import ipaddress
from functools import reduce


def get_client_agent(request, truncate=True):
    """
    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`,
    """
    user_agent = request.META.get('HTTP_USER_AGENT', '')
    if truncate:
        user_agent = user_agent[:255]
    return 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 check_ip_in_allowlist(ip, allowlist):
    # :ip 192.168.1.1
    # :allowlist ['192.168.1.1', '192.168.0.0/16']
    # Return `None` if not match, return matched ip-network if test passed.
    if not allowlist:
        return ip

    user_ip = ipaddress.ip_address(ip)
    for allow_ip in allowlist:
        if user_ip in ipaddress.ip_network(allow_ip, strict=False):
            return allow_ip