Imported Upstream version 0.1+svn102upstream/0.1+svn102

17 files changed, 1478 insertions, 0 deletions

diff --git a/tagging/__init__.py b/tagging/__init__.py
new file mode 100644
index 0000000..171b9e0
--- /dev/null
+++ b/tagging/__init__.py
@@ -0,0 +1 @@
+VERSION = (0, 2, 'pre')
diff --git a/tagging/fields.py b/tagging/fields.py
new file mode 100644
index 0000000..1e66458
--- /dev/null
+++ b/tagging/fields.py
@@ -0,0 +1,109 @@
+from django.db.models import signals
+from django.db.models.fields import CharField
+from django.dispatch import dispatcher
+
+from tagging import settings
+from tagging.models import Tag
+from tagging.validators import isTagList
+
+class TagField(CharField):
+    """
+    A "special" character field that actually works as a relationship to tags
+    "under the hood". This exposes a space-separated string of tags, but does
+    the splitting/reordering/etc. under the hood.
+    """
+    def __init__(self, **kwargs):
+        kwargs['max_length'] = kwargs.get('max_length', 255)
+        kwargs['blank'] = kwargs.get('blank', True)
+        kwargs['validator_list'] = [isTagList] + kwargs.get('validator_list', [])
+        super(TagField, self).__init__(**kwargs)
+
+    def contribute_to_class(self, cls, name):
+        super(TagField, self).contribute_to_class(cls, name)
+
+        # Make this object the descriptor for field access.
+        setattr(cls, self.name, self)
+
+        # Save tags back to the database post-save
+        dispatcher.connect(self._save, signal=signals.post_save, sender=cls)
+
+    def __get__(self, instance, owner=None):
+        """
+        Tag getter. Returns an instance's tags if accessed on an instance, and
+        all of a model's tags if called on a class. That is, this model::
+
+            class Link(models.Model):
+                ...
+                tags = TagField()
+
+        Lets you do both of these::
+
+            >>> l = Link.objects.get(...)
+            >>> l.tags
+            'tag1 tag2 tag3'
+
+            >>> Link.tags
+            'tag1 tag2 tag3 tag4'
+
+        """
+        # Handle access on the model (i.e. Link.tags)
+        if instance is None:
+            return tags2str(Tag.objects.usage_for_model(owner))
+
+        tags = self._get_instance_tag_cache(instance)
+        if tags is None:
+            if instance._get_pk_val() is None:
+                self._set_instance_tag_cache(instance, '')
+            else:
+                self._set_instance_tag_cache(instance, tags2str(Tag.objects.get_for_object(instance)))
+        return self._get_instance_tag_cache(instance)
+
+    def __set__(self, instance, value):
+        """
+        Set an object's tags.
+        """
+        if instance is None:
+            raise AttributeError('%s can only be set on instances.' % self.name)
+        if settings.FORCE_LOWERCASE_TAGS and value is not None:
+            self._set_instance_tag_cache(instance, value.lower())
+        else:
+            self._set_instance_tag_cache(instance, value)
+
+    def _save(self, signal, sender, instance):
+        """
+        Save tags back to the database
+        """
+        tags = self._get_instance_tag_cache(instance)
+        if tags is not None :
+            Tag.objects.update_tags(instance, tags)
+
+    def __delete__(self, instance):
+        """
+        Clear all of an object's tags.
+        """
+        self._set_instance_tag_cache(instance, '')
+
+    def _get_instance_tag_cache(self, instance):
+        """
+        Helper: get an instance's tag cache.
+        """
+        return getattr(instance, '_%s_cache' % self.attname, None)
+
+    def _set_instance_tag_cache(self, instance, tags):
+        """
+        Helper: set an instance's tag cache.
+        """
+        setattr(instance, '_%s_cache' % self.attname, tags)
+
+    def get_internal_type(self):
+        return 'CharField'
+
+    def formfield(self, **kwargs):
+        from tagging import forms
+        defaults = {'form_class': forms.TagField}
+        defaults.update(kwargs)
+        return super(TagField, self).formfield(**defaults)
+
+# Helper
+def tags2str(tagset):
+    return u' '.join([t.name for t in tagset])
diff --git a/tagging/forms.py b/tagging/forms.py
new file mode 100644
index 0000000..875c598
--- /dev/null
+++ b/tagging/forms.py
@@ -0,0 +1,22 @@
+from django import newforms as forms
+
+from tagging.utils import get_tag_name_list
+from tagging.validators import tag_list_re
+
+class TagField(forms.CharField):
+    def clean(self, value):
+        """
+        Validates that the input is a valid list of tag names,
+        separated by a single comma, a single space or a comma
+        followed by a space.
+        """
+        value = super(TagField, self).clean(value)
+        if value == u'':
+            return value
+        if not tag_list_re.search(value):
+            raise forms.ValidationError(u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.')
+        tag_names = get_tag_name_list(value)
+        for tag_name in tag_names:
+            if len(tag_name) > 50:
+                raise forms.ValidationError(u'Tag names must be no longer than 50 characters.')
+        return value
diff --git a/tagging/managers.py b/tagging/managers.py
new file mode 100644
index 0000000..5e47605
--- /dev/null
+++ b/tagging/managers.py
@@ -0,0 +1,366 @@
+"""
+Custom Managers for generic tagging Models.
+"""
+import types
+
+from django.db import connection
+from django.db.models import Manager
+from django.db.models.query import QuerySet, parse_lookup
+from django.contrib.contenttypes.models import ContentType
+
+from tagging import settings
+from tagging.utils import calculate_cloud, get_tag_name_list, get_tag_list, LOGARITHMIC
+from tagging.validators import tag_re
+
+# Python 2.3 compatibility
+if not hasattr(__builtins__, 'set'):
+    from sets import Set as set
+
+qn = connection.ops.quote_name
+
+class TagManager(Manager):
+    def update_tags(self, obj, tag_names):
+        """
+        Update tags associated with an object.
+        """
+        ctype = ContentType.objects.get_for_model(obj)
+        current_tags = list(self.filter(items__content_type__pk=ctype.id,
+                                        items__object_id=obj._get_pk_val()))
+        updated_tag_names = set(get_tag_name_list(tag_names))
+        if settings.FORCE_LOWERCASE_TAGS:
+            updated_tag_names = [t.lower() for t in updated_tag_names]
+
+        TaggedItemModel = self._get_related_model_by_accessor('items')
+
+        # Remove tags which no longer apply
+        tags_for_removal = [tag for tag in current_tags \
+                            if tag.name not in updated_tag_names]
+        if len(tags_for_removal) > 0:
+            TaggedItemModel._default_manager.filter(content_type__pk=ctype.id,
+                                                    object_id=obj._get_pk_val(),
+                                                    tag__in=tags_for_removal).delete()
+
+        # Add new tags
+        current_tag_names = [tag.name for tag in current_tags]
+        for tag_name in updated_tag_names:
+            if tag_name not in current_tag_names:
+                tag, created = self.get_or_create(name=tag_name)
+                TaggedItemModel._default_manager.create(tag=tag, object=obj)
+
+    def add_tag(self, obj, tag_name):
+        """
+        Associates the given object with a tag.
