Update version number.

core_lib/i18n.py

@@ -0,0 +1,58 @@
+"""Small, dependency-free translation catalog used by the launcher UI."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+from PySide6.QtCore import QObject, Signal
+
+
+SUPPORTED_LANGUAGES = ("en", "zh-TW")
+
+
+class TranslationManager(QObject):
+    """Load JSON catalogs and notify widgets when the language changes."""
+
+    language_changed = Signal(str)
+
+    def __init__(self, catalog_dir: Path, language: str = "en") -> None:
+        super().__init__()
+        self.catalog_dir = Path(catalog_dir)
+        self._language = "en"
+        self._catalog: dict[str, str] = {}
+        self.set_language(language, emit=False)
+
+    @property
+    def language(self) -> str:
+        return self._language
+
+    def set_language(self, language: str, *, emit: bool = True) -> None:
+        if language not in SUPPORTED_LANGUAGES:
+            language = "en"
+
+        catalog: dict[str, str] = {}
+        path = self.catalog_dir / f"{language}.json"
+        if path.is_file():
+            try:
+                raw = json.loads(path.read_text(encoding="utf-8"))
+                catalog = {
+                    str(key): str(value)
+                    for key, value in raw.items()
+                    if isinstance(value, str)
+                }
+            except (OSError, json.JSONDecodeError):
+                # An invalid optional catalog must not prevent the launcher starting.
+                catalog = {}
+
+        changed = language != self._language or catalog != self._catalog
+        self._language = language
+        self._catalog = catalog
+        if emit and changed:
+            self.language_changed.emit(language)
+
+    def translate(self, key: str, /, **values: Any) -> str:
+        text = self._catalog.get(key, key)
+        return text.format(**values) if values else text
+