models_database.py

# coding: utf-8
from __future__ import unicode_literals
from django.utils.encoding import python_2_unicode_compatible
from datetime import datetime
try:
    import ujson as json_reader
except ImportError:
    try:
        import simplejson as json_reader
    except:
        import json as json_reader

from math import ceil
import shutil

from django.conf import settings
from django.contrib.auth.models import User
from django.core.urlresolvers import reverse
from django.db import models
from django.http import Http404
from django.utils.http import urlencode
from django.utils.translation import ugettext_lazy as _
from django.db.models.signals import pre_delete, post_delete
from django.dispatch import receiver

from git import Repo, BadObject
from gitdb.exc import BadName
import os
from uuslug import uuslug

from zds.forum.models import Topic
from zds.gallery.models import Image, Gallery, UserGallery
from zds.tutorialv2.utils import get_content_from_json, BadManifestError
from zds.utils import get_current_user
from zds.utils.models import SubCategory, Licence, HelpWriting, Comment, Tag
from zds.utils.tutorials import get_blob
from zds.tutorialv2.models import TYPE_CHOICES, STATUS_CHOICES
from zds.tutorialv2.models.models_versioned import NotAPublicVersion
from zds.tutorialv2.managers import PublishedContentManager, PublishableContentManager
import logging

ALLOWED_TYPES = ['pdf', 'md', 'html', 'epub', 'zip']


@python_2_unicode_compatible
class PublishableContent(models.Model):
    """A tutorial whatever its size or an article.

    A PublishableContent retains metadata about a content in database, such as

    - authors, description, source (if the content comes from another website), subcategory, tags and licence ;
    - Thumbnail and gallery ;
    - Creation, publication and update date ;
    - Public, beta, validation and draft sha, for versioning ;
    - Comment support ;
    - Type, which is either "ARTICLE" or "TUTORIAL"
    """
    class Meta:
        verbose_name = 'Contenu'
        verbose_name_plural = 'Contenus'

    title = models.CharField('Titre', max_length=80)
    slug = models.CharField('Slug', max_length=80)
    description = models.CharField('Description', max_length=200)
    source = models.CharField('Source', max_length=200, blank=True, null=True)
    authors = models.ManyToManyField(User, verbose_name='Auteurs', db_index=True)
    old_pk = models.IntegerField(db_index=True, default=0)
    subcategory = models.ManyToManyField(SubCategory,
                                         verbose_name='Sous-Catégorie',
                                         blank=True, db_index=True)

    tags = models.ManyToManyField(Tag, verbose_name='Tags du contenu', blank=True, db_index=True)
    # store the thumbnail for tutorial or article
    image = models.ForeignKey(Image,
                              verbose_name='Image du tutoriel',
                              blank=True, null=True,
                              on_delete=models.SET_NULL)

    # every publishable content has its own gallery to manage images
    gallery = models.ForeignKey(Gallery,
                                verbose_name='Galerie d\'images',
                                blank=True, null=True, db_index=True)

    creation_date = models.DateTimeField('Date de création')
    pubdate = models.DateTimeField('Date de publication',
                                   blank=True, null=True, db_index=True)
    update_date = models.DateTimeField('Date de mise à jour',
                                       blank=True, null=True)

    sha_public = models.CharField('Sha1 de la version publique',
                                  blank=True, null=True, max_length=80, db_index=True)
    sha_beta = models.CharField('Sha1 de la version beta publique',
                                blank=True, null=True, max_length=80, db_index=True)
    sha_validation = models.CharField('Sha1 de la version en validation',
                                      blank=True, null=True, max_length=80, db_index=True)
    sha_draft = models.CharField('Sha1 de la version de rédaction',
                                 blank=True, null=True, max_length=80, db_index=True)
    beta_topic = models.ForeignKey(Topic, verbose_name='Sujet beta associé', default=None, blank=True, null=True)
    licence = models.ForeignKey(Licence,
                                verbose_name='Licence',
                                blank=True, null=True, db_index=True)
    # as of ZEP 12 this field is no longer the size but the type of content (article/tutorial)
    type = models.CharField(max_length=10, choices=TYPE_CHOICES, db_index=True)
    # zep03 field
    helps = models.ManyToManyField(HelpWriting, verbose_name='Aides', blank=True, db_index=True)

