Implement threaded comment tree model [ci skip]

commentary/abstracts.py

@@ -4,7 +4,8 @@
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.contrib.contenttypes.models import ContentType
 from django.contrib.sites.models import Site
-from django.db import models
+from django.core.validators import int_list_validator
+from django.db import models, transaction
 from django.urls import reverse
 from django.utils.encoding import python_2_unicode_compatible
 from django.utils.html import strip_tags
@@ -15,6 +16,9 @@
 from .managers import CommentManager
 
 
+tree_path_validator = int_list_validator('/', 'Invalid comment tree path')
+
+
 class BaseCommentAbstractModel(models.Model):
     """
     An abstract base class that any custom comment models probably should
@@ -30,12 +34,44 @@ class BaseCommentAbstractModel(models.Model):
         ct_field='content_type', fk_field='object_pk'
     )
 
+    # Comment content
+    body = models.TextField(_('comment'), db_column='comment')
+
     # Metadata about the comment
     site = models.ForeignKey(Site, on_delete=models.CASCADE)
+    is_public = models.BooleanField(
+        _('is public'), default=True, help_text=_(
+            'Uncheck this box to make the comment '
+            'effectively disappear from the site.'
+        )
+    )
+    is_removed = models.BooleanField(
+        _('is removed'), default=False, help_text=_(
+            'Check this box if the comment is inappropriate. A "This '
+            'comment has been removed" message will be displayed instead.'
+        )
+    )
+
+    # Dates
+    submit_date = models.DateTimeField(
+        _('date/time submitted'), auto_now_add=True, db_index=True
+    )
+    edit_date = models.DateTimeField(
+        _('date/time of last edit'), auto_now=True, db_index=True
+    )
 
     class Meta:
         abstract = True
 
+    @property
+    def is_edited(self):
+        """Check whether this comment has been edited."""
+        return self.submit_date != self.edit_date
+
+    @cached_property
+    def _date(self):
+        return self.submit_date.date()
+
     def get_content_object_url(self):
         """
         Get a URL suitable for redirecting to the content object.
@@ -45,54 +81,66 @@ def get_content_object_url(self):
             args=(self.content_type_id, self.object_pk)
         )
 
+    def get_absolute_url(self, anchor_pattern='#c%(id)s'):
+        return self.get_content_object_url() + (anchor_pattern % self.__dict__)
 
-@python_2_unicode_compatible
-class CommentAbstractModel(BaseCommentAbstractModel):
-    """
-    A user comment about some object.
-    """
-    user = models.ForeignKey(
-        settings.AUTH_USER_MODEL,
-        related_name='%(class)s_comments',
-        verbose_name=_('user'), blank=True,
+
+class AbstractTreeModel(models.Model):
+    """An abstract model class representing a tree structure."""
+    parent = models.ForeignKey(
+        'self', related_name='replies', blank=True,
+        null=True, on_delete=models.CASCADE
+    )
+    path = models.TextField(
+        'tree path', editable=False, db_index=True,
+        validators=(tree_path_validator,)
+    )
+    leaf = models.ForeignKey(
+        'self', verbose_name='last child', blank=True,
         null=True, on_delete=models.SET_NULL
     )
 
-    body = models.TextField(_('comment'), db_column='comment')
+    @property
+    def _nodes(self):
+        """Get the nodes of the path."""
+        return self.path.split('/')
 
-    submit_date = models.DateTimeField(
-        _('date/time submitted'), auto_now_add=True, db_index=True
-    )
-    edit_date = models.DateTimeField(
-        _('date/time of last edit'), auto_now=True, db_index=True
-    )
+    @property
+    def depth(self):
+        """Get the depth of the tree."""
+        return len(self._nodes)
 
-    is_public = models.BooleanField(
-        _('is public'), default=True, help_text=_(
-            'Uncheck this box to make the comment '
-            'effectively disappear from the site.'
-        )
-    )
-    is_removed = models.BooleanField(
-        _('is removed'), default=False, help_text=_(
-            'Check this box if the comment is inappropriate. A "This '
-            'comment has been removed" message will be displayed instead.'
-        )
-    )
+    @property
+    def root(self):
+        """Get the id of the root node."""
+        return int(self._nodes[0])
 
-    parent = models.ForeignKey(
-        'self', related_name='replies', blank=True,
-        null=True, on_delete=models.CASCADE
-    )
+    @property
+    def ancestors(self):
+        """Get all nodes in the path excluding the last one."""
+        return AbstractTreeModel.objects.filter(pk__in=self._nodes[:-1])
 
