gdrive_client/log.py

"""Maintain a global logger instance."""
from argparse import ArgumentParser, FileType
import logging
import sys
from typing import IO, Text


LOG_LEVEL = logging.INFO
LOG_FORMAT = "%(asctime)s | [%(levelname)s] %(name)s: %(message)s"
LEVELS = [
    logging.NOTSET,
    logging.DEBUG,
    logging.INFO,
    logging.WARNING,
    logging.ERROR,
    logging.CRITICAL,
]


def compute_level(verbose: int, quiet: int) -> int:
    """Compute a log level based on input.

    Log level is based on LOG_LEVEL.

    :param int verbose:
        Number of levels to increase log level.
    :param int quiet:
        Number of levels to decrease log level.
    :returns int:
        New log level. Either of NOTSET, DEBUG, INFO, WARNING, ERROR, CRITICAL.
    """
    if verbose < 0 or quiet < 0:
        raise ValueError("Input must not be less than 0")
    default_index = LEVELS.index(LOG_LEVEL)
    index = min(len(LEVELS) - 1, max(0, default_index + quiet - verbose))
    return LEVELS[index]


def configure_logger(
    name: Text, stream: IO[str], verbose: int, quiet: int
) -> None:
    """Create handler for logging to an IO stream.

    :param Text name:
        Name of logger, e.g. __package__.
    :param IO[str] stream:
        Stream to log to, e.g. sys.stderr.
    :param int verbose:
        Number of levels to increase log level.
    :param int quiet:
        Number of levels to decrease log level.
    """
    log_level = compute_level(verbose, quiet)
    handler = logging.StreamHandler(stream)
    handler.setFormatter(logging.Formatter(LOG_FORMAT))
    handler.setLevel(log_level)

    logger = logging.getLogger(name)
    logger.setLevel(handler.level)
    logger.addHandler(handler)


def add_logging_arguments(parser: ArgumentParser) -> ArgumentParser:
    """Add logging options to a parser of commandline arguments."""
    parser.add_argument(
        "--log",
        default=sys.stderr,
        type=FileType("w"),
        help="Log file. Default: stderr.",
    )
    parser.add_argument(
        "-v",
        "--verbose",
        default=0,
        action="count",
        help="Increase log level. May be used several times.",
    )
    parser.add_argument(
        "-q",
        "--quiet",
        default=0,
        action="count",
        help="Decrease log level. May be used several times.",
    )
    return parser