feat: i18n — Locale-basierte Strings (DE/EN) statt hardcoded Deutsch

Liest LANG aus Umgebung oder /etc/locale.conf und liefert deutsche
oder englische UI-Strings. Alle hardcoded Strings in greeter.py
durch Strings-Dataclass ersetzt. Fallback auf Englisch bei
unbekannter Locale.

src/moongreet/greeter.py

@@ -15,6 +15,7 @@ gi.require_version("Gdk", "4.0")
 from gi.repository import Gtk, Gdk, GLib, GdkPixbuf
 
 from moongreet.config import load_config
+from moongreet.i18n import load_strings, Strings
 from moongreet.ipc import create_session, post_auth_response, start_session, cancel_session
 from moongreet.users import User, get_users, get_avatar_path, get_user_gtk_theme
 from moongreet.sessions import Session, get_sessions
@@ -27,13 +28,15 @@ DEFAULT_AVATAR_PATH = PACKAGE_DATA / "default-avatar.svg"
 AVATAR_SIZE = 128
 
 
-def faillock_warning(attempt_count: int) -> str | None:
+def faillock_warning(attempt_count: int, strings: Strings | None = None) -> str | None:
     """Return a warning if the user is approaching or has reached the faillock limit."""
+    if strings is None:
+        strings = load_strings()
     remaining = FAILLOCK_MAX_ATTEMPTS - attempt_count
     if remaining <= 0:
-        return "Konto ist möglicherweise gesperrt"
+        return strings.faillock_locked
     if remaining == 1:
-        return f"Noch {remaining} Versuch vor Kontosperrung!"
+        return strings.faillock_attempts_remaining.format(n=remaining)
     return None
 
 
@@ -46,6 +49,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
         self.set_default_size(1920, 1080)
 
         self._config = load_config()
+        self._strings = load_strings()
         self._users = get_users()
         self._sessions = get_sessions()
         self._selected_user: User | None = None
@@ -140,7 +144,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
         # Password entry
         self._password_entry = Gtk.PasswordEntry()
         self._password_entry.set_hexpand(True)
-        self._password_entry.set_property("placeholder-text", "Passwort")
+        self._password_entry.set_property("placeholder-text", self._strings.password_placeholder)
         self._password_entry.set_property("show-peek-icon", True)
         self._password_entry.add_css_class("password-entry")
         self._password_entry.connect("activate", self._on_login_activate)
@@ -190,14 +194,14 @@ class GreeterWindow(Gtk.ApplicationWindow):
         reboot_btn = Gtk.Button()
         reboot_btn.set_icon_name("system-reboot-symbolic")
         reboot_btn.add_css_class("power-button")
-        reboot_btn.set_tooltip_text("Neustart")
+        reboot_btn.set_tooltip_text(self._strings.reboot_tooltip)
         reboot_btn.connect("clicked", self._on_reboot_clicked)
         power_box.append(reboot_btn)
 
         shutdown_btn = Gtk.Button()
         shutdown_btn.set_icon_name("system-shutdown-symbolic")
         shutdown_btn.add_css_class("power-button")
-        shutdown_btn.set_tooltip_text("Herunterfahren")
+        shutdown_btn.set_tooltip_text(self._strings.shutdown_tooltip)
         shutdown_btn.connect("clicked", self._on_shutdown_clicked)
         power_box.append(shutdown_btn)
 
@@ -341,7 +345,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
         password = entry.get_text()
         session = self._get_selected_session()
         if not session:
-            self._show_error("Keine Session ausgewählt")
+            self._show_error(self._strings.no_session_selected)
             return
 
         self._attempt_login(self._selected_user, password, session)
@@ -350,15 +354,15 @@ class GreeterWindow(Gtk.ApplicationWindow):
         """Validate that GREETD_SOCK points to an absolute path and a real socket."""
         path = Path(sock_path)
         if not path.is_absolute():
-            self._show_error("GREETD_SOCK ist kein absoluter Pfad")
+            self._show_error(self._strings.greetd_sock_not_absolute)
             return False
         try:
             mode = path.stat().st_mode
             if not stat.S_ISSOCK(mode):
-                self._show_error("GREETD_SOCK zeigt nicht auf einen Socket")
+                self._show_error(self._strings.greetd_sock_not_socket)
                 return False
         except OSError:
-            self._show_error("GREETD_SOCK nicht erreichbar")
+            self._show_error(self._strings.greetd_sock_unreachable)
             return False
         return True
 
