from __future__ import annotations

import datetime
import sys
import syslog

from typing import TYPE_CHECKING

if TYPE_CHECKING:

    from typing import Final

# fmt: disable # don't conflate
# yapf: disable # don't conflate
EMERG         = int(syslog.LOG_EMERG)
ALERT         = int(syslog.LOG_ALERT)
CRIT          = int(syslog.LOG_CRIT)
ERR           = int(syslog.LOG_ERR)
WARNING       = int(syslog.LOG_WARNING)
NOTICE        = int(syslog.LOG_NOTICE)
INFO          = int(syslog.LOG_INFO)
DEBUG         = int(syslog.LOG_DEBUG)
DEVEL         = int(syslog.LOG_DEBUG + 1)
OFF           = DEVEL + 1

_log_level    = NOTICE
_last_tstamp  = datetime.datetime.now()
_first_tstamp = _last_tstamp

_LOG_LEVEL_NAME_BY_VALUE: Final[dict[int, str]] = {
    EMERG:    'EMERG',
    ALERT:    'ALERT',
    CRIT:     'CRIT',
    ERR:      'ERR',
    WARNING:  'WARNING',
    NOTICE:   'NOTICE',
    INFO:     'INFO',
    DEBUG:    'DEBUG',
    DEVEL:    'DEVEL',
    OFF:      'OFF',
}
# yapf: enable
# fmt: enable

_LOG_LEVEL_VALUE_BY_NAME: Final[dict[str, int]] = {
    alias: value
    for value, name in _LOG_LEVEL_NAME_BY_VALUE.items()
    for alias in (name, name.lower())
}

def get_log_level_name(level: int) -> str:
    return _LOG_LEVEL_NAME_BY_VALUE[level]

def parse_log_level(level: str | int) -> int:

    def __int_level(level: int) -> int:
        if level >= 0 and level <= DEVEL:
            return level
        raise Exception(f'Invalid log level number {level}')

    if isinstance(level, int):
        return __int_level(level)
    if level in _LOG_LEVEL_VALUE_BY_NAME:
        return _LOG_LEVEL_VALUE_BY_NAME[level]
    return __int_level(int(level))

def set_log_level(level: str | int | None = None) -> int:
    global _log_level
    ret = _log_level
    if level is not None:
        _log_level = parse_log_level(level)
    return ret

def set_log_flags(*args, **kwargs):
    pass

def log(prio: int, *args, **kwargs):
    global _log_level
    if prio > _log_level:
        return
    print(*args, file = sys.stderr)

def log_time_diff(prio: int, *args, **kwargs):
    global _last_tstamp
    now = datetime.datetime.now()
    log(prio, now - _last_tstamp, now - _first_tstamp, *args)
    _last_tstamp = now