from __future__ import unicode_literals

from email import message_from_string
from email.header import decode_header
import imaplib
import json
import logging
import os
import poplib
import subprocess

import sh
import yaml

try:
    scanimage = sh.Command('/usr/bin/scanimage')
except sh.CommandNotFound:
    scanimage = None

from django.core.exceptions import ValidationError
from django.core.files import File
from django.core.files.base import ContentFile
from django.db import models, transaction
from django.utils.encoding import force_text, python_2_unicode_compatible
from django.utils.timezone import now
from django.utils.translation import ugettext_lazy as _

from model_utils.managers import InheritanceManager

from common.compat import collapse_rfc2231_value
from common.compressed_files import CompressedFile, NotACompressedFile
from common.utils import TemporaryFile
from converter.models import Transformation
from djcelery.models import PeriodicTask, IntervalSchedule
from documents.models import Document, DocumentType
from documents.settings import setting_language
from metadata.api import set_bulk_metadata
from metadata.models import MetadataType

from .classes import Attachment, PseudoFile, SourceUploadedFile, StagingFile
from .exceptions import SourceException
from .literals import (
    DEFAULT_INTERVAL, DEFAULT_POP3_TIMEOUT, DEFAULT_IMAP_MAILBOX,
    DEFAULT_METADATA_ATTACHMENT_NAME, SCANNER_ADF_MODE_CHOICES,
    SCANNER_ADF_MODE_SIMPLEX, SCANNER_MODE_COLOR, SCANNER_MODE_CHOICES,
    SCANNER_SOURCE_CHOICES, SCANNER_SOURCE_FLATBED,
    SOURCE_CHOICES, SOURCE_CHOICE_STAGING, SOURCE_CHOICE_WATCH,
    SOURCE_CHOICE_WEB_FORM, SOURCE_INTERACTIVE_UNCOMPRESS_CHOICES,
    SOURCE_UNCOMPRESS_CHOICES, SOURCE_UNCOMPRESS_CHOICE_N,
    SOURCE_UNCOMPRESS_CHOICE_Y, SOURCE_CHOICE_EMAIL_IMAP,
    SOURCE_CHOICE_EMAIL_POP3, SOURCE_CHOICE_SANE_SCANNER,
)
from .settings import setting_scanimage_path
from .wizards import WizardStep

logger = logging.getLogger(__name__)


@python_2_unicode_compatible
class Source(models.Model):
    label = models.CharField(max_length=64, verbose_name=_('Label'))
    enabled = models.BooleanField(default=True, verbose_name=_('Enabled'))

    objects = InheritanceManager()

    class Meta:
        ordering = ('label',)
        verbose_name = _('Source')
        verbose_name_plural = _('Sources')

    def __str__(self):
        return '%s' % self.label

    @classmethod
    def class_fullname(cls):
        return force_text(dict(SOURCE_CHOICES).get(cls.source_type))

    def clean_up_upload_file(self, upload_file_object):
        pass
        # TODO: Should raise NotImplementedError?

    def fullname(self):
        return ' '.join([self.class_fullname(), '"%s"' % self.label])

    def handle_upload(self, file_object, description=None, document_type=None, expand=False, label=None, language=None, user=None):
        """
        Handle an upload request from a file object which may be an individual
        document or a compressed file containing multiple documents.
        """
        if not document_type:
            document_type = self.document_type

        kwargs = {
            'description': description, 'document_type': document_type,
            'label': label, 'language': language,
            'user': user
        }

        if expand:
            try:
                compressed_file = CompressedFile(file_object)
                for compressed_file_child in compressed_file.children():
                    kwargs.update({'label': force_text(compressed_file_child)})
                    self.upload_document(
                        file_object=File(compressed_file_child), **kwargs
                    )
                    compressed_file_child.close()

            except NotACompressedFile:
                logging.debug('Exception: NotACompressedFile')
                self.upload_document(file_object=file_object, **kwargs)
        else:
            self.upload_document(file_object=file_object, **kwargs)

    def get_upload_file_object(self, form_data):
        pass
        # TODO: Should raise NotImplementedError?

