start experiment with /newest page

on the first page of /newest, shift out stories that got enough
traction that they're probably on the front page (currently 5
points)

then take the bottom half of the list and fill it with random,
unpopular stories from the past few days (currently 3)

app/controllers/home_controller.rb

@@ -1,6 +1,12 @@
class HomeController < ApplicationController
  STORIES_PER_PAGE = 25

  # how many points a story has to be bumped off the newest page
  HOT_STORY_POINTS = 5

  # how many days old a story can be to get on the bottom half of /newest
  NEWEST_DAYS_OLD = 3

  # for rss feeds, load the user's tag filters if a token is passed
  before_filter :find_user_from_rss_token, :only => [ :index, :newest ]

@@ -186,6 +192,31 @@ def _find_stories_for_user_and_tag_and_newest_and_by_user(user, tag = nil,
      )
    end

    if newest && @page == 1
      # try to help recently-submitted stories that didn't gain traction

      # grab the list of stories from the past n days, shifting out popular
      # stories that did gain traction
      story_ids = stories.select(:id, :upvotes, :downvotes).
        where(Story.arel_table[:created_at].gt(NEWEST_DAYS_OLD.days.ago)).
        order("stories.created_at DESC").
        reject{|s| s.score > HOT_STORY_POINTS }

      if story_ids.length > STORIES_PER_PAGE + 1
        # keep the top half (newest stories)
        keep_ids = story_ids[0 .. ((STORIES_PER_PAGE + 1) * 0.5)]
        story_ids = story_ids[keep_ids.length - 1 ... story_ids.length]

        # make the bottom half a random selection of older stories
        while keep_ids.length <= STORIES_PER_PAGE + 1
          story_ids.shuffle!
          keep_ids.push story_ids.shift
        end

        stories = Story.where(:id => keep_ids)
      end
    end

    stories = stories.includes(
      :user, :taggings => :tag
    ).limit(
@@ -197,15 +228,11 @@ def _find_stories_for_user_and_tag_and_newest_and_by_user(user, tag = nil,
    ).to_a

    show_more = false

    if stories.count > STORIES_PER_PAGE
      show_more = true
      stories.pop
    end

    # TODO: figure out a better sorting algorithm for newest, including some
    # older stories that got one or two votes

    if user
      votes = Vote.votes_by_user_for_stories_hash(user.id,
        stories.map{|s| s.id })