# Copyright (c) OpenMMLab. All rights reserved.
import logging
from typing import Optional

logger_initialized = {}


def get_logger(name: str,
               log_file: Optional[str] = None,
               log_level: int = logging.INFO,
               file_mode: str = 'w'):
    """Initialize and get a logger by name.

    If the logger has not been initialized, this method will initialize the
    logger by adding one or two handlers, otherwise the initialized logger will
    be directly returned. During initialization, a StreamHandler will always be
    added. If `log_file` is specified, a FileHandler will also be added.
    Args:
        name (str): Logger name.
        log_file (str | None): The log filename. If specified, a FileHandler
            will be added to the logger.
        log_level (int): The logger level.
        file_mode (str): The file mode used in opening log file.
            Defaults to 'w'.
    Returns:
        logging.Logger: The expected logger.
    """
    logger = logging.getLogger(name)
    if name in logger_initialized:
        return logger
    # handle hierarchical names
    # e.g., logger "a" is initialized, then logger "a.b" will skip the
    # initialization since it is a child of "a".
    for logger_name in logger_initialized:
        if name.startswith(logger_name):
            return logger

    # handle duplicate logs to the console
    for handler in logger.root.handlers:
        if type(handler) is logging.StreamHandler:
            handler.setLevel(logging.ERROR)

    stream_handler = logging.StreamHandler()
    handlers = [stream_handler]

    if log_file is not None:
        # Here, the default behaviour of the official logger is 'a'. Thus, we
        # provide an interface to change the file mode to the default
        # behaviour.
        file_handler = logging.FileHandler(log_file, file_mode)
        handlers.append(file_handler)

    formatter = logging.Formatter(
        '%(asctime)s - %(name)s - %(levelname)s - %(message)s')
    for handler in handlers:
        handler.setFormatter(formatter)
        handler.setLevel(log_level)
        logger.addHandler(handler)

    logger.setLevel(log_level)
    logger_initialized[name] = True

    return logger