    relative_images_path = models.CharField(
        'chemin relatif images',
        blank=True,
        null=True,
        max_length=200)

    last_note = models.ForeignKey('ContentReaction', blank=True, null=True,
                                  related_name='last_note',
                                  verbose_name='Derniere note')
    is_locked = models.BooleanField('Est verrouillé', default=False)
    js_support = models.BooleanField('Support du Javascript', default=False)

    must_reindex = models.BooleanField(u'Si le contenu doit-être ré-indexé', default=True)

    public_version = models.ForeignKey(
        'PublishedContent', verbose_name=u'Version publiée', blank=True, null=True, on_delete=models.SET_NULL)

    objects = PublishableContentManager()

    def __str__(self):
        return self.title

    def textual_type(self):
        """Create a internationalized string with the human readable type of this content e.g The Article

        :return: internationalized string
        :rtype: str
        """
        if self.is_article():
            return _(u"L'Article")
        else:
            return _(u"Le Tutoriel")

    def save(self, *args, **kwargs):
        """
        Rewrite the `save()` function to handle slug uniqueness
        """
        if kwargs.pop('force_slug_update', True):
            self.slug = uuslug(self.title, instance=self, max_length=80)
        update_date = kwargs.pop("update_date", True)
        if update_date:
            self.update_date = datetime.now()
        super(PublishableContent, self).save(*args, **kwargs)

    def get_absolute_url(self):
        """NOTE: it's better to use the version contained in `VersionedContent`, if possible !

        :return: absolute URL to the draf version the content
        :rtype: str
        """

        return reverse('content:view', kwargs={'pk': self.pk, 'slug': self.slug})

    def get_absolute_url_beta(self):
        """NOTE: it's better to use the version contained in `VersionedContent`, if possible !

        :return: absolute URL to the beta version the content
        :rtype: str
        """

        return reverse('content:beta-view', kwargs={'pk': self.pk, 'slug': self.slug})

    def get_absolute_url_online(self):
        """NOTE: it's better to use the version contained in `VersionedContent`, if possible !

        :return:  absolute URL to the public version the content, if `self.public_version` is defined
        :rtype: str
        """

        if self.public_version:
            return self.public_version.get_absolute_url_online()

        return ''

    def get_absolute_contact_url(self, title=u'Collaboration'):
        """ Get url to send a new PM for collaboration

        :param title: what is going to be in the title of the PM before the name of the content
        :type title: str
        :return: url to the PM creation form
        :rtype: str
        """
        get = '?' + urlencode({'title': u'{} - {}'.format(title, self.title)})

        for author in self.authors.all():
            get += '&' + urlencode({'username': author.username})

        return reverse('mp-new') + get

    def get_repo_path(self, relative=False):
        """Get the path to the tutorial repository

        :param relative: if ``True``, the path will be relative, absolute otherwise.
        :return: physical path
        :rtype: str
        """
        if relative:
            return ''
        else:
            # get the full path (with tutorial/article before it)
            return os.path.join(settings.ZDS_APP['content']['repo_private_path'], self.slug)

    def in_beta(self):
        """A tutorial is not in beta if sha_beta is ``None`` or empty


        :return: ``True`` if the tutorial is in beta, ``False`` otherwise
        :rtype: bool
        """
        return (self.sha_beta is not None) and (self.sha_beta.strip() != '')

    def in_validation(self):
        """A tutorial is not in validation if sha_validation is ``None`` or empty

        :return: ``True`` if the tutorial is in validation, ``False`` otherwise
        :rtype: bool
        """
        return (self.sha_validation is not None) and (self.sha_validation.strip() != '')

    def in_drafting(self):
        """A tutorial is not in draft if sha_draft is ``None`` or empty

        :return: ``True`` if the tutorial is in draft, ``False`` otherwise
        :rtype: bool
        """
        return (self.sha_draft is not None) and (self.sha_draft.strip() != '')

    def in_public(self):
        """A tutorial is not in on line if sha_public is ``None`` or empty

        :return: ``True`` if the tutorial is on line, ``False`` otherwise
        :rtype: bool
        """
        return (self.sha_public is not None) and (self.sha_public.strip() != '')

    def is_beta(self, sha):
        """Is this version of the content the beta version ?