+        """
+        if not tag_re.match(tag_name):
+            raise AttributeError(u'An invalid tag name was given: %s. Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens.' % tag_name)
+        if settings.FORCE_LOWERCASE_TAGS:
+            tag_name = tag_name.lower()
+        tag, created = self.get_or_create(name=tag_name)
+        ctype = ContentType.objects.get_for_model(obj)
+        TaggedItemModel = self._get_related_model_by_accessor('items')
+        TaggedItemModel._default_manager.get_or_create(
+            tag=tag, content_type=ctype, object_id=obj._get_pk_val())
+
+    def get_for_object(self, obj):
+        """
+        Create a queryset matching all tags associated with the given
+        object.
+        """
+        ctype = ContentType.objects.get_for_model(obj)
+        return self.filter(items__content_type__pk=ctype.id,
+                           items__object_id=obj._get_pk_val())
+
+    def usage_for_model(self, Model, counts=False, min_count=None, filters=None):
+        """
+        Obtain a list of tags associated with instances of the given
+        Model.
+
+        If ``counts`` is True, a ``count`` attribute will be added to
+        each tag, indicating how many times it has been used against
+        the Model in question.
+
+        If ``min_count`` is given, only tags which have a ``count``
+        greater than or equal to ``min_count`` will be returned.
+        Passing a value for ``min_count`` implies ``counts=True``.
+
+        To limit the tags (and counts, if specified) returned to those
+        used by a subset of the Model's instances, pass a dictionary
+        of field lookups to be applied to the given Model as the
+        ``filters`` argument.
+        """
+        if filters is None: filters = {}
+        if min_count is not None: counts = True
+
+        model_table = qn(Model._meta.db_table)
+        model_pk = '%s.%s' % (model_table, qn(Model._meta.pk.column))
+        query = """
+        SELECT DISTINCT %(tag)s.id, %(tag)s.name%(count_sql)s
+        FROM
+            %(tag)s
+            INNER JOIN %(tagged_item)s
+                ON %(tag)s.id = %(tagged_item)s.tag_id
+            INNER JOIN %(model)s
+                ON %(tagged_item)s.object_id = %(model_pk)s
+            %%s
+        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
+            %%s
+        GROUP BY %(tag)s.id, %(tag)s.name
+        %%s
+        ORDER BY %(tag)s.name ASC""" % {
+            'tag': qn(self.model._meta.db_table),
+            'count_sql': counts and (', COUNT(%s)' % model_pk) or '',
+            'tagged_item': qn(self._get_related_model_by_accessor('items')._meta.db_table),
+            'model': model_table,
+            'model_pk': model_pk,
+            'content_type_id': ContentType.objects.get_for_model(Model).id,
+        }
+
+        extra_joins = ''
+        extra_criteria = ''
+        min_count_sql = ''
+        params = []
+        if len(filters) > 0:
+            joins, where, params = parse_lookup(filters.items(), Model._meta)
+            extra_joins = ' '.join(['%s %s AS %s ON %s' % (join_type, table, alias, condition)
+                                    for (alias, (table, join_type, condition)) in joins.items()])
+            extra_criteria = 'AND %s' % (' AND '.join(where))
+        if min_count is not None:
+            min_count_sql = 'HAVING COUNT(%s) >= %%s' % model_pk
+            params.append(min_count)
+
+        cursor = connection.cursor()
+        cursor.execute(query % (extra_joins, extra_criteria, min_count_sql), params)
+        tags = []
+        for row in cursor.fetchall():
+            t = self.model(*row[:2])
+            if counts:
+                t.count = row[2]
+            tags.append(t)
+        return tags
+
+    def related_for_model(self, tags, Model, counts=False, min_count=None):
+        """
+        Obtain a list of tags related to a given list of tags - that
+        is, other tags used by items which have all the given tags.
+
+        If ``counts`` is True, a ``count`` attribute will be added to
+        each tag, indicating the number of items which have it in
+        addition to the given list of tags.
+
+        If ``min_count`` is given, only tags which have a ``count``
+        greater than or equal to ``min_count`` will be returned.
+        Passing a value for ``min_count`` implies ``counts=True``.
+        """
+        if min_count is not None: counts = True
+        tags = get_tag_list(tags)
+        tag_count = len(tags)
+        tagged_item_table = qn(self._get_related_model_by_accessor('items')._meta.db_table)
+        query = """
+        SELECT %(tag)s.id, %(tag)s.name%(count_sql)s
+        FROM %(tagged_item)s INNER JOIN %(tag)s ON %(tagged_item)s.tag_id = %(tag)s.id
+        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
+          AND %(tagged_item)s.object_id IN
+          (
+              SELECT %(tagged_item)s.object_id
+              FROM %(tagged_item)s, %(tag)s
+              WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
+                AND %(tag)s.id = %(tagged_item)s.tag_id
+                AND %(tag)s.id IN (%(tag_id_placeholders)s)
+              GROUP BY %(tagged_item)s.object_id
+              HAVING COUNT(%(tagged_item)s.object_id) = %(tag_count)s
+          )
+          AND %(tag)s.id NOT IN (%(tag_id_placeholders)s)
+        GROUP BY %(tag)s.id, %(tag)s.name
+        %(min_count_sql)s
+        ORDER BY %(tag)s.name ASC""" % {
+            'tag': qn(self.model._meta.db_table),
+            'count_sql': counts and ', COUNT(%s.object_id)' % tagged_item_table or '',
+            'tagged_item': tagged_item_table,
+            'content_type_id': ContentType.objects.get_for_model(Model).id,
+            'tag_id_placeholders': ','.join(['%s'] * tag_count),
+            'tag_count': tag_count,
+            'min_count_sql': min_count is not None and ('HAVING COUNT(%s.object_id) >= %%s' % tagged_item_table) or '',
+        }
+
+        params = [tag.id for tag in tags] * 2
+        if min_count is not None:
+            params.append(min_count)
+
+        cursor = connection.cursor()
+        cursor.execute(query, params)
+        related = []
+        for row in cursor.fetchall():
+            tag = self.model(*row[:2])
+            if counts is True:
+                tag.count = row[2]
+            related.append(tag)
+        return related
+
+    def cloud_for_model(self, Model, steps=4, distribution=LOGARITHMIC, filters=None, min_count=None):
+        """
+        Obtain a list of tags associated with instances of the given
+        Model, giving each tag a ``count`` attribute indicating how
+        many times it has been used and a ``font_size`` attribute for
+        use in displaying a tag cloud.
+
+        ``steps`` defines the range of font sizes - ``font_size`` will
+        be an integer between 1 and ``steps`` (inclusive).
+
+        ``distribution`` defines the type of font size distribution
+        algorithm which will be used - logarithmic or linear. It must
+        be either ``tagging.utils.LOGARITHMIC`` or
+        ``tagging.utils.LINEAR``.
+
+        To limit the tags displayed in the cloud to those associated
+        with a subset of the Model's instances, pass a dictionary of
+        field lookups to be applied to the given Model as the
+        ``filters`` argument.
+
+        To limit the tags displayed in the cloud to those with a
+        ``count`` greater than or equal to ``min_count``, pass a value
+        for the ``min_count`` argument.
