`TypeMap` and `HashLookupTypeMap` shouldn't be in Active Model

These are used by the connection adapters to convert SQL type
information into the appropriate type object, and makes no sense outside
of the context of Active Record

2 files changed, 87 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/type/hash_lookup_type_map.rb b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
new file mode 100644
index 0000000000..3b01e3f8ca
--- /dev/null
+++ b/activerecord/lib/active_record/type/hash_lookup_type_map.rb
@@ -0,0 +1,23 @@
+module ActiveRecord
+  module Type
+    class HashLookupTypeMap < TypeMap # :nodoc:
+      def alias_type(type, alias_type)
+        register_type(type) { |_, *args| lookup(alias_type, *args) }
+      end
+
+      def key?(key)
+        @mapping.key?(key)
+      end
+
+      def keys
+        @mapping.keys
+      end
+
+      private
+
+      def perform_fetch(type, *args, &block)
+        @mapping.fetch(type, block).call(type, *args)
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/type/type_map.rb b/activerecord/lib/active_record/type/type_map.rb
new file mode 100644
index 0000000000..8ce36cc9af
--- /dev/null
+++ b/activerecord/lib/active_record/type/type_map.rb
@@ -0,0 +1,64 @@
+require 'concurrent'
+
+module ActiveRecord
+  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