>
+  <p>Alternatively, you can visit the <a href="{{ url_for('main.index') }}">Main Page</a> or read <a class="modal-trigger" href="#more-information-modal">more information</a> about this type of error.</p>
+</div>
+
+<div class="modal" id="more-information-modal">
+  <div class="modal-content">
+    <h2>About the "{{ title }}" error</h2>
+    <p>The server cannot handle the request (because it is overloaded or down for maintenance). Generally, this is a temporary state.</p>
+  </div>
+  <div class="modal-footer">
+    <a href="#!" class="btn-flat modal-close waves-effect waves-green">Close</a>
+  </div>
+</div>
+{% endblock page_content %}