Added version to post content

boards/migrations/0045_post_version.py

@@ -0,0 +1,20 b''
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.5 on 2016-05-11 09:23
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('boards', '0044_globalid_content'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='post',
+            name='version',
+            field=models.IntegerField(default=1),
+        ),
+    ]

boards/admin.py

@@ -1,136 +1,151 b''
 from django.contrib import admin
 from django.utils.translation import ugettext_lazy as _
 from django.core.urlresolvers import reverse
+from django.db.models import F
 from boards.models import Post, Tag, Ban, Thread, Banner, PostImage, KeyPair, GlobalId
 
 
 @admin.register(Post)
 class PostAdmin(admin.ModelAdmin):
 
     list_display = ('id', 'title', 'text', 'poster_ip', 'linked_images', 'linked_global_id')
     list_filter = ('pub_time',)
     search_fields = ('id', 'title', 'text', 'poster_ip')
     exclude = ('referenced_posts', 'refmap', 'images', 'global_id')
     readonly_fields = ('poster_ip', 'threads', 'thread', 'linked_images',
-            'attachments', 'uid', 'url', 'pub_time', 'opening', 'linked_global_id')
+            'attachments', 'uid', 'url', 'pub_time', 'opening', 'linked_global_id',
+            'version')
 
     def ban_poster(self, request, queryset):
         bans = 0
         for post in queryset:
             poster_ip = post.poster_ip
             ban, created = Ban.objects.get_or_create(ip=poster_ip)
             if created:
                 bans += 1
         self.message_user(request, _('{} posters were banned').format(bans))
 
     def ban_with_hiding(self, request, queryset):
         bans = 0
         hidden = 0
         for post in queryset:
             poster_ip = post.poster_ip
             ban, created = Ban.objects.get_or_create(ip=poster_ip)
             if created:
                 bans += 1
             posts = Post.objects.filter(poster_ip=poster_ip, id__gte=post.id)
             hidden += posts.count()
             posts.update(hidden=True)
         self.message_user(request, _('{} posters were banned, {} messages were hidden').format(bans, hidden))
 
     def linked_images(self, obj: Post):
         images = obj.images.all()
         image_urls = ['<a href="{}"><img src="{}" /></a>'.format(
             reverse('admin:%s_%s_change' % (image._meta.app_label,
                                             image._meta.model_name),
                     args=[image.id]), image.image.url_200x150) for image in images]
         return ', '.join(image_urls)
     linked_images.allow_tags = True
 
     def linked_global_id(self, obj: Post):
         global_id = obj.global_id
         if global_id is not None:
             return '<a href="{}">{}</a>'.format(
                 reverse('admin:%s_%s_change' % (global_id._meta.app_label,
                                                 global_id._meta.model_name),
                         args=[global_id.id]), str(global_id))
     linked_global_id.allow_tags = True
 
+    def save_model(self, request, obj, form, change):
+        obj.increment_version()
+        obj.save()
+        obj.clear_cache()
+
     actions = ['ban_poster', 'ban_with_hiding']
 
 
 @admin.register(Tag)
 class TagAdmin(admin.ModelAdmin):
 
     def thread_count(self, obj: Tag) -> int:
         return obj.get_thread_count()
 
     def display_children(self, obj: Tag):
         return ', '.join([str(child) for child in obj.get_children().all()])
 
     def save_model(self, request, obj, form, change):
         super().save_model(request, obj, form, change)
         for thread in obj.get_threads().all():
             thread.refresh_tags()
     list_display = ('name', 'thread_count', 'display_children')
     search_fields = ('name',)
 
 
 @admin.register(Thread)
 class ThreadAdmin(admin.ModelAdmin):
 
     def title(self, obj: Thread) -> str:
         return obj.get_opening_post().get_title()
 
     def reply_count(self, obj: Thread) -> int:
         return obj.get_reply_count()
 
     def ip(self, obj: Thread):
         return obj.get_opening_post().poster_ip
 
     def display_tags(self, obj: Thread):
         return ', '.join([str(tag) for tag in obj.get_tags().all()])
 
     def op(self, obj: Thread):
         return obj.get_opening_post_id()
 
