require 'units/units'

class Object # :nodoc:
  
  alias :method_missing_before_units :method_missing 
  
  def method_missing(method,*args)
    begin
      s = method.to_s.split('_')
      if s.select{|e| e == 'per'}.size > 0
        per_ratio method, args
      elsif s.select{|e| e == 'in'}.size > 0
        per_ratio method.to_s.sub(/_in_/,'_per_').to_sym, args
      else
        convert_unit_value method, args
      end
    rescue Exception => exception
      method_missing_before_units method, args
    end
  end

  def convert_unit_value(method,*args)
    if Units.defining?
      reference = Units.make_forward_reference(method,Units.defining?)
      begin
        value = Units.convert 1, method
        Units.release_forward_reference reference
        value
      rescue MissingUnitsException
        Units.hold_forward_reference
      rescue UnitsException => exception
        units_problem("definition",exception,method,args)
      rescue Exception => exception
        method_missing_before_units(method,args)
      end
    else
      begin
        Units.convert 1, method
      rescue UnitsException => exception
        units_problem("use",exception,method,args)
      rescue Exception
        method_missing_before_units(method,args)
      end
    end
  end

  def per_ratio(method,*args)
    if Units.defining?
      reference = Units.make_forward_reference(method,Units.defining?)
      begin
        value = convert_per_ratio method
	Units.release_forward_reference reference
	value
      rescue MissingUnitsException
        Units.hold_forward_reference
      rescue UnitsException => exception
        units_problem("definition",exception,method,args)
      rescue Exception
        method_missing_before_units(method,args)
      end
    else
      convert_per_ratio method
    end
  end

  def convert_per_ratio(method)
    ps = method.to_s.split '_per_'
    raise UnitsException('invalid per method') if ps.size != 2
    value = (1.unite ps[1]) / (1.unite ps[0])
    raise UnitsException.new("per ratio has units") if
      value.kind_of? NumericWithUnits
    value
  end
  
  def units_problem(state,exception,method,args)
    raise exception
  end

end