    def upload_document(self, file_object, document_type, description=None, label=None, language=None, querystring=None, user=None):
        """
        Upload an individual document
        """
        try:
            with transaction.atomic():
                document = Document(
                    description=description or '', document_type=document_type,
                    label=label or file_object.name,
                    language=language or setting_language.value
                )
                document.save(_user=user)
        except Exception as exception:
            logger.critical(
                'Unexpected exception while trying to create new document '
                '"%s" from source "%s"; %s',
                label or file_object.name, self, exception
            )
            raise
        else:
            try:
                document_version = document.new_version(
                    file_object=file_object, _user=user,
                )

                if user:
                    document.add_as_recent_document_for_user(user)

                Transformation.objects.copy(
                    source=self, targets=document_version.pages.all()
                )

            except Exception as exception:
                logger.critical(
                    'Unexpected exception while trying to create version for '
                    'new document "%s" from source "%s"; %s',
                    label or file_object.name, self, exception, exc_info=True
                )
                document.delete(to_trash=False)
                raise
            else:
                WizardStep.post_upload_process(
                    document=document, querystring=querystring
                )
                return document


class InteractiveSource(Source):
    objects = InheritanceManager()

    class Meta:
        verbose_name = _('Interactive source')
        verbose_name_plural = _('Interactive sources')


class SaneScanner(InteractiveSource):
    can_compress = False
    is_interactive = True
    source_type = SOURCE_CHOICE_SANE_SCANNER

    device_name = models.CharField(
        max_length=255,
        help_text=_('Device name as returned by the SANE backend.'),
        verbose_name=_('Device name')
    )
    mode = models.CharField(
        blank=True, choices=SCANNER_MODE_CHOICES, default=SCANNER_MODE_COLOR,
        help_text=_(
            'Selects the scan mode (e.g., lineart, monochrome, or color). '
            'If this option is not supported by your scanner, leave it blank.'
        ), max_length=16, verbose_name=_('Mode')
    )
    resolution = models.PositiveIntegerField(
        blank=True, null=True, help_text=_(
            'Sets the resolution of the scanned image in DPI (dots per inch). '
            'Typical value is 200. If this option is not supported by your '
            'scanner, leave it blank.'
        ), verbose_name=_('Resolution')
    )
    source = models.CharField(
        blank=True, choices=SCANNER_SOURCE_CHOICES,
        default=SCANNER_SOURCE_FLATBED, help_text=_(
            'Selects the scan source (such as a document-feeder). If this '
            'option is not supported by your scanner, leave it blank.'
        ), max_length=32,
        verbose_name=_('Paper source')
    )
    adf_mode = models.CharField(
        blank=True, choices=SCANNER_ADF_MODE_CHOICES,
        default=SCANNER_ADF_MODE_SIMPLEX, help_text=_(
            'Selects the document feeder mode (simplex/duplex). If this '
            'option is not supported by your scanner, leave it blank.'
        ), max_length=16, verbose_name=_('ADF mode')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('SANE Scanner')
        verbose_name_plural = _('SANE Scanners')

    def clean_up_upload_file(self, upload_file_object):
        pass

    def get_upload_file_object(self, form_data):
        temporary_file_object = TemporaryFile()
        command_line = [
            setting_scanimage_path.value, '-d', self.device_name,
            '--format', 'tiff',
        ]

        if self.resolution:
            command_line.extend(
                ['--resolution', '{}'.format(self.resolution)]
            )

        if self.mode:
            command_line.extend(
                ['--mode', self.mode]
            )

        if self.source:
            command_line.extend(
                ['--source', self.source]
            )

        if self.adf_mode:
            command_line.extend(
                ['--adf-mode', self.adf_mode]
            )

        filestderr = TemporaryFile()

        try:
            logger.debug('Scan command line: %s', command_line)
            subprocess.check_call(
                command_line, stdout=temporary_file_object, stderr=filestderr
            )
        except subprocess.CalledProcessError:
            filestderr.seek(0)
            error_message = filestderr.read()
            logger.error(
                'Exception while scanning from source:%s ; %s', self,
                error_message
            )

            message = _('Error while scanning; %s') % error_message
            self.logs.create(message=message)
            raise SourceException(message)
        else:
            return SourceUploadedFile(
                source=self, file=PseudoFile(
                    file=temporary_file_object, name='scan {}'.format(now())
                )
            )


