#!python3
#coding:ascii


import argparse
import base64
import hashlib
import hmac
import os
import secrets
import time
import threading

from urllib.parse import urlparse

URLS = [
    'otpauth://totp/user@company.domain?secret=BBBASE32'
]


def get_totp_timestamp(timestamp:int=None):
    """https://www.rfc-editor.org/rfc/rfc6238"""
    t = timestamp or int(time.time())
    T = t // 30
    return T
    

def compute_hotp(secret, factor:int):
    """https://www.rfc-editor.org/rfc/rfc4226"""
    C = factor.to_bytes(8, 'big')
    mac = hmac.digest(secret, C, 'sha1')
    offset = mac[19] & 0xf
    result = mac[offset:offset+4]
    result = int.from_bytes(result, 'big')
    result = (result & 0x7fffffff) % 1_000_000
    return result
    
   
def hotp_to_pin(hotp:int):
    h = str(hotp).zfill(6)
    h = h[:3] + ' ' + h[3:]
    return h
    

def decode_url(totp_url):
    url = urlparse(totp_url)
    query = {}
    for arg in url.query.split('&'):
        k, v = arg.split('=', 1)
        k = k.lower()
        query[k] = v
    path = url.path.split('/')[-1]
    return (path, query)

    
    
def _cli():
    def _show_time_remaining(n):
        for i in range(n, 0, -1):
            print(f'  Time remaining: {i:2}', end='\r', flush=True)
            time.sleep(1)

    while True:
        os.system('cls')
        totps = {}
        tm = get_totp_timestamp()
        for url in URLS:
            provider, query = decode_url(url)
            secret = query.get('secret')
            if not secret:
                continue
            secret = base64.b32decode(secret.upper())
            totp = hotp_to_pin(compute_hotp(secret, tm))
            totps[provider] = totp
            
        width = max([len(p) for p in totps.keys()])
        fmt = f'{{:{width}}}\t{{}}'
        print()
        print('\n'.join(
            fmt.format(k,v) for k,v in totps.items()
        ), end='\n\n')
        
        time_remaining = 30 - int(time.time() % 30)
        threading.Thread(
            target=_show_time_remaining, 
            args=(time_remaining,),
            daemon=True,
        ).start()
        time.sleep(time_remaining)
        

def cli():
    try:
        _cli()
    except (KeyboardInterrupt, EOFError):
        pass
    finally:
        print()  # restore newline feed after \r


    
def test():
    """Test cases taken from RFCs"""
    print('----------HTOP----------')
    secret = bytes.fromhex('3132333435363738393031323334353637383930')    
    for i in range(10):
        print(
            i, 
            hmac.digest(secret, i.to_bytes(8, 'big'), 'sha1').hex(), 
            compute_hotp(secret, i),
        )
    
    print('------------TOTP Timestamp--------------')
    print(59, hex(get_totp_timestamp(59)), 1)
    print(1111111109, hex(get_totp_timestamp(1111111109)), '23523EC')
    print(1234567890 , hex(get_totp_timestamp(1234567890 )), '273EF07')
    
    print('----------6-Digit TOTP---------------')
    secret = b'12345678901234567890'
    print(59, compute_hotp(secret, get_totp_timestamp(59)), '287082')
    print(1111111109, compute_hotp(secret, get_totp_timestamp(1111111109)), '081804')
    print(1234567890, compute_hotp(secret, get_totp_timestamp(1234567890)), '005924')
    
    
        

def main():
    cli()
    
    raise SystemExit

    # TODO: add encrypted URL cache
    parser = argparse.ArgumentParser()
    mode = parser.add_mutually_exclusive_group()
    mode.add_argument('-a', '--add-url', type=str, desc='Add a new TOTP url')
    mode.add_argument('-d', '--delete-url', type=int, desc='Delete a known URL by its ID')
    mode.add_argument('-p', '--password', type=str, desc='Password on the database')
    mode.add_argument('-s', '--set-password', type=str, desc="Set password. Leave blank for interactive prompt")
    mode.add_argument('-c', '--cli', action='store_true', desc='Show TOTPs in CLI application')
    
    args = parser.parse_arguments()
    
    

if __name__ == '__main__':
    main()