"""Logging.

The logging library provides the handler that sends the logs to a regular HTTPS
provider (in our case we use Loggly). The message is also formatted in a
specific format (json), which includes fields that are specific to the Orchard,
such as the service name, the correlation id.
"""

import datetime
import logging
import logging.handlers
import traceback

from requests_futures.sessions import FuturesSession

from grass import config

session = FuturesSession()


def callback(session, resp):
    """Post callback.

    When the post has been dispatched to loggly, handle the response (in our
    case we don't have anything to do).

    Args:
        session (FutureSession): the session that triggered the request.
        resp (object): the response of the request to the service.
    """
    pass


class DSNHandler(logging.Handler):
    """DNSHandler."""

    def __init__(self, dsn):
        """Constructor of HTTPSHandler.

        Args:
            dsn (str): the full dsn to send the log to.

        Returns:
            HTTPSHandler: the created handler.
        """
        logging.Handler.__init__(self)
        self.dsn = dsn

    def get_full_message(self, record):
        """Get the full message for a record.

        Some of our systems might still require this data to be sent to loggly,
        so instead of sending the message of the record, we send the exception
        information.

        Args:
            record (LogRecord): the record to log.

        Returns:
            mixed: the string or an object (dictionary).
        """
        if record.exc_info:
            return '\n'.join(traceback.format_exception(*record.exc_info))
        else:
            return record.msg

    def emit(self, record):
        """Emit a record.

        From the documentation: do whatever it takes to actually log the
        specified logging record. Here: we send it to the provider. The payload
        matches Orchard format.

        Args:
            record (LogRecord): the record to log.
        """
        try:
            payload = {
                'tag': 'ows1',
                'timestamp': datetime.datetime.fromtimestamp(
                    record.created
                ).isoformat(),
                'level': record.levelname,
                'correlation_id': record.correlation_id,
                'message': self.get_full_message(record),
                'service': config.SERVICE_NAME,
                'service_version': config.SERVICE_VERSION,
                'environment': config.environment,
                'meta': {
                    'file_name': record.filename,
                    'function_name': record.funcName,
                    'line': record.lineno,
                },
            }

            session.post(self.dsn, json=payload, background_callback=callback)

        except (KeyboardInterrupt, SystemExit):
            raise
        except:
            self.handleError(record)


class CustomAdapter(logging.LoggerAdapter):
    """Custom logger adapter.

    This adapter expects the passed in dict-like object to have a
    'correlation_id' key, whose value is prepended to the log message.
    """

    def process(self, msg, kwargs):
        kwargs['extra'] = self.extra
        return '[%s] %s' % (self.extra.get('correlation_id', ''), msg), kwargs