+        """
+        tags = list(self.usage_for_model(Model, counts=True, filters=filters, min_count=min_count))
+        return calculate_cloud(tags, steps)
+
+    def _get_related_model_by_accessor(self, accessor):
+        """
+        Returns the model for the related object accessed by the
+        given attribute name.
+
+        Since we sometimes need to access the ``TaggedItem`` model
+        when managing tagging and the``Tag`` model does not have a
+        field representing this relationship, this method is used to
+        retrieve the ``TaggedItem`` model, avoiding circular imports
+        betweeen the `models` and `managers` modules.
+        """
+        for rel_obj in self.model._meta.get_all_related_objects():
+            if rel_obj.get_accessor_name() == accessor:
+                return rel_obj.model
+        raise ValueError('Could not find a related object with the accessor "%s".' % accessor)
+
+class TaggedItemManager(Manager):
+    def get_by_model(self, Model, tags):
+        """
+        Create a queryset matching instances of the given Model
+        associated with a given Tag or list of Tags.
+        """
+        tags = get_tag_list(tags)
+        tag_count = len(tags)
+        if tag_count == 0:
+            return [] # No existing tags were given
+        elif tag_count == 1:
+            tag = tags[0] # Optimisation for single tag
+        else:
+            return self.get_intersection_by_model(Model, tags)
+        ctype = ContentType.objects.get_for_model(Model)
+        rel_table = qn(self.model._meta.db_table)
+        return Model._default_manager.extra(
+            tables=[self.model._meta.db_table], # Use a non-explicit join
+            where=[
+                '%s.content_type_id = %%s' % rel_table,
+                '%s.tag_id = %%s' % rel_table,
+                '%s.%s = %s.object_id' % (qn(Model._meta.db_table),
+                                          qn(Model._meta.pk.column),
+                                          rel_table)
+            ],
+            params=[ctype.id, tag.id],
+        )
+
+    def get_intersection_by_model(self, Model, tags):
+        """
+        Create a queryset matching instances of the given Model
+        associated with all the given list of Tags.
+
+        FIXME The query currently used to grab the ids of objects
+              which have all the tags should be all that we need run,
+              using a non-explicit join for the QuerySet returned, as
+              in get_by_model, but there's currently no way to get the
+              required GROUP BY and HAVING clauses into Django's ORM.
+
+              Once the ORM is capable of this, we should have a
+              solution which requires only a single query and won't
+              have the problem where the number of ids in the IN
+              clause in the QuerySet could exceed the length allowed,
+              as could currently happen.
+        """
+        tags = get_tag_list(tags)
+        tag_count = len(tags)
+        model_table = qn(Model._meta.db_table)
+        # This query selects the ids of all objects which have all the
+        # given tags.
+        query = """
+        SELECT %(model_pk)s
+        FROM %(model)s, %(tagged_item)s
+        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
+          AND %(tagged_item)s.tag_id IN (%(tag_id_placeholders)s)
+          AND %(model_pk)s = %(tagged_item)s.object_id
+        GROUP BY %(model_pk)s
+        HAVING COUNT(%(model_pk)s) = %(tag_count)s""" % {
+            'model_pk': '%s.%s' % (model_table, qn(Model._meta.pk.column)),
+            'model': model_table,
+            'tagged_item': qn(self.model._meta.db_table),
+            'content_type_id': ContentType.objects.get_for_model(Model).id,
+            'tag_id_placeholders': ','.join(['%s'] * tag_count),
+            'tag_count': tag_count,
+        }
+
+        cursor = connection.cursor()
+        cursor.execute(query, [tag.id for tag in tags])
+        object_ids = [row[0] for row in cursor.fetchall()]
+        if len(object_ids) > 0:
+            return Model._default_manager.filter(pk__in=object_ids)
+        else:
+            return Model._default_manager.none()
+
+    def get_related(self, obj, Model, num=None):
+        """
+        Retrieve instances of ``Model`` which share tags with the
+        model instance ``obj``, ordered by the number of shared tags
+        in descending order.
+
+        If ``num`` is given, a maximum of ``num`` instances will be
+        returned.
+        """
+        model_table = qn(Model._meta.db_table)
+        content_type = ContentType.objects.get_for_model(obj)
+        related_content_type = ContentType.objects.get_for_model(Model)
+        query = """
+        SELECT %(model_pk)s, COUNT(related_tagged_item.object_id) AS %(count)s
+        FROM %(model)s, %(tagged_item)s, %(tag)s, %(tagged_item)s related_tagged_item
+        WHERE %(tagged_item)s.object_id = %%s
+          AND %(tagged_item)s.content_type_id = %(content_type_id)s
+          AND %(tag)s.id = %(tagged_item)s.tag_id
+          AND related_tagged_item.content_type_id = %(related_content_type_id)s
+          AND related_tagged_item.tag_id = %(tagged_item)s.tag_id
+          AND %(model_pk)s = related_tagged_item.object_id"""
+        if content_type.id == related_content_type.id:
+            # Exclude the given instance itself if determining related
+            # instances for the same model.
+            query += """
+          AND related_tagged_item.object_id != %(tagged_item)s.object_id"""
+        query += """
+        GROUP BY %(model_pk)s
+        ORDER BY %(count)s DESC
+        %(limit_offset)s"""
+        query = query % {
+            'model_pk': '%s.%s' % (model_table, qn(Model._meta.pk.column)),
+            'count': qn('count'),
+            'model': model_table,
+            'tagged_item': qn(self.model._meta.db_table),
+            'tag': qn(self.model._meta.get_field('tag').rel.to._meta.db_table),
+            'content_type_id': content_type.id,
+            'related_content_type_id': related_content_type.id,
+            'limit_offset': num is not None and connection.ops.limit_offset_sql(num) or '',
+        }
+
+        cursor = connection.cursor()
+        cursor.execute(query, [obj._get_pk_val()])
+        object_ids = [row[0] for row in cursor.fetchall()]
+        if len(object_ids) > 0:
+            # Use in_bulk here instead of an id__in lookup, because id__in would
+            # clobber the ordering.
+            object_dict = Model._default_manager.in_bulk(object_ids)
+            return [object_dict[object_id] for object_id in object_ids]
+        else:
+            return Model._default_manager.none()
diff --git a/tagging/models.py b/tagging/models.py
new file mode 100644
index 0000000..199e5eb
--- /dev/null
+++ b/tagging/models.py
@@ -0,0 +1,53 @@
+"""
+Models for generic tagging.
+"""
+from django.db import models
+from django.contrib.contenttypes import generic
+from django.contrib.contenttypes.models import ContentType
+
+from tagging.managers import TagManager, TaggedItemManager
+from tagging.validators import isTag
+
+class Tag(models.Model):
+    """
+    A basic tag.
+    """
+    name = models.CharField(max_length=50, unique=True, db_index=True, validator_list=[isTag])
+
+    objects = TagManager()
+
+    class Meta:
+        db_table = 'tag'
+        verbose_name = 'Tag'
+        verbose_name_plural = 'Tags'
+        ordering = ('name',)
+
+    class Admin:
+        pass
+
+    def __unicode__(self):
+        return self.name
+
+class TaggedItem(models.Model):
+    """
+    Holds the relationship between a tag and the item being tagged.
