Improve sequential paginator

fixes #2044, fixes #1298

app/helpers/pagination_helper.rb

@@ -3,12 +3,14 @@ module PaginationHelper
     html = '<div class="paginator"><menu>'
 
     if records.any?
-      if params[:page] =~ /[ab]/
+      if params[:page] =~ /[ab]/ && !records.is_first_page?
         html << '<li>' + link_to("< Previous", params.merge(:page => "a#{records[0].id}"), :rel => "prev") + '</li>'
       end
 
+      unless records.is_last_page?
         html << '<li>' + link_to("Next >", params.merge(:page => "b#{records[-1].id}"), :rel => "next") + '</li>'
       end
+    end
 
     html << "</menu></div>"
     html.html_safe

lib/danbooru/paginator/active_record_extension.rb

@@ -31,7 +31,7 @@ module Danbooru
         end
 
         def paginate_sequential_before(before_id = nil)
-          c = limit(records_per_page)
+          c = limit(records_per_page + 1)
 
           if before_id.to_i > 0
             c = c.where("#{table_name}.id < ?", before_id.to_i)
@@ -44,7 +44,7 @@ module Danbooru
         end
 
         def paginate_sequential_after(after_id)
-          limit(records_per_page).where("#{table_name}.id > ?", after_id.to_i).reorder("#{table_name}.id asc").tap do |obj|
+          limit(records_per_page + 1).where("#{table_name}.id > ?", after_id.to_i).reorder("#{table_name}.id asc").tap do |obj|
             obj.extend(SequentialCollectionExtension)
             obj.sequential_paginator_mode = :after
           end

lib/danbooru/paginator/sequential_collection_extension.rb

@@ -4,18 +4,26 @@ module Danbooru
       attr_accessor :sequential_paginator_mode
 
       def is_first_page?
-        size == 0
+        if sequential_paginator_mode == :before
+          false
+        else
+          size <= records_per_page
+        end
       end
 
       def is_last_page?
-        size == 0
+        if sequential_paginator_mode == :after
+          false
+        else
+          size <= records_per_page
+        end
       end
 
       def to_a
         if sequential_paginator_mode == :before
-          super
+          super.first(records_per_page)
         else
-          super.reverse
+          super.first(records_per_page).reverse
         end
       end
     end

test/unit/post_sets/favorite_test.rb

@@ -34,10 +34,15 @@ module PostSets
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
-      context "a favorite set for after the second most recent post" do
+      context "a favorite set for after the third most recent post" do
         setup do
           id = ::Favorite.where(:user_id => @user.id, :post_id => @post_2.id).first.id
           ::Favorite.stubs(:records_per_page).returns(1)
@@ -45,10 +50,55 @@ module PostSets
         end
 
         context "a sequential paginator" do
-          should "return the most recent element" do
+          should "return the second most recent element" do
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
+        end
+      end
+
+      context "a favorite set for before the second most recent post" do
+        setup do
+          id = ::Favorite.where(:user_id => @user.id, :post_id => @post_1.id).first.id
+          ::Favorite.stubs(:records_per_page).returns(1)
+          @set = PostSets::Favorite.new(@user.id, "b#{id}")
+        end
+
+        context "a sequential paginator" do
+          should "return the third most recent element" do
+            assert_equal(1, @set.posts.size)
+            assert_equal(@post_2.id, @set.posts.first.id)
+          end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            assert(@set.favorites.is_last_page?)
+          end
+        end
+      end
+
+      context "a favorite set for after the second most recent post" do
+        setup do
+          id = ::Favorite.where(:user_id => @user.id, :post_id => @post_1.id).first.id
+          ::Favorite.stubs(:records_per_page).returns(1)
+          @set = PostSets::Favorite.new(@user.id, "a#{id}")
+        end
+
+        context "a sequential paginator" do
+          should "return the most recent element" do
+            assert_equal(1, @set.posts.size)
+            assert_equal(@post_3.id, @set.posts.first.id)
+          end
+
+          should "know what page it's on" do
+            assert(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
@@ -63,6 +113,11 @@ module PostSets
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
@@ -76,6 +131,11 @@ module PostSets
           assert_equal(1, @set.posts.size)
           assert_equal(@post_3.id, @set.posts.first.id)
         end
+
+        should "know what page it's on" do
+          assert(@set.favorites.is_first_page?)
+          refute(@set.favorites.is_last_page?)
+        end
       end
     end
   end