        :param sha: version
        :return: ``True`` if the tutorial is in beta, ``False`` otherwise
        :rtype: bool
        """
        return self.in_beta() and sha == self.sha_beta

    def is_validation(self, sha):
        """Is this version of the content the validation version ?

        :param sha: version
        :return: ``True`` if the tutorial is in validation, ``False`` otherwise
        :rtype: bool
        """
        return self.in_validation() and sha == self.sha_validation

    def is_public(self, sha):
        """Is this version of the content the published version ?

        :param sha: version
        :return: ``True`` if the tutorial is in public, ``False`` otherwise
        :rtype: bool
        """
        return self.in_public() and sha == self.sha_public

    def is_article(self):
        """
        :return: ``True`` if article, ``False`` otherwise
        :rtype: bool
        """
        return self.type == 'ARTICLE'

    def is_tutorial(self):
        """
        :return: ``True`` if tutorial, ``False`` otherwise
        :rtype: bool
        """
        return self.type == 'TUTORIAL'

    def load_version_or_404(self, sha=None, public=None):
        """Using git, load a specific version of the content. if `sha` is `None`, the draft/public version is used (if
        `public` is `True`).

        :param sha: version
        :param public: if set with the right object, return the public version
        :type public: PublishedContent
        :raise Http404: if sha is not None and related version could not be found
        :return: the versioned content
        :rtype: zds.tutorialv2.models.models_versioned.ViersionedContent
        """
        try:
            return self.load_version(sha, public)
        except (BadObject, BadName, IOError) as error:
            raise Http404(
                u"Le code sha existe mais la version demandée ne peut pas être trouvée à cause de {}:{}".format(
                    type(error), str(error)))

    def load_version(self, sha=None, public=None):
        """Using git, load a specific version of the content. if ``sha`` is ``None``,
        the draft/public version is used (if ``public`` is ``True``).

        .. attention::

            for practical reason, the returned object is filled with information from DB.

        :param sha: version
        :param public: if set with the right object, return the public version
        :type public: PublishedContent
        :raise BadObject: if sha is not None and related version could not be found
        :raise IOError: if the path to the repository is wrong
        :raise NotAPublicVersion: if the sha does not correspond to a public version
        :return: the versioned content
        :rtype: zds.tutorialv2.models.models_versioned.VersionedContent
        """

        # load the good manifest.json
        if sha is None:
            if not public:
                sha = self.sha_draft
            else:
                sha = self.sha_public
        max_title_length = PublishableContent._meta.get_field("title").max_length
        if public and isinstance(public, PublishedContent):  # use the public (altered and not versioned) repository
            path = public.get_prod_path()
            slug = public.content_public_slug

            if not os.path.isdir(path):
                raise IOError(path)

            if sha != public.sha_public:
                raise NotAPublicVersion

            manifest = open(os.path.join(path, 'manifest.json'), 'r')
            json = json_reader.loads(manifest.read())
            versioned = get_content_from_json(json, public.sha_public,
                                              slug, public=True, max_title_len=max_title_length)

        else:  # draft version, use the repository (slower, but allows manipulation)
            path = self.get_repo_path()
            slug = self.slug

            if not os.path.isdir(path):
                raise IOError(path)

            repo = Repo(path)
            data = get_blob(repo.commit(sha).tree, 'manifest.json')
            try:
                json = json_reader.loads(data)
            except ValueError:
                raise BadManifestError(
                    _(u'Une erreur est survenue lors de la lecture du manifest.json, est-ce du JSON ?'))

            versioned = get_content_from_json(json, sha, self.slug, max_title_len=max_title_length)

        self.insert_data_in_versioned(versioned)
        return versioned

    def insert_data_in_versioned(self, versioned):
        """Insert some additional data from database in a VersionedContent

        :param versioned: the VersionedContent to fill
        """

        attrs = [
            'pk', 'authors', 'subcategory', 'image', 'creation_date', 'pubdate', 'update_date', 'source',
            'sha_draft', 'sha_beta', 'sha_validation', 'sha_public'
        ]

        fns = [
            'in_beta', 'in_validation', 'in_public', 'is_article', 'is_tutorial', 'get_absolute_contact_url',
            'get_note_count', 'antispam'
        ]

        # load functions and attributs in `versioned`
        for attr in attrs:
            setattr(versioned, attr, getattr(self, attr))
        for fn in fns:
            setattr(versioned, fn, getattr(self, fn)())