+    """
+    tag = models.ForeignKey(Tag, related_name='items')
+    content_type = models.ForeignKey(ContentType)
+    object_id = models.PositiveIntegerField()
+    object = generic.GenericForeignKey('content_type', 'object_id')
+
+    objects = TaggedItemManager()
+
+    class Meta:
+        db_table = 'tagged_item'
+        verbose_name = 'Tagged Item'
+        verbose_name_plural = 'Tagged Items'
+        # Enforce unique tag association per object
+        unique_together = (('tag', 'content_type', 'object_id'),)
+
+    class Admin:
+        pass
+
+    def __unicode__(self):
+        return u'%s [%s]' % (self.object, self.tag)
diff --git a/tagging/settings.py b/tagging/settings.py
new file mode 100644
index 0000000..18321bd
--- /dev/null
+++ b/tagging/settings.py
@@ -0,0 +1,13 @@
+"""
+Convenience module for access of custom tagging application settings,
+which enforces default settings when the main settings module which has
+been configured does not contain the appropriate settings.
+"""
+from django.conf import settings
+
+# Whether to force all tags to lowercase before they are saved to the
+# database. Default is False.
+try:
+    FORCE_LOWERCASE_TAGS = settings.FORCE_LOWERCASE_TAGS
+except AttributeError:
+    FORCE_LOWERCASE_TAGS = False
diff --git a/tagging/templatetags/__init__.py b/tagging/templatetags/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tagging/templatetags/__init__.py
diff --git a/tagging/templatetags/tagging_tags.py b/tagging/templatetags/tagging_tags.py
new file mode 100644
index 0000000..fb4347f
--- /dev/null
+++ b/tagging/templatetags/tagging_tags.py
@@ -0,0 +1,114 @@
+from django.db.models import get_model
+from django.template import Library, Node, TemplateSyntaxError, resolve_variable
+from tagging.models import Tag, TaggedItem
+
+register = Library()
+
+class TagsForModelNode(Node):
+    def __init__(self, model, context_var, counts):
+        self.model = model
+        self.context_var = context_var
+        self.counts = counts
+
+    def render(self, context):
+        model = get_model(*self.model.split('.'))
+        context[self.context_var] = Tag.objects.usage_for_model(model, counts=self.counts)
+        return ''
+
+class TagsForObjectNode(Node):
+    def __init__(self, obj, context_var):
+        self.obj = obj
+        self.context_var = context_var
+
+    def render(self, context):
+        obj = resolve_variable(self.obj, context)
+        context[self.context_var] = Tag.objects.get_for_object(obj)
+        return ''
+
+class TaggedObjectsNode(Node):
+    def __init__(self, tag, model, context_var):
+        self.tag = tag
+        self.context_var = context_var
+        self.model = model
+
+    def render(self, context):
+        tag = resolve_variable(self.tag, context)
+        model = get_model(*self.model.split('.'))
+        context[self.context_var] = TaggedItem.objects.get_by_model(model,
+                                                                    tag)
+        return ''
+
+def do_tags_for_model(parser, token):
+    """
+    Retrieves a list of ``Tag`` objects associated with a given model
+    and stores them in a context variable.
+
+    The model is specified in ``[appname].[modelname]`` format.
+
+    If specified - by providing extra ``with counts`` arguments - adds
+    a ``count`` attribute to each tag containing the number of
+    instances of the given model which have been tagged with it.
+
+    Example usage::
+
+        {% tags_for_model products.Widget as widget_tags %}
+
+        {% tags_for_model products.Widget as widget_tags with counts %}
+    """
+    bits = token.contents.split()
+    len_bits = len(bits)
+    if len_bits not in (4, 6):
+        raise TemplateSyntaxError('%s tag requires either three or five arguments' % bits[0])
+    if bits[2] != 'as':
+        raise TemplateSyntaxError("second argument to %s tag must be 'as'" % bits[0])
+    if len_bits == 6:
+        if bits[4] != 'with':
+            raise TemplateSyntaxError("if given, fourth argument to %s tag must be 'with'" % bits[0])
+        if bits[5] != 'counts':
+            raise TemplateSyntaxError("if given, fifth argument to %s tag must be 'counts'" % bits[0])
+    if len_bits == 4:
+        return TagsForModelNode(bits[1], bits[3], counts=False)
+    else:
+        return TagsForModelNode(bits[1], bits[3], counts=True)
+
+def do_tags_for_object(parser, token):
+    """
+    Retrieves a list of ``Tag`` objects associated with an object and
+    stores them in a context variable.
+
+    Example usage::
+
+        {% tags_for_object foo_object as tag_list %}
+    """
+    bits = token.contents.split()
+    if len(bits) != 4:
+        raise TemplateSyntaxError('%s tag requires exactly three arguments' % bits[0])
+    if bits[2] != 'as':
+        raise TemplateSyntaxError("second argument to %s tag must be 'as'" % bits[0])
+    return TagsForObjectNode(bits[1], bits[3])
+
+def do_tagged_objects(parser, token):
+    """
+    Retrieves a list of objects for a given Model which are tagged with
+    a given Tag and stores them in a context variable.
+
+    The tag must be an instance of a ``Tag``, not the name of a tag.
+
+    The model is specified in ``[appname].[modelname]`` format.
