module OptparsePlus
  module ExecutionStrategy
    # Base for any ExecutionStrategy implementation.  Currently, this is nothing more than an interface
    # specification.
    class Base
      # Executes the command and returns the results back.  This
      # should do no logging or other logic other than to execute the
      # command and return the required results.  If command is an
      # array, use exec directly bypassing any tokenization, shell or
      # otherwise; otherwise use the normal shell interpretation of
      # the command string.
      #
      # command:: the command-line to run, as an Array or a String
      #
      # Returns an array of size 3:
      # <tt>[0]</tt>:: The standard output of the command as a String, never nil
      # <tt>[1]</tt>:: The standard error output of the command as a String, never nil
      # <tt>[2]</tt>:: A Process::Status-like objects that responds to <tt>exitstatus</tt> which returns
      #                the exit code of the command (e.g. 0 for success).
      def run_command(command)
        subclass_must_implement!
      end

      # Returns the class that, if caught by calling #run_command, represents the underlying command
      # not existing.  For example, in MRI Ruby, if you try to execute a non-existent command,
      # you get a Errno::ENOENT.
      def exception_meaning_command_not_found
        subclass_must_implement!
      end
    protected
      def subclass_must_implement!; raise "subclass must implement"; end
    end
  end
end