@@ -375,7 +379,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
         """Attempt to authenticate and start a session via greetd IPC."""
         sock_path = os.environ.get("GREETD_SOCK")
         if not sock_path:
-            self._show_error("GREETD_SOCK nicht gesetzt")
+            self._show_error(self._strings.greetd_sock_not_set)
             return
 
         if not self._validate_greetd_sock(sock_path):
@@ -391,7 +395,7 @@ class GreeterWindow(Gtk.ApplicationWindow):
             response = create_session(sock, user.username)
 
             if response.get("type") == "error":
-                self._show_greetd_error(response, "Authentifizierung fehlgeschlagen")
+                self._show_greetd_error(response, self._strings.auth_failed)
                 self._close_greetd_sock()
                 return
 
@@ -401,8 +405,8 @@ class GreeterWindow(Gtk.ApplicationWindow):
 
                 if response.get("type") == "error":
                     self._failed_attempts[user.username] = self._failed_attempts.get(user.username, 0) + 1
-                    self._show_greetd_error(response, "Falsches Passwort")
-                    warning = faillock_warning(self._failed_attempts[user.username])
+                    self._show_greetd_error(response, self._strings.wrong_password)
+                    warning = faillock_warning(self._failed_attempts[user.username], self._strings)
                     if warning:
                         current = self._error_label.get_text()
                         self._error_label.set_text(f"{current}\n{warning}")
@@ -413,14 +417,14 @@ class GreeterWindow(Gtk.ApplicationWindow):
                     # Multi-stage auth (e.g. TOTP) is not supported
                     cancel_session(sock)
                     self._close_greetd_sock()
-                    self._show_error("Mehrstufige Authentifizierung wird nicht unterstützt")
+                    self._show_error(self._strings.multi_stage_unsupported)
                     return
 
             # Step 3: Start session
             if response.get("type") == "success":
                 cmd = shlex.split(session.exec_cmd)
                 if not cmd or not Path(cmd[0]).is_absolute():
-                    self._show_error("Ungültiger Session-Befehl")
+                    self._show_error(self._strings.invalid_session_command)
                     cancel_session(sock)
                     self._close_greetd_sock()
                     return
@@ -432,16 +436,16 @@ class GreeterWindow(Gtk.ApplicationWindow):
                     self.get_application().quit()
                     return
                 else:
-                    self._show_greetd_error(response, "Session konnte nicht gestartet werden")
+                    self._show_greetd_error(response, self._strings.session_start_failed)
 
             self._close_greetd_sock()
 
         except ConnectionError as e:
             self._close_greetd_sock()
-            self._show_error(f"Verbindungsfehler: {e}")
+            self._show_error(self._strings.connection_error.format(error=e))
         except OSError as e:
             self._close_greetd_sock()
-            self._show_error(f"Socket-Fehler: {e}")
+            self._show_error(self._strings.socket_error.format(error=e))
 
     def _cancel_pending_session(self) -> None:
         """Cancel any in-progress greetd session."""
@@ -483,14 +487,14 @@ class GreeterWindow(Gtk.ApplicationWindow):
         try:
             reboot()
         except subprocess.CalledProcessError:
-            self._show_error("Neustart fehlgeschlagen")
+            self._show_error(self._strings.reboot_failed)
 
     def _on_shutdown_clicked(self, button: Gtk.Button) -> None:
         """Handle shutdown button click."""
         try:
             shutdown()
         except subprocess.CalledProcessError:
-            self._show_error("Herunterfahren fehlgeschlagen")
+            self._show_error(self._strings.shutdown_failed)
 
