#!/usr/bin/env python3

"""backup-check: Periodically compare checksums of backups in multiple
locations. It's mainly to do a weekly check of all my backup locations and
identify bit rot before it's too late.

Install via `crontab -e`:
0 2 * * 0 /home/noah/bin/backup-check

--Kirsle
http://sh.kirsle.net/
"""

import codecs
import os.path
import subprocess

# Directories to compare with each other.
DIRECTORIES = [
    "/mnt/Midnight/Images/Organized",
    "/run/media/noah/Cyro/Pictures/Organized",
    "/run/media/noah/Obelisk/Redundant/Images/Organized",
    "/home/noah/Dropbox/Photos/Organized",
    "/home/noah/ownCloud/Photos/Organized",
]
ERROR_OUT = "/home/noah/Desktop/Checksum Error.txt"

def main():
    # First available disk becomes the common denominator.
    master = None
    for disk in DIRECTORIES:
        if os.path.isdir(disk):
            if master is None:
                print("Master disk chosen as:", disk)
                master = disk

            if disk != master:
                # Do the comparison.
                print("Compare {} <=> {}".format(master, disk))
                out = subprocess.check_output(["diff", "-aqr", master, disk])
                if len(out):
                    # Problem!
                    error(out)
                    break

def error(out):
    """Error, panic!"""
    fh = codecs.open(ERROR_OUT, "w", "utf-8")
    fh.write(out.decode("utf-8"))
    fh.close()

if __name__ == "__main__":
    main()