--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gpp/forums/tools.py	Sun Dec 13 08:11:16 2009 +0000
@@ -0,0 +1,69 @@
+"""
+This module contains misc. utility functions for forum management.
+"""
+from forums.models import Post, Topic, Forum, ForumLastVisit, TopicLastVisit
+
+
+def delete_user_posts(user):
+    """
+    This function deletes all the posts for a given user.
+    It also cleans up any last visit database records for the user.
+    This function adjusts the last post foreign keys before deleting
+    the posts to avoid the cascading delete behavior.
+    """
+    posts = Post.objects.filter(user=user).select_related()
+
+    # build a set of topics and forums affected by the post deletions
+
+    topics = set(post.topic for post in posts)
+    forums = set(topic.forum for topic in topics)
+
+    post_ids = [post.pk for post in posts]
+    pending_delete = []
+
+    for topic in topics:
+        if topic.last_post.pk in post_ids:
+            topic_posts = Post.objects.filter(topic=topic).exclude(
+                    pk__in=post_ids)
+            topic.post_count = topic_posts.count()
+            if topic.post_count > 0:
+                topic.last_post = topic_posts.latest()
+                topic.update_date = topic.last_post.creation_date
+                topic.save()
+            else:
+                # Topic should be deleted, it has no posts;
+                # We can't delete it now as it could cascade and take out a 
+                # forum. Remember it for later deletion.
+                pending_delete.append(topic)
+
+    for forum in forums:
+        if forum.last_post.pk in post_ids:
+            forum_posts = Post.objects.filter(topic__forum=forum).exclude(
+                    pk__in=post_ids)
+            forum.post_count = forum_posts.count()
+            if forum.post_count > 0:
+                forum.last_post = forum_posts.latest()
+            else:
+                forum.last_post = None
+            forum.save()
+    
+    # Delete pending topics now because forums have just adjusted their
+    # foreign keys into Post
+    if pending_delete:
+        topic_ids = [topic.pk for topic in pending_delete]
+        Topic.objects.filter(pk__in=topic_ids).delete()
+
+        # Topics have been deleted, re-compute topic counts for forums
+        for forum in forums:
+            forum.topic_count = Topic.objects.filter(forum=forum).count()
+            forum.save()
+            
+    # All foreign keys are accounted for, we can now delete the posts in bulk.
+    # Since some posts in our original queryset may have been deleted already,
+    # run a new query (although it may be ok)
+    Post.objects.filter(pk__in=post_ids).delete()
+
+    # delete all the last visit records for this user
+    TopicLastVisit.objects.filter(user=user).delete()
+    ForumLastVisit.objects.filter(user=user).delete()
+