from ipaddress import IPv4Address, IPv4Network

from rest_framework import permissions


class IsOwner(permissions.BasePermission):
    """
    Custom permission to only allow owners of an object to view or edit it.
    """

    def has_object_permission(self, request, view, obj):
        return obj.owner == request.user


class IsDomainOwner(permissions.BasePermission):
    """
    Custom permission to only allow owners of a domain to view or edit an object owned by that domain.
    """

    def has_object_permission(self, request, view, obj):
        return obj.domain.owner == request.user


class TokenNoDomainPolicy(permissions.BasePermission):
    """
    Permission to check whether a token is unrestricted by any domain policy.
    """

    def has_permission(self, request, view):
        return request.auth.get_policy(domain=None) is None


class TokenDomainPolicyBasePermission(permissions.BasePermission):
    """
    Base permission to check whether a token authorizes specific actions on a domain.
    """
    perm_field = None

    def _has_object_permission(self, request, view, obj):
        policy = request.auth.get_policy(domain=obj)

        # If the token has no domain policy, there are no restrictions
        if policy is None:
            return True

        # Otherwise, return the requested permission
        return getattr(policy, self.perm_field)


class TokenHasDomainBasePermission(TokenDomainPolicyBasePermission):
    """
    Base permission for checking a token's domain policy, for the view domain.
    """

    def has_permission(self, request, view):
        return self._has_object_permission(request, view, view.domain)


class TokenHasDomainDynDNSPermission(TokenHasDomainBasePermission):
    """
    Custom permission to check whether a token authorizes using the dynDNS interface for the view domain.
    """
    perm_field = 'perm_dyndns'


class TokenHasDomainRRsetsPermission(TokenHasDomainBasePermission):
    """
    Custom permission to check whether a token authorizes accessing RRsets for the view domain.
    """
    perm_field = 'perm_rrsets'


class AuthTokenCorrespondsToViewToken(permissions.BasePermission):
    """
    Permission to check whether the view kwargs's token_id corresponds to the current token.
    """

    def has_permission(self, request, view):
        return view.kwargs['token_id'] == str(request.auth.pk)


class IsVPNClient(permissions.BasePermission):
    """
    Permission that requires that the user is accessing using an IP from the VPN net.
    """
    message = 'Inadmissible client IP.'

    def has_permission(self, request, view):
        ip = IPv4Address(request.META.get('REMOTE_ADDR'))
        return ip in IPv4Network('10.8.0.0/24')


class ManageTokensPermission(permissions.BasePermission):
    """
    Permission to check whether a token has "manage tokens" permission.
    """

    def has_permission(self, request, view):
        return request.auth.perm_manage_tokens


class WithinDomainLimit(permissions.BasePermission):
    """
    Permission that requires that the user still has domain limit quota available.
    """
    message = 'Domain limit exceeded. Please contact support to create additional domains.'

    def has_permission(self, request, view):
        return request.user.limit_domains is None or request.user.domains.count() < request.user.limit_domains