Fix #4917: Add down_score/up_score orders and metasearches.

Add `upvotes:N`, `downvotes:N`, `order:upvotes`, `order:downvotes`,
`order:upvotes_asc`, `order:downvotes_asc` metatags.

In the API, the field is called up_score / down_score. Here it's called
`upvotes` and `downvotes` because this should be easier to understand
for end users.

Note that internally, `down_score` is negative. A post that matches
`downvotes:>5` will have down_score < -5 internally.

app/logical/post_query_builder.rb

@@ -37,7 +37,7 @@ class PostQueryBuilder
     flagger appealer upvote downvote fav ordfav favgroup ordfavgroup pool
     ordpool note comment commentary id rating source status filetype
     disapproved parent child search embedded md5 width height mpixels ratio
-    score favcount filesize date age order limit tagcount pixiv_id pixiv
+    score upvotes downvotes favcount filesize date age order limit tagcount pixiv_id pixiv
     unaliased exif duration
   ] + COUNT_METATAGS + COUNT_METATAG_SYNONYMS + CATEGORY_COUNT_METATAGS
 
@@ -45,6 +45,8 @@ class PostQueryBuilder
     id id_desc
     md5 md5_asc
     score score_asc
+    upvotes upvotes_asc
+    downvotes downvotes_asc
     favcount favcount_asc
     created_at created_at_asc
     change change_asc
@@ -138,6 +140,10 @@ class PostQueryBuilder
       attribute_matches(value, "ROUND(1.0 * posts.image_width / GREATEST(1, posts.image_height), 2)", :ratio)
     when "score"
       attribute_matches(value, :score)
+    when "upvotes"
+      attribute_matches(value, :up_score)
+    when "downvotes"
+      attribute_matches(value, "ABS(posts.down_score)")
     when "favcount"
       attribute_matches(value, :fav_count)
     when "filesize"
@@ -572,6 +578,19 @@ class PostQueryBuilder
     when "score_asc"
       relation = relation.order("posts.score ASC, posts.id ASC")
 
+    when "upvotes", "upvotes_desc"
+      relation = relation.order("posts.up_score DESC, posts.id DESC")
+
+    when "upvotes_asc"
+      relation = relation.order("posts.up_score ASC, posts.id ASC")
+
+    # XXX down_score is negative so order:downvotes sorts lowest-to-highest so that most downvoted is first.
+    when "downvotes", "downvotes_desc"
+      relation = relation.order("posts.down_score ASC, posts.id ASC")
+
+    when "downvotes_asc"
+      relation = relation.order("posts.down_score DESC, posts.id DESC")
+
     when "favcount"
       relation = relation.order("posts.fav_count DESC, posts.id DESC")
 

test/unit/post_query_builder_test.rb

@@ -235,6 +235,30 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
       assert_tag_match([posts[1]], "id:>#{posts[0].id} id:<#{posts[2].id}")
     end
 
+    should "return posts for the score:<N> metatag" do
+      post1 = create(:post, score: 5)
+      post2 = create(:post, score: 0)
+
+      assert_tag_match([post1], "score:5")
+      assert_tag_match([post2], "score:0")
+    end
+
+    should "return posts for the upvotes:<N> metatag" do
+      post1 = create(:post, up_score: 5)
+      post2 = create(:post, up_score: 0)
+
+      assert_tag_match([post1], "upvotes:5")
+      assert_tag_match([post2], "upvotes:0")
+    end
+
+    should "return posts for the downvotes:<N> metatag" do
+      post1 = create(:post, down_score: -5)
+      post2 = create(:post, down_score: 0)
+
+      assert_tag_match([post1], "downvotes:5")
+      assert_tag_match([post2], "downvotes:0")
+    end
+
     should "return posts for the fav:<name> metatag" do
       user1 = create(:user)
       user2 = create(:user)
@@ -1013,6 +1037,8 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
         p = create(
           :post,
           score: n,
+          up_score: n,
+          down_score: -n,
           md5: n.to_s,
           fav_count: n,
           file_size: 1.megabyte * n,
@@ -1033,6 +1059,8 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
 
       assert_tag_match(posts.reverse, "order:id_desc")
       assert_tag_match(posts.reverse, "order:score")
+      assert_tag_match(posts.reverse, "order:upvotes")
+      assert_tag_match(posts.reverse, "order:downvotes")
       assert_tag_match(posts.reverse, "order:favcount")
       assert_tag_match(posts.reverse, "order:change")
       assert_tag_match(posts.reverse, "order:comment")
@@ -1058,6 +1086,8 @@ class PostQueryBuilderTest < ActiveSupport::TestCase
 
       assert_tag_match(posts, "order:id_asc")
       assert_tag_match(posts, "order:score_asc")
+      assert_tag_match(posts, "order:upvotes_asc")
+      assert_tag_match(posts, "order:downvotes_asc")
       assert_tag_match(posts, "order:favcount_asc")
       assert_tag_match(posts, "order:change_asc")
       assert_tag_match(posts, "order:comment_asc")