        # general information
        versioned.is_beta = self.is_beta(versioned.current_version)
        versioned.is_validation = self.is_validation(versioned.current_version)
        versioned.is_public = self.is_public(versioned.current_version)

    def get_note_count(self):
        """Count all the reactions to this content. Warning, if you did not pre process this number, \
        a query will be sent

        :return: number of notes in the tutorial.
        :rtype: int
        """
        try:
            return self.count_note
        except AttributeError:
            self.count_note = ContentReaction.objects.filter(related_content__pk=self.pk).count()
            return self.count_note

    def get_last_note(self):
        """
        :return: the last answer in the thread, if any.
        :rtype: ContentReaction|None
        """
        return ContentReaction.objects.all()\
            .select_related('related_content')\
            .select_related('related_content__public_version')\
            .filter(related_content__pk=self.pk)\
            .order_by('-pubdate')\
            .first()

    def first_note(self):
        """

        :return: the first post of a topic, written by topic's author, if any.
        :rtype: ContentReaction
        """
        return ContentReaction.objects\
            .select_related('related_content')\
            .select_related('related_content__public_version')\
            .filter(related_content=self)\
            .order_by('pubdate')\
            .first()

    def last_read_note(self):
        """

        :return: the last post the user has read.
        :rtype: ContentReaction
        """
        user = get_current_user()

        if user and user.is_authenticated():
            try:
                read = ContentRead.objects\
                    .select_related('note')\
                    .select_related('note__related_content')\
                    .select_related('note__related_content__public_version')\
                    .filter(content=self, user__pk=user.pk)\
                    .latest('note__pubdate')
                if read is not None and read.note:  # one case can show a read without note : the author has just
                    # published his content and one comment has been posted by someone else.
                    return read.note

            except ContentRead.DoesNotExist:
                pass

        return self.first_note()

    def first_unread_note(self, user=None):
        """
        :return: Return the first note the user has unread.
        :rtype: ContentReaction
        """
        if user is None:
            user = get_current_user()

        if user and user.is_authenticated():
            try:
                read = ContentRead.objects\
                    .filter(content=self, user__pk=user.pk)\
                    .latest('note__pubdate')

                if read and read.note:
                    last_note = read.note

                    next_note = ContentReaction.objects\
                        .select_related('related_content')\
                        .select_related('related_content__public_version')\
                        .filter(
                            related_content__pk=self.pk,
                            pk__gt=last_note.pk)\
                        .select_related("author").first()

                    if next_note:
                        return next_note
                    else:
                        return last_note

            except ContentRead.DoesNotExist:
                pass

        return self.first_note()

    def antispam(self, user=None):
        """Check if the user is allowed to post in an tutorial according to the SPAM_LIMIT_SECONDS value.

        :param user: the user to check antispam. If ``None``, current user is used.
        :return: ``True`` if the user is not able to note (the elapsed time is not enough), ``False`` otherwise.
        :rtype: bool
        """
        if user is None:
            user = get_current_user()

        if user and user.is_authenticated():
            last_user_notes = ContentReaction.objects\
                .filter(related_content=self)\
                .filter(author=user.pk)\
                .order_by('-position')

            if last_user_notes and last_user_notes[0] == self.last_note:
                last_user_note = last_user_notes[0]
                t = datetime.now() - last_user_note.pubdate
                if t.total_seconds() < settings.ZDS_APP['forum']['spam_limit_seconds']:
                    return True

    def repo_delete(self):
        """
        Delete the entities and their filesystem counterparts
        """
        if os.path.exists(self.get_repo_path()):
            shutil.rmtree(self.get_repo_path(), False)
        if self.in_public() and self.public_version:
            if os.path.exists(self.public_version.get_prod_path()):
                shutil.rmtree(self.public_version.get_prod_path())

        Validation.objects.filter(content=self).delete()

    def add_tags(self, tag_collection):
        """
        Add all tags contained in `tag_collection` to this content.
        If a tag is unknown, it is added to the system.
        :param tag_collection: A collection of tags.
        :type tag_collection: list
        """
        for tag in tag_collection:
            try:
                current_tag, created = Tag.objects.get_or_create(title=tag.lower().strip())
                self.tags.add(current_tag)
            except ValueError as e:
                logging.getLogger("zds.tutorialv2").warn(e)

        self.save()