     # Save parent tags when editing tags
     def save_related(self, request, form, formsets, change):
         super().save_related(request, form, formsets, change)
         form.instance.refresh_tags()
+
+    def save_model(self, request, obj, form, change):
+        op = obj.get_opening_post()
+        op.increment_version()
+        op.save(update_fields=['version'])
+        obj.save()
+        op.clear_cache()
+
     list_display = ('id', 'op', 'title', 'reply_count', 'status', 'ip',
             'display_tags')
     list_filter = ('bump_time', 'status')
     search_fields = ('id', 'title')
     filter_horizontal = ('tags',)
 
 
 @admin.register(KeyPair)
 class KeyPairAdmin(admin.ModelAdmin):
     list_display = ('public_key', 'primary')
     list_filter = ('primary',)
     search_fields = ('public_key',)
 
 
 @admin.register(Ban)
 class BanAdmin(admin.ModelAdmin):
     list_display = ('ip', 'can_read')
     list_filter = ('can_read',)
     search_fields = ('ip',)
 
 
 @admin.register(Banner)
 class BannerAdmin(admin.ModelAdmin):
     list_display = ('title', 'text')
 
 
 @admin.register(PostImage)
 class PostImageAdmin(admin.ModelAdmin):
     search_fields = ('alias',)
 
 
 @admin.register(GlobalId)
 class GlobalIdAdmin(admin.ModelAdmin):
     def is_linked(self, obj):
         return Post.objects.filter(global_id=obj).exists()
 
     list_display = ('__str__', 'is_linked',)
     readonly_fields = ('content',)

boards/models/post/__init__.py

@@ -1,381 +1,393 b''
 import uuid
 
 import re
 from boards import settings
 from boards.abstracts.tripcode import Tripcode
 from boards.models import PostImage, Attachment, KeyPair, GlobalId
 from boards.models.base import Viewable
 from boards.models.post.export import get_exporter, DIFF_TYPE_JSON
 from boards.models.post.manager import PostManager
 from boards.utils import datetime_to_epoch
 from django.core.exceptions import ObjectDoesNotExist
 from django.core.urlresolvers import reverse
 from django.db import models
-from django.db.models import TextField, QuerySet
+from django.db.models import TextField, QuerySet, F
 from django.template.defaultfilters import truncatewords, striptags
 from django.template.loader import render_to_string
 
 CSS_CLS_HIDDEN_POST = 'hidden_post'
 CSS_CLS_DEAD_POST = 'dead_post'
 CSS_CLS_ARCHIVE_POST = 'archive_post'
 CSS_CLS_POST = 'post'
 CSS_CLS_MONOCHROME = 'monochrome'
 
 TITLE_MAX_WORDS = 10
 
 APP_LABEL_BOARDS = 'boards'
 
 BAN_REASON_AUTO = 'Auto'
 
 IMAGE_THUMB_SIZE = (200, 150)
 
 TITLE_MAX_LENGTH = 200
 
 REGEX_REPLY = re.compile(r'\[post\](\d+)\[/post\]')
 REGEX_GLOBAL_REPLY = re.compile(r'\[post\](\w+)::([^:]+)::(\d+)\[/post\]')
 REGEX_URL = re.compile(r'https?\://[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(/\S*)?')
 REGEX_NOTIFICATION = re.compile(r'\[user\](\w+)\[/user\]')
 
 PARAMETER_TRUNCATED = 'truncated'
 PARAMETER_TAG = 'tag'
 PARAMETER_OFFSET = 'offset'
 PARAMETER_DIFF_TYPE = 'type'
 PARAMETER_CSS_CLASS = 'css_class'
 PARAMETER_THREAD = 'thread'
 PARAMETER_IS_OPENING = 'is_opening'
 PARAMETER_POST = 'post'
 PARAMETER_OP_ID = 'opening_post_id'
 PARAMETER_NEED_OPEN_LINK = 'need_open_link'
 PARAMETER_REPLY_LINK = 'reply_link'
 PARAMETER_NEED_OP_DATA = 'need_op_data'
 
 POST_VIEW_PARAMS = (
     'need_op_data',
     'reply_link',
     'need_open_link',
     'truncated',
     'mode_tree',
     'perms',
     'tree_depth',
 )
 
 
 class Post(models.Model, Viewable):
     """A post is a message."""
 
