Gold goal: switch to dynamic goal

Previously the goal was simply a static amount, this changes it so that
it is set to 110% of the average revenue from the previous 7 days
(disregarding highest and lowest revenues). To prevent too large of
swings due to "spikes", the goal is restricted to no more than a 20%
change from the previous day's goal.

r2/r2/lib/pages/pages.py

@@ -34,6 +34,7 @@ from r2.models.gold import (
     gold_payments_by_user,
     gold_received_by_user,
     days_to_pennies,
+    gold_goal_on,
     gold_revenue_on,
 )
 from r2.models.promo import (
@@ -4285,10 +4286,12 @@ class Goldvertisement(Templated):
         revenue_today = gold_revenue_on(today)
         yesterday = today - datetime.timedelta(days=1)
         revenue_yesterday = gold_revenue_on(yesterday)
-        revenue_goal = g.live_config["gold_revenue_goal"]
+        revenue_goal = gold_goal_on(today)
+        revenue_goal_yesterday = gold_goal_on(yesterday)
 
         self.percent_filled = int((revenue_today / revenue_goal) * 100)
-        self.percent_filled_yesterday = int((revenue_yesterday / revenue_goal) * 100)
+        self.percent_filled_yesterday = int((revenue_yesterday /
+                                             revenue_goal_yesterday) * 100)
         self.hours_paid = ServerSecondsBar.current_value_of_month()
         self.time_left_today = timeuntil(end_time, precision=60)
         Templated.__init__(self)

r2/r2/models/gold.py

@@ -24,7 +24,7 @@ from r2.lib.db.tdb_sql import make_metadata, index_str, create_table
 
 from pylons import g, c
 from pylons.i18n import _
-from datetime import datetime
+from datetime import datetime, timedelta
 import sqlalchemy as sa
 from sqlalchemy.exc import IntegrityError, OperationalError
 from sqlalchemy.ext.declarative import declarative_base
@@ -48,6 +48,7 @@ from r2.models.wiki import WikiPage
 from r2.lib.memoize import memoize
 
 gold_bonus_cutoff = datetime(2010,7,27,0,0,0,0,g.tz)
+gold_static_goal_cutoff = datetime(2013, 11, 7, tzinfo=g.display_tz)
 
 ENGINE_NAME = 'authorize'
 
@@ -455,3 +456,31 @@ def gold_revenue_on(date):
                 .where(sa.func.date_trunc('day', gold_table.c.date) == date))
     rows = ENGINE.execute(query)
     return rows.fetchone()[0] or 0
+
+
+@memoize("gold-goal")
+def gold_goal_on(date):
+    """Returns the gold revenue goal (in pennies) for a given date."""
+    # handle the old static goal
+    if date <= gold_static_goal_cutoff.date():
+        return g.live_config["gold_revenue_goal"]
+
+    # fetch the revenues from the previous 7 days
+    previous_date = date - timedelta(days=1)
+    previous_revenues = []
+    while previous_date >= date - timedelta(days=7):
+        previous_revenues.append(gold_revenue_on(previous_date))
+        previous_date -= timedelta(days=1)
+
+    # throw out highest and lowest values and set goal to 110% of average
+    previous_revenues = sorted(previous_revenues)[1:-1]
+    average_revenue = sum(previous_revenues) / float(len(previous_revenues))
+    goal = average_revenue * 1.1
+
+    # don't let this be more than 20% different from the previous goal
+    previous_goal = gold_goal_on(date - timedelta(days=1))
+    goal = min(previous_goal * 1.2, goal)
+    goal = max(previous_goal * 0.8, goal)
+
+    return round(goal, 0)
+