From fdb67396242c79cf407a9975a20cbb6a2f8cdf3d Mon Sep 17 00:00:00 2001
From: David King <dking@ketralnis.com>
Date: Mon, 11 Feb 2013 22:54:51 -0800
Subject: [PATCH] Add models and skeleton for recommender

---
 r2/r2/lib/db/tdb_cassandra.py | 10 +++--
 r2/r2/lib/recommender.py      | 76 +++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 3 deletions(-)
 create mode 100644 r2/r2/lib/recommender.py

diff --git a/r2/r2/lib/db/tdb_cassandra.py b/r2/r2/lib/db/tdb_cassandra.py
index 9a4118961..35fc4141a 100644
--- a/r2/r2/lib/db/tdb_cassandra.py
+++ b/r2/r2/lib/db/tdb_cassandra.py
@@ -34,7 +34,7 @@ from pycassa.cassandra.ttypes import ConsistencyLevel, NotFoundException
 from pycassa.system_manager import (SystemManager, UTF8_TYPE,
                                     COUNTER_COLUMN_TYPE, TIME_UUID_TYPE,
                                     ASCII_TYPE)
-from pycassa.types import DateType
+from pycassa.types import DateType, LongType, IntegerType
 from r2.lib.utils import tup, Storage
 from r2.lib import cache
 from uuid import uuid1, UUID
@@ -646,7 +646,9 @@ class ThingBase(object):
         self._column_ttls.clear()
 
     def __getattr__(self, attr):
-        if attr.startswith('_'):
+        if isinstance(attr, basestring) and attr.startswith('_'):
+            # TODO: I bet this interferes with Views whose column names can
+            # start with a _
             try:
                 return self.__dict__[attr]
             except KeyError:
@@ -669,7 +671,9 @@ class ThingBase(object):
         if attr == '_id' and self._committed:
             raise ValueError('cannot change _id on a committed %r' % (self.__class__))
 
-        if attr.startswith('_'):
+        if isinstance(attr, basestring) and attr.startswith('_'):
+            # TODO: I bet this interferes with Views whose column names can
+            # start with a _
             return object.__setattr__(self, attr, val)
 
         try:
diff --git a/r2/r2/lib/recommender.py b/r2/r2/lib/recommender.py
new file mode 100644
index 000000000..37c1d2de1
--- /dev/null
+++ b/r2/r2/lib/recommender.py
@@ -0,0 +1,76 @@
+# The contents of this file are subject to the Common Public Attribution
+# License Version 1.0. (the "License"); you may not use this file except in
+# compliance with the License. You may obtain a copy of the License at
+# http://code.reddit.com/LICENSE. The License is based on the Mozilla Public
+# License Version 1.1, but Sections 14 and 15 have been added to cover use of
+# software over a computer network and provide for limited attribution for the
+# Original Developer. In addition, Exhibit A has been modified to be consistent
+# with Exhibit B.
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
+# the specific language governing rights and limitations under the License.
+#
+# The Original Code is reddit.
+#
+# The Original Developer is the Initial Developer.  The Initial Developer of
+# the Original Code is reddit Inc.
+#
+# All portions of the code written by reddit are Copyright (c) 2006-2012 reddit
+# Inc. All Rights Reserved.
+###############################################################################
+
+from datetime import timedelta
+
+from r2.models import Subreddit
+from r2.lib.db import tdb_cassandra
+from r2.lib.memoize import memoize
+
+def get_recommendations(srs):
+    """
+    Return the subreddits recommended if you like the given subreddit
+    """
+
+    # for now, but keep the API open for multireddits later
+    assert len(srs) == 1 and srs[0].__class__ == Subreddit
+
+    sr = srs[0]
+    recs = _get_recommendations(sr._id36)
+    if not recs:
+        return []
+
+    srs = Subreddit._byID36(recs, return_dict=True, data=True)
+
+    return srs
+
+@memoize('_get_recommendations', stale=True)
+def _get_recommendations(srid36):
+    return SRRecommendation.for_sr(srid36)
+
+class SRRecommendation(tdb_cassandra.View):
+    _use_db = True
+
+    _compare_with = tdb_cassandra.LongType()
+
+    # don't keep these around if a run hasn't happened lately, or if the last
+    # N runs didn't generate recommendations for a given subreddit
+    _ttl = timedelta(days=2)
+
+    @classmethod
+    def for_sr(cls, srid36, count=5):
+        """
+        Return the subreddits ID36s recommended by the sr whose id36 is passed
+        """
+
+        cq = tdb_cassandra.ColumnQuery(cls, [srid36],
+                                       column_count = count+1)
+        recs = [ r[1] for r in cq if r[1] != srid36 ][:count]
+
+        return recs
+
+    def _to_recs(self):
+        recs = self._values() # [ {rank, srid} ]
+        recs = sorted(recs.items(), key=lambda x: int(x[0]))
+        recs = [x[1] for x in recs]
+        return recs
+