-    # TODO: add upvotes & downvotes
+    class Meta:
+        abstract = True
+        ordering = ('path',)
+
+
+@python_2_unicode_compatible
+class CommentAbstractModel(AbstractTreeModel, BaseCommentAbstractModel):
+    """A user's comment about some object."""
+    user = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        related_name='%(class)s_comments',
+        verbose_name=_('user'), blank=True,
+        null=True, on_delete=models.SET_NULL
+    )
 
     # Manager
     objects = CommentManager()
 
     class Meta:
         abstract = True
-        ordering = ('submit_date',)
+        ordering = ('path', 'submit_date')
         permissions = (
             ('can_moderate', 'Can moderate comments'),
         )
@@ -102,23 +150,11 @@ class Meta:
     def __str__(self):
         return '%s: %s...' % (self.user_display, strip_tags(self.body)[:50])
 
-    @property
-    def is_edited(self):
-        """Check whether this comment has been edited."""
-        return self.submit_date != self.edit_date
-
     @property
     def user_display(self):
         """Display the full name/username of the commenter."""
         return get_user_display(self.user)
 
-    @cached_property
-    def _date(self):
-        return self.submit_date.date()
-
-    def get_absolute_url(self, anchor_pattern='#c%(id)s'):
-        return self.get_content_object_url() + (anchor_pattern % self.__dict__)
-
     def strip_body(self):
         return strip_tags(self.body) if COMMENTS_ALLOW_HTML else self.body
 
@@ -136,3 +172,27 @@ def get_as_text(self):
             'domain': self.site.domain,
             'url': self.get_absolute_url()
         }
+
+    def is_editable_by(self, user):
+        """Check if a comment can be edited or removed by a user."""
+        return user == self.user
+
+    @transaction.atomic
+    def save(self, *args, **kwargs):
+        super(CommentAbstractModel, self).save(*args, **kwargs)
+        tree_path = str(self.id)
+        if self.parent:
+            tree_path = '%s/%s' % (self.parent.path, tree_path)
+            self.parent.leaf = self
+            CommentManager.filter(pk=self.parent_id).update(leaf=self.id)
+        self.path = tree_path
+        CommentManager.filter(id=self.id).update(path=self.path)
+
+    def delete(self, *args, **kwargs):
+        if self.parent_id:
+            qs = CommentManager.filter(id=self.parent_id)
+            qs.update(leaf=models.Subquery(
+                qs.exclude(id=self.id).only('id')
+                .order_by('-submit_date').values('id')[:1]
+            ))
+        super(CommentAbstractModel, self).delete(*args, **kwargs)

commentary/admin.py

@@ -14,7 +14,7 @@
 
 class CommentsAdmin(admin.ModelAdmin):
     list_display = (
-        'user', 'content_type', 'object_pk',
+        'user', 'content_type', 'object_pk', 'parent',
         'submit_date', 'is_public', 'is_removed'
     )
     list_filter = (
@@ -23,7 +23,7 @@ class CommentsAdmin(admin.ModelAdmin):
     )
     date_hierarchy = 'submit_date'
     ordering = ('-submit_date',)
-    raw_id_fields = ('user',)
+    raw_id_fields = ('user', 'parent')
     search_fields = ('body', USERNAME_FIELD)
     actions = ('flag_comments', 'approve_comments', 'remove_comments')
 

commentary/migrations/0001_initial.py

@@ -1,8 +1,8 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from django.db import models, migrations
 from django.conf import settings
+from django.db import migrations, models
 
