#!/usr/bin/env python3

import subprocess
import argparse
import platform
import sys
import os
import time
import tempfile

distro, version, identity = platform.linux_distribution()
date = time.strftime("%Y-%m-%d")
os.environ['GZIP'] = '-6'

exclusions = [
    'dev/*', 'media/*', 'mnt/*',
    'proc/*', 'run/*', 'sys/*',
    'tmp/*', 'Documents/*', 'Downloads/*',
    'Music/*', 'Videos/*', 'photos'
    ]


def clean_on_error(message, tarball):
    """Takes a string and the full tarball path. Displays the string as
    error message, and removes the incomplete tarball.
    """
    try:
        print(message, '\ncleaning ...')
        os.remove(tarball)

    except OSError:
        pass


def genpath(destination, parameters):
    """Takes the destination directory and a list of the elements which
    forms the tarball name, adds the name to the list of exclusions and
    returns the full tarball path.
    """
    tarball_name = "-".join(i for i in parameters if i is not None) + '.tar.gz'
    tarball_path = os.path.join(destination, tarball_name)
    exclusions.append(tarball_name)

    return tarball_path


def parse_cmd_line():
    """Function to parse script options and generate an help page."""
    parser = argparse.ArgumentParser(
        description="A script to create tarball backups of the entire system"
        )

    parser.add_argument(
        'destination',
        help = 'The backup destination directory',
        action = 'store',
        type = str
        )

    parser.add_argument(
        '-l', '--level',
        help = 'Choose compression level (1-9). Default to 6',
        action = 'store',
        dest = 'level',
        type = int,
        metavar = ''
        )

    parser.add_argument(
        '-c', '--compare',
        help = 'Compare tarball against filesystem',
        action = 'store_true'
        )

    parser.add_argument(
        '-s', '--simulate',
        help = 'Simulate the tarball extraction',
        action = 'store_true'
        )

    parser.add_argument(
        '-a', '--add',
        help = 'Append given string to the tarball name',
        dest = 'tag',
        metavar = ''
        )

    return parser.parse_args()


def main():
    args = parse_cmd_line()

    if args.level in range(1,10): os.environ['GZIP'] = '-' + str(args.level)
    tarball = genpath(args.destination, [distro, version, args.tag, date])

    # check that user is root and destination dir exists

    if os.getuid() != 0:
        print("Error: you must be root to run this script")
        sys.exit(1)

    if not os.path.isdir(args.destination):
        print("Error: destination directory does not exist")
        sys.exit(1)

    # create temporary file

    tmp = tempfile.NamedTemporaryFile(prefix='tarbackup', dir='/tmp')
    for i in exclusions:
        i = i + "\n"
        tmp.write(bytes(i, 'UTF-8'))

    tmp.seek(0)
    tmp.read().decode()

    tmp_file_path = os.path.join('/tmp', tmp.name)

    try:
        print('Creating the tarball, please wait ...')
        subprocess.check_call(
                [
                    'tar', '--auto-compress', '--directory=/',
                    '-X', tmp_file_path, '--xattrs',
                    '--selinux', '--acls', '--check-links',
                    '--numeric-owner', '--create', '-f',
                    tarball, '.'
                ]
            )

        if args.compare:
            print('Comparing tarball content against filesystem ...')
            subprocess.check_call(
                ['tar', '--directory=/', '--compare', '-f', tarball]
                )

        if args.simulate:
            print('Simulating the tarball extraction ...')
            subprocess.check_call(
                ['tar', '--extract', '--to-stdout', '-f', tarball],
                stdout=open('/dev/null','w')
                )

    except subprocess.CalledProcessError as error:
        print('tar exit status: ', error.returncode)
        clean_on_error('An error occurred!', tarball)
        sys.exit(1)

    except KeyboardInterrupt:
        clean_on_error('Script interrupted!', tarball)
        sys.exit(1)

    else:
        print('All done! have a nice day!')

    finally:
        tmp.close()

if  __name__ == '__main__':
    main()