1 files changed, 151 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/registry.rb b/activemodel/lib/active_model/type/registry.rb
new file mode 100644
index 0000000000..8070a4bd38
--- /dev/null
+++ b/activemodel/lib/active_model/type/registry.rb
@@ -0,0 +1,151 @@
+module ActiveModel
+  # :stopdoc:
+  module Type
+    class Registry
+      def initialize
+        @registrations = []
+      end
+
+      def register(type_name, klass = nil, **options, &block)
+        block ||= proc { |_, *args| klass.new(*args) }
+        registrations << registration_klass.new(type_name, block, **options)
+      end
+
+      def lookup(symbol, *args)
+        registration = registrations
+          .select { |r| r.matches?(symbol, *args) }
+          .max
+
+        if registration
+          registration.call(self, symbol, *args)
+        else
+          raise ArgumentError, "Unknown type #{symbol.inspect}"
+        end
+      end
+
+      def add_modifier(options, klass, **args)
+        registrations << decoration_registration_klass.new(options, klass, **args)
+      end
+
+      protected
+
+      attr_reader :registrations
+      
+      private
+      
+      def registration_klass
+        Registration
+      end
+      
+      def decoration_registration_klass
+        DecorationRegistration
+      end
+    end
+
+    class Registration
+      def initialize(name, block, override: nil)
+        @name = name
+        @block = block
+        @override = override
+      end
+
+      def call(_registry, *args, **kwargs)
+        if kwargs.any? # https://bugs.ruby-lang.org/issues/10856
+          block.call(*args, **kwargs)
+        else
+          block.call(*args)
+        end
+      end
+
+      def matches?(type_name, *args, **kwargs)
+        type_name == name# && matches_adapter?(**kwargs)
+      end
+
+      def <=>(other)
+        # if conflicts_with?(other)
+        #   raise TypeConflictError.new("Type #{name} was registered for all
+        #                               adapters, but shadows a native type with
+        #                               the same name for #{other.adapter}".squish)
+        # end
+        priority <=> other.priority
+      end
+
+      protected
+
+      attr_reader :name, :block, :override
+
+      def priority
+        result = 0
+        # if adapter
+        #   result |= 1
+        # end
+        if override
+          result |= 2
+        end
+        result
+      end
+
+      # def priority_except_adapter
+      #   priority & 0b111111100
+      # end
+
+      private
+
+      # def matches_adapter?(adapter: nil, **)
+      #   (self.adapter.nil? || adapter == self.adapter)
+      # end
+
+      # def conflicts_with?(other)
+      #   same_priority_except_adapter?(other) &&
+      #     has_adapter_conflict?(other)
+      # end
+
+      # def same_priority_except_adapter?(other)
+      #   priority_except_adapter == other.priority_except_adapter
+      # end
+
+      # def has_adapter_conflict?(other)
+      #   (override.nil? && other.adapter) ||
+      #     (adapter && other.override.nil?)
+      # end
+    end
+
+    class DecorationRegistration < Registration
+      def initialize(options, klass)
+        @options = options
+        @klass = klass
+        # @adapter = adapter
+      end
+
+      def call(registry, *args, **kwargs)
+        subtype = registry.lookup(*args, **kwargs.except(*options.keys))
+        klass.new(subtype)
+      end
+
+      def matches?(*args, **kwargs)
+        matches_options?(**kwargs)
+      end
+
+      def priority
+        super | 4
+      end
+
+      protected
+
+      attr_reader :options, :klass
+
+      private
+
+      def matches_options?(**kwargs)
+        options.all? do |key, value|
+          kwargs[key] == value
+        end
+      end
+    end
+  end
+
+  class TypeConflictError < StandardError
+  end
+
+  # :startdoc:
+end