# Copyright (c) 2020 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'contrast/components/interface'

module Contrast
  module Utils
    # Util for information about an IO
    class IOUtil
      include Contrast::Components::Interface

      access_component :logging

      # We're only going to call rewind on things that we believe are safe to
      # call it on. This method white lists those cases and returns false in
      # all others.
      def self.should_rewind? potential_io
        return true if potential_io.is_a?(StringIO)
        return false unless io?(potential_io)

        should_rewind_io?(potential_io)
      rescue StandardError => e
        logger.debug('Encountered an issue determining if rewindable', e, module: potential_io.cs__class.name)
        false
      end

      # IO cannot be used with streams such as pipes, ttys, and sockets.
      def self.should_rewind_io? io
        return false if io.tty?

        status = io.stat
        return false unless status
        return false if status.pipe?
        return false if status.socket?

        true
      end

      # A class is IO if it is a decedent or delegate of IO
      def self.io? object
        return true if object.is_a?(IO)

        # DelegateClass, which is a Delegator, defines __getobj__ as a way to
        # get the object that the class wraps around (delegates to)
        return false unless object.is_a?(Delegator)

        object.__getobj__.is_a?(IO)
      end
    end
  end
end