Deduplicate post/comment sorting & time filtering.

Ported in from upstream with adjustments for TheMotte, most notably
universal default to 'new' and fixes to 'hot'. Lumped into this PR
because eager comment loading uses it.

files/helpers/contentsorting.py

@@ -0,0 +1,53 @@
+import time
+
+from sqlalchemy.sql import func
+
+from files.helpers.const import *
+
+
+def apply_time_filter(objects, t, cls):
+	now = int(time.time())
+	if t == 'hour':
+		cutoff = now - (60 * 60)
+	elif t == 'day':
+		cutoff = now - (24 * 60 * 60)
+	elif t == 'week':
+		cutoff = now - (7 * 24 * 60 * 60)
+	elif t == 'month':
+		cutoff = now - (30 * 24 * 60 * 60)
+	elif t == 'year':
+		cutoff = now - (365 * 24 * 60 * 60)
+	else:
+		cutoff = 0
+	return objects.filter(cls.created_utc >= cutoff)
+
+
+def sort_objects(objects, sort, cls):
+	if sort == 'hot':
+		ti = int(time.time()) + 3600
+		return objects.order_by(
+			-100000
+				* (cls.upvotes + 1)
+				/ (func.power((ti - cls.created_utc) / 1000, 1.23)),
+			cls.created_utc.desc())
+	elif sort == 'bump' and cls.__name__ == 'Submission':
+		return objects.filter(cls.comment_count > 1).order_by(
+			cls.bump_utc.desc(), cls.created_utc.desc())
+	elif sort == 'comments' and cls.__name__ == 'Submission':
+		return objects.order_by(
+			cls.comment_count.desc(), cls.created_utc.desc())
+	elif sort == 'controversial':
+		return objects.order_by(
+			(cls.upvotes + 1) / (cls.downvotes + 1)
+				+ (cls.downvotes + 1) / (cls.upvotes + 1),
+			cls.downvotes.desc(), cls.created_utc.desc())
+	elif sort == 'top':
+		return objects.order_by(
+			cls.downvotes - cls.upvotes, cls.created_utc.desc())
+	elif sort == 'bottom':
+		return objects.order_by(
+			cls.upvotes - cls.downvotes, cls.created_utc.desc())
+	elif sort == 'old':
+		return objects.order_by(cls.created_utc)
+	else: # default, or sort == 'new'
+		return objects.order_by(cls.created_utc.desc())