import os
from pkg_resources import resource_filename, cleanup_resources, resource_string
import atexit
from pathlib import Path

atexit.register(cleanup_resources, force=True)
os.environ["KRB5_CONFIG"] = str(
    Path(resource_filename(__name__, "krb5.conf")).resolve()
)

import kadmin
import getpass
import argparse
import secrets
import string
import shutil
import logging

from ldap3 import Server, Connection, LEVEL
from ldap3.utils.conv import escape_filter_chars
from ldap3.utils.dn import escape_rdn

import subprocess

import smtplib
from jinja2 import Template
from email.message import EmailMessage

FROM_LDAP = object()

parser = argparse.ArgumentParser()
parser.add_argument("--admin", default=getpass.getuser())
parser.add_argument("--verbose", action="store_true")
subparsers = parser.add_subparsers(dest="cmd", help="command")
reset_password = subparsers.add_parser(
    "reset_password",
    help="change user password to newly generated one and send it to his email address from LDAP",
)
reset_password.add_argument("user")
reset_password.add_argument(
    "--show-password", action="store_true", help="print generated password"
)
reset_password.add_argument("email_address", default=FROM_LDAP, nargs="?")

APG_CMD = shutil.which("apg")


def generage_password(length=15):
    if APG_CMD is None:
        logging.warning("apg command not found. Using built in password generator")
        pool = string.ascii_lowercase + string.ascii_uppercase + string.digits
        password = "".join([secrets.choice(pool) for _ in range(length)])
    else:
        password = (
            subprocess.run(
                [APG_CMD, "-m", str(length), "-n", "1", "-M", "NCL"],
                check=True,
                capture_output=True,
            )
            .stdout.decode()
            .strip()
        )

    if len(password) != length:
        raise Exception("Password generation failed")
    return password


def main():
    args = parser.parse_args()
    logging.basicConfig(level=logging.DEBUG if args.verbose else logging.INFO)
    if args.cmd == "reset_password":
        admin_pass = getpass.getpass(f"{args.admin}@HACKERSPACE.PL password: ")
        logging.debug("initializing kadmin")
        k = kadmin.init_with_password(f"{args.admin}/admin", admin_pass)
        logging.debug("kadmin initialized")
        user = args.user
        if user is None:
            user = input("User: ")
        p = k.get_principal(user)

        password = generage_password()
        if args.email_address is not FROM_LDAP:
            address = args.email_address
        else:
            address = get_email_address(args.admin, admin_pass, user)

        if args.show_password:
            print(f'password: "{password}"')

        i = input(
            f"Type yes to reset {user}'s password and send email to {address}\n"
        ).strip()
        if i != "yes":
            print("Aborted")
            return

        p.change_password(password)
        print("password changed")

        send_mail(args.admin, admin_pass, password, user, address)
        print("email sent")
    else:
        parser.print_help()


def get_email_address(admin, admin_pass, uid):
    logging.debug("fetching email address from LDAP")
    s = Server("ldap.hackerspace.pl", use_ssl=True)
    with Connection(
        s,
        user=f"uid={escape_rdn(admin)},ou=People,dc=hackerspace,dc=pl",
        password=admin_pass,
        raise_exceptions=True,
    ) as c:
        logging.debug("connected to LDAP server")
        c.search(
            search_base="ou=People,dc=hackerspace,dc=pl",
            search_filter=f"(uid={escape_filter_chars(uid)})",
            search_scope=LEVEL,
            attributes=["mailRoutingAddress"],
        )
        if not c.entries:
            raise Exception("empty response")
        if len(c.entries) > 1:
            raise Exception("too many responses")
        address = c.entries[0]["mailRoutingAddress"]
        logging.debug(f"got mail address from LDAP: {address}")
        return address


def send_mail(admin, admin_password, password, user, address):
    mail_template = Template(
        resource_string(__name__, "password_reset.jinja2").decode()
    )
    msg = EmailMessage()
    config = {"password": password, "user": user, "admin": admin}
    msg.set_content(mail_template.render(config))
    msg["Subject"] = f"Password  reset for {user}@hackerspace.pl"
    msg["From"] = f"{admin}@hackerspace.pl"
    msg["To"] = address

    with smtplib.SMTP_SSL("mail.hackerspace.pl") as s:
        s.login(admin, admin_password)
        s.send_message(msg)