# Used by +Rtml::ReverseEngineering::Simulator+ to track the value of a variable. Attempts
# to build a logical value by processing the setvar's :lo, :op and :ro attributes. References to
# other variables are automatically resolved. References to nonexistent values assume built-in variables
# and assign generic values to them.
#
# Implements a #== method to see if one variable's value is equal to another's, though this may not always be accurate.
#
class Rtml::ReverseEngineering::Simulator::VariableValue
  include Rtml::ReverseEngineering::Simulator::VariableLookup
  attr_reader :value

  def initialize(setvar, all_variables, known_variable_types)
    @setvar, @all_variables, @known_variable_types = setvar, all_variables, known_variable_types
    @value = setvar.to_s

    %w(lo op ro).each { |i| instance_variable_set("@#{i}", resolve(self.send(i), all_variables, known_variable_types)) }
    catch(:done) do
      check_for_assignment
      check_for_operation
    end

    do_casting
    check_boundaries
  end

  def ==(other)
    self.value == other.value
  end

  private
  attr_reader :setvar, :all_variables, :known_variable_types

  def type
    @type ||= known_variable_types[setvar['name']]
  end

  def check_boundaries
    case type
      when :integer
        unless (-999999999..999999999).include? @value
          raise RulesViolationError, "TML numbers must be no more than 9 digits in length: #{@value}"
        end
    end
  end

  def do_casting
    @value = case type
      when :integer then value.to_i
      else value.to_s
    end
  end

  def check_for_operation
    unless setvar['op'].blank?
      method_name = "perform_operation_#{setvar['op']}"
      @value = self.send(method_name)
      throw :done
    end
  rescue NoMethodError
    raise Rtml::Error::InvalidOperation
  end

  def check_for_assignment
    if setvar['op'].blank? && !setvar['lo'].blank?
      @value = setvar['lo']
      throw :done
    end
  end

  def lo; @lo ||= setvar['lo']; end
  def op; @op ||= setvar['op']; end
  def ro; @ro ||= setvar['ro']; end

  def perform_operation_plus
    case type
      when :integer then lo.to_i + ro.to_i
      when :string  then lo.to_s + ro.to_s
      when :date then "#{lo.to_s} + #{ro.to_s}"
      else raise Rtml::Errors::InvalidOperation
    end
  end

  def perform_operation_minus
    case type
      when :integer then lo.to_i - ro.to_i
      when :string  then lo.to_s[0..-(ro.to_i+1)]
      when :date then "#{lo.to_s} - #{ro.to_s}"
      else raise Rtml::Errors::InvalidOperation
    end
  end

  def perform_operation_number
    case type
      when :integer then lo.split(/;/).length
      else raise Rtml::Errors::InvalidOperation
    end
  end

  def perform_operation_item
    case type
      when :string then lo.split(/;/)[ro.to_i]
      else raise Rtml::Errors::InvalidOperation
    end
  end
end