class Link
  attr_accessor :source, :target

  def initialize(arg)
    @args = arg
    @source = @args.delete(:source)
    @target = @args.delete(:target)

    raise Exception.new("source cant be nil") unless @source
    raise Exception.new("target cant be nil") unless @target
    raise Exception.new("source must be of type Node") unless @source.is_a? Node
    raise Exception.new("target must be of type Node") unless @target.is_a? Node

    @args[:weight] ||= 1

    @source.neighbours << @target
    @target.neighbours << @source
  end

  def method_missing(name, *args)
    super unless args.empty?
    @args[name]
  end
end