     objects = PostManager()
 
     class Meta:
         app_label = APP_LABEL_BOARDS
         ordering = ('id',)
 
     title = models.CharField(max_length=TITLE_MAX_LENGTH, null=True, blank=True)
     pub_time = models.DateTimeField()
     text = TextField(blank=True, null=True)
     _text_rendered = TextField(blank=True, null=True, editable=False)
 
     images = models.ManyToManyField(PostImage, null=True, blank=True,
                                     related_name='post_images', db_index=True)
     attachments = models.ManyToManyField(Attachment, null=True, blank=True,
                                          related_name='attachment_posts')
 
     poster_ip = models.GenericIPAddressField()
 
     # TODO This field can be removed cause UID is used for update now
     last_edit_time = models.DateTimeField()
 
     referenced_posts = models.ManyToManyField('Post', symmetrical=False,
                                               null=True,
                                               blank=True, related_name='refposts',
                                               db_index=True)
     refmap = models.TextField(null=True, blank=True)
     threads = models.ManyToManyField('Thread', db_index=True,
                                      related_name='multi_replies')
     thread = models.ForeignKey('Thread', db_index=True, related_name='pt+')
 
     url = models.TextField()
     uid = models.TextField(db_index=True)
 
     # Global ID with author key. If the message was downloaded from another
     # server, this indicates the server.
     global_id = models.OneToOneField(GlobalId, null=True, blank=True,
                                      on_delete=models.CASCADE)
 
     tripcode = models.CharField(max_length=50, blank=True, default='')
     opening = models.BooleanField(db_index=True)
     hidden = models.BooleanField(default=False)
+    version = models.IntegerField(default=1)
 
     def __str__(self):
         return 'P#{}/{}'.format(self.id, self.get_title())
 
     def get_title(self) -> str:
         return self.title
 
     def get_title_or_text(self):
         title = self.get_title()
         if not title:
             title = truncatewords(striptags(self.get_text()), TITLE_MAX_WORDS)
 
         return title
 
     def build_refmap(self) -> None:
         """
         Builds a replies map string from replies list. This is a cache to stop
         the server from recalculating the map on every post show.
         """
 
         post_urls = [refpost.get_link_view()
                      for refpost in self.referenced_posts.all()]
 
         self.refmap = ', '.join(post_urls)
 
     def is_referenced(self) -> bool:
         return self.refmap and len(self.refmap) > 0
 
     def is_opening(self) -> bool:
         """
         Checks if this is an opening post or just a reply.
         """
 
         return self.opening
 
     def get_absolute_url(self, thread=None):
         url = None
 
         if thread is None:
             thread = self.get_thread()
 
             # Url is cached only for the "main" thread. When getting url
             # for other threads, do it manually.
             if self.url:
                 url = self.url
 
         if url is None:
             opening = self.is_opening()
             opening_id = self.id if opening else thread.get_opening_post_id()
             url = reverse('thread', kwargs={'post_id': opening_id})
             if not opening:
                 url += '#' + str(self.id)
 
         return url
 
     def get_thread(self):
         return self.thread
 
     def get_thread_id(self):
         return self.thread_id
 
     def get_threads(self) -> QuerySet:
         """
         Gets post's thread.
         """
 
         return self.threads
 
     def _get_cache_key(self):
         return [datetime_to_epoch(self.last_edit_time)]
 
     def get_view(self, *args, **kwargs) -> str:
         """
         Renders post's HTML view. Some of the post params can be passed over
         kwargs for the means of caching (if we view the thread, some params
         are same for every post and don't need to be computed over and over.
         """
 
         thread = self.get_thread()
 
         css_classes = [CSS_CLS_POST]
         if thread.is_archived():
             css_classes.append(CSS_CLS_ARCHIVE_POST)
         elif not thread.can_bump():
             css_classes.append(CSS_CLS_DEAD_POST)
         if self.is_hidden():
             css_classes.append(CSS_CLS_HIDDEN_POST)
         if thread.is_monochrome():
             css_classes.append(CSS_CLS_MONOCHROME)
 