 
 class Migration(migrations.Migration):
@@ -17,32 +17,59 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='Comment',
             fields=[
-                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
+                ('id', models.AutoField(
+                    verbose_name='ID', serialize=False,
+                    auto_created=True, primary_key=True
+                )),
                 ('object_pk', models.TextField(verbose_name='object ID')),
-                ('user_name', models.CharField(max_length=50, verbose_name="user's name", blank=True)),
-                ('user_email', models.EmailField(max_length=75, verbose_name="user's email address", blank=True)),
-                ('user_url', models.URLField(verbose_name="user's URL", blank=True)),
-                ('comment', models.TextField(max_length=3000, verbose_name='comment')),
-                ('submit_date', models.DateTimeField(default=None, verbose_name='date/time submitted')),
+                ('user_name', models.CharField(
+                    max_length=50, blank=True, verbose_name="user's name"
+                )),
+                ('user_email', models.EmailField(
+                    max_length=75, blank=True,
+                    verbose_name="user's email address"
+                )),
+                ('user_url', models.URLField(
+                    verbose_name="user's URL", blank=True
+                )),
+                ('comment', models.TextField(
+                    max_length=3000, verbose_name='comment'
+                )),
+                ('submit_date', models.DateTimeField(
+                    default=None, verbose_name='date/time submitted'
+                )),
                 ('ip_address', models.GenericIPAddressField(
-                    unpack_ipv4=True, null=True, verbose_name='IP address', blank=True)),
-                ('is_public', models.BooleanField(default=True,
-                    help_text='Uncheck this box to make the comment effectively disappear from the site.',
-                    verbose_name='is public')),
-                ('is_removed', models.BooleanField(default=False,
-                    help_text='Check this box if the comment is inappropriate. A "This comment has been removed"'
-                              ' message will be displayed instead.',
-                    verbose_name='is removed')),
-                ('content_type', models.ForeignKey(related_name='content_type_set_for_comment',
+                    unpack_ipv4=True, null=True,
+                    verbose_name='IP address', blank=True
+                )),
+                ('is_public', models.BooleanField(
+                    default=True, verbose_name='is public',
+                    help_text='Uncheck this box to make the comment'
+                              ' effectively disappear from the site.',
+                )),
+                ('is_removed', models.BooleanField(
+                    default=False, verbose_name='is removed',
+                    help_text='Check this box if the comment is inappropriate.'
+                              ' A "This comment has been removed" message'
+                              ' will be displayed instead.'
+                )),
+                ('content_type', models.ForeignKey(
+                    related_name='content_type_set_for_comment',
                     verbose_name='content type', to='contenttypes.ContentType',
-                    on_delete=models.CASCADE)),
-                ('site', models.ForeignKey(to='sites.Site', on_delete=models.CASCADE)),
-                ('user', models.ForeignKey(related_name='comment_comments', verbose_name='user',
-                    blank=True, to=settings.AUTH_USER_MODEL, null=True, on_delete=models.SET_NULL)),
+                    on_delete=models.CASCADE
+                )),
+                ('site', models.ForeignKey(
+                    to='sites.Site', on_delete=models.CASCADE
+                )),
+                ('user', models.ForeignKey(
+                    related_name='comment_comments', verbose_name='user',
+                    blank=True, to=settings.AUTH_USER_MODEL,
+                    null=True, on_delete=models.SET_NULL
+                )),
             ],
             options={
                 'ordering': ('submit_date',),
-                'db_table': 'commentary',
+                'db_table': 'django_comments',
                 'verbose_name': 'comment',
                 'verbose_name_plural': 'comments',
                 'permissions': [('can_moderate', 'Can moderate comments')],
@@ -52,13 +79,24 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='CommentFlag',
             fields=[
-                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
-                ('flag', models.CharField(max_length=30, verbose_name='flag', db_index=True)),
-                ('flag_date', models.DateTimeField(default=None, verbose_name='date')),
-                ('comment', models.ForeignKey(related_name='flags', verbose_name='comment',
-                    to='commentary.Comment', on_delete=models.CASCADE)),
-                ('user', models.ForeignKey(related_name='comment_flags', verbose_name='user',
-                    to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
+                ('id', models.AutoField(
+                    verbose_name='ID', serialize=False,
+                    auto_created=True, primary_key=True
+                )),
+                ('flag', models.CharField(
+                    max_length=30, verbose_name='flag', db_index=True
+                )),
+                ('flag_date', models.DateTimeField(
+                    default=None, verbose_name='date'
+                )),
+                ('comment', models.ForeignKey(
+                    related_name='flags', verbose_name='comment',
+                    to='commentary.Comment', on_delete=models.CASCADE
+                )),
+                ('user', models.ForeignKey(
+                    related_name='comment_flags', verbose_name='user',
+                    to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE
+                )),
             ],
             options={
                 'db_table': 'django_comment_flags',
@@ -69,6 +107,6 @@ class Migration(migrations.Migration):
         ),
         migrations.AlterUniqueTogether(
             name='commentflag',
-            unique_together=set([('user', 'comment', 'flag')]),
+            unique_together={'user', 'comment', 'flag'},
         ),
     ]

commentary/migrations/0002_update_user_email_field_length.py

@@ -15,7 +15,8 @@ class Migration(migrations.Migration):
             model_name='comment',
             name='user_email',
             field=models.EmailField(
-                max_length=254, verbose_name="user's email address",
-                blank=True),
+                max_length=254, blank=True,
+                verbose_name="user's email address",
+            ),
         ),
     ]

commentary/migrations/0003_add_submit_date_index.py

@@ -14,7 +14,10 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='comment',
             name='submit_date',
-            field=models.DateTimeField(default=None, verbose_name='date/time submitted', db_index=True),
+            field=models.DateTimeField(
+                default=None, db_index=True,
+                verbose_name='date/time submitted'
+            ),
             preserve_default=True,
         ),
     ]