import ipaddress
from functools import reduce
from urllib import parse

from django.conf import settings
from django.utils.http import url_has_allowed_host_and_scheme


def get_client_agent(request):
    """
    The simplest way to get client device.
    If you want to extend this function, try this:
    pip install django-user-agents
    `django-user-agents` is base on `ua-parser` `user-agents`,
    """
    return request.META.get('HTTP_USER_AGENT', '')


def get_client_ip(request):
    # FIX ME: It's dangerous to get ip from `HTTP_X_Forwarded_For` by this way.
    ip = request.META.get('HTTP_X_FORWARDED_FOR', '').split(',')[0]
    if ip:
        return ip

    ip = request.META.get('HTTP_X_REAL_IP')
    if ip:
        return ip
    return request.META.get('REMOTE_ADDR')


def ip_into_int(ip):
    return reduce(lambda x, y: (x << 8) + y, map(int, ip.split('.')))


def is_internal_ip(ip):
    if ip == '127.0.0.1':
        return True
    ip = ip_into_int(ip)
    net_a = ip_into_int('10.255.255.255') >> 24
    net_b = ip_into_int('172.31.255.255') >> 20
    net_c = ip_into_int('192.168.255.255') >> 16
    return ip >> 24 == net_a or ip >> 20 == net_b or ip >> 16 == net_c


def get_safe_redirect_uri(redirect_to, request):
    safe_hosts = settings.TRUSTED_HOSTS + [request.get_host()]
    if not url_has_allowed_host_and_scheme(redirect_to, allowed_hosts=safe_hosts):
        redirect_to = '{}://{}'.format(request.scheme, request.get_host())
    return redirect_to


def get_pure_url(url):
    _url_parse = parse.urlparse(url)
    return '{}://{}{}'.format(
        _url_parse.scheme, _url_parse.netloc, _url_parse.path
    )


def is_vpn_ip(ip):
    if not isinstance(ip, ipaddress.IPv4Address):
        ip = ipaddress.ip_address(ip)
    for vpn_ip in settings.VPN_IP_LIST:
        if ip in ipaddress.ip_network(vpn_ip, strict=False):
            return True
    return False