from __future__ import unicode_literals

import logging
import logging.config  # needed when logging_config doesn't start with logging.config
import sys
import warnings
from copy import copy

from django.conf import settings
from django.core import mail
from django.core.mail import get_connection
from django.utils.deprecation import RemovedInNextVersionWarning
from django.utils.module_loading import import_string
from django.views.debug import ExceptionReporter

# Default logging for Django. This sends an email to the site admins on every
# HTTP 500 error. Depending on DEBUG, all other log records are either sent to
# the console (DEBUG=True) or discarded by mean of the NullHandler (DEBUG=False).
DEFAULT_LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'filters': {
        'require_debug_false': {
            '()': 'django.utils.log.RequireDebugFalse',
        },
        'require_debug_true': {
            '()': 'django.utils.log.RequireDebugTrue',
        },
    },
    'handlers': {
        'console': {
            'level': 'INFO',
            'filters': ['require_debug_true'],
            'class': 'logging.StreamHandler',
        },
        'mail_admins': {
            'level': 'ERROR',
            'filters': ['require_debug_false'],
            'class': 'django.utils.log.AdminEmailHandler'
        }
    },
    'loggers': {
        'django': {
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
        },
        'py.warnings': {
            'handlers': ['console'],
        },
    }
}


def configure_logging(logging_config, logging_settings):
    if not sys.warnoptions:
        # Route warnings through python logging
        logging.captureWarnings(True)
        # RemovedInNextVersionWarning is a subclass of DeprecationWarning which
        # is hidden by default, hence we force the "default" behavior
        warnings.simplefilter("default", RemovedInNextVersionWarning)

    if logging_config:
        # First find the logging configuration function ...
        logging_config_func = import_string(logging_config)

        logging.config.dictConfig(DEFAULT_LOGGING)

        # ... then invoke it with the logging settings
        if logging_settings:
            logging_config_func(logging_settings)


class AdminEmailHandler(logging.Handler):
    """An exception log handler that emails log entries to site admins.

    If the request is passed as the first argument to the log record,
    request data will be provided in the email report.
    """

    def __init__(self, include_html=False, email_backend=None):
        logging.Handler.__init__(self)
        self.include_html = include_html
        self.email_backend = email_backend

    def emit(self, record):
        try:
            request = record.request
            subject = '%s (%s IP): %s' % (
                record.levelname,
                ('internal' if request.META.get('REMOTE_ADDR') in settings.INTERNAL_IPS
                 else 'EXTERNAL'),
                record.getMessage()
            )
        except Exception:
            subject = '%s: %s' % (
                record.levelname,
                record.getMessage()
            )
            request = None
        subject = self.format_subject(subject)

        # Since we add a nicely formatted traceback on our own, create a copy
        # of the log record without the exception data.
        no_exc_record = copy(record)
        no_exc_record.exc_info = None
        no_exc_record.exc_text = None

        if record.exc_info:
            exc_info = record.exc_info
        else:
            exc_info = (None, record.getMessage(), None)

        reporter = ExceptionReporter(request, is_email=True, *exc_info)
        message = "%s\n\n%s" % (self.format(no_exc_record), reporter.get_traceback_text())
        html_message = reporter.get_traceback_html() if self.include_html else None
        self.send_mail(subject, message, fail_silently=True, html_message=html_message)

    def send_mail(self, subject, message, *args, **kwargs):
        mail.mail_admins(subject, message, *args, connection=self.connection(), **kwargs)

    def connection(self):
        return get_connection(backend=self.email_backend, fail_silently=True)

    def format_subject(self, subject):
        """
        Escape CR and LF characters, and limit length.
        RFC 2822's hard limit is 998 characters per line. So, minus "Subject: "
        the actual subject must be no longer than 989 characters.
        """
        formatted_subject = subject.replace('\n', '\\n').replace('\r', '\\r')
        return formatted_subject[:989]


class CallbackFilter(logging.Filter):
    """
    A logging filter that checks the return value of a given callable (which
    takes the record-to-be-logged as its only parameter) to decide whether to
    log a record.
    """
    def __init__(self, callback):
        self.callback = callback

    def filter(self, record):
        if self.callback(record):
            return 1
        return 0


class RequireDebugFalse(logging.Filter):
    def filter(self, record):
        return not settings.DEBUG


class RequireDebugTrue(logging.Filter):
    def filter(self, record):
        return settings.DEBUG