from logging import Formatter, StreamHandler


class NamingCache:
  def __init__(self):
    self._cache = {}

  def __getitem__(self, key):
    if key not in self._cache:
      self._cache[key] = self.shorten(key)
    return self._cache[key]

  @staticmethod
  def shorten(logger_name: str) -> str:
    target_length = 18
    if len(logger_name) > target_length:
      parts = logger_name.split('.')
      part = 0
      while len(logger_name) > target_length:
        if part == len(parts) - 1:
          logger_name = f'...{logger_name[-(target_length - 3):]}'
          break
        parts[part] = parts[part][0]
        logger_name = '.'.join(parts)
        part += 1

    return logger_name.ljust(target_length)


class ApplicationFormatter(Formatter):
  def __init__(self, handler_prefix: str = ''):
    super().__init__()
    self._logger_names = NamingCache()
    self._handler_prefix = handler_prefix

  def format(self, record):
    from datetime import datetime
    timestamp = datetime.fromtimestamp(record.created).isoformat(sep=' ', timespec='milliseconds')
    level = record.levelname.replace('WARNING', 'WARN').rjust(5)
    thread_name = record.threadName.replace(' (', '#').replace(')', '').rjust(16)[-16:] # TODO: NamingCache?
    logger_name = self._logger_names[f"{self._handler_prefix}{record.name}"]
    message = record.getMessage()
    formatted = f"{timestamp} {level} [{thread_name}] {logger_name} : {message}"

    if record.exc_info:
      formatted += "\n" + self.formatException(record.exc_info)

    return formatted


class LoggingHandler(StreamHandler):
  def __init__(self):
    super().__init__()
    self.setFormatter(ApplicationFormatter(handler_prefix='karl.'))

class ExternalLoggingHandler(StreamHandler):
  def __init__(self):
    super().__init__()
    self.setFormatter(ApplicationFormatter())