Support for multiple languages

davtelepot/languages.py

@@ -0,0 +1,88 @@
+"""Bot support for multiple languages."""
+
+# Standard library modules
+import logging
+
+# Project modules
+from .utilities import extract
+
+
+class MultiLanguageObject(object):
+    """Make bot inherit from this class to make it support multiple languages.
+
+    Call MultiLanguage().get_message(
+        field1, field2, ...,
+        update, user_record, language,
+        format_kwarg1, format_kwarg2, ...
+    ) to get the corresponding message in the selected language.
+    """
+
+    def __init__(self):
+        """Instantiate MultiLanguage object, setting self.messages."""
+        self.messages = dict()
+
+    def get_message(self, *fields, update=dict(), user_record=dict(),
+                    language=None, **format_kwargs):
+        """Given a list of strings (`fields`), return proper message.
+
+        Language will be selected in this order:
+        - `language` parameter
+        - `user_record['selected_language_code']`: language selected by user
+        - `update['language_code']`: language of incoming telegram update
+        - Fallback to English if none of the above fits
+
+        `format_kwargs` will be passed to format function on the result.
+        """
+        # Choose language
+        if (
+            language is None
+            and 'selected_language_code' in user_record
+        ):
+            language = user_record['selected_language_code']
+        if (
+            language is None
+            and 'from' in update
+            and 'language_code' in update['from']
+        ):
+            language = update['from']['language_code']
+        if language is None:
+            language = 'en'
+        # Find result for `language`
+        result = self.messages
+        for field in fields:
+            if field not in result:
+                logging.error(
+                    "Please define self.message{f}".format(
+                        f=''.join(
+                            '[\'{field}\']'.format(
+                                field=field
+                            )
+                            for field in fields
+                        )
+                    )
+                )
+                return "Invalid message!"
+            result = result[field]
+        if language not in result:
+            # For specific languages, try generic ones
+            language = extract(
+                language,
+                ender='-'
+            )
+            if language not in result:
+                language = 'en'
+                if language not in result:
+                    logging.error(
+                        "Please define self.message{f}['en']".format(
+                            f=''.join(
+                                '[\'{field}\']'.format(
+                                    field=field
+                                )
+                                for field in fields
+                            )
+                        )
+                    )
+                    return "Invalid message!"
+        return result[language].format(
+            **format_kwargs
+        )