# Copyright 2019 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.  If not, see <http://www.gnu.org/licenses/>.

import os
import time

from datetime import timedelta

from hurry.filesize import size
from hurry.filesize import alternative

from vyos.config import Config
from vyos.ifconfig import Interface
from vyos.ifconfig import Operational
from vyos.template import is_ipv6

import random
from random import seed, getrandbits
from ipaddress import IPv6Network, IPv6Address

class WireGuardOperational(Operational):
    def _dump(self):
        """Dump wireguard data in a python friendly way."""
        last_device = None
        output = {}

        # Dump wireguard connection data
        _f = self._cmd('wg show all dump')
        for line in _f.split('\n'):
            if not line:
                # Skip empty lines and last line
                continue
            items = line.split('\t')

            if last_device != items[0]:
                # We are currently entering a new node
                device, private_key, public_key, listen_port, fw_mark = items
                last_device = device

                output[device] = {
                    'private_key': None if private_key == '(none)' else private_key,
                    'public_key': None if public_key == '(none)' else public_key,
                    'listen_port': int(listen_port),
                    'fw_mark': None if fw_mark == 'off' else int(fw_mark),
                    'peers': {},
                }
            else:
                # We are entering a peer
                device, public_key, preshared_key, endpoint, allowed_ips, latest_handshake, transfer_rx, transfer_tx, persistent_keepalive = items
                if allowed_ips == '(none)':
                    allowed_ips = []
                else:
                    allowed_ips = allowed_ips.split('\t')
                output[device]['peers'][public_key] = {
                    'preshared_key': None if preshared_key == '(none)' else preshared_key,
                    'endpoint': None if endpoint == '(none)' else endpoint,
                    'allowed_ips': allowed_ips,
                    'latest_handshake': None if latest_handshake == '0' else int(latest_handshake),
                    'transfer_rx': int(transfer_rx),
                    'transfer_tx': int(transfer_tx),
                    'persistent_keepalive': None if persistent_keepalive == 'off' else int(persistent_keepalive),
                }
        return output

    def show_interface(self):
        wgdump = self._dump().get(self.config['ifname'], None)

        c = Config()

        c.set_level(["interfaces", "wireguard", self.config['ifname']])
        description = c.return_effective_value(["description"])
        ips = c.return_effective_values(["address"])

        answer = "interface: {}\n".format(self.config['ifname'])
        if (description):
            answer += "  description: {}\n".format(description)
        if (ips):
            answer += "  address: {}\n".format(", ".join(ips))

        answer += "  public key: {}\n".format(wgdump['public_key'])
        answer += "  private key: (hidden)\n"
        answer += "  listening port: {}\n".format(wgdump['listen_port'])
        answer += "\n"

        for peer in c.list_effective_nodes(["peer"]):
            if wgdump['peers']:
                pubkey = c.return_effective_value(["peer", peer, "pubkey"])
                if pubkey in wgdump['peers']:
                    wgpeer = wgdump['peers'][pubkey]

                    answer += "  peer: {}\n".format(peer)
                    answer += "    public key: {}\n".format(pubkey)

                    """ figure out if the tunnel is recently active or not """
                    status = "inactive"
                    if (wgpeer['latest_handshake'] is None):
                        """ no handshake ever """
                        status = "inactive"
                    else:
                        if int(wgpeer['latest_handshake']) > 0:
                            delta = timedelta(seconds=int(
                                time.time() - wgpeer['latest_handshake']))
                            answer += "    latest handshake: {}\n".format(delta)
                            if (time.time() - int(wgpeer['latest_handshake']) < (60*5)):
                                """ Five minutes and the tunnel is still active """
                                status = "active"
                            else:
                                """ it's been longer than 5 minutes """
                                status = "inactive"
                        elif int(wgpeer['latest_handshake']) == 0:
                            """ no handshake ever """
                            status = "inactive"
                        answer += "    status: {}\n".format(status)

                    if wgpeer['endpoint'] is not None:
                        answer += "    endpoint: {}\n".format(wgpeer['endpoint'])

                    if wgpeer['allowed_ips'] is not None:
                        answer += "    allowed ips: {}\n".format(
                            ",".join(wgpeer['allowed_ips']).replace(",", ", "))

                    if wgpeer['transfer_rx'] > 0 or wgpeer['transfer_tx'] > 0:
                        rx_size = size(
                            wgpeer['transfer_rx'], system=alternative)
                        tx_size = size(
                            wgpeer['transfer_tx'], system=alternative)
                        answer += "    transfer: {} received, {} sent\n".format(
                            rx_size, tx_size)

                    if wgpeer['persistent_keepalive'] is not None:
                        answer += "    persistent keepalive: every {} seconds\n".format(
                            wgpeer['persistent_keepalive'])
                answer += '\n'
        return answer + super().formated_stats()


