allow non-logged-in users to define tag filters

when not logged in, store the filters in a long-lasting cookie and
do not cache the home page

for that one guy on hacker news that complained about lobste.rs not
having this

app/controllers/application_controller.rb

@@ -5,6 +5,8 @@ class ApplicationController < ActionController::Base
 
   TRAFFIC_DECREMENTER = 0.15
 
+  TAG_FILTER_COOKIE = :tag_filters
+
   def authenticate_user
     if session[:u]
       @user = User.find_by_session_token(session[:u].to_s)
@@ -55,6 +57,12 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  @_tags_filtered = nil
+  def tags_filtered_by_cookie
+    @_tags_filtered ||= cookies[TAG_FILTER_COOKIE].to_s.split(",").map{|t|
+      Tag.find_by_tag(t) }.reject{|tf| !tf }
+  end
+
   def user_is_spider?
     !!request.env["HTTP_USER_AGENT"].to_s.match(/Googlebot/)
   end

app/controllers/filters_controller.rb

@@ -1,11 +1,19 @@
 class FiltersController < ApplicationController
-  before_filter :require_logged_in_user
+  before_filter :authenticate_user
 
   def index
     @cur_url = "/filters"
     @title = "Filtered Tags"
 
-    @filtered_tags = @user.tag_filters.reload
+    if @user
+      @filtered_tags = @user.tag_filters.reload
+    else
+      @filtered_tags = tags_filtered_by_cookie.map{|t|
+        tf = TagFilter.new
+        tf.tag = t
+        tf
+      }
+    end
 
     render :action => "index"
   end
@@ -20,22 +28,26 @@ class FiltersController < ApplicationController
       end
     end
 
-    @user.tag_filters(:include => :tag).each do |tf|
-      if tf.tag && new_filters.include?(tf.tag.tag)
-        new_filters.reject!{|t| t == tf.tag.tag }
-      else
-        tf.destroy
+    if @user
+      @user.tag_filters(:include => :tag).each do |tf|
+        if tf.tag && new_filters.include?(tf.tag.tag)
+          new_filters.reject!{|t| t == tf.tag.tag }
+        else
+          tf.destroy
+        end
       end
+
+      new_filters.each do |t|
+        tf = TagFilter.new
+        tf.user_id = @user.id
+        tf.tag_id = Tag.find_by_tag(t).id
+        tf.save!
+      end
+    else
+      cookies.permanent[TAG_FILTER_COOKIE] = new_filters.join(",")
     end
 
-    new_filters.each do |t|
-      tf = TagFilter.new
-      tf.user_id = @user.id
-      tf.tag_id = Tag.find_by_tag(t).id
-      tf.save
-    end
-
-    flash.now[:success] = "Your filters have been updated."
-    index
+    flash[:success] = "Your filters have been updated."
+    return redirect_to "/filters"
   end
 end

app/controllers/home_controller.rb

@@ -96,8 +96,9 @@ private
       @page = params[:page].to_i
     end
 
-    # guest views have caching, but don't bother for logged-in users (or dev)
-    if Rails.env == "development" || user
+    # guest views have caching, but don't bother for logged-in users or dev or
+    # when the user has tag filters
+    if Rails.env == "development" || user || tags_filtered_by_cookie.any?
       stories, @show_more =
         _find_stories_for_user_and_tag_and_newest_and_by_user(user, tag,
         newest, by_user)
@@ -129,7 +130,8 @@ private
       filtered_tag_ids = @user.tag_filters.map{|tf| tf.tag_id }
     else
       # for logged-out users, filter defaults
-      filtered_tag_ids = Tag.where(:filtered_by_default => true).map{|t| t.id }
+      filtered_tag_ids = Tag.where(:filtered_by_default => true).
+        map{|t| t.id } + tags_filtered_by_cookie.map{|t| t.id }
     end
 
     if tag

app/models/tag.rb

@@ -5,7 +5,7 @@ class Tag < ActiveRecord::Base
   attr_accessor :filtered_count
 
   scope :accessible_to, ->(user) do
-    user.is_admin?? all : where(:privileged => false)
+    user && user.is_admin?? all : where(:privileged => false)
   end
 
   def self.all_with_filtered_counts_for(user)

app/views/filters/index.html.erb

@@ -8,6 +8,14 @@
   check them below.
   </p>
 
+  <% if !@user %>
+    <p>
+    Since you are not logged in, your filters will be stored in a long-lasting
+    browser cookie.  To permanently store your tag filters and have them work
+    across browsers, <a href="/login">login</a> to your account.
+    </p>
+  <% end %>
+
   <%= form_tag "/filters", :method => :post do %>
     <table class="data zebra" cellspacing=0 width="75%">
     <tr>

app/views/layouts/application.html.erb

@@ -66,10 +66,9 @@
 
       <div id="headerright" class="<%= @user ? "loggedin" : "" %>">
         <span class="headerlinks">
+        <a href="/filters" <%= @cur_url == "/filters" ?
+          raw("class=\"cur_url\"") : "" %>>Filters</a>
         <% if @user %>
-          <a href="/filters" <%= @cur_url == "/filters" ?
-            raw("class=\"cur_url\"") : "" %>>Filters</a>
-
           <% if (count = @user.unread_message_count) > 0 %>
             <a href="/messages" class="new_messages <%= @cur_url == "/messages" ?
               "cur_url" : "" %>"><%= count %> New Message<%= count == 1 ? "" :