lib/multicodecs/registry.rb in multicodecs-0.1.0 vs lib/multicodecs/registry.rb in multicodecs-0.2.0

@@ -1,10 +1,18 @@
 # frozen_string_literal: true
 
 module Multicodecs
+  class AutoHashCollection < Hash
+    def [](key)
+      self[key] = [] unless key?(key)
+      super
+    end
+  end
+
   # rubocop:disable Style/MutableConstant
   REGISTRATIONS = {}
+  REGISTRATIONS_PER_TAG = AutoHashCollection.new
   # rubocop:enable Style/MutableConstant
 
   Registration = Struct.new(:code, :name, :tag) do
     def hash
       name.hash
@@ -27,15 +35,14 @@
   def [](entry)
     find_by(code: entry, name: entry)
   end
 
   def register(code:, name:, tag:)
-    Multicodecs::REGISTRATIONS[name] = Registration.new(
-      code,
-      name,
-      tag
-    )
+    Registration.new(code, name, tag).tap do |registration|
+      Multicodecs::REGISTRATIONS[name] = registration
+      Multicodecs::REGISTRATIONS_PER_TAG[tag] << registration
+    end
   end
 
   def fetch_by!(code: nil, name: nil)
     return Multicodecs::REGISTRATIONS.fetch(name) if name
 
@@ -54,7 +61,25 @@
     Multicodecs::REGISTRATIONS.values.map(&:code)
   end
 
   def names
     Multicodecs::REGISTRATIONS.keys
+  end
+
+  def tags
+    Multicodecs::REGISTRATIONS_PER_TAG.keys
+  end
+
+  def where(tag:)
+    Multicodecs::REGISTRATIONS_PER_TAG[tag]
+  end
+
+  def each(tag: nil)
+    arr = tag.nil? ? Multicodecs::REGISTRATIONS.values : Multicodecs.where(tag: tag)
+
+    if block_given?
+      return arr.each { |registration| yield registration }
+    end
+
+    arr.each
   end
 end