     @staticmethod
     def _load_last_user() -> str | None:

src/moongreet/i18n.py

@@ -0,0 +1,113 @@
+# ABOUTME: Locale detection and string lookup for the greeter UI.
+# ABOUTME: Reads system locale (LANG or /etc/locale.conf) and provides DE or EN strings.
+
+import os
+from dataclasses import dataclass
+from pathlib import Path
+
+DEFAULT_LOCALE_CONF = Path("/etc/locale.conf")
+
+
+@dataclass(frozen=True)
+class Strings:
+    """All user-visible strings for the greeter UI."""
+
+    # UI labels
+    password_placeholder: str
+    reboot_tooltip: str
+    shutdown_tooltip: str
+
+    # Error messages
+    no_session_selected: str
+    greetd_sock_not_set: str
+    greetd_sock_not_absolute: str
+    greetd_sock_not_socket: str
+    greetd_sock_unreachable: str
+    auth_failed: str
+    wrong_password: str
+    multi_stage_unsupported: str
+    invalid_session_command: str
+    session_start_failed: str
+    reboot_failed: str
+    shutdown_failed: str
+
+    # Templates (use .format())
+    connection_error: str
+    socket_error: str
+    faillock_attempts_remaining: str
+    faillock_locked: str
+
+
+_STRINGS_DE = Strings(
+    password_placeholder="Passwort",
+    reboot_tooltip="Neustart",
+    shutdown_tooltip="Herunterfahren",
+    no_session_selected="Keine Session ausgewählt",
+    greetd_sock_not_set="GREETD_SOCK nicht gesetzt",
+    greetd_sock_not_absolute="GREETD_SOCK ist kein absoluter Pfad",
+    greetd_sock_not_socket="GREETD_SOCK zeigt nicht auf einen Socket",
+    greetd_sock_unreachable="GREETD_SOCK nicht erreichbar",
+    auth_failed="Authentifizierung fehlgeschlagen",
+    wrong_password="Falsches Passwort",
+    multi_stage_unsupported="Mehrstufige Authentifizierung wird nicht unterstützt",
+    invalid_session_command="Ungültiger Session-Befehl",
+    session_start_failed="Session konnte nicht gestartet werden",
+    reboot_failed="Neustart fehlgeschlagen",
+    shutdown_failed="Herunterfahren fehlgeschlagen",
+    connection_error="Verbindungsfehler: {error}",
+    socket_error="Socket-Fehler: {error}",
+    faillock_attempts_remaining="Noch {n} Versuch(e) vor Kontosperrung!",
+    faillock_locked="Konto ist möglicherweise gesperrt",
+)
+
+_STRINGS_EN = Strings(
+    password_placeholder="Password",
+    reboot_tooltip="Reboot",
+    shutdown_tooltip="Shut down",
+    no_session_selected="No session selected",
+    greetd_sock_not_set="GREETD_SOCK not set",
+    greetd_sock_not_absolute="GREETD_SOCK is not an absolute path",
+    greetd_sock_not_socket="GREETD_SOCK does not point to a socket",
+    greetd_sock_unreachable="GREETD_SOCK unreachable",
+    auth_failed="Authentication failed",
+    wrong_password="Wrong password",
+    multi_stage_unsupported="Multi-stage authentication is not supported",
+    invalid_session_command="Invalid session command",
+    session_start_failed="Failed to start session",
+    reboot_failed="Reboot failed",
+    shutdown_failed="Shutdown failed",
+    connection_error="Connection error: {error}",
+    socket_error="Socket error: {error}",
+    faillock_attempts_remaining="{n} attempt(s) remaining before lockout!",
+    faillock_locked="Account may be locked",
+)
+
+_LOCALE_MAP: dict[str, Strings] = {
+    "de": _STRINGS_DE,
+    "en": _STRINGS_EN,
+}
+
+
+def detect_locale(locale_conf_path: Path = DEFAULT_LOCALE_CONF) -> str:
+    """Determine the system language from LANG env var or /etc/locale.conf."""
+    lang = os.environ.get("LANG")
+
+    if not lang and locale_conf_path.exists():
+        for line in locale_conf_path.read_text().splitlines():
+            if line.startswith("LANG="):
+                lang = line.split("=", 1)[1].strip()
+                break
+
+    if not lang or lang in ("C", "POSIX"):
+        return "en"
+
+    # Extract language prefix: "de_DE.UTF-8" → "de"
+    lang = lang.split("_")[0].split(".")[0]
+    return lang
+
+
+def load_strings(locale: str | None = None) -> Strings:
+    """Return the string table for the given locale, defaulting to English."""
+    if locale is None:
+        locale = detect_locale()
+    return _LOCALE_MAP.get(locale, _STRINGS_EN)

