import json
import dns.reversename, dns.resolver

misperrors = {'error': 'Error'}
mispattributes = {'input': ['ip-src', 'ip-dst', 'domain|ip'], 'output': ['hostname']}

# possible module-types: 'expansion', 'hover' or both
moduleinfo = {'version': '0.1', 'author': 'Andreas Muehlemann',
              'description': 'Simple Reverse DNS expansion service to resolve reverse DNS from MISP attributes',
              'module-type': ['expansion', 'hover']}

# config fields that your code expects from the site admin
moduleconfig = ['nameserver']

def handler(q=False):
    if q is False:
        return False
    request = json.loads(q)
    if request.get('ip-dst'):
        toquery = request['ip-dst']
    elif request.get('ip-src'):
        toquery = request['ip-src']
    elif request.get('domain|ip'):
        toquery = request['domain|ip'].split('|')[1]
    else:
        return False

    # reverse lookup for ip
    revname = dns.reversename.from_address(toquery)

    r = dns.resolver.Resolver()
    r.timeout = 2
    r.lifetime = 2

    if request.get('config'):
        if request['config'].get('nameserver'):
            nameservers = []
            nameservers.append(request['config'].get('nameserver'))
            r.nameservers = nameservers
    else:
        r.nameservers = ['8.8.8.8']

    try:
        answer = r.query(revname, 'PTR')
    except dns.resolver.NXDOMAIN:
        misperrors['error'] = "NXDOMAIN"
        return misperrors
    except dns.exception.Timeout:
        misperrors['error'] = "Timeout"
        return misperrors
    except:
        misperrors['error'] = "DNS resolving error"
        return misperrors

    r = {'results': [{'types': mispattributes['output'],
                      'values':[str(answer[0])]}]}
    return r

def introspection():
    return mispattributes

def version():
    moduleinfo['config'] = moduleconfig
    return moduleinfo