class Vips::Introspect

def initialize name
  # if there's a trailing "!", this is a destructive version of an
  # operation
  if name[-1] == "!"
    @destructive = true
    # strip the trailing "!"
    @vips_name = name[0...-1]
  else
    @destructive = false
    @vips_name = name
  end
  @op = Operation.new @vips_name
  @args = []
  @required_input = []
  @optional_input = {}
  @required_output = []
  @optional_output = {}
  # find all the arguments the operator can take
  @op.argument_map do |pspec, argument_class, _argument_instance|
    flags = argument_class[:flags]
    if (flags & ARGUMENT_CONSTRUCT) != 0
      # names can include - as punctuation, but we always use _ in
      # Ruby
      arg_name = pspec[:name].tr("-", "_")
      @args << {
        arg_name: arg_name,
        flags: flags,
        gtype: pspec[:value_type]
      }
    end
    nil
  end
  @args.each do |details|
    arg_name = details[:arg_name]
    flags = details[:flags]
    if (flags & ARGUMENT_INPUT) != 0
      if (flags & ARGUMENT_REQUIRED) != 0 &&
          (flags & ARGUMENT_DEPRECATED) == 0
        @required_input << details
      else
        # we allow deprecated optional args
        @optional_input[arg_name] = details
      end
      # MODIFY INPUT args count as OUTPUT as well in non-destructive mode
      if (flags & ARGUMENT_MODIFY) != 0 &&
          !@destructive
        if (flags & ARGUMENT_REQUIRED) != 0 &&
            (flags & ARGUMENT_DEPRECATED) == 0
          @required_output << details
        else
          @optional_output[arg_name] = details
        end
      end
    elsif (flags & ARGUMENT_OUTPUT) != 0
      if (flags & ARGUMENT_REQUIRED) != 0 &&
          (flags & ARGUMENT_DEPRECATED) == 0
        @required_output << details
      else
        # again, allow deprecated optional args
        @optional_output[arg_name] = details
      end
    end
  end
  # in destructive mode, the first required input arg must be MODIFY and
  # must be an image
  if @destructive
    if @required_input.length < 1 ||
        @required_input[0][:flags] & ARGUMENT_MODIFY == 0 ||
        @required_input[0][:gtype] != IMAGE_TYPE
      raise Vips::Error, "operation #{@vips_name} is not destructive"
    end
  end
end