class StagingFolderSource(InteractiveSource):
    """
    The Staging folder source is interactive but instead of displaying an
    HTML form (like the Webform source) that allows users to freely choose a
    file from their computers, shows a list of files from a filesystem folder.
    When creating staging folders administrators choose a folder in the same
    machine where Mayan is installed. This folder is then used as the
    destination location of networked scanners or multifunctional copiers.
    The scenario for staging folders is as follows: An user walks up to the
    networked copier, scan several papers documents, returns to their
    computer, open Mayan, select to upload a new document but choose the
    previously defined staging folder source, now they see the list of
    documents with a small preview and can proceed to process one by one and
    convert the scanned files into Mayan EDMS documents. Staging folders are
    useful when many users share a few networked scanners.
    """
    can_compress = True
    is_interactive = True
    source_type = SOURCE_CHOICE_STAGING

    folder_path = models.CharField(
        max_length=255, help_text=_('Server side filesystem path.'),
        verbose_name=_('Folder path')
    )
    preview_width = models.IntegerField(
        help_text=_('Width value to be passed to the converter backend.'),
        verbose_name=_('Preview width')
    )
    preview_height = models.IntegerField(
        blank=True, null=True,
        help_text=_('Height value to be passed to the converter backend.'),
        verbose_name=_('Preview height')
    )
    uncompress = models.CharField(
        choices=SOURCE_INTERACTIVE_UNCOMPRESS_CHOICES, max_length=1,
        help_text=_('Whether to expand or not compressed archives.'),
        verbose_name=_('Uncompress')
    )
    delete_after_upload = models.BooleanField(
        default=True,
        help_text=_(
            'Delete the file after is has been successfully uploaded.'
        ),
        verbose_name=_('Delete after upload')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('Staging folder')
        verbose_name_plural = _('Staging folders')

    def clean_up_upload_file(self, upload_file_object):
        if self.delete_after_upload:
            try:
                upload_file_object.extra_data.delete()
            except Exception as exception:
                logger.error(
                    'Error deleting staging file: %s; %s', upload_file_object,
                    exception
                )
                raise Exception(
                    _('Error deleting staging file; %s') % exception
                )

    def get_file(self, *args, **kwargs):
        return StagingFile(staging_folder=self, *args, **kwargs)

    def get_files(self):
        try:
            for entry in sorted([os.path.normcase(f) for f in os.listdir(self.folder_path) if os.path.isfile(os.path.join(self.folder_path, f))]):
                yield self.get_file(filename=entry)
        except OSError as exception:
            logger.error(
                'Unable get list of staging files from source: %s; %s', self,
                exception
            )
            raise Exception(
                _('Unable get list of staging files: %s') % exception
            )

    def get_upload_file_object(self, form_data):
        staging_file = self.get_file(
            encoded_filename=form_data['staging_file_id']
        )
        return SourceUploadedFile(
            source=self, file=staging_file.as_file(), extra_data=staging_file
        )


class WebFormSource(InteractiveSource):
    """
    The webform source is an HTML form with a drag and drop window that opens
    a file browser on the user's computer. This Source is interactive, meaning
    users control live what documents they want to upload. This source is
    useful when admins want to allow users to upload any kind of file as
    documents from their own computers such as when each user has their own
    scanner.
    """
    can_compress = True
    is_interactive = True
    source_type = SOURCE_CHOICE_WEB_FORM

    # TODO: unify uncompress as an InteractiveSource field
    uncompress = models.CharField(
        choices=SOURCE_INTERACTIVE_UNCOMPRESS_CHOICES,
        help_text=_('Whether to expand or not compressed archives.'),
        max_length=1, verbose_name=_('Uncompress')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('Web form')
        verbose_name_plural = _('Web forms')