@Interface.register
class WireGuardIf(Interface):
    OperationalClass = WireGuardOperational

    default = {
        'type': 'wireguard',
        'port': 0,
        'private_key': None,
        'pubkey': None,
        'psk': '',
        'allowed_ips': [],
        'fwmark': 0x00,
        'endpoint': None,
        'keepalive': 0
    }
    definition = {
        **Interface.definition,
        **{
            'section': 'wireguard',
            'prefixes': ['wg', ],
            'bridgeable': True,
        }
    }
    options = Interface.options + \
        ['port', 'private_key', 'pubkey', 'psk',
         'allowed_ips', 'fwmark', 'endpoint', 'keepalive']
         
    
    def generate_link_local():
        # Linux Kernel does not generate IPv6 Link Local address do to missing MAC
        # We have to generate address manually and assign to interface
        net = IPv6Network("FE80::/16")
        rand_net = IPv6Network((net.network_address + (random.getrandbits(64 - net.prefixlen) << 64 ),64))
        network = IPv6Network(rand_net)
        address = str(IPv6Address(network.network_address + getrandbits(network.max_prefixlen - network.prefixlen)))+'/'+str(network.prefixlen)
        
        return address
    
    def _create(self):
        super()._create(self)
        # Assign generated IPv6 Link Local address to the interface
        self.add_addr(self.generate_link_local())
    
    def update(self, config):
        """ General helper function which works on a dictionary retrived by
        get_config_dict(). It's main intention is to consolidate the scattered
        interface setup code and provide a single point of entry when workin
        on any interface. """

        # remove no longer associated peers first
        if 'peer_remove' in config:
            for tmp in config['peer_remove']:
                peer = config['peer_remove'][tmp]
                peer['ifname'] = config['ifname']

                cmd = 'wg set {ifname} peer {pubkey} remove'
                self._cmd(cmd.format(**peer))

        # Wireguard base command is identical for every peer
        base_cmd  = 'wg set {ifname} private-key {private_key}'
        if 'port' in config:
            base_cmd += ' listen-port {port}'
        if 'fwmark' in config:
            base_cmd += ' fwmark {fwmark}'

        base_cmd = base_cmd.format(**config)

        for tmp in config['peer']:
            peer = config['peer'][tmp]

            # start of with a fresh 'wg' command
            cmd = base_cmd + ' peer {pubkey}'

            # If no PSK is given remove it by using /dev/null - passing keys via
            # the shell (usually bash) is considered insecure, thus we use a file
            no_psk_file = '/dev/null'
            psk_file = no_psk_file
            if 'preshared_key' in peer:
                psk_file = '/tmp/tmp.wireguard.psk'
                with open(psk_file, 'w') as f:
                    f.write(peer['preshared_key'])
            cmd += f' preshared-key {psk_file}'

            # Persistent keepalive is optional
            if 'persistent_keepalive'in peer:
                cmd += ' persistent-keepalive {persistent_keepalive}'

            # Multiple allowed-ip ranges can be defined - ensure we are always
            # dealing with a list
            if isinstance(peer['allowed_ips'], str):
                peer['allowed_ips'] = [peer['allowed_ips']]
            cmd += ' allowed-ips ' + ','.join(peer['allowed_ips'])

            # Endpoint configuration is optional
            if {'address', 'port'} <= set(peer):
                if is_ipv6(config['address']):
                    cmd += ' endpoint [{address}]:{port}'
                else:
                    cmd += ' endpoint {address}:{port}'

            self._cmd(cmd.format(**peer))

            # PSK key file is not required to be stored persistently as its backed by CLI
            if psk_file != no_psk_file and os.path.exists(psk_file):
                os.remove(psk_file)

        # call base class
        super().update(config)

        # Enable/Disable of an interface must always be done at the end of the
        # derived class to make use of the ref-counting set_admin_state()
        # function. We will only enable the interface if 'up' was called as
        # often as 'down'. This is required by some interface implementations
        # as certain parameters can only be changed when the interface is
        # in admin-down state. This ensures the link does not flap during
        # reconfiguration.
        state = 'down' if 'disable' in config else 'up'
        self.set_admin_state(state)