1 files changed, 66 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/number_helper/rounding_helper.rb b/activesupport/lib/active_support/number_helper/rounding_helper.rb
new file mode 100644
index 0000000000..2ad8d49c4e
--- /dev/null
+++ b/activesupport/lib/active_support/number_helper/rounding_helper.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module ActiveSupport
+  module NumberHelper
+    class RoundingHelper # :nodoc:
+      attr_reader :options
+
+      def initialize(options)
+        @options = options
+      end
+
+      def round(number)
+        return number unless precision
+        number = convert_to_decimal(number)
+        if significant && precision > 0
+          round_significant(number)
+        else
+          round_without_significant(number)
+        end
+      end
+
+      def digit_count(number)
+        return 1 if number.zero?
+        (Math.log10(absolute_number(number)) + 1).floor
+      end
+
+      private
+        def round_without_significant(number)
+          number = number.round(precision)
+          number = number.to_i if precision == 0 && number.finite?
+          number = number.abs if number.zero? # prevent showing negative zeros
+          number
+        end
+
+        def round_significant(number)
+          return 0 if number.zero?
+          digits = digit_count(number)
+          multiplier = 10**(digits - precision)
+          (number / BigDecimal(multiplier.to_f.to_s)).round * multiplier
+        end
+
+        def convert_to_decimal(number)
+          case number
+          when Float, String
+            BigDecimal(number.to_s)
+          when Rational
+            BigDecimal(number, digit_count(number.to_i) + precision)
+          else
+            number.to_d
+          end
+        end
+
+        def precision
+          options[:precision]
+        end
+
+        def significant
+          options[:significant]
+        end
+
+        def absolute_number(number)
+          number.respond_to?(:abs) ? number.abs : number.to_d.abs
+        end
+    end
+  end
+end