    # Default path
    def get_upload_file_object(self, form_data):
        return SourceUploadedFile(source=self, file=form_data['file'])


class OutOfProcessSource(Source):
    is_interactive = False

    objects = models.Manager()

    class Meta:
        verbose_name = _('Out of process')
        verbose_name_plural = _('Out of process')


class IntervalBaseModel(OutOfProcessSource):
    interval = models.PositiveIntegerField(
        default=DEFAULT_INTERVAL,
        help_text=_('Interval in seconds between checks for new documents.'),
        verbose_name=_('Interval')
    )
    document_type = models.ForeignKey(
        DocumentType,
        help_text=_(
            'Assign a document type to documents uploaded from this source.'
        ), on_delete=models.CASCADE,
        verbose_name=_('Document type')
    )
    uncompress = models.CharField(
        choices=SOURCE_UNCOMPRESS_CHOICES,
        help_text=_('Whether to expand or not, compressed archives.'),
        max_length=1, verbose_name=_('Uncompress')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('Interval source')
        verbose_name_plural = _('Interval sources')

    def _delete_periodic_task(self, pk=None):
        try:
            periodic_task = PeriodicTask.objects.get(
                name=self._get_periodic_task_name(pk)
            )

            interval_instance = periodic_task.interval

            if tuple(interval_instance.periodictask_set.values_list('id', flat=True)) == (periodic_task.pk,):
                # Only delete the interval if nobody else is using it
                interval_instance.delete()
            else:
                periodic_task.delete()
        except PeriodicTask.DoesNotExist:
            logger.warning(
                'Tried to delete non existant periodic task "%s"',
                self._get_periodic_task_name(pk)
            )

    def _get_periodic_task_name(self, pk=None):
        return 'check_interval_source-%i' % (pk or self.pk)

    def delete(self, *args, **kwargs):
        pk = self.pk
        super(IntervalBaseModel, self).delete(*args, **kwargs)
        self._delete_periodic_task(pk)

    def save(self, *args, **kwargs):
        new_source = not self.pk
        super(IntervalBaseModel, self).save(*args, **kwargs)

        if not new_source:
            self._delete_periodic_task()

        interval_instance, created = IntervalSchedule.objects.get_or_create(
            every=self.interval, period='seconds'
        )
        # Create a new interval or reuse someone else's
        PeriodicTask.objects.create(
            name=self._get_periodic_task_name(),
            interval=interval_instance,
            task='sources.tasks.task_check_interval_source',
            kwargs=json.dumps({'source_id': self.pk})
        )


class EmailBaseModel(IntervalBaseModel):
    """
    POP3 email and IMAP email sources are non-interactive sources that
    periodically fetch emails from an email account using either the POP3 or
    IMAP email protocol. These sources are useful when users need to scan
    documents outside their office, they can photograph a paper document with
    their phones and send the image to a designated email that is setup as a
    Mayan POP3 or IMAP source. Mayan will periodically download the emails
    and process them as Mayan documents.
    """
    host = models.CharField(max_length=128, verbose_name=_('Host'))
    ssl = models.BooleanField(default=True, verbose_name=_('SSL'))
    port = models.PositiveIntegerField(blank=True, null=True, help_text=_(
        'Typical choices are 110 for POP3, 995 for POP3 over SSL, 143 for '
        'IMAP, 993 for IMAP over SSL.'), verbose_name=_('Port')
    )
    username = models.CharField(max_length=96, verbose_name=_('Username'))
    password = models.CharField(max_length=96, verbose_name=_('Password'))
    metadata_attachment_name = models.CharField(
        default=DEFAULT_METADATA_ATTACHMENT_NAME,
        help_text=_(
            'Name of the attachment that will contains the metadata type '
            'names and value pairs to be assigned to the rest of the '
            'downloaded attachments. Note: This attachment has to be the '
            'first attachment.'
        ), max_length=128, verbose_name=_('Metadata attachment name')
    )
    subject_metadata_type = models.ForeignKey(
        blank=True, help_text=_(
            'Select a metadata type valid for the document type selected in '
            'which to store the email\'s subject.'
        ), on_delete=models.CASCADE, null=True, related_name='email_subject',
        to=MetadataType, verbose_name=_('Subject metadata type')
    )
    from_metadata_type = models.ForeignKey(
        blank=True, help_text=_(
            'Select a metadata type valid for the document type selected in '
            'which to store the email\'s "from" value.'
        ), on_delete=models.CASCADE, null=True, related_name='email_from',
        to=MetadataType, verbose_name=_('From metadata type')
    )
    store_body = models.BooleanField(
        default=True, help_text=_(
            'Store the body of the email as a text document.'
        ), verbose_name=_('Store email body')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('Email source')
        verbose_name_plural = _('Email sources')

