--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/frontends/tools/jid.py	Fri Jun 02 14:12:38 2023 +0200
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+
+# Libervia XMPP
+# Copyright (C) 2009-2023 Jérôme Poisson (goffi@goffi.org)
+
+# 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 <http://www.gnu.org/licenses/>.
+
+from typing import Optional, Tuple
+
+
+class JID(str):
+    """This class helps manage JID (<local>@<domain>/<resource>)"""
+
+    def __new__(cls, jid_str: str) -> "JID":
+        return str.__new__(cls, cls._normalize(jid_str))
+
+    def __init__(self, jid_str: str):
+        self._node, self._domain, self._resource = self._parse()
+
+    @staticmethod
+    def _normalize(jid_str: str) -> str:
+        """Naive normalization before instantiating and parsing the JID"""
+        if not jid_str:
+            return jid_str
+        tokens = jid_str.split("/")
+        tokens[0] = tokens[0].lower()  # force node and domain to lower-case
+        return "/".join(tokens)
+
+    def _parse(self) -> Tuple[Optional[str], str, Optional[str]]:
+        """Find node, domain, and resource from JID"""
+        node_end = self.find("@")
+        if node_end < 0:
+            node_end = 0
+        domain_end = self.find("/")
+        if domain_end == 0:
+            raise ValueError("a jid can't start with '/'")
+        if domain_end == -1:
+            domain_end = len(self)
+        node = self[:node_end] or None
+        domain = self[(node_end + 1) if node_end else 0 : domain_end]
+        resource = self[domain_end + 1 :] or None
+        return node, domain, resource
+
+    @property
+    def node(self) -> Optional[str]:
+        return self._node
+
+    @property
+    def local(self) -> Optional[str]:
+        return self._node
+
+    @property
+    def domain(self) -> str:
+        return self._domain
+
+    @property
+    def resource(self) -> Optional[str]:
+        return self._resource
+
+    @property
+    def bare(self) -> "JID":
+        if not self.node:
+            return JID(self.domain)
+        return JID(f"{self.node}@{self.domain}")
+
+    def change_resource(self, resource: str) -> "JID":
+        """Build a new JID with the same node and domain but a different resource.
+
+        @param resource: The new resource for the JID.
+        @return: A new JID instance with the updated resource.
+        """
+        return JID(f"{self.bare}/{resource}")
+
+    def is_valid(self) -> bool:
+        """
+        @return: True if the JID is XMPP compliant
+        """
+        # Simple check for domain part
+        if not self.domain or self.domain.startswith(".") or self.domain.endswith("."):
+            return False
+        if ".." in self.domain:
+            return False
+        return True
+
+
+def new_resource(entity: JID, resource: str) -> JID:
+    """Build a new JID from the given entity and resource.
+
+    @param entity: original JID
+    @param resource: new resource
+    @return: a new JID instance
+    """
+    return entity.change_resource(resource)