Extract ActiveSupport::NumberHelper methods to classes

Due to the overall complexity of each method individually as well as the
global shared private module methods, this pulls each helper into it's
own converter class inheriting from a generic `NumberBuilder` class.

* The `NumberBuilder` class contains the private methods needed for each helper
method an eliminates the need for special definition of specialized private
module methods.
* The `ActiveSupport::NumberHelper::DEFAULTS` constant has been moved
into the `NumberBuilder` class because the `NumberBuilder` is the only
class which needs access to it.
* For each of the builders, the `#convert` method is broken down to
smaller parts and extracted into private methods for clarity of purpose.
* Most of the mutation that once was necessary has now been eliminated.
* Several of the mathematical operations for percentage, delimited, and
rounded have been moved into private methods to ease readability and
clarity.
* Internationalization is still a bit crufty, and definitely could be
improved, but it is functional and a bit easier to follow.

The following helpers were extracted into their respective classes.

* `#number_to_percentage` -> `NumberToPercentageConverter`
* `#number_to_delimited` -> `NumberToDelimitedConverter`
* `#number_to_phone` -> `NumberToPhoneConverter`
* `#number_to_currency` -> `NumberToCurrencyConverter`
* `#number_to_rounded` -> `NumberToRoundedConverter`
* `#number_to_human_size` -> `NumberToHumanSizeConverter`
* `#number_to_human` -> `NumberToHumanConverter`

1 files changed, 71 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/number_helper/number_to_human.rb b/activesupport/lib/active_support/number_helper/number_to_human.rb
new file mode 100644
index 0000000000..2b57c75720
--- /dev/null
+++ b/activesupport/lib/active_support/number_helper/number_to_human.rb
@@ -0,0 +1,71 @@
+require 'active_support/number_helper/number_converter'
+require 'active_support/number_helper/number_to_rounded'
+
+module ActiveSupport
+  module NumberHelper
+    class NumberToHumanConverter < NumberConverter # :nodoc:
+
+      DECIMAL_UNITS = { 0 => :unit, 1 => :ten, 2 => :hundred, 3 => :thousand, 6 => :million, 9 => :billion, 12 => :trillion, 15 => :quadrillion,
+        -1 => :deci, -2 => :centi, -3 => :mili, -6 => :micro, -9 => :nano, -12 => :pico, -15 => :femto }
+
+      self.namespace        = :human
+      self.need_valid_float = true
+
+      def convert # :nodoc:
+        @number = Float(@number)
+
+        # for backwards compatibility with those that didn't add strip_insignificant_zeros to their locale files
+        unless options.key?(:strip_insignificant_zeros)
+          options[:strip_insignificant_zeros] = true
+        end
+
+        units = opts[:units]
+        exponent = calculate_exponent(units)
+        @number = @number / (10 ** exponent)
+
+        unit = determine_unit(units, exponent)
+
+        rounded_number = NumberToRoundedConverter.new(@number, options).execute
+        format.gsub(/%n/, rounded_number).gsub(/%u/, unit).strip
+      end
+
+      private
+
+        def format
+          options[:format] || translate_in_locale('human.decimal_units.format')
+        end
+
+        def determine_unit(units, exponent)
+          exp = DECIMAL_UNITS[exponent]
+          case units
+          when Hash
+            units[exp] || ''
+          when String, Symbol
+            I18n.translate("#{units}.#{exp}", :locale => options[:locale], :count => number.to_i)
+          else
+            translate_in_locale("human.decimal_units.units.#{exp}", count: number.to_i)
+          end
+        end
+
+        def calculate_exponent(units)
+          exponent = number != 0 ? Math.log10(number.abs).floor : 0
+          unit_exponents(units).find { |e| exponent >= e } || 0
+        end
+
+        def unit_exponents(units)
+          inverted_decimal_units = DECIMAL_UNITS.invert
+          case units
+          when Hash
+            units
+          when String, Symbol
+            I18n.translate(units.to_s, :locale => options[:locale], :raise => true)
+          when nil
+            translate_in_locale("human.decimal_units.units", raise: true)
+          else
+            raise ArgumentError, ":units must be a Hash or String translation scope."
+          end.keys.map { |e_name| inverted_decimal_units[e_name] }.sort_by{ |e| -e }
+        end
+
+    end
+  end
+end