"""
login.py - Implement core login abstraction.
"""

from pylinkirc import conf, utils, world
from pylinkirc.log import log

# PyLink's global password context
pwd_context = None

_DEFAULT_CRYPTCONTEXT_SETTINGS = {
    'schemes': ["pbkdf2_sha256", "sha512_crypt"]
}
def _make_cryptcontext():
    try:
        from passlib.context import CryptContext
    except ImportError:
        log.warning("Hashed passwords are disabled because passlib is not installed. Please install "
                    "it (pip3 install passlib) and rehash for this feature to work.")
        return

    context_settings = conf.conf.get('login', {}).get('cryptcontext_settings') or _DEFAULT_CRYPTCONTEXT_SETTINGS
    global pwd_context
    if pwd_context is None:
        log.debug("Initialized new CryptContext with settings: %s", context_settings)
        pwd_context = CryptContext(**context_settings)
    else:
        log.debug("Updated CryptContext with settings: %s", context_settings)
        pwd_context.update(**context_settings)

_make_cryptcontext()  # This runs at startup and in rehash (control.py)

def _get_account(accountname):
    """
    Returns the login data block for the given account name (case-insensitive), or False if none
    exists.
    """
    accounts = {k.lower(): v for k, v in
                conf.conf['login'].get('accounts', {}).items()}

    try:
        return accounts[accountname.lower()]
    except KeyError:
        return False

def check_login(user, password):
    """Checks whether the given user and password is a valid combination."""
    account = _get_account(user)

    if account:
        passhash = account.get('password')
        if not passhash:
            # No password given, return. XXX: we should allow plugins to override
            # this in the future.
            return False

        # Hashing in account passwords is optional.
        if account.get('encrypted', False):
            return verify_hash(password, passhash)
        else:
            return password == passhash

    return False

def verify_hash(password, passhash):
    """Checks whether the password given matches the hash."""
    if password:
        if not pwd_context:
            raise utils.NotAuthorizedError("Cannot log in to an account with a hashed password "
                                           "because passlib is not installed.")

        return pwd_context.verify(password, passhash)
    return False  # No password given!

def _irc_try_login(irc, source, username, skip_checks=False):
    """Internal function to process logins via IRC."""
    if irc.is_internal_client(source):
        irc.error("Cannot use 'identify' via a command proxy.")
        return

    if not skip_checks:
        logindata = _get_account(username)

        network_filter = logindata.get('networks')
        require_oper = logindata.get('require_oper', False)
        hosts_filter = logindata.get('hosts', [])

        if network_filter and irc.name not in network_filter:
            log.warning("(%s) Failed login to %r from %s (wrong network: networks filter says %r but we got %r)",
                        irc.name, username, irc.get_hostmask(source), ', '.join(network_filter), irc.name)
            raise utils.NotAuthorizedError("Account is not authorized to login on this network.")

        elif require_oper and not irc.is_oper(source):
            log.warning("(%s) Failed login to %r from %s (needs oper)", irc.name, username, irc.get_hostmask(source))
            raise utils.NotAuthorizedError("You must be opered.")

        elif hosts_filter and not any(irc.match_host(host, source) for host in hosts_filter):
            log.warning("(%s) Failed login to %r from %s (hostname mismatch)", irc.name, username, irc.get_hostmask(source))
            raise utils.NotAuthorizedError("Hostname mismatch.")

    irc.users[source].account = username
    irc.reply('Successfully logged in as %s.' % username)
    log.info("(%s) Successful login to %r by %s",
             irc.name, username, irc.get_hostmask(source))
    return True

def identify(irc, source, args):
    """<username> <password>

    Logs in to PyLink using the configured administrator account."""
    if irc.is_channel(irc.called_in):
        irc.reply('Error: This command must be sent in private. '
                  '(Would you really type a password inside a channel?)')
        return
    try:
        username, password = args[0], args[1]
    except IndexError:
        irc.reply('Error: Not enough arguments.')
        return

    # Process new-style accounts.
    if check_login(username, password):
        _irc_try_login(irc, source, username)
        return

    # Process legacy logins (login:user).
    if username.lower() == conf.conf['login'].get('user', '').lower() and password == conf.conf['login'].get('password'):
        realuser = conf.conf['login']['user']
        _irc_try_login(irc, source, realuser, skip_checks=True)
        return

    # Username not found or password incorrect.
    log.warning("(%s) Failed login to %r from %s", irc.name, username, irc.get_hostmask(source))
    raise utils.NotAuthorizedError('Bad username or password.')

utils.add_cmd(identify, aliases=('login', 'id'))