Multi-currency support: Money + Currency class improvements (#553)

* Money improvements

* Replace all old money usage

lib/money.rb

@@ -0,0 +1,61 @@
+class Money
+    include Comparable
+    include Arithmetic
+
+    attr_reader :amount, :currency
+
+    class << self
+        def default_currency
+            @default ||= Money::Currency.new(:usd)
+        end
+
+        def default_currency=(object)
+            @default = Money::Currency.new(object)
+        end
+    end
+
+    def initialize(obj, currency = Money.default_currency)
+        unless obj.is_a?(Money) || obj.is_a?(Numeric) || obj.is_a?(BigDecimal)
+            raise ArgumentError, "obj must be an instance of Money, Numeric, or BigDecimal"
+        end
+
+        @amount = obj.is_a?(Money) ? obj.amount : BigDecimal(obj.to_s)
+        @currency = obj.is_a?(Money) ? obj.currency : Money::Currency.new(currency)
+    end
+
+    def cents_str(precision = @currency.default_precision)
+        format_str = "%.#{precision}f"
+        amount_str = format_str % @amount
+        parts = amount_str.split(@currency.separator)
+
+        return "" if parts.length < 2
+
+        parts.last.ljust(precision, "0")
+    end
+
+    # Basic formatting only.  Use the Rails number_to_currency helper for more advanced formatting.
+    alias to_s format
+    def format
+        whole_part, fractional_part = sprintf("%.#{@currency.default_precision}f", @amount).split(".")
+        whole_with_delimiters = whole_part.chars.to_a.reverse.each_slice(3).map(&:join).join(@currency.delimiter).reverse
+        formatted_amount = "#{whole_with_delimiters}#{@currency.separator}#{fractional_part}"
+        @currency.default_format.gsub("%n", formatted_amount).gsub("%u", @currency.symbol)
+    end
+
+    def <=>(other)
+        raise TypeError, "Money can only be compared with other Money objects except for 0" unless other.is_a?(Money) || other.eql?(0)
+        return @amount <=> other if other.is_a?(Numeric)
+        amount_comparison = @amount <=> other.amount
+        return amount_comparison unless amount_comparison == 0
+        @currency <=> other.currency
+    end
+
+    def default_format_options
+        {
+            unit: @currency.symbol,
+            precision: @currency.default_precision,
+            delimiter: @currency.delimiter,
+            separator: @currency.separator
+        }
+    end
+end