import logging as _logging

from syslogformat.helpers import check_level, py_to_sys_lvl


class SyslogFormatter(_logging.Formatter):
    """
    logging.Formatter subclass for doing three things:
        1) Format exception log messages into one-liners,
        2) prepend a syslog oriented log level number to be recognized by systemd, and
        3) append more details ([module].[function].[line]) to every message, when specified level is exceeded.
    """
    def __init__(self, *args, **kwargs):
        self.detail_threshold = check_level(kwargs.pop('detail_threshold', _logging.WARNING))
        self.prepend_lvl_name = check_level(kwargs.pop('prepend_lvl_name', True))
        super().__init__(*args, **kwargs)

    def formatException(self, exc_info) -> str:
        """Format an exception so that it prints on a single line."""
        return repr(super().formatException(exc_info))

    def format(self, record: _logging.LogRecord) -> str:
        """
        Format to be compatible with syslog levels and replace the newlines.
        The entire message format is hard-coded here, so no format needs to be specified in the usual config.
        """
        record.message = record.getMessage()

        # Prepend syslog level depending on record level
        s = f"<{py_to_sys_lvl(record.levelno)}>"
        if self.prepend_lvl_name:
            s += f"{record.levelname:<8} | "
        s += self.formatMessage(record)

        # If record level exceeds the threshold, append additional details
        if record.levelno >= self.detail_threshold:
            s += f" | {record.module}.{record.funcName}.{record.lineno}"

        if record.exc_info and not record.exc_text:
            record.exc_text = self.formatException(record.exc_info)
        if record.exc_text:
            s += ' | ' + record.exc_text
        if record.stack_info:
            s += self.formatStack(record.stack_info)

        # Reformat exception line
        return s.replace("\n", "")


if __name__ == '__main__':

    log = _logging.getLogger()
    hdl = _logging.StreamHandler()
    fmt = SyslogFormatter()
    hdl.setFormatter(fmt)
    log.addHandler(hdl)
    log.setLevel(_logging.NOTSET)

    log.debug("foo")
    log.info("bar")
    log.warning("baz")
    try:
        raise ValueError("this is bad")
    except ValueError as e:
        log.exception("oh no")