# Copyright 2018 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 netifaces
import ipaddress

def is_ipv4(addr):
    """
    Check addr if it is an IPv4 address/network.

    Return True/False
    """
    if ipaddress.ip_network(addr).version == 4:
        return True
    else:
        return False

def is_ipv6(addr):
    """
    Check addr if it is an IPv6 address/network.

    Return True/False
    """
    if ipaddress.ip_network(addr).version == 6:
        return True
    else:
        return False

def is_addr_assigned(addr):
    """
    Verify if the given IPv4/IPv6 address is assigned to any interface on this
    system.

    Return True/False
    """

    # determine IP version (AF_INET or AF_INET6) depending on passed address
    addr_type = netifaces.AF_INET
    if is_ipv6(addr):
        addr_type = netifaces.AF_INET6

    for interface in netifaces.interfaces():
        # check if the requested address type is configured at all
        if addr_type in netifaces.ifaddresses(interface).keys():
            # Check every IP address on this interface for a match
            for ip in netifaces.ifaddresses(interface)[addr_type]:
                # Check if it matches to the address requested
                if ip['addr'] == addr:
                    return True

    return False

def is_subnet_connected(subnet, primary=False):
    """
    Verify is the given IPv4/IPv6 subnet is connected to any interface on this
    system.

    primary check if the subnet is reachable via the primary IP address of this
    interface. E.g. ISC DHCP can only listen on primary addresses.

    Return True/False
    """

    # determine IP version (AF_INET or AF_INET6) depending on passed address
    addr_type = netifaces.AF_INET
    if is_ipv6(subnet):
        addr_type = netifaces.AF_INET6

    for interface in netifaces.interfaces():
        # check if the requested address type is configured at all
        if addr_type not in netifaces.ifaddresses(interface).keys():
            return False

        # An interface can have multiple addresses, but some software components
        # only support the primary address :(
        if primary:
            ip = netifaces.ifaddresses(interface)[addr_type][0]['addr']
            if ipaddress.ip_address(ip) in ipaddress.ip_network(subnet):
                return True
        else:
            # Check every assigned IP address if it is connected to the subnet
            # in question
            for ip in netifaces.ifaddresses(interface)[addr_type]:
                if ipaddress.ip_address(ip['addr']) in ipaddress.ip_network(subnet):
                    return True

    return False