tests/test_i18n.py

@@ -0,0 +1,118 @@
+# ABOUTME: Tests for locale detection and string lookup.
+# ABOUTME: Verifies DE/EN selection based on system locale.
+
+from pathlib import Path
+
+import pytest
+
+from moongreet.i18n import detect_locale, load_strings, Strings
+
+
+class TestDetectLocale:
+    """Tests for system locale detection."""
+
+    def test_reads_lang_env(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "de_DE.UTF-8")
+
+        result = detect_locale()
+
+        assert result == "de"
+
+    def test_reads_lang_without_region(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "en_US.UTF-8")
+
+        result = detect_locale()
+
+        assert result == "en"
+
+    def test_falls_back_to_locale_conf(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.delenv("LANG", raising=False)
+        locale_conf = tmp_path / "locale.conf"
+        locale_conf.write_text("LANG=de_AT.UTF-8\n")
+
+        result = detect_locale(locale_conf_path=locale_conf)
+
+        assert result == "de"
+
+    def test_defaults_to_english(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.delenv("LANG", raising=False)
+        missing = tmp_path / "nonexistent"
+
+        result = detect_locale(locale_conf_path=missing)
+
+        assert result == "en"
+
+    def test_handles_bare_language_code(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "de")
+
+        result = detect_locale()
+
+        assert result == "de"
+
+    def test_handles_c_locale(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "C")
+
+        result = detect_locale()
+
+        assert result == "en"
+
+    def test_handles_posix_locale(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setenv("LANG", "POSIX")
+
+        result = detect_locale()
+
+        assert result == "en"
+
+
+class TestLoadStrings:
+    """Tests for loading the correct string table."""
+
+    def test_loads_german_strings(self) -> None:
+        strings = load_strings("de")
+
+        assert strings.password_placeholder == "Passwort"
+        assert strings.reboot_tooltip == "Neustart"
+        assert strings.shutdown_tooltip == "Herunterfahren"
+
+    def test_loads_english_strings(self) -> None:
+        strings = load_strings("en")
+
+        assert strings.password_placeholder == "Password"
+        assert strings.reboot_tooltip == "Reboot"
+        assert strings.shutdown_tooltip == "Shut down"
+
+    def test_unknown_locale_falls_back_to_english(self) -> None:
+        strings = load_strings("fr")
+
+        assert strings.password_placeholder == "Password"
+
+    def test_returns_strings_dataclass(self) -> None:
+        strings = load_strings("de")
+
+        assert isinstance(strings, Strings)
+
+    def test_error_messages_are_present(self) -> None:
+        strings = load_strings("en")
+
+        assert strings.wrong_password
+        assert strings.auth_failed
+        assert strings.reboot_failed
+        assert strings.shutdown_failed
+        assert strings.no_session_selected
+        assert strings.multi_stage_unsupported
+        assert strings.invalid_session_command
+        assert strings.session_start_failed
+        assert strings.faillock_locked
+
+    def test_faillock_warning_template(self) -> None:
+        strings = load_strings("de")
+
+        # Template should accept an int for remaining attempts
+        result = strings.faillock_attempts_remaining.format(n=1)
+        assert "1" in result
+
+    def test_connection_error_template(self) -> None:
+        strings = load_strings("en")
+
+        result = strings.connection_error.format(error="timeout")
+        assert "timeout" in result