+
+    Example usage::
+
+        {% tagged_objects foo_tag in tv.Model as object_list %}
+    """
+    bits = token.contents.split()
+    if len(bits) != 6:
+        raise TemplateSyntaxError('%s tag requires exactly five arguments' % bits[0])
+    if bits[2] != 'in':
+        raise TemplateSyntaxError("second argument to %s tag must be 'in'" % bits[0])
+    if bits[4] != 'as':
+        raise TemplateSyntaxError("fourth argument to %s tag must be 'as'" % bits[0])
+    return TaggedObjectsNode(bits[1], bits[3], bits[5])
+
+register.tag('tags_for_model', do_tags_for_model)
+register.tag('tags_for_object', do_tags_for_object)
+register.tag('tagged_objects', do_tagged_objects)
\ No newline at end of file
diff --git a/tagging/tests/__init__.py b/tagging/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tagging/tests/__init__.py
diff --git a/tagging/tests/models.py b/tagging/tests/models.py
new file mode 100644
index 0000000..86754cd
--- /dev/null
+++ b/tagging/tests/models.py
@@ -0,0 +1,38 @@
+from django.db import models
+
+from tagging.fields import TagField
+
+class Perch(models.Model):
+    size = models.IntegerField()
+    smelly = models.BooleanField(default=True)
+
+class Parrot(models.Model):
+    state = models.CharField(max_length=50)
+    perch = models.ForeignKey(Perch, null=True)
+
+    def __unicode__(self):
+        return self.state
+
+    class Meta:
+        ordering = ['state']
+
+class Link(models.Model):
+    name = models.CharField(max_length=50)
+
+    def __unicode__(self):
+        return self.name
+
+    class Meta:
+        ordering = ['name']
+
+class Article(models.Model):
+    name = models.CharField(max_length=50)
+
+    def __unicode__(self):
+        return self.name
+
+    class Meta:
+        ordering = ['name']
+
+class FormTest(models.Model):
+    tags = TagField()
diff --git a/tagging/tests/runtests.py b/tagging/tests/runtests.py
new file mode 100644
index 0000000..ab1d49c
--- /dev/null
+++ b/tagging/tests/runtests.py
@@ -0,0 +1,8 @@
+import os, sys
+os.environ['DJANGO_SETTINGS_MODULE'] = 'tagging.tests.settings'
+
+from django.test.simple import run_tests
+
+failures = run_tests(None, verbosity=9)
+if failures:
+    sys.exit(failures)
diff --git a/tagging/tests/settings.py b/tagging/tests/settings.py
new file mode 100644
index 0000000..26e659b
--- /dev/null
+++ b/tagging/tests/settings.py
@@ -0,0 +1,27 @@
+import os
+DIRNAME = os.path.dirname(__file__)
+
+DEFAULT_CHARSET = 'utf-8'
+
+DATABASE_ENGINE = 'sqlite3'
+DATABASE_NAME = os.path.join(DIRNAME, 'tagging_test.db')
+
+#DATABASE_ENGINE = 'mysql'
+#DATABASE_NAME = 'tagging_test'
+#DATABASE_USER = 'root'
+#DATABASE_PASSWORD = ''
+#DATABASE_HOST = 'localhost'
+#DATABASE_PORT = '3306'
+
+#DATABASE_ENGINE = 'postgresql_psycopg2'
+#DATABASE_NAME = 'tagging_test'
+#DATABASE_USER = 'postgres'
+#DATABASE_PASSWORD = ''
+#DATABASE_HOST = 'localhost'
+#DATABASE_PORT = '5432'
+
+INSTALLED_APPS = (
+    'django.contrib.contenttypes',
+    'tagging',
+    'tagging.tests',
+)
diff --git a/tagging/tests/tags.txt b/tagging/tests/tags.txt
new file mode 100644
index 0000000..8543411
--- /dev/null
+++ b/tagging/tests/tags.txt
@@ -0,0 +1,122 @@
+NewMedia 53
+Website 45
+PR 44
+Status 44
+Collaboration 41
+Drupal 34
+Journalism 31
+Transparency 30
+Theory 29
+Decentralization 25
+EchoChamberProject 24
+OpenSource 23
+Film 22
+Blog 21
+Interview 21
+Political 21
+Worldview 21
+Communications 19
+Conference 19
+Folksonomy 15
+MediaCriticism 15
+Volunteer 15
+Dialogue 13
+InternationalLaw 13
+Rosen 12
+Evolution 11
+KentBye 11
+Objectivity 11
+Plante 11
+ToDo 11
+Advisor 10
+Civics 10
+Roadmap 10
+Wilber 9
+About 8
+CivicSpace 8
+Ecosystem 8
+Choice 7
+Murphy 7
+Sociology 7
+ACH 6
+del.icio.us 6
+IntelligenceAnalysis 6
+Science 6
+Credibility 5
+Distribution 5
+Diversity 5
+Errors 5
+FinalCutPro 5
+Fundraising 5
+Law 5
+PhilosophyofScience 5
+Podcast 5
+PoliticalBias 5
+Activism 4
+Analysis 4
+CBS 4
+DeceptionDetection 4
+Editing 4
+History 4
+RSS 4
+Social 4
+Subjectivity 4
+Vlog 4
+ABC 3
+ALTubes 3
+Economics 3
+FCC 3
+NYT 3
+Sirota 3
+Sundance 3
+Training 3
+Wiki 3
+XML 3
+Borger 2
+Brody 2
+Deliberation 2
+EcoVillage 2
+Identity 2
+LAMP 2
+Lobe 2
+Maine 2
+May 2
+MediaLogic 2
+Metaphor 2
+Mitchell 2
+NBC 2
+OHanlon 2
+Psychology 2
+Queen 2
+Software 2
+SpiralDynamics 2
+Strobel 2
+Sustainability 2
+Transcripts 2
+Brown 1
+Buddhism 1
+Community 1
+DigitalDivide 1
+Donnelly 1
+Education 1
+FairUse 1
+FireANT 1
+Google 1
+HumanRights 1
+KM 1
+Kwiatkowski 1
+Landay 1
+Loiseau 1
+Math 1
+Music 1
+Nature 1
+Schechter 1
+Screencast 1
+Sivaraksa 1
+Skype 1
+SocialCapital 1
+TagCloud 1
+Thielmann 1
+Thomas 1
+Tiger 1
+Wedgwood 1
\ No newline at end of file
diff --git a/tagging/tests/tests.py b/tagging/tests/tests.py
new file mode 100644
index 0000000..41a7895
--- /dev/null
+++ b/tagging/tests/tests.py
@@ -0,0 +1,384 @@
+# -*- coding: utf-8 -*-
+r"""
+>>> import os
+>>> from django import newforms as forms
+>>> from tagging import settings
+>>> from tagging.models import Tag, TaggedItem
+>>> from tagging.tests.models import Article, Link, Perch, Parrot, FormTest
+>>> from tagging.utils import calculate_cloud, get_tag_name_list, get_tag_list, get_tag, LINEAR
+>>> from tagging.validators import isTagList, isTag
+>>> from tagging.forms import TagField
+
+#############
+# Utilities #
+#############
+
+# Tag input ###################################################################
+
+# Tag names
+>>> get_tag_name_list(None)
+[]
+>>> get_tag_name_list('')
+[]
+>>> get_tag_name_list('foo')
+[u'foo']
+>>> get_tag_name_list('foo bar')
+[u'foo', u'bar']
+>>> get_tag_name_list('foo,bar')
+[u'foo', u'bar']
+>>> get_tag_name_list(',  , foo   ,   bar ,  ,baz, , ,')
+[u'foo', u'bar', u'baz']
+>>> get_tag_name_list('foo,ŠĐĆŽćžšđ')
+[u'foo', u'\u0160\u0110\u0106\u017d\u0107\u017e\u0161\u0111']
+
+# Normalised Tag list input
+>>> cheese = Tag.objects.create(name='cheese')
+>>> toast = Tag.objects.create(name='toast')
+>>> get_tag_list(cheese)
+[<Tag: cheese>]
+>>> get_tag_list('cheese toast')
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list(u'cheese toast')
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list([])
+[]
+>>> get_tag_list(['cheese',  'toast'])
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list([cheese.id,  toast.id])
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list(['cheese',  'toast', 'ŠĐĆŽćžšđ'])
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list([cheese,  toast])
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list((cheese,  toast))
+(<Tag: cheese>, <Tag: toast>)
+>>> get_tag_list(Tag.objects.filter(name__in=['cheese', 'toast']))
+[<Tag: cheese>, <Tag: toast>]
+>>> get_tag_list(['cheese', toast])
+Traceback (most recent call last):
+    ...
+ValueError: If a list or tuple of tags is provided, they must all be tag names, Tag objects or Tag ids.
+>>> get_tag_list(29)
+Traceback (most recent call last):
+    ...
+ValueError: The tag input given was invalid.
