refactor: prepare backend refactor

backend-legacy/logger.py

@@ -0,0 +1,42 @@
+import logging
+import enum
+
+
+def _build_logger() -> tuple[logging.Logger, logging.Handler]:
+    # Create a new logger which is independent with Flask
+    logger = logging.getLogger("my_console_logger")
+    # Avoid message was propagated to root logger or captured by Flask logger.
+    logger.propagate = False
+    # Set initial level.
+    logger.setLevel(logging.INFO)
+
+    # Create StreamHandler to output into stderr.
+    console_handler = logging.StreamHandler()
+    console_handler.setLevel(logging.DEBUG)
+    # Set format for it.
+    formatter = logging.Formatter("[%(levelname)s] %(message)s")
+    console_handler.setFormatter(formatter)
+    # Add handler
+    logger.addHandler(console_handler)
+
+    return (logger, console_handler)
+
+
+(LOGGER, CONSOLE_HANDLER) = _build_logger()
+
+
+class LoggerLevel(enum.IntEnum):
+    DEBUG = enum.auto()
+    INFO = enum.auto()
+
+
+def set_level(level: LoggerLevel) -> None:
+    logging_level: int = logging.INFO
+    match level:
+        case LoggerLevel.DEBUG:
+            logging_level = logging.DEBUG
+        case LoggerLevel.INFO:
+            logging_level = logging.INFO
+
+    LOGGER.setLevel(logging_level)
+    CONSOLE_HANDLER.setLevel(logging_level)