@receiver(pre_delete, sender=PublishableContent)
def delete_repo(sender, instance, **kwargs):
    """catch the pre_delete signal to ensure the deletion of the repository if a PublishableContent is deleted"""
    instance.repo_delete()


@receiver(post_delete, sender=PublishableContent)
def delete_gallery(sender, instance, **kwargs):
    """catch the post_delete signal to ensure the deletion of the gallery (otherwise, you generate a loop)"""
    if instance.gallery:
        instance.gallery.delete()


@python_2_unicode_compatible
class PublishedContent(models.Model):
    """A class that contains information on the published version of a content.

    Used for quick url resolution, quick listing, and to know where the public version of the files are.

    Linked to a ``PublishableContent`` for the rest. Don't forget to add a ``.prefetch_related("content")`` !!
    """

    class Meta:
        verbose_name = 'Contenu publié'
        verbose_name_plural = 'Contenus publiés'

    content = models.ForeignKey(PublishableContent, verbose_name='Contenu')

    content_type = models.CharField(max_length=10, choices=TYPE_CHOICES, db_index=True, verbose_name='Type de contenu')
    content_public_slug = models.CharField('Slug du contenu publié', max_length=80)
    content_pk = models.IntegerField('Pk du contenu publié', db_index=True)

    publication_date = models.DateTimeField('Date de publication', db_index=True, blank=True, null=True)
    update_date = models.DateTimeField('Date de mise à jour', db_index=True, blank=True, null=True, default=None)
    sha_public = models.CharField('Sha1 de la version publiée', blank=True, null=True, max_length=80, db_index=True)

    must_redirect = models.BooleanField(
        'Redirection vers  une version plus récente', blank=True, db_index=True, default=False)

    authors = models.ManyToManyField(User, verbose_name='Auteurs', db_index=True)

    objects = PublishedContentManager()
    versioned_model = None

    # sizes contain a python dict (as a string in database) with all information about file sizes
    sizes = models.CharField('Tailles des fichiers téléchargeables', max_length=512, default='{}')

    def __str__(self):
        return _('Version publique de "{}"').format(self.content.title)

    def title(self):
        if self.versioned_model:
            return self.versioned_model.title
        else:
            return self.load_public_version().title

    def description(self):
        if self.versioned_model:
            return self.versioned_model.description
        else:
            return self.load_public_version().description

    def get_prod_path(self, relative=False):
        if not relative:
            return os.path.join(settings.ZDS_APP['content']['repo_public_path'], self.content_public_slug)
        else:
            return ''

    def get_absolute_url_online(self):
        """

        :return: the URL of the published content
        :rtype: str
        """
        reversed_ = self.content_type.lower()

        return reverse(reversed_ + ':view', kwargs={'pk': self.content_pk, 'slug': self.content_public_slug})

    def load_public_version_or_404(self):
        """
        :return: the public content
        :rtype: zds.tutorialv2.models.models_database.PublicContent
        :raise Http404: if the version is not available
        """
        self.versioned_model = self.content.load_version_or_404(sha=self.sha_public, public=self)
        return self.versioned_model

    def load_public_version(self):
        """
        :rtype: zds.tutorialv2.models.models_database.PublicContent
        :return: the public content
        """
        self.versioned_model = self.content.load_version(sha=self.sha_public, public=self)
        return self.versioned_model

    def is_article(self):
        """

        :return: ``True`` if it is an article, ``False`` otherwise.
        :rtype: bool
        """
        return self.content_type == "ARTICLE"

    def is_tutorial(self):
        """

        :return: ``True`` if it is an article, ``False`` otherwise.
        :rtype: bool
        """
        return self.content_type == "TUTORIAL"

    def get_extra_contents_directory(self):
        """
        :return: path to all the "extra contents"
        :rtype: str
        """
        return os.path.join(self.get_prod_path(), settings.ZDS_APP['content']['extra_contents_dirname'])

    def have_type(self, type_):
        """check if a given extra content exists

        :return: ``True`` if the file exists, ``False`` otherwhise
        :rtype: bool
        """

        if type_ in ALLOWED_TYPES:
            return os.path.isfile(
                os.path.join(self.get_extra_contents_directory(), self.content_public_slug + '.' + type_))

        return False

    def have_md(self):
        """Check if the markdown version of the content is available

