#! /usr/bin/env python3

from sys import argv
from argparse import ArgumentParser
from shutil import copy
from time import time
from subprocess import run, PIPE
import os

S = {
    'installDir': '/usr/local/bin/',
    'app': 'Ixesha',
    'dir': {
        'input': None,
        'output': None,
    },
    'tag': {
        'progress': 'progress',
        'current': 'current',
    },
}

parser = ArgumentParser(prog='{}'.format(S['app']),
                        description='{app} - Incremental Snapshot Backup System'.format(app=S['app']))

parser.add_argument('-i', '--install', action='store_true',
                    help='Install script')
parser.add_argument('-u', '--uninstall', action='store_true',
                    help='Uninstall script')
parser.add_argument('-b', '--from', '--backup', nargs=1, dest='backup',  metavar='<folder-to-be-backed-up>',
                    help='Directory to be backed up')
parser.add_argument('-o', '--to', '--output', nargs=1, dest='output', metavar='<backup-location>',
                    help='Where to save your backup')


def install():
    copy(
        os.path.abspath(__file__),
        os.path.abspath(S['installDir']))
    print('Successfully installed {app} in: {path}'.format(
        app=S['app'], path=S['installDir']))


def uninstall():
    os.remove(
        os.path.join(
            os.path.abspath(S['installDir']),
            os.path.basename(__file__)
        )
    )
    print('Successfully uninstalled {app} from: {path}'.format(
        app=S['app'], path=S['installDir']))


def backup(i, o):

    # Backup
    now = time()
    id = round(now)
    input = '{input}/'.format(input=i)

    # Define paths and files
    tmp = '{output}/{id}.{tag}'.format(output=o,
                                       id=id, tag=S['tag']['progress'])
    final = '{output}/{id}'.format(output=o, id=id)
    cur = '{output}/{tag}'.format(output=o, tag=S['tag']['current'])

    # If fist time backing up make fake current dir
    first = False
    if not os.path.exists(cur):
        first = True

    # Starting the actual backup
    # If no current folder is found, take the current bkp dir as comparison
    print('Backing up...')
    cmd = 'rsync -az --delete --link-dest="{cur}" "{input}" "{tmp}"'.format(
        cur=o if first else cur, input=input, tmp=tmp)
    ret = run(cmd, shell=True, stdout=PIPE)
    print('Done. ({}s)'.format(round(time() - now, 1)))

    # Cleaning Up
    print('Cleaning up...')

    os.rename(tmp, final)
    if not first:
        os.remove(cur)
    os.symlink(final, cur)


def error(msg):
    print('{}\n'.format(msg))
    parser.print_help()


def init():
    opt = parser.parse_args(argv[1:])

    if opt.install and opt.uninstall:
        error('Cannot install and uninstall at the same time.')
        return

    if opt.install:
        install()
        return

    if opt.uninstall:
        uninstall()
        return

    if opt.backup is None and opt.output is None:
        error('Need a backup and output directory')
        return

    input = os.path.abspath(opt.backup[0])
    output = os.path.abspath(opt.output[0])

    if not os.path.isdir(input):
        raise NotADirectoryError('{}'.format(input))

    if not os.path.isdir(output):
        try:
            os.makedirs(output)
        except:
            raise PermissionError('Cannot write to: {}'.format(output))

    backup(input, output)


init()