Add in_order_of to Resource

lib/perron/relation.rb

@@ -47,5 +47,20 @@ def pluck(*attributes)
         end
       end
     end
+
+    def in_order_of(attribute, values, filter: true)
+      return Relation.new([]) if values.empty?
+
+      indexed = values.each_with_index.to_h
+
+      resources = if filter
+        select { indexed.key?(it.public_send(attribute)) }
+          .sort_by { indexed[it.public_send(attribute)] }
+      else
+        sort_by { indexed[it.public_send(attribute)] || Float::INFINITY }
+      end
+
+      Relation.new(resources)
+    end
   end
 end

lib/perron/resource/class_methods.rb

@@ -22,6 +22,8 @@ def count = all.size
 
         def order(attribute, direction = :asc) = all.order(attribute, direction)
 
+        def in_order_of(attribute, values, filter: true) = all.in_order_of(attribute, values, filter:)
+
         def first(n = nil)
           n ? all.first(n) : all[0]
         end

test/dummy/app/content/posts/2023-05-15-sample-post.md

@@ -5,6 +5,7 @@ image: https://example.com/images/sample.jpg
 author_id: rails-designer
 updated_at: 2023-05-15
 processor_class: custom-from-metadata
+category: news
 ---
 
 Labore qui mollit commodo id nulla qui exercitation nulla reprehenderit nulla excepteur aute eu sint. Minim sit aute et ad ut esse aute sunt magna voluptate duis tempor. Commodo commodo qui amet ullamco Lorem ex cillum ea occaecat deserunt elit amet consequat nulla Lorem. Reprehenderit id aute dolor minim aliquip officia et reprehenderit nisi. Aute labore ex veniam enim enim duis sint elit proident aute sunt consectetur ut aliqua. Laboris elit exercitation veniam non commodo magna sunt in sunt id.

test/dummy/app/content/posts/2023-06-15-another-post.md

@@ -3,6 +3,7 @@ title: Another Sample Post
 description: Describing another sample post
 image: https://example.com/images/sample.jpg
 author: Kendall
+category: tutorial
 ---
 
 Content goes here…

test/dummy/app/models/content/post.rb

@@ -28,7 +28,7 @@ class Content::Post < Perron::Resource
   belongs_to :author
   belongs_to :editor, class_name: "Content::Data::Editors"
 
-  delegate :title, to: :metadata
+  delegate :title, :category, to: :metadata
 
   scope :ordered, -> { order(:slug) }
   scope :limited, -> { limit(2) }

test/perron/relation_test.rb

@@ -101,4 +101,27 @@ class Perron::RelationTest < ActiveSupport::TestCase
     assert_equal 2, slugs.size
     assert_equal "another-post", slugs.first
   end
+
+  test "#in_order_of filters and sorts by values (filter: true by default)" do
+    result = @posts.in_order_of(:category, %w[tutorial news])
+
+    assert_instance_of Perron::Relation, result
+    assert_equal 2, result.size
+    assert_equal "tutorial", result.first.category
+    assert_equal "news", result.second.category
+  end
+
+  test "#in_order_of sorts all records with filter: false" do
+    result = @posts.in_order_of(:category, %w[tutorial], filter: false)
+
+    assert_equal 4, result.size
+    assert_equal "tutorial", result.first.category
+  end
+
+  test "#in_order_of returns empty relation for empty values" do
+    result = @posts.in_order_of(:category, [])
+
+    assert_instance_of Perron::Relation, result
+    assert_equal 0, result.size
+  end
 end