#!/usr/bin/python3

import subprocess
import sys
import os
import argparse
import json

if __name__ == "__main__":

    parser = argparse.ArgumentParser(description="Backup Dir Size helper")
    parser.add_argument('PATH')
    parser.add_argument('--save-new-size', action='store_const',
                            default=False, const=True)
    args = parser.parse_args()
    
    # check parameter #
    if not args.PATH.replace("/", "").replace("-","").isalnum():
        print("Illegal Path: {} (must be alphanum + /)".format(args.PATH))
        sys.exit(1)
    elif not args.PATH.startswith("/"):
        print("Path mus be absolute ({})".format(args.PATH))
        sys.exit(1)
    elif not os.path.isdir(args.PATH):
        print("Path does not exist ({}".format(args.PATH))
        sys.exit(1)

    savedir = "/opt/backup-info"
    savepath = os.path.join(savedir, args.PATH.lstrip("/").replace("/", "-"))
    currentSize = 0
    if os.path.isfile(savepath):
        with open(savepath) as f:
            currentSize = int(f.read())

    # check #
    p = subprocess.run(["du", args.PATH], capture_output=True, encoding="utf-8")
    size = int(p.stdout.split("\n")[-2].split("\t")[0])
    
    if currentSize and currentSize == size:
        result = { "changed" : False, "old" : currentSize, "new" : size }
    else:
        result = { "changed" : True, "old" : currentSize, "new" : size }


    if args.save_new_size:
        with open(savepath, "w") as f:
            f.write(str(size))

    # return result
    print(json.dumps(result))