         params = dict()
         for param in POST_VIEW_PARAMS:
             if param in kwargs:
                 params[param] = kwargs[param]
 
         params.update({
             PARAMETER_POST: self,
             PARAMETER_IS_OPENING: self.is_opening(),
             PARAMETER_THREAD: thread,
             PARAMETER_CSS_CLASS: ' '.join(css_classes),
         })
 
         return render_to_string('boards/post.html', params)
 
     def get_search_view(self, *args, **kwargs):
         return self.get_view(need_op_data=True, *args, **kwargs)
 
     def get_first_image(self) -> PostImage:
         return self.images.earliest('id')
 
     def set_global_id(self, key_pair=None):
         """
         Sets global id based on the given key pair. If no key pair is given,
         default one is used.
         """
 
         if key_pair:
             key = key_pair
         else:
             try:
                 key = KeyPair.objects.get(primary=True)
             except KeyPair.DoesNotExist:
                 # Do not update the global id because there is no key defined
                 return
         global_id = GlobalId(key_type=key.key_type,
                              key=key.public_key,
                              local_id=self.id)
         global_id.save()
 
         self.global_id = global_id
 
         self.save(update_fields=['global_id'])
 
     def get_pub_time_str(self):
         return str(self.pub_time)
 
     def get_replied_ids(self):
         """
         Gets ID list of the posts that this post replies.
         """
 
         raw_text = self.get_raw_text()
 
         local_replied = REGEX_REPLY.findall(raw_text)
         global_replied = []
         for match in REGEX_GLOBAL_REPLY.findall(raw_text):
             key_type = match[0]
             key = match[1]
             local_id = match[2]
 
             try:
                 global_id = GlobalId.objects.get(key_type=key_type,
                                                  key=key, local_id=local_id)
                 for post in Post.objects.filter(global_id=global_id).only('id'):
                     global_replied.append(post.id)
             except GlobalId.DoesNotExist:
                 pass
         return local_replied + global_replied
 
     def get_post_data(self, format_type=DIFF_TYPE_JSON, request=None,
                       include_last_update=False) -> str:
         """
         Gets post HTML or JSON data that can be rendered on a page or used by
         API.
         """
 
         return get_exporter(format_type).export(self, request,
                                                 include_last_update)
 
     def notify_clients(self, recursive=True):
         """
         Sends post HTML data to the thread web socket.
         """
 
         if not settings.get_bool('External', 'WebsocketsEnabled'):
             return
 
         thread_ids = list()
         for thread in self.get_threads().all():
             thread_ids.append(thread.id)
 
             thread.notify_clients()
 
         if recursive:
             for reply_number in re.finditer(REGEX_REPLY, self.get_raw_text()):
                 post_id = reply_number.group(1)
 
                 try:
                     ref_post = Post.objects.get(id=post_id)
 
                     if ref_post.get_threads().exclude(id__in=thread_ids).exists():
                         # If post is in this thread, its thread was already notified.
                         # Otherwise, notify its thread separately.
                         ref_post.notify_clients(recursive=False)
                 except ObjectDoesNotExist:
                     pass
 
     def build_url(self):
         self.url = self.get_absolute_url()
         self.save(update_fields=['url'])
 
     def save(self, force_insert=False, force_update=False, using=None,
              update_fields=None):
         new_post = self.id is None
 
         self.uid = str(uuid.uuid4())
         if update_fields is not None and 'uid' not in update_fields:
             update_fields += ['uid']
 
         if not new_post:
             for thread in self.get_threads().all():
                 thread.last_edit_time = self.last_edit_time
 
                 thread.save(update_fields=['last_edit_time', 'status'])
 
         super().save(force_insert, force_update, using, update_fields)
 
         if self.url is None:
             self.build_url()
 
     def get_text(self) -> str:
         return self._text_rendered
 
     def get_raw_text(self) -> str:
         return self.text
 
     def get_sync_text(self) -> str:
         """
         Returns text applicable for sync. It has absolute post reflinks.
         """
 
         replacements = dict()
         for post_id in REGEX_REPLY.findall(self.get_raw_text()):
             absolute_post_id = str(Post.objects.get(id=post_id).global_id)
             replacements[post_id] = absolute_post_id
 
