Implement a basic user session management (#104)

This patch introduces a basic user session management that relies on the
/etc/machine-id and the effective user id

command_line_assistant/daemon/session.py

@@ -0,0 +1,71 @@
+"""Session management module for the daemon."""
+
+import logging
+import uuid
+from pathlib import Path
+from typing import Optional
+
+#: Path to the machine ID file
+MACHINE_ID_PATH: Path = Path("/etc/machine-id")
+
+logger = logging.getLogger(__name__)
+
+
+class UserSessionManager:
+    """Manage user session information."""
+
+    def __init__(self, effective_user: str) -> None:
+        """Initialize the session manager.
+
+        Args:
+            effective_user (str): The effective user id
+        """
+        self._machine_uuid: Optional[uuid.UUID] = None
+        self._effective_user: str = effective_user
+        self._session_uuid: Optional[uuid.UUID] = None
+
+    @property
+    def machine_id(self) -> uuid.UUID:
+        """Property that holds the machine UUID.
+
+        Reference:
+            https://www.freedesktop.org/software/systemd/man/latest/machine-id.html
+
+        Raises:
+            FileNotFoundError: If the machine-id file doesn't exist
+            ValueError: If the machine-id file is empty or malformed
+
+        Returns:
+            uuid.UUID: The UUID generated from machine-id
+        """
+        if not self._machine_uuid:
+            try:
+                machine_id = MACHINE_ID_PATH.read_text().strip()
+                if not machine_id:
+                    logger.error("Machine ID file is empty")
+                    raise ValueError(f"Machine ID at {MACHINE_ID_PATH} is empty")
+                # Create a UUID from the machine-id string
+                self._machine_uuid = uuid.UUID(machine_id)
+            except FileNotFoundError as e:
+                logger.error("Machine ID file not found at %s", MACHINE_ID_PATH)
+                raise FileNotFoundError(
+                    f"Machine ID file not found at {MACHINE_ID_PATH}"
+                ) from e
+
+        return self._machine_uuid
+
+    @property
+    def session_id(self) -> uuid.UUID:
+        """Property that generates a unique session ID combining machine and user effective id.
+
+        Returns:
+            uuid.UUID: A unique session identifier
+        """
+        if not self._session_uuid:
+            # Combine machine ID and effective user to create a unique namespace
+            namespace = self.machine_id
+
+            # Generate a UUID using the effective username as name in the namespace
+            self._session_uuid = uuid.uuid5(namespace, self._effective_user)
+
+        return self._session_uuid

docs/source/daemon/clad.rst

@@ -1,7 +1,7 @@
-Command Line Assistant Daemon
-=============================
+Session
+=======
 
-.. automodule:: command_line_assistant.daemon.clad
+.. automodule:: command_line_assistant.daemon.session
    :members:
    :undoc-members:
    :private-members:

docs/source/daemon/session.rst

@@ -0,0 +1,8 @@
+Command Line Assistant Daemon
+=============================
+
+.. automodule:: command_line_assistant.daemon.clad
+   :members:
+   :undoc-members:
+   :private-members:
+   :no-index:

tests/daemon/test_session.py

@@ -0,0 +1,96 @@
+import uuid
+from unittest.mock import patch
+
+import pytest
+
+from command_line_assistant.daemon.session import UserSessionManager
+
+
+def test_initialize_user_session_manager():
+    session = UserSessionManager("1000")
+    assert session._effective_user == "1000"
+    assert not session._machine_uuid
+    assert not session._session_uuid
+
+
+def test_read_machine_id(tmp_path):
+    machine_id = tmp_path / "machine-id"
+    machine_id.write_text("09e28913cb074ed995a239c93b07fd8a")
+    with patch("command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id):
+        session = UserSessionManager("1000")
+        assert session.machine_id == uuid.UUID("09e28913cb074ed995a239c93b07fd8a")
+
+
+def test_generate_session_id(tmp_path):
+    machine_id = tmp_path / "machine-id"
+    machine_id.write_text("09e28913cb074ed995a239c93b07fd8a")
+    with patch("command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id):
+        session = UserSessionManager("1000")
+        assert session.session_id == uuid.UUID("4d465f1c-0507-5dfa-9ea0-e2de1a9e90a5")
+
+
+def test_generate_session_id_twice(tmp_path):
+    """This verifies that the session ID is generated only once."""
+    machine_id = tmp_path / "machine-id"
+    machine_id.write_text("09e28913cb074ed995a239c93b07fd8a")
+    with patch("command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id):
+        session = UserSessionManager("1000")
+        assert session.session_id == uuid.UUID("4d465f1c-0507-5dfa-9ea0-e2de1a9e90a5")
+
+        session = UserSessionManager("1000")
+        assert session.session_id == uuid.UUID("4d465f1c-0507-5dfa-9ea0-e2de1a9e90a5")
+
+
+@pytest.mark.parametrize(
+    ("machine_id", "effective_user_id", "expected"),
+    (
+        (
+            "09e28913cb074ed995a239c93b07fd8a",
+            "1000",
+            "4d465f1c-0507-5dfa-9ea0-e2de1a9e90a5",
+        ),
+        # Different user on the same machine.
+        (
+            "09e28913cb074ed995a239c93b07fd8a",
+            "1001",
+            "9f522470-d57d-55e2-8f74-b90b19830e9d",
+        ),
+        # Same effective user id, but in a different machine
+        (
+            "771640198a6344bba7ad356cf525243a",
+            "1000",
+            "b4e5eb85-c750-5130-bd72-851e531e73c3",
+        ),
+    ),
+)
+def test_generate_session_id_different_users(
+    tmp_path, machine_id, effective_user_id, expected
+):
+    machine_id_file = tmp_path / "machine-id"
+    machine_id_file.write_text(machine_id)
+    with patch(
+        "command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id_file
+    ):
+        session = UserSessionManager(effective_user_id)
+        assert session.session_id == uuid.UUID(expected)
+
+
+def test_empty_machine_id_file(tmp_path):
+    machine_id_file = tmp_path / "machine-id"
+    machine_id_file.write_text("")
+    with patch(
+        "command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id_file
+    ):
+        session = UserSessionManager("1000")
+        with pytest.raises(ValueError, match="Machine ID at .* is empty"):
+            assert session.machine_id
+
+
+def test_machine_id_file_not_found(tmp_path):
+    machine_id_file = tmp_path / "test" / "machine-id"
+    with patch(
+        "command_line_assistant.daemon.session.MACHINE_ID_PATH", machine_id_file
+    ):
+        session = UserSessionManager("1000")
+        with pytest.raises(FileNotFoundError, match="Machine ID file not found at .*"):
+            assert session.machine_id