        :return: ``True`` if available, ``False`` otherwise
        :rtype: bool
        """
        return self.have_type('md')

    def have_html(self):
        """Check if the html version of the content is available

        :return: ``True`` if available, ``False`` otherwise
        :rtype: bool
        """
        return self.have_type('html')

    def have_pdf(self):
        """Check if the pdf version of the content is available

        :return: ``True`` if available, ``False`` otherwise
        :rtype: bool
        """
        return self.have_type('pdf')

    def have_epub(self):
        """Check if the standard epub version of the content is available

        :return: ``True`` if available, ``False`` otherwise
        :rtype: bool
        """
        return self.have_type('epub')

    def have_zip(self):
        """Check if the standard zip version of the content is available

        :return: ``True`` if available, ``False`` otherwise
        :rtype: bool
        """
        return self.have_type('zip')

    def get_size_file_type(self, type_):
        """
        Get the size of a given extra content.
        Is the size is not in database we get it and store it for next time.

        :return: size of file
        :rtype: int
        """
        if type_ in ALLOWED_TYPES:
            sizes = eval(str(self.sizes))
            try:
                size = sizes[type_]
            except KeyError:
                # if size is not in database we store it
                sizes[type_] = os.path.getsize(os.path.join(
                    self.get_extra_contents_directory(), self.content_public_slug + '.' + type_))
                self.sizes = sizes
                self.save()
                size = sizes[type_]
            return size
        return None

    def get_size_md(self):
        """Get the size of md

        :return: size of file
        :rtype: int
        """
        return self.get_size_file_type('md')

    def get_size_html(self):
        """Get the size of html

        :return: size of file
        :rtype: int
        """
        return self.get_size_file_type('html')

    def get_size_pdf(self):
        """Get the size of pdf

        :return: size of file
        :rtype: int
        """
        return self.get_size_file_type('pdf')

    def get_size_epub(self):
        """Get the size of epub

        :return: size of file
        :rtype: int
        """
        return self.get_size_file_type('epub')

    def get_size_zip(self):
        """Get the size of zip

        :return: size of file
        :rtype: int
        """
        return self.get_size_file_type('zip')

    def get_absolute_url_to_extra_content(self, type_):
        """Get the url that point to the extra content the user may want to download

        :param type_: the type inside allowed_type
        :type type_: str
        :return: URL to a given extra content (note that no check for existence is done)
        :rtype: str
        """

        if type_ in ALLOWED_TYPES:
            reversed_ = self.content_type.lower()

            return reverse(
                reversed_ + ':download-' + type_, kwargs={'pk': self.content_pk, 'slug': self.content_public_slug})

        return ''

    def get_absolute_url_md(self):
        """wrapper around ``self.get_absolute_url_to_extra_content('md')``

        :return: URL to the full markdown version of the published content
        :rtype: str
        """

        return self.get_absolute_url_to_extra_content('md')

    def get_absolute_url_html(self):
        """wrapper around ``self.get_absolute_url_to_extra_content('html')``

        :return: URL to the HTML version of the published content
        :rtype: str
        """

        return self.get_absolute_url_to_extra_content('html')

    def get_absolute_url_pdf(self):
        """wrapper around ``self.get_absolute_url_to_extra_content('pdf')``

        :return: URL to the PDF version of the published content
        :rtype: str
        """

        return self.get_absolute_url_to_extra_content('pdf')

    def get_absolute_url_epub(self):
        """wrapper around ``self.get_absolute_url_to_extra_content('epub')``

        :return: URL to the epub version of the published content
        :rtype: str
        """

        return self.get_absolute_url_to_extra_content('epub')

    def get_absolute_url_zip(self):
        """wrapper around ``self.get_absolute_url_to_extra_content('zip')``

        :return: URL to the zip archive of the published content
        :rtype: str
        """

        return self.get_absolute_url_to_extra_content('zip')

    def get_last_action_date(self):
        return self.update_date or self.publication_date


