TDesktop link generator

tdget.py

from Crypto.Hash import SHA
from Crypto.Signature import PKCS1_v1_5
from Crypto.PublicKey import RSA
from base64 import urlsafe_b64encode
from requests import get


def get_version_signature(version, private_key):
    signed_data = b'TelegramBeta_%x'%int(version)

    digest = SHA.new()
    digest.update(signed_data)

    signer = PKCS1_v1_5.new(private_key)
    sig = signer.sign(digest)

    sig64 = urlsafe_b64encode(sig).decode().replace('-', '8').replace('_', 'B')

    return sig64[19:][:32]

def format_version(v):
    s = str(v)
    if len(s)%3 != 0:
        s = s.rjust(len(s) + 3 - len(s)%3)

    blocks = []
    for d3, d2, d1 in zip(*[iter(s[::-1])]*3):
        blocks.append(str(int(d1+d2+d3)))

    return '.'.join(blocks[::-1])

if __name__ == '__main__':
    update_feed = get('http://updates.tdesktop.com/current').json()

    os = input('Enter OS ({}): '.format(', '.join(update_feed))).strip()

    versions = update_feed[os]
    print('Available versions:')
    for k, v in versions.items():
        print('{}: {} ({})'.format(k, format_version(v['released']), v['released']))

    vers = input('Enter version ({}): '.format(', '.join(versions))).strip()
    linkcontainer = versions[vers]

    installer = input('Download installer instead of update package? [Yn] ').strip().lower() != 'n'
    base = 'https://updates.tdesktop.com'
    link = linkcontainer['link']

    def_vers_code = linkcontainer['released']
    user_vers_code = input('Enter version (or empty for {}): '.format(def_vers_code))
    version_code = int(user_vers_code) if user_vers_code else def_vers_code

    if vers == 'alpha':
        with open ('tdbeta_key.pem') as f:
            private_key = RSA.importKey(f.read())
        signature = get_version_signature(version_code, private_key)

    if not installer:
        link = link.replace('{version}', str(version_code))
        if vers == 'alpha':
            link = link.replace('{signature}', signature)
    else:
        portable = False
        if os == 'win' and vers != 'alpha':
            portable = input('Download portable version? [yN] ').strip().lower() == 'y'

        if os != 'win':
            link = '/t{}/'.format(os)
        else:
            link = '/tsetup/'

        if vers == 'alpha':
            link = link + 'tbeta{}_{}.zip'.format(version_code, signature)
        else:
            pretty_version = format_version(version_code)
            if vers == 'beta':
                pretty_version = pretty_version + '.alpha'

            if os == 'win':
                ext = 'exe' if not portable else 'zip'
            elif 'mac' in os:
                ext = 'dmg'
            elif 'linux' in os:
                ext = 'tar.xz'

            prefix = 'tsetup' if not portable else 'tportable'

            link = link + '.'.join((prefix, pretty_version, ext))
    print(base + link)