         text = self.get_raw_text() or ''
         for key in replacements:
             text = text.replace('[post]{}[/post]'.format(key),
                                 '[post]{}[/post]'.format(replacements[key]))
         text = text.replace('\r\n', '\n').replace('\r', '\n')
 
         return text
 
     def connect_threads(self, opening_posts):
         for opening_post in opening_posts:
             threads = opening_post.get_threads().all()
             for thread in threads:
                 if thread.can_bump():
                     thread.update_bump_status()
 
                 thread.last_edit_time = self.last_edit_time
                 thread.save(update_fields=['last_edit_time', 'status'])
             self.threads.add(opening_post.get_thread())
 
     def get_tripcode(self):
         if self.tripcode:
             return Tripcode(self.tripcode)
 
     def get_link_view(self):
         """
         Gets view of a reflink to the post.
         """
         result = '<a href="{}">&gt;&gt;{}</a>'.format(self.get_absolute_url(),
                                                       self.id)
         if self.is_opening():
             result = '<b>{}</b>'.format(result)
 
         return result
 
     def is_hidden(self) -> bool:
         return self.hidden
 
     def set_hidden(self, hidden):
         self.hidden = hidden
+
+    def increment_version(self):
+        self.version = F('version') + 1
+
+    def clear_cache(self):
+        global_id = self.global_id
+        if global_id is not None and global_id.is_local()\
+                and global_id.content is not None:
+            global_id.content = None
+            global_id.save()
+            global_id.signature_set.all().delete()

boards/models/post/sync.py

@@ -1,284 +1,287 b''
 import xml.etree.ElementTree as et
 
 from boards.models.attachment.downloaders import download
 from boards.utils import get_file_mimetype, get_file_hash
 from django.db import transaction
 from boards.models import KeyPair, GlobalId, Signature, Post, Tag
 
 EXCEPTION_NODE = 'Sync node returned an error: {}'
 EXCEPTION_OP = 'Load the OP first'
 EXCEPTION_DOWNLOAD = 'File was not downloaded'
 EXCEPTION_HASH = 'File hash does not match attachment hash'
 EXCEPTION_SIGNATURE = 'Invalid model signature for {}'
 ENCODING_UNICODE = 'unicode'
 
 TAG_MODEL = 'model'
 TAG_REQUEST = 'request'
 TAG_RESPONSE = 'response'
 TAG_ID = 'id'
 TAG_STATUS = 'status'
 TAG_MODELS = 'models'
 TAG_TITLE = 'title'
 TAG_TEXT = 'text'
 TAG_THREAD = 'thread'
 TAG_PUB_TIME = 'pub-time'
 TAG_SIGNATURES = 'signatures'
 TAG_SIGNATURE = 'signature'
 TAG_CONTENT = 'content'
 TAG_ATTACHMENTS = 'attachments'
 TAG_ATTACHMENT = 'attachment'
 TAG_TAGS = 'tags'
 TAG_TAG = 'tag'
 TAG_ATTACHMENT_REFS = 'attachment-refs'
 TAG_ATTACHMENT_REF = 'attachment-ref'
 TAG_TRIPCODE = 'tripcode'
+TAG_VERSION = 'version'
 
 TYPE_GET = 'get'
 
 ATTR_VERSION = 'version'
 ATTR_TYPE = 'type'
 ATTR_NAME = 'name'
 ATTR_VALUE = 'value'
 ATTR_MIMETYPE = 'mimetype'
 ATTR_KEY = 'key'
 ATTR_REF = 'ref'
 ATTR_URL = 'url'
 ATTR_ID_TYPE = 'id-type'
 
 ID_TYPE_MD5 = 'md5'
 
