1 files changed, 62 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/number_helper/number_to_rounded.rb b/activesupport/lib/active_support/number_helper/number_to_rounded.rb
new file mode 100644
index 0000000000..817ac1ebb2
--- /dev/null
+++ b/activesupport/lib/active_support/number_helper/number_to_rounded.rb
@@ -0,0 +1,62 @@
+require 'active_support/number_helper/number_converter'
+
+module ActiveSupport
+  module NumberHelper
+    class NumberToRoundedConverter < NumberConverter # :nodoc:
+
+      self.namespace        = :precision
+      self.need_valid_float = true
+
+      def convert
+        @number = Float(@number)
+
+        precision = options.delete :precision
+        significant = options.delete :significant
+
+        if significant && precision > 0
+          digits, rounded_number = digits_and_rounded_number(precision)
+          precision -= digits
+          precision = 0 if precision < 0 # don't let it be negative
+        else
+          rounded_number = BigDecimal.new(@number.to_s).round(precision).to_f
+          rounded_number = rounded_number.abs if rounded_number.zero? # prevent showing negative zeros
+        end
+        delimited_number = NumberToDelimitedConverter.new("%01.#{precision}f" % rounded_number, options).execute
+        format_number(delimited_number)
+      end
+
+      private
+
+        def digits_and_rounded_number(precision)
+          return [1,0] if @number.zero?
+          digits = digit_count(@number)
+          multiplier = 10 ** (digits - precision)
+          rounded_number = calculate_rounded_number(multiplier)
+          digits = digit_count(rounded_number) # After rounding, the number of digits may have changed
+          [digits, rounded_number]
+        end
+
+        def calculate_rounded_number(multiplier)
+          (BigDecimal.new(@number.to_s) / BigDecimal.new(multiplier.to_f.to_s)).round.to_f * multiplier
+        end
+
+        def digit_count(number)
+          (Math.log10(number.abs) + 1).floor
+        end
+
+        def strip_insignificant_zeros
+          options[:strip_insignificant_zeros]
+        end
+
+        def format_number(number)
+          if strip_insignificant_zeros
+            escaped_separator = Regexp.escape(options[:separator])
+            number.sub(/(#{escaped_separator})(\d*[1-9])?0+\z/, '\1\2').sub(/#{escaped_separator}\z/, '')
+          else
+            number
+          end
+        end
+
+    end
+  end
+end