Continued:

- added script to check if instance aka. "domain" is valid, not blacklisted
  and not already registered
- in any of these conditions, an other status code is returned

diff --git a/check_instance.py b/check_instance.py
new file mode 100755 (executable)
index 0000000..d7711e1
--- /dev/null
+++ b/check_instance.py
@@ -0,0 +1,39 @@
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+
+# Fedi API Block - An aggregator for fetching blocking data from fediverse nodes
+# Copyright (C) 2023 Free Software Foundation
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import json
+import sys
+import validators
+from fba import *
+
+domain = sys.argv[1]
+
+if not validators.domain(domain):
+    print(f"WARNING: domain='{domain}' is not valid")
+    sys.exit(100)
+elif fba.is_blacklisted(domain):
+    print(f"WARNING: domain='{domain}' is blacklisted")
+    sys.exit(101)
+elif fba.is_instance_registered(domain):
+    print(f"WARNING: domain='{domain}' is already registered")
+    sys.exit(102)
+
+print(f"INFO: domain='{domain}' is not known")
+
+boot.shutdown()