    def clean(self):
        if self.subject_metadata_type:
            if self.subject_metadata_type.pk not in self.document_type.metadata.values_list('metadata_type', flat=True):
                raise ValidationError(
                    {
                        'subject_metadata_type': _(
                            'Subject metadata type "%(metadata_type)s" is not '
                            'valid for the document type: %(document_type)s'
                        ) % {
                            'metadata_type': self.subject_metadata_type,
                            'document_type': self.document_type
                        }
                    }
                )

        if self.from_metadata_type:
            if self.from_metadata_type.pk not in self.document_type.metadata.values_list('metadata_type', flat=True):
                raise ValidationError(
                    {
                        'from_metadata_type': _(
                            '"From" metadata type "%(metadata_type)s" is not '
                            'valid for the document type: %(document_type)s'
                        ) % {
                            'metadata_type': self.from_metadata_type,
                            'document_type': self.document_type
                        }
                    }
                )

    # From: http://bookmarks.honewatson.com/2009/08/11/
    #   python-gmail-imaplib-search-subject-get-attachments/
    # TODO: Add lock to avoid running more than once concurrent same document
    # download
    # TODO: Use message ID for lock

    @staticmethod
    def getheader(header_text, default='ascii'):

        headers = decode_header(header_text)
        header_sections = [
            force_text(text, charset or default) for text, charset in headers
        ]
        return ''.join(header_sections)

    @staticmethod
    def process_message(source, message):
        counter = 1
        email = message_from_string(message)
        metadata_dictionary = {}

        if source.subject_metadata_type:
            metadata_dictionary[
                source.subject_metadata_type.name
            ] = EmailBaseModel.getheader(email['Subject'])

        if source.from_metadata_type:
            metadata_dictionary[
                source.from_metadata_type.name
            ] = EmailBaseModel.getheader(email['From'])

        for part in email.walk():
            disposition = part.get('Content-Disposition', 'none')
            logger.debug('Disposition: %s', disposition)

            if disposition.startswith('attachment'):
                raw_filename = part.get_filename()

                if raw_filename:
                    filename = collapse_rfc2231_value(raw_filename)

                    # Decode base64 encoded filename
                    # https://stackoverflow.com/a/21859258/1364435
                    if decode_header(filename)[0][1] is not None:
                        filename = str(decode_header(filename)[0][0]).decode(decode_header(filename)[0][1])

                else:
                    filename = _('attachment-%i') % counter
                    counter += 1

                logger.debug('filename: %s', filename)

                with Attachment(part, name=filename) as file_object:
                    if filename == source.metadata_attachment_name:
                        metadata_dictionary = yaml.safe_load(
                            file_object.read()
                        )
                        logger.debug(
                            'Got metadata dictionary: %s', metadata_dictionary
                        )
                    else:
                        document = source.handle_upload(
                            document_type=source.document_type,
                            file_object=file_object, label=filename,
                            expand=(
                                source.uncompress == SOURCE_UNCOMPRESS_CHOICE_Y
                            )
                        )
                        if metadata_dictionary:
                            set_bulk_metadata(
                                document=document,
                                metadata_dictionary=metadata_dictionary
                            )
            else:
                logger.debug('No Content-Disposition')

                content_type = part.get_content_type()

                logger.debug('content_type: %s', content_type)

                if content_type == 'text/plain' and source.store_body:
                    content = part.get_payload(decode=True).decode(part.get_content_charset())
                    with ContentFile(content=content, name='email_body.txt') as file_object:
                        document = source.handle_upload(
                            document_type=source.document_type,
                            file_object=file_object,
                            expand=SOURCE_UNCOMPRESS_CHOICE_N, label='email_body.txt',
                        )
                        if metadata_dictionary:
                            set_bulk_metadata(
                                document=document,
                                metadata_dictionary=metadata_dictionary
                            )


class POP3Email(EmailBaseModel):
    source_type = SOURCE_CHOICE_EMAIL_POP3

    timeout = models.PositiveIntegerField(
        default=DEFAULT_POP3_TIMEOUT, verbose_name=_('Timeout')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('POP email')
        verbose_name_plural = _('POP email')

    def check_source(self):
        logger.debug('Starting POP3 email fetch')
        logger.debug('host: %s', self.host)
        logger.debug('ssl: %s', self.ssl)