 STATUS_SUCCESS = 'success'
 
 
 class SyncException(Exception):
     pass
 
 
 class SyncManager:
     @staticmethod
     def generate_response_get(model_list: list):
         response = et.Element(TAG_RESPONSE)
 
         status = et.SubElement(response, TAG_STATUS)
         status.text = STATUS_SUCCESS
 
         models = et.SubElement(response, TAG_MODELS)
 
         for post in model_list:
             model = et.SubElement(models, TAG_MODEL)
             model.set(ATTR_NAME, 'post')
 
             global_id = post.global_id
 
             images = post.images.all()
             attachments = post.attachments.all()
             if global_id.content:
                 model.append(et.fromstring(global_id.content))
                 if len(images) > 0 or len(attachments) > 0:
                     attachment_refs = et.SubElement(model, TAG_ATTACHMENT_REFS)
                     for image in images:
                         SyncManager._attachment_to_xml(
                             None, attachment_refs, image.image.file,
                             image.hash, image.image.url)
                     for file in attachments:
                         SyncManager._attachment_to_xml(
                             None, attachment_refs, file.file.file,
                             file.hash, file.file.url)
             else:
                 content_tag = et.SubElement(model, TAG_CONTENT)
 
                 tag_id = et.SubElement(content_tag, TAG_ID)
                 global_id.to_xml_element(tag_id)
 
                 title = et.SubElement(content_tag, TAG_TITLE)
                 title.text = post.title
 
                 text = et.SubElement(content_tag, TAG_TEXT)
                 text.text = post.get_sync_text()
 
                 thread = post.get_thread()
                 if post.is_opening():
                     tag_tags = et.SubElement(content_tag, TAG_TAGS)
                     for tag in thread.get_tags():
                         tag_tag = et.SubElement(tag_tags, TAG_TAG)
                         tag_tag.text = tag.name
                 else:
                     tag_thread = et.SubElement(content_tag, TAG_THREAD)
                     thread_id = et.SubElement(tag_thread, TAG_ID)
                     thread.get_opening_post().global_id.to_xml_element(thread_id)
 
                 pub_time = et.SubElement(content_tag, TAG_PUB_TIME)
                 pub_time.text = str(post.get_pub_time_str())
 
                 if post.tripcode:
                     tripcode = et.SubElement(content_tag, TAG_TRIPCODE)
                     tripcode.text = post.tripcode
 
                 if len(images) > 0 or len(attachments) > 0:
                     attachments_tag = et.SubElement(content_tag, TAG_ATTACHMENTS)
                     attachment_refs = et.SubElement(model, TAG_ATTACHMENT_REFS)
 
                     for image in images:
                         SyncManager._attachment_to_xml(
                             attachments_tag, attachment_refs, image.image.file,
                             image.hash, image.image.url)
                     for file in attachments:
                         SyncManager._attachment_to_xml(
                             attachments_tag, attachment_refs, file.file.file,
                             file.hash, file.file.url)
+                version_tag = et.SubElement(content_tag, TAG_VERSION)
+                version_tag.text = str(post.version)
 
                 global_id.content = et.tostring(content_tag, ENCODING_UNICODE)
                 global_id.save()
 
             signatures_tag = et.SubElement(model, TAG_SIGNATURES)
             post_signatures = global_id.signature_set.all()
             if post_signatures:
                 signatures = post_signatures
             else:
                 key = KeyPair.objects.get(public_key=global_id.key)
                 signature = Signature(
                     key_type=key.key_type,
                     key=key.public_key,
                     signature=key.sign(global_id.content),
                     global_id=global_id,
                 )
                 signature.save()
                 signatures = [signature]
             for signature in signatures:
                 signature_tag = et.SubElement(signatures_tag, TAG_SIGNATURE)
                 signature_tag.set(ATTR_TYPE, signature.key_type)
                 signature_tag.set(ATTR_VALUE, signature.signature)
                 signature_tag.set(ATTR_KEY, signature.key)
 
         return et.tostring(response, ENCODING_UNICODE)
 
     @staticmethod
     @transaction.atomic
     def parse_response_get(response_xml, hostname):
         tag_root = et.fromstring(response_xml)
         tag_status = tag_root.find(TAG_STATUS)
         if STATUS_SUCCESS == tag_status.text:
             tag_models = tag_root.find(TAG_MODELS)
             for tag_model in tag_models:
                 tag_content = tag_model.find(TAG_CONTENT)
 
                 content_str = et.tostring(tag_content, ENCODING_UNICODE)
                 signatures = SyncManager._verify_model(content_str, tag_model)
 
                 tag_id = tag_content.find(TAG_ID)
                 global_id, exists = GlobalId.from_xml_element(tag_id)
 
