#!/usr/bin/env python3

import argparse
import base64
import configparser
import json
import os
import pathlib
import subprocess
import sys
import traceback
import urllib.parse
import getpass

# use requests instead of urllib.request for keep-alive connection
import requests

def sign(data, keyfile, unlock_key=None, engine=None):
    #  pkcs11-tool --id 02 -s -p $PIN -m RSA-PKCS
    if engine is None:
        cmd = ['openssl', 'pkeyutl', '-sign', '-inkey', keyfile, '-pkeyopt', 'digest:sha256']
        raw_data = base64.b64decode(data)
        env = None
    elif engine == 'pkcs11':
        env = {'PIN': unlock_key}
        """magic_prefix is ASN.1 DER for
           DigestInfo ::= SEQUENCE {
               digestAlgorithm DigestAlgorithm,
               digest OCTET STRING
           }
        """
        magic_prefix = bytes.fromhex("3031300d060960864801650304020105000420")
        raw_data = magic_prefix + base64.b64decode(data)
        cmd = ['pkcs11-tool', '--id', keyfile, '-s', '-m', 'RSA-PKCS', '-p', 'env:PIN']
        # cmd = ['openssl', 'pkeyutl', '-sign', '-pkeyopt', 'digest:sha256', '-engine', 'pkcs11', '-keyform', 'engine', '-inkey', keyfile]
    p = subprocess.run(
        cmd,
        env=env,
        input=raw_data,
        capture_output=True)
    return base64.b64encode(p.stdout).decode()

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Fake the MargTools application.')
    parser.add_argument('url', type=urllib.parse.urlparse, help='bc-digsign:// url')
    parser.add_argument('-k', '--user-key', type=pathlib.Path, help='key file')
    parser.add_argument('-c', '--user-cert', type=pathlib.Path, help='certificate file')
    parser.add_argument('-e', '--engine', type=str, help='"pkcs11" for smart card')
    args = parser.parse_args()

    try:
        # parse query string
        params = urllib.parse.parse_qs(args.url.query)
        url = params['baseUrl'][0]
        token = params['accessToken'][0]

        # if missing, get user key and cert from section [url] in ~/.margfools
        config = configparser.ConfigParser()
        config.read(os.path.expanduser('~') + '/.margfools')
        if not args.user_key:
            args.user_key = config.get(url, 'user-key')
        if not args.user_cert:
            args.user_cert = config.get(url, 'user-cert', fallback=None)
        if not args.user_key:
            print('user key not specified', file=sys.stderr)
            sys.exit(1)
        if not args.engine:
            args.engine = config.get(url, 'engine')
        engine = args.engine
        user_keyfile = args.user_key
        # base64.b64encode
        unlock_key = None
        if engine is None:
            if not args.user_cert:
                print('user cert not specified', file=sys.stderr)
                sys.exit(1)
            user_cert = ''.join(line.strip() for line in open(args.user_cert) if not line.startswith('-----'))
        elif engine == 'pkcs11':
            user_cert = base64.b64encode(subprocess.run(["pkcs11-tool", "--read-object", "--type", "cert", "--id", user_keyfile], capture_output=True).stdout).decode()
            unlock_key = getpass.getpass("PIN:")
        session = requests.Session()
        headers={'Authorization': f'Bearer {token}'}

        # delete old signing session
        r = session.delete(f'{url}/signatures/{params["startSigningToken"][0]}', headers=headers)

        # register a certificate or sign a document, makes no difference to us
        if params.get('registerCertificate'):
            q = {'registerCertificate': 1}
        else:
            q = {'documentId': [i for i in params['documentId'][0].split(',')]}
        qs = urllib.parse.urlencode(q, doseq=True)
        r = session.post(f'{url}/signatures?{qs}', headers=headers)

        # get signature request and mix in my secrets and publics
        request = json.loads(r.text)
        request['AuthenticationToken'] = token
        request['CertificatePublicKey'] = user_cert
        # keep signing whatever they send us
        while True:
            for name in ('AttachmentHashes', 'XmlHashes'):
                if request.get(name) is not None:
                    request[f'Signed{name}'] = [sign(e, user_keyfile, unlock_key, engine=engine) for e in request[name]]
            d = json.dumps(request)
            d = d.encode()
            r = session.put(f'{url}signatures/{request["SignatureRequestId"]}',
                headers=headers | {'Content-Type': 'application/json; charset=utf-8'},
                data=json.dumps(request).encode())
            if not r.text:
                break
            request |= json.loads(r.text)
    except:
        traceback.print_exc()
        # Don't close terminal immediately on fail
        input()