diff --git a/README.md b/README.md
index da87bce..1b1b6e2 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ from internationalization import I18N
 I18N("localization_dir", "en")
 
 print(i18n['key'])
+print(i18n('key', some=123))
 print(i18n.get_phrase('key', some=123))
 ```
 
diff --git a/builtins.i18n.pyi.py b/builtins.i18n.pyi.py
index e69de29..8be3dc0 100644
--- a/builtins.i18n.pyi.py
+++ b/builtins.i18n.pyi.py
@@ -0,0 +1,36 @@
+class i18n:
+    @staticmethod
+    def set_lang(lang, encoding=None) -> None:
+        """
+        Set the language and encoding for the locale file.
+        :param lang: Use the language file with the given language.
+        :param encoding: Encoding of the language file.
+        :return: None
+        """
+    @staticmethod
+    def get_phrase(key: str, **kwargs) -> str:
+        """
+        Get the phrase from the locale file. If the phrase is not found, return the key in uppercase.
+
+        :param key: Key to search in the locale file.
+        :param kwargs: Arguments to format the phrase.
+        :return: The phrase from the locale file.
+        """
+    @staticmethod
+    def __call__(key: str, **kwargs) -> str:
+        """
+        Get the phrase from the locale file. If the phrase is not found, return the key in uppercase.
+
+        :param key: Key to search in the locale file.
+        :param kwargs: Arguments to format the phrase.
+        :return: The phrase from the locale file.
+        """
+    @staticmethod
+    def __getitem__(key: str) -> str:
+        """
+        Get the phrase from the locale file. If the phrase is not found, return the key in uppercase.
+
+        :param key: Key to search in the locale file.
+        :return: The phrase from the locale file.
+        """
+class i10n(i18n): ...
diff --git a/internationalization/i18n.py b/internationalization/i18n.py
index 743abf3..3b1c0dc 100644
--- a/internationalization/i18n.py
+++ b/internationalization/i18n.py
@@ -1,4 +1,73 @@
+import builtins
+from collections import defaultdict
+
+import json5
+from loguru import logger
+
+from . import utils
+
+log = logger.bind(module="i18n", prefix="init")
+log_load = logger.bind(module="i18n", prefix="load")
 
 class I18N:
-    def __init__(self, lock_dir, load_lang):
-        pass
+
+    def __init__(self, locale_dir, load_lang, encoding):
+        """
+        Load the language file and set the locale directory. Use JSON5 format for the language file.
+
+        :param locale_dir: {BASE_DIR}/resources/{locale_dir}
+        :param load_lang: some.lang
+        """
+        self._locale_dir = utils.get_file(locale_dir)  # {BASE_DIR}/resources/{locale_dir}
+        self._lang = load_lang
+        self._encoding = encoding
+
+        self._locale = {}
+        log.debug("Injecting to builtins")
+        builtins.i18n = self
+        builtins.i10n = self
+        log.debug("Ready")
+        self._load()
+
+    def _load(self):
+        if not self._locale_dir:
+            raise FileNotFoundError(f"Locale directory not found: {self._locale_dir}")
+        if (locale_file:=self._locale_dir / f"{self._lang}.json5").exists():
+            log_load.debug(f"Loading locale file: {locale_file}")
+            with open(locale_file, "r", encoding=self._encoding) as f:
+                data = json5.load(f)
+            self._locale = utils.flatten_dict(data)
+            log_load.debug("Loaded and flattened.")
+        else:
+            raise FileNotFoundError(f"Locale file not found: {locale_file}")
+
+    def set_lang(self, lang, encoding=None):
+        """
+        Set the language and encoding for the locale file.
+        :param lang: Use the language file with the given language.
+        :param encoding: Encoding of the language file.
+        :return: None
+        """
+        self._lang = lang
+        self._encoding = encoding or self._encoding
+        self._load()
+
+    def get_phrase(self, key: str, **kwargs) -> str:
+        """
+        Get the phrase from the locale file. If the phrase is not found, return the key in uppercase.
+
+        :param key: Key to search in the locale file.
+        :param kwargs: Arguments to format the phrase.
+        :return: The phrase from the locale file.
+        """
+        # key: some.key.here
+        phrase = self._locale.get(key)
+        if not phrase:
+            return key.upper()
+        return phrase.format_map(defaultdict(lambda: '???', kwargs))
+
+    def __call__(self, key: str, **kwargs):
+        return self.get_phrase(key, **kwargs)
+
+    def __getitem__(self, key: str):
+        return self.get_phrase(key)
diff --git a/internationalization/utils.py b/internationalization/utils.py
index 2e0b737..334fa54 100644
--- a/internationalization/utils.py
+++ b/internationalization/utils.py
@@ -11,3 +11,13 @@ def base_path():
 
 def get_file(filename):
     return base_path() / "resources" / filename
+
+def flatten_dict(d, parent_key='', sep='.'):
+    items = []
+    for k, v in d.items():
+        new_key = f"{parent_key}{sep}{k}" if parent_key else k
+        if isinstance(v, dict):
+            items.extend(flatten_dict(v, new_key, sep=sep).items())
+        else:
+            items.append((new_key, v))
+    return dict(items)