import shutil
import logging
import ipaddress

import luigi


class TargetList(luigi.ExternalTask):
    """ External task.  `TARGET_FILE` is generated manually by the user from target's scope. """

    target_file = luigi.Parameter()

    def output(self):
        """ Returns the target output for this task. target_file.ips || target_file.domains

        In this case, it expects a file to be present in the local filesystem.
        By convention, TARGET_NAME should be something like tesla or some other
        target identifier.  The returned target output will either be target_file.ips
        or target_file.domains, depending on what is found on the first line of the file.

        Example:  Given a TARGET_FILE of tesla where the first line is tesla.com; tesla.domains
        is written to disk.

        Returns:
            luigi.local_target.LocalTarget
        """
        try:
            with open(self.target_file) as f:
                first_line = f.readline()
                ipaddress.ip_interface(first_line.strip())  # is it a valid ip/network?
        except OSError as e:
            # can't open file; log error / return nothing
            return logging.error(f"opening {self.target_file}: {e.strerror}")
        except ValueError as e:
            # exception thrown by ip_interface; domain name assumed
            logging.debug(e)
            with_suffix = f"{self.target_file}.domains"
        else:
            # no exception thrown; ip address found
            with_suffix = f"{self.target_file}.ips"

        shutil.copy(self.target_file, with_suffix)  # copy file with new extension
        return luigi.LocalTarget(with_suffix)