1 files changed, 64 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/type_map.rb b/activemodel/lib/active_model/type/type_map.rb
new file mode 100644
index 0000000000..402b660a71
--- /dev/null
+++ b/activemodel/lib/active_model/type/type_map.rb
@@ -0,0 +1,64 @@
+require 'concurrent'
+
+module ActiveModel
+  module Type
+    class TypeMap # :nodoc:
+      def initialize
+        @mapping = {}
+        @cache = Concurrent::Map.new do |h, key|
+          h.fetch_or_store(key, Concurrent::Map.new)
+        end
+      end
+
+      def lookup(lookup_key, *args)
+        fetch(lookup_key, *args) { default_value }
+      end
+
+      def fetch(lookup_key, *args, &block)
+        @cache[lookup_key].fetch_or_store(args) do
+          perform_fetch(lookup_key, *args, &block)
+        end
+      end
+
+      def register_type(key, value = nil, &block)
+        raise ::ArgumentError unless value || block
+        @cache.clear
+
+        if block
+          @mapping[key] = block
+        else
+          @mapping[key] = proc { value }
+        end
+      end
+
+      def alias_type(key, target_key)
+        register_type(key) do |sql_type, *args|
+          metadata = sql_type[/\(.*\)/, 0]
+          lookup("#{target_key}#{metadata}", *args)
+        end
+      end
+
+      def clear
+        @mapping.clear
+      end
+
+      private
+
+      def perform_fetch(lookup_key, *args)
+        matching_pair = @mapping.reverse_each.detect do |key, _|
+          key === lookup_key
+        end
+
+        if matching_pair
+          matching_pair.last.call(lookup_key, *args)
+        else
+          yield lookup_key, *args
+        end
+      end
+
+      def default_value
+        @default_value ||= Value.new
+      end
+    end
+  end
+end