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('/custom')
@flask_login.login_required
def custom():
    if not flask_login.current_user.is_admin:
        return flask.Response('forbidden', status=403, mimetype='text/plain')
    with db.locked():
        keys = {ip: data for ip, data in db.read('wireguard').items() if data.get('networks') and not data.get('user')}
        ipsets = db.read('networks') | db.read('ipsets')
        return flask.render_template('vpn/custom.html', keys=keys, ipsets=ipsets.keys())

@blueprint.route('/list')
@flask_login.login_required
def list():
    # Return logged-in user’s keys, marking the key used for current connection (if any).
    user = flask_login.current_user.get_id()
    return flask.jsonify([
        data | {'ip': ip, 'active': flask.request.remote_addr in (ip, data.get('ip6'))}
            for ip, data in db.load('wireguard').items() if data.get('user') == user
    ])

@blueprint.route('/list-custom')
@flask_login.login_required
def list_custom():
    # Return all custom keys.
    if not flask_login.current_user.is_admin:
        return flask.Response('forbidden', status=403, mimetype='text/plain')
    return flask.jsonify([
        data | {'ip': ip, 'active': flask.request.remote_addr in (ip, data.get('ip6'))}
            for ip, data in db.load('wireguard').items() if data.get('networks') and not data.get('user')
    ])

@blueprint.route('/new', methods=('POST',))
@flask_login.login_required
def new():
    # Each key is assigned a new IPv4 address from the pool settings['wg_net'].
    # Each key is then assigned a corresponding 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 IPv6 network that can be assigned to this key.
        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', '')
    options = flask.request.json.get('options', {})
    if not re.match(wgkey_regex, pubkey):
        return flask.Response('invalid key', status=400, mimetype='text/plain')

    # Read server’s private key and find the corresponding public key.
    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()

    now = datetime.datetime.utcnow()
    key = {
        'key': pubkey,
        'time': now.timestamp(),
        'name': re.sub('[^-._A-Za-z0-9]', '', options.get('name', '')),
    }

    # Determine IPv4 and IPv6 addresses for the new key.
    host = ipaddress.ip_interface(settings.get('wg_net') or '10.0.0.1/24')
    key['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'):
                    key['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')

        # Add remaining attributes to new key and update key database.
        if flask_login.current_user.is_admin and flask.request.json.get('networks'):
            key['networks'] = flask.request.json.get('networks')
        else:
            key['user'] = flask_login.current_user.get_id()
        keys[str(ip)] = key
        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,
        'timestamp': now,
        'ip': str(ip),
        'ip6': key['ip6'],
        'name': key['name'],
        'user': key.get('user', 'custom'),
        'dns': settings.get('wg_dns', '') if options.get('use-dns', True) else False,
        'allowed_nets': settings.get('wg_allowed_nets', ''),
        'add_default': options.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 = {
            ip: data for ip, data in db.read('wireguard').items()
                if not (data.get('key') == pubkey and (data.get('user') == user or flask_login.current_user.is_admin))
        }
        db.write('wireguard', keys)

    system.run(system.save_config)

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