popular posts: fix date range handling.

* Fix the next button for the weekly timescale to jump to the next week,
  not the next day.
* Show the start and end dates for the weekly timescale.
* Use `Time.zone.today` instead of `Date.today` to respect the user's
  timezone setting.

app/controllers/explore/posts_controller.rb

@@ -1,24 +1,24 @@
 module Explore
   class PostsController < ApplicationController
     respond_to :html, :xml, :json
-    before_action :set_date, only: [:searches, :viewed]
 
     def popular
-      @date = params[:date] ? Date.parse(params[:date]) : Date.today
-      @scale = params[:scale]
-      @scale = "day" unless @scale.in?(["day", "week", "month"])
+      @date, @scale, @min_date, @max_date = parse_date(params)
 
       limit = params.fetch(:limit, CurrentUser.user.per_page)
-      @posts = popular_posts(@date, @scale).paginate(params[:page], limit: limit)
+      @posts = popular_posts(@min_date, @max_date).paginate(params[:page], limit: limit)
+
       respond_with(@posts)
     end
 
     def viewed
+      @date, @scale, @min_date, @max_date = parse_date(params)
       @posts = PostViewCountService.new.popular_posts(@date)
       respond_with(@posts)
     end
 
     def searches
+      @date, @scale, @min_date, @max_date = parse_date(params)
       @search_service = PopularSearchService.new(@date)
     end
 
@@ -28,19 +28,17 @@ module Explore
 
     private
 
-    def set_date
-      @date = params[:date] ? Date.parse(params[:date]) : Date.today
+    def parse_date(params)
+      date = params[:date] ? Date.parse(params[:date]) : Time.zone.today
+      scale = params[:scale].in?(["day", "week", "month"]) ? params[:scale] : "day"
+      min_date = date.send("beginning_of_#{scale}")
+      max_date = date.send("next_#{scale}").send("beginning_of_#{scale}")
+
+      [date, scale, min_date, max_date]
     end
 
-    def popular_posts(date, scale)
-      if scale == "day"
-        Post.tag_match("date:#{date} order:score")
-      else
-        min_date = date.send("beginning_of_#{scale}").to_date.to_s
-        max_date = date.send("end_of_#{scale}").to_date.to_s
-        search = "date:#{min_date}..#{max_date} order:score"
-        Post.tag_match(search)
-      end
+    def popular_posts(min_date, max_date)
+      Post.where(created_at: min_date..max_date).tag_match("order:score")
     end
   end
 end