1 files changed, 74 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/decimal.rb b/activemodel/lib/active_model/type/decimal.rb
new file mode 100644
index 0000000000..b37dad1c41
--- /dev/null
+++ b/activemodel/lib/active_model/type/decimal.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require "bigdecimal/util"
+
+module ActiveModel
+  module Type
+    class Decimal < Value # :nodoc:
+      include Helpers::Numeric
+      BIGDECIMAL_PRECISION = 18
+
+      def type
+        :decimal
+      end
+
+      def serialize(value)
+        cast(value)
+      end
+
+      def type_cast_for_schema(value)
+        value.to_s.inspect
+      end
+
+      private
+
+        def cast_value(value)
+          casted_value = \
+            case value
+            when ::Float
+              convert_float_to_big_decimal(value)
+            when ::Numeric
+              BigDecimal(value, precision || BIGDECIMAL_PRECISION)
+            when ::String
+              begin
+                value.to_d
+              rescue ArgumentError
+                BigDecimal(0)
+              end
+            else
+              if value.respond_to?(:to_d)
+                value.to_d
+              else
+                cast_value(value.to_s)
+              end
+            end
+
+          apply_scale(casted_value)
+        end
+
+        def convert_float_to_big_decimal(value)
+          if precision
+            BigDecimal(apply_scale(value), float_precision)
+          else
+            value.to_d
+          end
+        end
+
+        def float_precision
+          if precision.to_i > ::Float::DIG + 1
+            ::Float::DIG + 1
+          else
+            precision.to_i
+          end
+        end
+
+        def apply_scale(value)
+          if scale
+            value.round(scale)
+          else
+            value
+          end
+        end
+    end
+  end
+end