#!/usr/bin/env python3


from pprint import pprint
import daemon
import time
import argparse
import os
import json
from pyf import download, prt, sha256


WORKDIR = os.getcwd()


def init_parser():
    ''' initialize the argument parser
        @return agrs: the parsed arguments
    '''
    parser = argparse.ArgumentParser(description='flash linux operating systems on the fly')
    parser.add_argument('os',
                        default='arch',
                        metavar='os',
                        help='the operating system that should be flashed')
    parser.add_argument('storage',
                        metavar='storage',
                        help='the storage where the os shall be flashed')
    return parser.parse_args()


def check_update(distributions):
    ''' check if distributions are up to date '''

    from os import path
    from datetime import datetime

    # go through distributions
    for name, dist in distributions.items():
        prt('checking operating system {} for updates ...'.format(name))

        if not dist['file_url'] or not dist['interval']:
            prt('ERROR in distributions.json: *file_url* and *interval* \
must be specified, skipping {} ...'.format(name))
            continue

        # get absolute file name
        if not dist['file_name']:
            dist['file_name'] = dist['file_url'].split('/')[-1]
        file_name = '{}/dist/{}'.format(WORKDIR, dist['file_name'])

        if not path.isfile(file_name):
            prt('{} does not yet exist, downloading ...'.format(file_url))
            download(dist['file_url'], file_name)
            continue

        # is the file younger than interval?
        file_mod = datetime.fromtimestamp(path.getmtime(file_name))
        file_age = (datetime.now() - file_mod).days
        if file_age < int(dist['interval']):
            prt('{} is younger than {} days, skipping ...'.format(
                name, dist['interval']))
            continue
        prt('{} is older than {} days, checking test file ...'.format(name, file_age))

        if not dist['test_url']:
            prt('distributions.json: `test_url` not specified, downloading {} ...'.format(file_url))
            download(dist['file_url'], file_name)
            continue

        # get absolute test name
        if not dist['test_name']:
            dist['test_name'] = dist['test_url'].split('/')[-1]
        test_name = '{}/dist/{}'.format(WORKDIR, dist['test_name'])

        if not path.isfile(test_name):
            prt('{} does not yet exist, downloading ...'.format(dist['test_url']))
            download(dist['test_url'], test_name)
            download(dist['file_url'], file_name)
            continue

        # did sha256 of test files change?
        test_sha256_old = sha256(test_name)
        download(dist['test_url'], test_name)
        test_sha256_new = sha256(test_name)
        if not test_sha256_old == test_sha256_new:
            prt('`test_file` {} has changed, downloading {}'.format(test_name, dist['test_url']))
            download(dist['file_url'], file_name)
            continue

        prt('{} is still up to date, skipping ...'.format(name))


def get_distributions():
    ''' read distributions.json and @return it as json object '''
    with open('{}/distributions.json'.format(WORKDIR), 'r') as f:
        #TODO catch json format errors and stuff like that
        return json.load(f)


# https://stackoverflow.com/questions/4637420/efficient-python-daemon#8375012
def run_daemon():
    ''' run the daemon '''
    with daemon.DaemonContext():
        check_update()


if __name__ == '__main__':
    args = init_parser()
    distributions = get_distributions()
    check_update(distributions)
#     run_daemon()