Added partial support for comment threading.

[zzz-floof.git] / floof / model / comments.py

diff --git a/floof/model/comments.py b/floof/model/comments.py
index 4504b6f..e1ad150 100644 (file)
--- a/floof/model/comments.py
+++ b/floof/model/comments.py
@@ -1,15 +1,62 @@
 import datetime
 
 from elixir import *
+from sqlalchemy import func
 
 class Discussion(Entity):
     """Represents a collection of comments attached to some other object."""
     count = Field(Integer)
-    comments = OneToMany('Comment')
+    comments = OneToMany('Comment', order_by='left')
 
 class Comment(Entity):
     time = Field(DateTime, default=datetime.datetime.now)
     text = Field(Unicode(65536))
 
+    # Comments are a tree, and are stored as a nested set, because:
+    # - It's easy to get a subtree with a single query.
+    # - It's easy to get a comment's depth.
+    # - It's easy to sort comments without recursion.
+    # The only real disadvantage is that adding a comment requires a quick
+    # update of all the following comments (in post-order), but that's rare
+    # enough that it shouldn't be a problem.
+    left = Field(Integer, index=True)
+    right = Field(Integer)
+
     discussion = ManyToOne('Discussion')
     user = ManyToOne('User')
+
+    def __init__(self, parent=None, **kwargs):
+        """Constructor override to set left/right correctly on a new comment.
+        """
+        super(Comment, self).__init__(**kwargs)
+
+        # Keep the comment count updated
+        self.discussion.count += 1
+
+        if parent:
+            # Parent comment given.  Add this comment just before the parent's
+            # right side...
+            self.left = parent.right
+            self.right = parent.right + 1
+
+            # ...then adjust all rightward comments accordingly
+            Comment.query.filter(Comment.discussion == self.discussion) \
+                         .filter(Comment.right > parent.right) \
+                         .update({ Comment.left:  Comment.left + 2,
+                                   Comment.right: Comment.right + 2 })
+
+            # And, finally, update the parent's right endpoint
+            parent.right += 2
+
+        else:
+            query = session.query(func.max(Comment.right)) \
+                           .filter(Comment.discussion == self.discussion)
+            (max_right,) = query.one()
+
+            if not max_right:
+                # No comments yet.  Use 1 and 2
+                self.left = 1
+                self.right = 2
+            else:
+                self.left = max_right + 1
+                self.right = max_right + 2