@python_2_unicode_compatible
class ContentReaction(Comment):
    """
    A comment written by any user about a PublishableContent he just read.
    """
    class Meta:
        verbose_name = 'note sur un contenu'
        verbose_name_plural = 'notes sur un contenu'

    related_content = models.ForeignKey(PublishableContent, verbose_name='Contenu',
                                        related_name="related_content_note", db_index=True)

    def __str__(self):
        return '<Réaction pour "{0}", #{1}>'.format(self.related_content, self.pk)

    def get_absolute_url(self):
        """Find the url to the reaction

        :return: the url of the comment
        :rtype: str
        """
        page = int(ceil(float(self.position) / settings.ZDS_APP["content"]["notes_per_page"]))
        return '{0}?page={1}#p{2}'.format(self.related_content.get_absolute_url_online(), page, self.pk)

    def get_notification_title(self):
        return self.related_content.title


@python_2_unicode_compatible
class ContentRead(models.Model):
    """
    Small model which keeps track of the user viewing tutorials.

    It remembers the PublishableContent he looked and what was the last Note at this time.
    """
    class Meta:
        verbose_name = 'Contenu lu'
        verbose_name_plural = 'Contenu lus'

    content = models.ForeignKey(PublishableContent, db_index=True)
    note = models.ForeignKey(ContentReaction, db_index=True, null=True)
    user = models.ForeignKey(User, related_name='content_notes_read', db_index=True)

    def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
        """
        Save this model but check that if we have not a related note it is because the user is content author.
        """
        if self.user not in self.content.authors.all() and self.note is None:
            raise ValueError(_(u"La note doit exister ou l'utilisateur doit être l'un des auteurs."))

        return super(ContentRead, self).save(force_insert, force_update, using, update_fields)

    def __str__(self):
        return '<Contenu "{}" lu par {}, #{}>'.format(self.content, self.user, self.note.pk)


@python_2_unicode_compatible
class Validation(models.Model):
    """
    Content validation.
    """
    class Meta:
        verbose_name = 'Validation'
        verbose_name_plural = 'Validations'

    content = models.ForeignKey(PublishableContent, null=True, blank=True,
                                verbose_name='Contenu proposé', db_index=True)
    version = models.CharField('Sha1 de la version',
                               blank=True, null=True, max_length=80, db_index=True)
    date_proposition = models.DateTimeField('Date de proposition', db_index=True, null=True, blank=True)
    comment_authors = models.TextField('Commentaire de l\'auteur', null=True, blank=True)
    validator = models.ForeignKey(User,
                                  verbose_name='Validateur',
                                  related_name='author_content_validations',
                                  blank=True, null=True, db_index=True)
    date_reserve = models.DateTimeField('Date de réservation',
                                        blank=True, null=True)
    date_validation = models.DateTimeField('Date de validation',
                                           blank=True, null=True)
    comment_validator = models.TextField('Commentaire du validateur',
                                         blank=True, null=True)
    status = models.CharField(
        max_length=10,
        choices=STATUS_CHOICES,
        default='PENDING')

    def __str__(self):
        return _('Validation de « {} »').format(self.content.title)

    def is_pending(self):
        """Check if the validation is pending

        :return: ``True`` if status is pending, ``False`` otherwise
        :rtype: bool
        """
        return self.status == 'PENDING'

    def is_pending_valid(self):
        """Check if the validation is pending (but there is a validator)

        :return: ``True`` if status is pending/valid, ``False`` otherwise
        :rtype: bool
        """
        return self.status == 'PENDING_V'

    def is_accept(self):
        """Check if the content is accepted

        :return: ``True`` if status is accepted, ``False`` otherwise
        :rtype: bool
        """
        return self.status == 'ACCEPT'

    def is_reject(self):
        """Check if the content is rejected

        :return: ``True`` if status is rejected, ``False`` otherwise
        :rtype: bool
        """
        return self.status == 'REJECT'

    def is_cancel(self):
        """Check if the content is canceled

        :return: ``True`` if status is canceled, ``False`` otherwise
        :rtype: bool
        """
        return self.status == 'CANCEL'


@receiver(models.signals.pre_delete, sender=User)
def transfer_paternity_receiver(sender, instance, **kwargs):
    """
    transfer paternity to external user on user deletion
    """
    external = sender.objects.get(username=settings.ZDS_APP["member"]["external_account"])
    PublishableContent.objects.transfer_paternity(instance, external, UserGallery)
    PublishedContent.objects.transfer_paternity(instance, external)