module Tins::DeepConstGet

def self.const_defined_in?(modul, constant)
  modul.const_defined?(constant)
end

def self.const_defined_in?(modul, constant)
  modul.const_defined?(constant, false)
end

def deep_const_get(path, start_module = Object)
  path.to_s.split('::').inject(start_module) do |p, c|
    case
    when c.empty?
      if start_module == Object
        Object
      else
        raise ArgumentError, "top level constants cannot be reached from"\
          " start module #{start_module.inspect}"
      end
    when ::Tins::DeepConstGet.const_defined_in?(p, c) then p.const_get(c)
    else
      begin
        p.const_missing(c)
      rescue NameError => e
        raise ArgumentError, "can't get const #{path}: #{e}"
      end
    end
  end
end