+
+# Normalised Tag input
+>>> get_tag(cheese)
+<Tag: cheese>
+>>> get_tag('cheese')
+<Tag: cheese>
+>>> get_tag(cheese.id)
+<Tag: cheese>
+>>> get_tag('mouse')
+
+# Tag clouds ##################################################################
+>>> tags = []
+>>> for line in open(os.path.join(os.path.dirname(__file__), 'tags.txt')).readlines():
+...     name, count = line.rstrip().split()
+...     tag = Tag(name=name)
+...     tag.count = int(count)
+...     tags.append(tag)
+
+>>> sizes = {}
+>>> for tag in calculate_cloud(tags, steps=5):
+...     sizes[tag.font_size] = sizes.get(tag.font_size, 0) + 1
+
+# This isn't a pre-calculated test, just making sure it's consistent
+>>> sizes
+{1: 48, 2: 20, 3: 24, 4: 19, 5: 11}
+
+>>> sizes = {}
+>>> for tag in calculate_cloud(tags, steps=5, distribution=LINEAR):
+...     sizes[tag.font_size] = sizes.get(tag.font_size, 0) + 1
+
+# This isn't a pre-calculated test, just making sure it's consistent
+>>> sizes
+{1: 97, 2: 12, 3: 7, 4: 2, 5: 4}
+
+>>> calculate_cloud(tags, steps=5, distribution='cheese')
+Traceback (most recent call last):
+    ...
+ValueError: Invalid font size distribution algorithm specified: cheese.
+
+##############
+# Validators #
+##############
+
+>>> isTagList('foo', {})
+>>> isTagList('foo bar baz', {})
+>>> isTagList('foo,bar,baz', {})
+>>> isTagList('foo, bar, baz', {})
+>>> isTagList('foo, ŠĐĆŽćžšđ, baz', {})
+>>> isTagList('foo qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvb bar', {})
+>>> isTagList('', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> isTagList(' foo', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> isTagList('foo ', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> isTagList('foo  bar', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> isTagList('foo qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbn bar', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must be no longer than 50 characters.']
+>>> isTag('f-o_1o', {})
+>>> isTag('ŠĐĆŽćžšđ', {})
+>>> isTag('f o o', {})
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens.']
+
+###############
+# Form Fields #
+###############
+
+>>> t = TagField()
+>>> t.clean('foo')
+u'foo'
+>>> t.clean('foo bar baz')
+u'foo bar baz'
+>>> t.clean('foo,bar,baz')
+u'foo,bar,baz'
+>>> t.clean('foo, bar, baz')
+u'foo, bar, baz'
+>>> t.clean('foo qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvb bar')
+u'foo qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvb bar'
+>>> t.clean(' foo')
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> t.clean('foo ')
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> t.clean('foo  bar')
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.']
+>>> t.clean('foo qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbn bar')
+Traceback (most recent call last):
+    ...
+ValidationError: [u'Tag names must be no longer than 50 characters.']
+
+# Ensure that automatically created forms use TagField
+>>> TestForm = forms.form_for_model(FormTest)
+>>> form = TestForm()
+>>> form.fields['tags'].__class__.__name__
+'TagField'
+>>> instance = FormTest(tags='one two three')
+>>> TestInstanceForm = forms.form_for_instance(instance)
+>>> form = TestInstanceForm()
+>>> form.fields['tags'].__class__.__name__
+'TagField'
+
+###########
+# Tagging #
+###########
+
+# Basic tagging ###############################################################
+
+>>> dead = Parrot.objects.create(state='dead')
+>>> Tag.objects.update_tags(dead, 'foo bar ter')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: foo>, <Tag: ter>]
+>>> Tag.objects.update_tags(dead, 'foo bar baz')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>]
+>>> Tag.objects.add_tag(dead, 'foo')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>]
+>>> Tag.objects.add_tag(dead, 'zip')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>, <Tag: zip>]
+>>> Tag.objects.add_tag(dead, 'f o o')
+Traceback (most recent call last):
+    ...
+AttributeError: An invalid tag name was given: f o o. Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens.
+
+# Note that doctest in Python 2.4 (and maybe 2.5?) doesn't support non-ascii
+# characters in output, so we're displaying the repr() here.
+>>> Tag.objects.update_tags(dead, 'ŠĐĆŽćžšđ')
+>>> repr(Tag.objects.get_for_object(dead))
+'[<Tag: \xc5\xa0\xc4\x90\xc4\x86\xc5\xbd\xc4\x87\xc5\xbe\xc5\xa1\xc4\x91>]'
+
+>>> Tag.objects.update_tags(dead, None)
+>>> Tag.objects.get_for_object(dead)
+[]
+
+# Using a model's TagField
+>>> f1 = FormTest.objects.create(tags=u'test3 test2 test1')
+>>> Tag.objects.get_for_object(f1)
+[<Tag: test1>, <Tag: test2>, <Tag: test3>]
+>>> f1.tags = u'test4'
+>>> f1.save()
+>>> Tag.objects.get_for_object(f1)
+[<Tag: test4>]
+>>> f1.tags = ''
+>>> f1.save()
+>>> Tag.objects.get_for_object(f1)
+[]
+
+# Forcing tags to lowercase
+>>> settings.FORCE_LOWERCASE_TAGS = True
+>>> Tag.objects.update_tags(dead, 'foO bAr Ter')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: foo>, <Tag: ter>]
+>>> Tag.objects.update_tags(dead, 'foO bAr baZ')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>]
+>>> Tag.objects.add_tag(dead, 'FOO')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>]
+>>> Tag.objects.add_tag(dead, 'Zip')
+>>> Tag.objects.get_for_object(dead)
+[<Tag: bar>, <Tag: baz>, <Tag: foo>, <Tag: zip>]
+>>> Tag.objects.update_tags(dead, None)
+>>> f1.tags = u'TEST5'
+>>> f1.save()
+>>> Tag.objects.get_for_object(f1)
+[<Tag: test5>]
+>>> f1.tags
+u'test5'
+
+# Retrieving tags by Model ####################################################
+
+>>> Tag.objects.usage_for_model(Parrot)
+[]
+>>> parrot_details = (
+...     ('pining for the fjords', 9, True,  'foo bar'),
+...     ('passed on',             6, False, 'bar baz ter'),
+...     ('no more',               4, True,  'foo ter'),
+...     ('late',                  2, False, 'bar ter'),
+... )
+
+>>> for state, perch_size, perch_smelly, tags in parrot_details:
+...     perch = Perch.objects.create(size=perch_size, smelly=perch_smelly)
+...     parrot = Parrot.objects.create(state=state, perch=perch)
+...     Tag.objects.update_tags(parrot, tags)
+
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, counts=True)]
+[(u'bar', 3), (u'baz', 1), (u'foo', 2), (u'ter', 3)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, min_count=2)]
+[(u'bar', 3), (u'foo', 2), (u'ter', 3)]
+
+# Limiting results to a subset of the model
