module Tins
  module DeepConstGet
    if ::Object.method(:const_defined?).arity == 1
      # :nocov:
      # We do not create coverage on 1.8
      def self.const_defined_in?(modul, constant)
        modul.const_defined?(constant)
      end
      # :nocov:
    else
      def self.const_defined_in?(modul, constant)
        modul.const_defined?(constant, false)
      end
    end

    def self.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 const_defined_in?(p, c)
          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

    def deep_const_get(path, start_module = Object)
      ::Tins::DeepConstGet.deep_const_get(path, start_module)
    end
  end
end