        if self.ssl:
            mailbox = poplib.POP3_SSL(self.host, self.port)
        else:
            mailbox = poplib.POP3(self.host, self.port, timeout=self.timeout)

        mailbox.getwelcome()
        mailbox.user(self.username)
        mailbox.pass_(self.password)
        messages_info = mailbox.list()

        logger.debug('messages_info:')
        logger.debug(messages_info)
        logger.debug('messages count: %s', len(messages_info[1]))

        for message_info in messages_info[1]:
            message_number, message_size = message_info.split()
            logger.debug('message_number: %s', message_number)
            logger.debug('message_size: %s', message_size)

            complete_message = '\n'.join(mailbox.retr(message_number)[1])

            EmailBaseModel.process_message(
                source=self, message=complete_message
            )
            mailbox.dele(message_number)

        mailbox.quit()


class IMAPEmail(EmailBaseModel):
    source_type = SOURCE_CHOICE_EMAIL_IMAP

    mailbox = models.CharField(
        default=DEFAULT_IMAP_MAILBOX,
        help_text=_('IMAP Mailbox from which to check for messages.'),
        max_length=64, verbose_name=_('Mailbox')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('IMAP email')
        verbose_name_plural = _('IMAP email')

    # http://www.doughellmann.com/PyMOTW/imaplib/
    def check_source(self):
        logger.debug('Starting IMAP email fetch')
        logger.debug('host: %s', self.host)
        logger.debug('ssl: %s', self.ssl)

        if self.ssl:
            mailbox = imaplib.IMAP4_SSL(self.host, self.port)
        else:
            mailbox = imaplib.IMAP4(self.host, self.port)

        mailbox.login(self.username, self.password)
        mailbox.select(self.mailbox)

        status, data = mailbox.search(None, 'NOT', 'DELETED')
        if data:
            messages_info = data[0].split()
            logger.debug('messages count: %s', len(messages_info))

            for message_number in messages_info:
                logger.debug('message_number: %s', message_number)
                status, data = mailbox.fetch(message_number, '(RFC822)')
                EmailBaseModel.process_message(
                    source=self, message=data[0][1]
                )
                mailbox.store(message_number, '+FLAGS', '\\Deleted')

        mailbox.expunge()
        mailbox.close()
        mailbox.logout()


class WatchFolderSource(IntervalBaseModel):
    """
    The watch folder is another non-interactive source that like the email
    source, works by periodically checking and processing documents. This
    source instead of using an email account, monitors a filesystem folder.
    Administrators can define watch folders, examples /home/mayan/watch_bills
    or /home/mayan/watch_invoices and users just need to copy the documents
    they want to upload as a bill or invoice to the respective filesystem
    folder. Mayan will periodically scan these filesystem locations and
    upload the files as documents, deleting them if configured.
    """
    source_type = SOURCE_CHOICE_WATCH

    folder_path = models.CharField(
        help_text=_('Server side filesystem path.'), max_length=255,
        verbose_name=_('Folder path')
    )

    objects = models.Manager()

    class Meta:
        verbose_name = _('Watch folder')
        verbose_name_plural = _('Watch folders')

    def check_source(self):
        # Force self.folder_path to unicode to avoid os.listdir returning
        # str for non-latin filenames, gh-issue #163
        for file_name in os.listdir(force_text(self.folder_path)):
            full_path = os.path.join(self.folder_path, file_name)
            if os.path.isfile(full_path):
                with File(file=open(full_path, mode='rb')) as file_object:
                    self.handle_upload(
                        file_object=file_object,
                        expand=(self.uncompress == SOURCE_UNCOMPRESS_CHOICE_Y),
                        label=file_name
                    )
                    os.unlink(full_path)


class SourceLog(models.Model):
    source = models.ForeignKey(
        on_delete=models.CASCADE, related_name='logs', to=Source,
        verbose_name=_('Source')
    )
    datetime = models.DateTimeField(
        auto_now_add=True, editable=False, verbose_name=_('Date time')
    )
    message = models.TextField(
        blank=True, editable=False, verbose_name=_('Message')
    )

    class Meta:
        get_latest_by = 'datetime'
        ordering = ('-datetime',)
        verbose_name = _('Log entry')
        verbose_name_plural = _('Log entries')