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, counts=True, filters=dict(state='no more'))]
+[(u'foo', 1), (u'ter', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, counts=True, filters=dict(state__startswith='p'))]
+[(u'bar', 2), (u'baz', 1), (u'foo', 1), (u'ter', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, counts=True, filters=dict(perch__size__gt=4))]
+[(u'bar', 2), (u'baz', 1), (u'foo', 1), (u'ter', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, counts=True, filters=dict(perch__smelly=True))]
+[(u'bar', 1), (u'foo', 2), (u'ter', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.usage_for_model(Parrot, min_count=2, filters=dict(perch__smelly=True))]
+[(u'foo', 2)]
+>>> [(tag.name, hasattr(tag, 'counts')) for tag in Tag.objects.usage_for_model(Parrot, filters=dict(perch__size__gt=4))]
+[(u'bar', False), (u'baz', False), (u'foo', False), (u'ter', False)]
+>>> [(tag.name, hasattr(tag, 'counts')) for tag in Tag.objects.usage_for_model(Parrot, filters=dict(perch__size__gt=99))]
+[]
+
+# Related tags
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(Tag.objects.filter(name__in=['bar']), Parrot, counts=True)]
+[(u'baz', 1), (u'foo', 1), (u'ter', 2)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(Tag.objects.filter(name__in=['bar']), Parrot, min_count=2)]
+[(u'ter', 2)]
+>>> [tag.name for tag in Tag.objects.related_for_model(Tag.objects.filter(name__in=['bar']), Parrot, counts=False)]
+[u'baz', u'foo', u'ter']
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(Tag.objects.filter(name__in=['bar', 'ter']), Parrot, counts=True)]
+[(u'baz', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(Tag.objects.filter(name__in=['bar', 'ter', 'baz']), Parrot, counts=True)]
+[]
+
+# Once again, with feeling (strings)
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model('bar', Parrot, counts=True)]
+[(u'baz', 1), (u'foo', 1), (u'ter', 2)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model('bar', Parrot, min_count=2)]
+[(u'ter', 2)]
+>>> [tag.name for tag in Tag.objects.related_for_model('bar', Parrot, counts=False)]
+[u'baz', u'foo', u'ter']
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(['bar', 'ter'], Parrot, counts=True)]
+[(u'baz', 1)]
+>>> [(tag.name, tag.count) for tag in Tag.objects.related_for_model(['bar', 'ter', 'baz'], Parrot, counts=True)]
+[]
+
+# Retrieving tagged objects by Model ##########################################
+
+>>> foo = Tag.objects.get(name='foo')
+>>> bar = Tag.objects.get(name='bar')
+>>> baz = Tag.objects.get(name='baz')
+>>> ter = Tag.objects.get(name='ter')
+>>> TaggedItem.objects.get_by_model(Parrot, foo)
+[<Parrot: no more>, <Parrot: pining for the fjords>]
+>>> TaggedItem.objects.get_by_model(Parrot, bar)
+[<Parrot: late>, <Parrot: passed on>, <Parrot: pining for the fjords>]
+
+# Intersections are supported
+>>> TaggedItem.objects.get_by_model(Parrot, [foo, baz])
+[]
+>>> TaggedItem.objects.get_by_model(Parrot, [foo, bar])
+[<Parrot: pining for the fjords>]
+>>> TaggedItem.objects.get_by_model(Parrot, [bar, ter])
+[<Parrot: late>, <Parrot: passed on>]
+
+# You can also pass Tag QuerySets
+>>> TaggedItem.objects.get_by_model(Parrot, Tag.objects.filter(name__in=['foo', 'baz']))
+[]
+>>> TaggedItem.objects.get_by_model(Parrot, Tag.objects.filter(name__in=['foo', 'bar']))
+[<Parrot: pining for the fjords>]
+>>> TaggedItem.objects.get_by_model(Parrot, Tag.objects.filter(name__in=['bar', 'ter']))
+[<Parrot: late>, <Parrot: passed on>]
+
+# You can also pass strings and lists of strings
+>>> TaggedItem.objects.get_by_model(Parrot, 'foo baz')
+[]
+>>> TaggedItem.objects.get_by_model(Parrot, 'foo bar')
+[<Parrot: pining for the fjords>]
+>>> TaggedItem.objects.get_by_model(Parrot, 'bar ter')
+[<Parrot: late>, <Parrot: passed on>]
+>>> TaggedItem.objects.get_by_model(Parrot, ['foo', 'baz'])
+[]
+>>> TaggedItem.objects.get_by_model(Parrot, ['foo', 'bar'])
+[<Parrot: pining for the fjords>]
+>>> TaggedItem.objects.get_by_model(Parrot, ['bar', 'ter'])
+[<Parrot: late>, <Parrot: passed on>]
+
+# Issue 50 - Get by non-existent tag
+>>> TaggedItem.objects.get_by_model(Parrot, 'argatrons')
+[]
+
+# Retrieving related objects by Model #########################################
+
+# Related instances of the same Model
+>>> l1 = Link.objects.create(name='link 1')
+>>> Tag.objects.update_tags(l1, 'tag1 tag2 tag3 tag4 tag5')
+>>> l2 = Link.objects.create(name='link 2')
+>>> Tag.objects.update_tags(l2, 'tag1 tag2 tag3')
+>>> l3 = Link.objects.create(name='link 3')
+>>> Tag.objects.update_tags(l3, 'tag1')
+>>> l4 = Link.objects.create(name='link 4')
+>>> TaggedItem.objects.get_related(l1, Link)
+[<Link: link 2>, <Link: link 3>]
+>>> TaggedItem.objects.get_related(l1, Link, num=1)
+[<Link: link 2>]
+>>> TaggedItem.objects.get_related(l4, Link)
+[]
+
+# Related instance of a different Model
+>>> a1 = Article.objects.create(name='article 1')
+>>> Tag.objects.update_tags(a1, 'tag1 tag2 tag3 tag4')
+>>> TaggedItem.objects.get_related(a1, Link)
+[<Link: link 1>, <Link: link 2>, <Link: link 3>]
+>>> Tag.objects.update_tags(a1, 'tag6')
+>>> TaggedItem.objects.get_related(a1, Link)
+[]
+"""
diff --git a/tagging/utils.py b/tagging/utils.py
new file mode 100644
index 0000000..af50bac
--- /dev/null
+++ b/tagging/utils.py
@@ -0,0 +1,140 @@
+import math
+import re
+import types
+
+from django.db.models.query import QuerySet
+from django.utils.encoding import force_unicode, smart_unicode
+
+# Python 2.3 compatibility
+if not hasattr(__builtins__, 'set'):
+    from sets import Set as set
+
+find_tag_re = re.compile(r'[-\w]+', re.U)
+
+def get_tag_name_list(tag_names):
+    """
+    Finds tag names in the given string and return them as a list.
+    """
+    if tag_names is not None:
+        tag_names = force_unicode(tag_names)
+    results = find_tag_re.findall(tag_names or '')
+    return results
+
+def get_tag_list(tags):
+    """
+    Utility function for accepting tag input in a flexible manner.
+
+    If a ``Tag`` object is given, it will be returned in a list as
+    its single occupant.
+
+    If given, the tag names in the following will be used to create a
+    ``Tag`` ``QuerySet``:
+
+        * A string, which may contain multiple tag names.
+        * A list or tuple of strings corresponding to tag names.
+        * A list or tuple of integers corresponding to tag ids.
+
+    If given, the following will be returned as-is:
+
+        * A list or tuple of ``Tag`` objects.
+        * A ``Tag`` ``QuerySet``.
