import datetime
import ipaddress
import json
import re
import subprocess

import flask
import flask_login

from . import db
from . import system

blueprint = flask.Blueprint('vpn', __name__)
wgkey_regex = re.compile(r'^[A-Za-z0-9/+=]{44}$')

@blueprint.route('/')
@flask_login.login_required
def index():
    return flask.render_template('vpn/index.html')

@blueprint.route('/list')
@flask_login.login_required
def list():
    user = flask_login.current_user.get_id()
    return flask.jsonify(
        {k: v | {'active': flask.request.remote_addr in (v.get('ip'), v.get('ip6'))}
         for k, v in db.load('wireguard').items() if v.get('user') == user})

@blueprint.route('/new', methods=('POST',))
@flask_login.login_required
def new():
    # Each key is associated with a new IPv4 address from the pool settings['wg_net'].
    # Each key gets an IPv6 subnet depending on the amount of surplus addresses available.
    # For wg_net 10.10.0.0/18 and wg_net6 1234:5678:90ab:cdef::/64,
    # the key for 10.10.0.10/32 would get 1234:5678:90ab:cdef:a::/80.
    def ipv4to6(net4, ip4, net6):
        # Calculate the address and prefix length for the assigned IPv6 network.
        len4 = (net4.max_prefixlen - net4.prefixlen)
        len6 = (net6.max_prefixlen - net6.prefixlen)
        # Make sure the network address ends at a colon. Wastes some addresses but IPv6.
        assigned = (len6 - len4) - (len6 - len4) % 16
        ip6 = (net6.network_address + (index<<assigned)).compressed
        return ip6 + '/' + str(net6.max_prefixlen - assigned)

    pubkey = flask.request.json.get('pubkey', '')
    if not re.match(wgkey_regex, pubkey):
        return flask.Response('invalid key', status=400, mimetype='text/plain')

    settings = db.load('settings')
    server_pubkey = subprocess.run([f'wg pubkey'], input=settings.get('wg_key'),
            text=True, capture_output=True, shell=True).stdout.strip()

    host = ipaddress.ip_interface(settings.get('wg_net') or '10.0.0.1/24')
    ip6 = None
    with db.locked():
        # Find a free address for the new key.
        keys = db.read('wireguard')
        for index, ip in enumerate(host.network.hosts(), start=1):
            if ip != host.ip and str(ip) not in keys:
                if wg_net6 := settings.get('wg_net6'):
                    ip6 = ipv4to6(host.network, ip, ipaddress.ip_interface(wg_net6).network)
                break
        else:
            return flask.Response('no more available IP addresses', status=500, mimetype='text/plain')
        now = datetime.datetime.utcnow()
        name = re.sub('[^-._A-Za-z0-9]', '', flask.request.json.get('name', ''))

        keys[str(ip)] = {
            'key': pubkey,
            'ip6': str(ip6) if ip6 else None,
            'time': now.timestamp(),
            'user': flask_login.current_user.get_id(),
            'name': name,
        }
        db.write('wireguard', keys)

    # Generate a new config archive for firewall nodes.
    system.run(system.save_config)

    # Template arguments.
    args = {
        'server': settings.get('wg_endpoint'),
        'port': settings.get('wg_port') or '51820',
        'server_key': server_pubkey,
        'pubkey': pubkey,
        'ip': str(ip),
        'ip6': str(ip6) if ip6 else None,
        'timestamp': now,
        'name': name,
        'dns': settings.get('wg_dns') if flask.request.json.get('use_dns', True) else False,
        'allowed_nets': settings.get('wg_allowed_nets', ''),
        'add_default': flask.request.json.get('add_default', False),
    }
    return flask.render_template('vpn/wg-fri.conf', **args)

@blueprint.route('/del', methods=('POST',))
@flask_login.login_required
def delete():
    pubkey = flask.request.json.get('pubkey', '')
    if not wgkey_regex.match(pubkey):
        return flask.Response('invalid key', status=400, mimetype='text/plain')

    with db.locked():
        user = flask_login.current_user.get_id()
        keys = {k: v for k, v in db.read('wireguard').items() if v.get('user') != user or v.get('key') != pubkey}
        db.write('wireguard', keys)

    system.run(system.save_config)

    return flask.Response(f'deleted key {pubkey}', status=200, mimetype='text/plain')