Source code for utils.backup_data

""" Simple backup script which just creates the root structure in an other
folder and syncs everything which recursevely lies within one of the source
folders. For files bigger than a threshold they are first gziped.

https://codereview.stackexchange.com/questions/101616/simple-backup-script-in-python
"""

import argparse
import gzip
import os
import shutil
import sys
import threading

def parse_input():
    parser = argparse.ArgumentParser()
    parser.add_argument('-target', nargs=1, required=True,
                        help='Target Backup folder')
    parser.add_argument('-source', nargs='+', required=True,
                        help='Source Files to be added')
    parser.add_argument('-compress', nargs=1,  type=int,
                        help='Gzip threshold in bytes', default=[100000])

    # no input means show me the help
    if len(sys.argv) == 1:
        parser.print_help()
        sys.exit()

    return parser.parse_args()


def size_if_newer(source, target):
    """ If newer it returns size, otherwise it returns False """

    src_stat = os.stat(source)
    try:
        target_ts = os.stat(target).st_mtime
    except FileNotFoundError:
        try:
            target_ts = os.stat(target + '.gz').st_mtime
        except FileNotFoundError:
            target_ts = 0

    # The time difference of one second is necessary since subsecond accuracy
    # of os.st_mtime is striped by copy2
    return src_stat.st_size if (src_stat.st_mtime - target_ts > 1) else False

def threaded_sync_file(source, target, compress):
    size = size_if_newer(source, target)

    if size:
        thread = threading.Thread(target=transfer_file, 
                                  args=(source, target, size > compress))
        thread.start()
        return thread

def sync_file(source, target, compress):
    size = size_if_newer(source, target)

    if size:
        transfer_file(source, target, size > compress)


def transfer_file(source, target, compress):
    """ Either copy or compress and copies the file """

    try:
        if compress:
            with gzip.open(target + '.gz', 'wb') as target_fid:
                with open(source, 'rb') as source_fid:
                    target_fid.writelines(source_fid)
            print('Compress {}'.format(source))
        else:
            shutil.copy2(source, target)
            print('Copy {}'.format(source))
    except FileNotFoundError:
        os.makedirs(os.path.dirname(target))
        transfer_file(source, target, compress)


def sync_root(root, arg):
    target = arg.target[0]
    compress = arg.compress[0]
    threads = []

    for path, _, files in os.walk(root):
        for source in files:
            source = path + '/' + source
            threads.append(threaded_sync_file(source, 
                           target + source, compress))
#            sync_file(source, target + source, compress)
    for thread in threads:
        thread.join()


if __name__ == '__main__':
    arg = parse_input()
    print('### Start copy ####')
    for root in arg.source:
        sync_root(root, arg)
    print('### Done ###')