+    """
+    from tagging.models import Tag
+    if isinstance(tags, Tag):
+        return [tags]
+    elif isinstance(tags, QuerySet) and tags.model is Tag:
+        return tags
+    elif isinstance(tags, types.StringTypes):
+        return Tag.objects.filter(name__in=get_tag_name_list(tags))
+    elif isinstance(tags, (types.ListType, types.TupleType)):
+        if len(tags) == 0:
+            return tags
+        contents = set()
+        for item in tags:
+            if isinstance(item, types.StringTypes):
+                contents.add('string')
+            elif isinstance(item, Tag):
+                contents.add('tag')
+            elif isinstance(item, (types.IntType, types.LongType)):
+                contents.add('int')
+        if len(contents) == 1:
+            if 'string' in contents:
+                return Tag.objects.filter(name__in=[smart_unicode(tag) \
+                                                    for tag in tags])
+            elif 'tag' in contents:
+                return tags
+            elif 'int' in contents:
+                return Tag.objects.filter(id__in=tags)
+        else:
+            raise ValueError(u'If a list or tuple of tags is provided, they must all be tag names, Tag objects or Tag ids.')
+    else:
+        raise ValueError(u'The tag input given was invalid.')
+
+def get_tag(tag):
+    """
+    Utility function for accepting single tag input in a flexible
+    manner.
+
+    If a ``Tag`` object is given it will be returned as-is; if a
+    string or integer are given, they will be used to lookup the
+    appropriate ``Tag``.
+
+    If no matching tag can be found, ``None`` will be returned.
+    """
+    from tagging.models import Tag
+    if isinstance(tag, Tag):
+        return tag
+
+    try:
+        if isinstance(tag, types.StringTypes):
+            return Tag.objects.get(name=tag)
+        elif isinstance(tag, (types.IntType, types.LongType)):
+            return Tag.objects.get(id=tag)
+    except Tag.DoesNotExist:
+        pass
+
+    return None
+
+# Font size distribution algorithms
+LOGARITHMIC, LINEAR = 1, 2
+
+def calculate_cloud(tags, steps=4, distribution=LOGARITHMIC):
+    """
+    Add a ``font_size`` attribute to each tag according to the
+    frequency of its use, as indicated by its ``count``
+    attribute.
+
+    ``steps`` defines the range of font sizes - ``font_size`` will
+    be an integer between 1 and ``steps`` (inclusive).
+
+    ``distribution`` defines the type of font size distribution
+    algorithm which will be used - logarithmic or linear. It must be
+    either ``tagging.utils.LOGARITHMIC`` or ``tagging.utils.LINEAR``.
+
+    The algorithm to scale the tags logarithmically is from a
+    blog post by Anders Pearson, 'Scaling tag clouds':
+    http://thraxil.com/users/anders/posts/2005/12/13/scaling-tag-clouds/
+    """
+    if len(tags) > 0:
+        thresholds = []
+        counts = [tag.count for tag in tags]
+        max_weight = float(max(counts))
+        min_weight = float(min(counts))
+
+        # Set up the appropriate thresholds
+        if distribution == LOGARITHMIC:
+            thresholds = [math.pow(max_weight - min_weight + 1, float(i) / float(steps)) \
+                          for i in range(1, steps + 1)]
+        elif distribution == LINEAR:
+            delta = (max_weight - min_weight) / float(steps)
+            thresholds = [min_weight + i * delta for i in range(1, steps + 1)]
+        else:
+            raise ValueError(u'Invalid font size distribution algorithm specified: %s.' % distribution)
+
+        for tag in tags:
+            font_set = False
+            for i in range(steps):
+                if not font_set and tag.count <= thresholds[i]:
+                    tag.font_size = i + 1
+                    font_set = True
+    return tags
diff --git a/tagging/validators.py b/tagging/validators.py
new file mode 100644
index 0000000..363fa6d
--- /dev/null
+++ b/tagging/validators.py
@@ -0,0 +1,33 @@
+import re
+
+from django.core.validators import ValidationError
+from django.utils.encoding import smart_unicode
+
+from tagging.utils import get_tag_name_list
+
+tag_re = re.compile(r'^[-\w]+$', re.U)
+tag_list_re = re.compile(r'^[-\w]+(?:(?:,\s|[,\s])[-\w]+)*$', re.U)
+
+def isTagList(field_data, all_data):
+    """
+    Validates that ``field_data`` is a valid list of tag names,
+    separated by a single comma, a single space or a comma followed
+    by a space.
+    """
+    if field_data is not None:
+        field_data = smart_unicode(field_data)
+    if not tag_list_re.search(field_data):
+        raise ValidationError(u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens, with a comma, space or comma followed by space used to separate each tag name.')
+    tag_names = get_tag_name_list(field_data)
+    for tag_name in tag_names:
+        if len(tag_name) > 50:
+            raise ValidationError(u'Tag names must be no longer than 50 characters.')
+
+def isTag(field_data, all_data):
+    """
+    Validates that ``field_data`` is a valid tag name.
+    """
+    if field_data is not None:
+        field_data = smart_unicode(field_data)
+    if not tag_re.match(field_data):
+        raise ValidationError(u'Tag names must contain only unicode alphanumeric characters, numbers, underscores or hyphens.')
diff --git a/tagging/views.py b/tagging/views.py
new file mode 100644
index 0000000..4e424f1
--- /dev/null
+++ b/tagging/views.py
@@ -0,0 +1,48 @@
+from django.http import Http404
+from django.views.generic.list_detail import object_list
+
+from tagging.models import Tag, TaggedItem
+from tagging.utils import get_tag
+
+def tagged_object_list(request, model=None, tag=None, related_tags=False,
+        related_tag_counts=True, **kwargs):
+    """
+    A thin wrapper around
+    ``django.views.generic.list_detail.object_list`` which creates a
+    ``QuerySet`` containing instances of the given model tagged with
+    the given tag.
+
+    In addition to the context variables set up by ``object_list``, a
+    ``tag`` context variable will contain the ``Tag`` instance
+    for the given tag.
+
+    If ``related_tags`` is ``True``, a ``related_tags`` context variable
+    will contain tags related to the given tag for the given model.
+    Additionally, if ``related_tag_counts`` is ``True``, each related tag
+    will have a ``count`` attribute indicating the number of items which
+    have it in addition to the given tag.
+    """
+    if model is None:
+        try:
+            model = kwargs['model']
+        except KeyError:
+            raise AttributeError(u'tagged_object_list must be called with a model.')
+
+    if tag is None:
+        try:
+            tag = kwargs['tag']
+        except KeyError:
+            raise AttributeError(u'tagged_object_list must be called with a tag.')
+
+    tag_instance = get_tag(tag)
+    if tag_instance is None:
+        raise Http404(u'No Tag found matching "%s".' % tag)
+    queryset = TaggedItem.objects.get_by_model(model, tag_instance)
+    if not kwargs.has_key('extra_context'):
+        kwargs['extra_context'] = {}
+    kwargs['extra_context']['tag'] = tag_instance
+    if related_tags:
+        kwargs['extra_context']['related_tags'] = \
+            Tag.objects.related_for_model(tag_instance, model,
+                                          counts=related_tag_counts)
+    return object_list(request, queryset, **kwargs)