                 if exists:
                     print('Post with same ID already exists')
                 else:
                     global_id.content = content_str
                     global_id.save()
                     for signature in signatures:
                         signature.global_id = global_id
                         signature.save()
 
                     title = tag_content.find(TAG_TITLE).text or ''
                     text = tag_content.find(TAG_TEXT).text or ''
                     pub_time = tag_content.find(TAG_PUB_TIME).text
                     tripcode_tag = tag_content.find(TAG_TRIPCODE)
                     if tripcode_tag is not None:
                         tripcode = tripcode_tag.text or ''
                     else:
                         tripcode = ''
 
                     thread = tag_content.find(TAG_THREAD)
                     tags = []
                     if thread:
                         thread_id = thread.find(TAG_ID)
                         op_global_id, exists = GlobalId.from_xml_element(thread_id)
                         if exists:
                             opening_post = Post.objects.get(global_id=op_global_id)
                         else:
                             raise SyncException(EXCEPTION_OP)
                     else:
                         opening_post = None
                         tag_tags = tag_content.find(TAG_TAGS)
                         for tag_tag in tag_tags:
                             tag, created = Tag.objects.get_or_create(
                                 name=tag_tag.text)
                             tags.append(tag)
 
                     # TODO Check that the replied posts are already present
                     # before adding new ones
 
                     files = []
                     tag_attachments = tag_content.find(TAG_ATTACHMENTS) or list()
                     tag_refs = tag_model.find(TAG_ATTACHMENT_REFS)
                     for attachment in tag_attachments:
                         tag_ref = tag_refs.find("{}[@ref='{}']".format(
                             TAG_ATTACHMENT_REF, attachment.text))
                         url = tag_ref.get(ATTR_URL)
                         attached_file = download(hostname + url)
                         if attached_file is None:
                             raise SyncException(EXCEPTION_DOWNLOAD)
 
                         hash = get_file_hash(attached_file)
                         if hash != attachment.text:
                             raise SyncException(EXCEPTION_HASH)
 
                         files.append(attached_file)
 
                     Post.objects.import_post(
                         title=title, text=text, pub_time=pub_time,
                         opening_post=opening_post, tags=tags,
                         global_id=global_id, files=files, tripcode=tripcode)
         else:
             raise SyncException(EXCEPTION_NODE.format(tag_status.text))
 
     @staticmethod
     def generate_response_list():
         response = et.Element(TAG_RESPONSE)
 
         status = et.SubElement(response, TAG_STATUS)
         status.text = STATUS_SUCCESS
 
         models = et.SubElement(response, TAG_MODELS)
 
         for post in Post.objects.prefetch_related('global_id').all():
             tag_id = et.SubElement(models, TAG_ID)
             post.global_id.to_xml_element(tag_id)
 
         return et.tostring(response, ENCODING_UNICODE)
 
     @staticmethod
     def _verify_model(content_str, tag_model):
         """
         Verifies all signatures for a single model.
         """
 
         signatures = []
 
         tag_signatures = tag_model.find(TAG_SIGNATURES)
         for tag_signature in tag_signatures:
             signature_type = tag_signature.get(ATTR_TYPE)
             signature_value = tag_signature.get(ATTR_VALUE)
             signature_key = tag_signature.get(ATTR_KEY)
 
             signature = Signature(key_type=signature_type,
                                   key=signature_key,
                                   signature=signature_value)
 
             if not KeyPair.objects.verify(signature, content_str):
                 raise SyncException(EXCEPTION_SIGNATURE.format(content_str))
 
             signatures.append(signature)
 
         return signatures
 
     @staticmethod
     def _attachment_to_xml(tag_attachments, tag_refs, file, hash, url):
         if tag_attachments is not None:
             mimetype = get_file_mimetype(file)
             attachment = et.SubElement(tag_attachments, TAG_ATTACHMENT)
             attachment.set(ATTR_MIMETYPE, mimetype)
             attachment.set(ATTR_ID_TYPE, ID_TYPE_MD5)
             attachment.text = hash
 
         attachment_ref = et.SubElement(tag_refs, TAG_ATTACHMENT_REF)
         attachment_ref.set(ATTR_REF, hash)
         attachment_ref.set(ATTR_URL, url)