"""
NETCONF for APK Distributions server:
    Server module

Copyright © 2020 Adélie Software in the Public Benefit, Inc.

Released under the terms of the NCSA license.  See the LICENSE file included
with this source distribution for more information.

SPDX-License-Identifier: NCSA
"""

import logging

from lxml import etree

import netconf.base
import paramiko

from netconf import error, util
from netconf.server import NetconfSSHServer, SSHAuthorizedKeysController

from ncserver.base.log import configure_logging, LOG_AUTH, LOG_CONFIG, \
                              LOG_OPERATIONAL
from ncserver.base.modman import MODMAN
from ncserver.base.util import user_for_session
from ncserver.config import ConfigManager


QName = etree.QName  # pylint: disable=I1101


def log_read(session, rpc):
    """Log a configuration read."""
    LOG_CONFIG.debug(
            '%s on session %d is requesting configuration: %s',
            user_for_session(session), session.session_id, etree.tostring(rpc)
    )


def log_write(session, rpc):
    """Log a configuration write attempt."""
    LOG_CONFIG.debug(
            '%s on session %d is editing configuration: %s',
            user_for_session(session), session.session_id, etree.tostring(rpc)
    )


class AuthenticationController(SSHAuthorizedKeysController):
    """Authentication controller that logs failures."""
    def check_auth_publickey(self, username, key):
        result = super().check_auth_publickey(username, key)
        if result == paramiko.AUTH_FAILED:
            LOG_AUTH.error('Authentication failed for %s', username)
        return result


_open_session = getattr(netconf.base.NetconfSession, '_open_session')


def _open_session_and_log(self, is_server):
    """Log that authentication has been successful."""
    _open_session(self, is_server)
    peername = self.pkt_stream.stream.getpeername()
    ipaddr = peername[0]
    port = peername[1]
    if ':' in ipaddr:
        ipaddr = '[' + ipaddr + ']'
    LOG_AUTH.notice(
            'Authentication granted to %s from %s:%d, session %d',
            user_for_session(self), ipaddr, port, self.session_id
    )


setattr(netconf.base.NetconfSession, '_open_session', _open_session_and_log)


class Server:
    """The NETCONF server component."""

    def __init__(self, port=830):
        """Create the NETCONF server.

        :param int port:
        The port number to listen on.  Typically 830.
        """
        self.config = ConfigManager()
        self.auth = AuthenticationController(
                users=self.config.get_list('server', 'users')
        )

        self.debug = self.config.get('server', 'debug')
        if self.debug:
            configure_logging(logging.DEBUG)
        else:
            loglevel = 'notice'
            try:
                loglevel = self.config.get('server', 'loglevel')
            except KeyError:
                pass
            configure_logging(getattr(logging, loglevel.upper()))

        self.server = NetconfSSHServer(
            self.auth, self, port, self.config.get('server', 'host_key'),
            self.debug
        )
        for module in self.config.get_list('server', 'modules'):
            MODMAN.load_module(module)

    def __getattr__(self, attr):
        """Maybe pass RPC calls on."""
        if attr.startswith("rpc_"):
            return self._rpc_wrapper
        raise AttributeError("'Server' object has no attribute '" + attr + "'")

    def close(self):
        """Close all connections."""
        self.server.close()

    def nc_append_capabilities(self, capabilities):
        """List all capabilities of this NETCONF server."""
        our_capabs = [
            # Write directly to the `running` datastore.
            'urn:ietf:params:netconf:capability:writable-running:1.0',
            # Filter with XPath in addition to subtrees.
            'urn:ietf:params:netconf:capability:xpath:1.0'
        ]
        for capab in MODMAN.capabilities():
            util.subelm(capabilities, 'capability').text = capab
        for capab in our_capabs:
            util.subelm(capabilities, 'capability').text = capab

    def _rpc_wrapper(self, session, rpc, *params):
        """Handle module RPCs."""
        name = QName(rpc[0].tag).localname
        LOG_OPERATIONAL.info(
                'RPC %s invoked by %s on session %d',
                name, user_for_session(session), session.session_id
        )
        if MODMAN.has_rpc(name):
            try:
                result = MODMAN.rpc(name)(session, rpc, *params)
                LOG_OPERATIONAL.info(
                    'RPC %s invoked by %s on session %d completed',
                    name, user_for_session(session), session.session_id
                )
                return result
            except error.RPCServerError as rpc_error:
                LOG_OPERATIONAL.error(
                    'RPC %s invoked by %s on session %d encountered error %s',
                    name, user_for_session(session), session.session_id,
                    rpc_error
                )
                raise
        else:
            LOG_OPERATIONAL.warning(
                    'RPC %s invoked by %s on session %d is unknown',
                    name, user_for_session(session), session.session_id
            )
            raise error.OperationNotSupportedProtoError(rpc)

    def rpc_get(self, session, rpc, filter_or_none):  # pylint: disable=W0613
        """Handle the <get/> RPC."""
        log_read(session, rpc)
        root = util.elm('nc:data')
        MODMAN.collect_operational(root)

        return util.filter_results(rpc, root, filter_or_none, self.debug)

    # pylint: disable=W0613
    def rpc_get_config(self, session, rpc, source, filter_or_none):
        """Handle the <get-config/> RPC."""
        log_read(session, rpc)
        root = util.elm('nc:data')
        MODMAN.collect_running(root)

        return util.filter_results(rpc, root, filter_or_none, self.debug)

    # pylint: disable=R0913
    def rpc_edit_config(self, session, rpc, target, config, default_or_none):
        """Handle the <edit-config/> RPC."""
        if len(target) != 1:
            # We must have exactly 1 target.
            raise error.BadElementProtoError(rpc, target)

        log_write(session, rpc)

        # strip the xmlns off the tag name.
        datastore = QName(target[0].tag).localname
        if datastore != "running":
            raise error.InvalidValueAppError(rpc)

        if default_or_none is None:
            def_op = 'merge'
        else:
            def_op = default_or_none.text

        MODMAN.collect_edit(session, rpc, config, def_op)

        root = util.elm('nc:ok')
        return root

if __name__ == "__main__":
    s = Server()
    try:
        s.server.join()
    except KeyboardInterrupt:
        s.close()