import binascii
import requests
import random
import subprocess as sp
import ipaddress

from decouple import config
from pyotp import TOTP
from config import VM_POOL, etcd_client, IMAGE_PREFIX


def check_otp(name, realm, token):
    try:
        data = {
            "auth_name": config("AUTH_NAME", ""),
            "auth_token": TOTP(config("AUTH_SEED", "")).now(),
            "auth_realm": config("AUTH_REALM", ""),
            "name": name,
            "realm": realm,
            "token": token,
        }
    except binascii.Error:
        return 400

    response = requests.get(
        "{OTP_SERVER}{OTP_VERIFY_ENDPOINT}".format(
            OTP_SERVER=config("OTP_SERVER", ""),
            OTP_VERIFY_ENDPOINT=config("OTP_VERIFY_ENDPOINT", "verify"),
        ),
        json=data,
    )
    return response.status_code


def resolve_vm_name(name, owner):
    """Return UUID of Virtual Machine of name == name and owner == owner
    
    Input: name of vm, owner of vm.
    Output: uuid of vm if found otherwise None
    """
    result = next(
        filter(
            lambda vm: vm.value["owner"] == owner and vm.value["name"] == name,
            VM_POOL.vms,
        ),
        None,
    )
    if result:
        return result.key.split("/")[-1]

    return None


def resolve_image_name(name, etcd_client):
    """Return image uuid given its name and its store
       
       * If the provided name is not in correct format
         i.e {store_name}:{image_name} return ValueError
       * If no such image found then return KeyError

    """

    seperator = ":"
    
    # Ensure, user/program passed valid name that is of type string
    try:
        store_name_and_image_name = name.split(seperator)

        """
        Examples, where it would work and where it would raise exception
        "images:alpine" --> ["images", "alpine"]
        
        "images" --> ["images"] it would raise Exception as non enough value to unpack
        
        "images:alpine:meow" --> ["images", "alpine", "meow"] it would raise Exception
                                                              as too many values to unpack
        """
        store_name, image_name = store_name_and_image_name
    except Exception:
        raise ValueError("Image name not in correct format i.e {store_name}:{image_name}")

    images = etcd_client.get_prefix(IMAGE_PREFIX, value_in_json=True)

    # Try to find image with name == image_name and store_name == store_name
    try:
        image = next(filter(lambda im: im.value['name'] == image_name \
                                       and im.value['store_name'] == store_name, images))
    except StopIteration:
        raise KeyError("No image with name {} found.".format(name))
    else:
        image_uuid = image.key.split('/')[-1]
    
    return image_uuid


def random_bytes(num=6):
    return [random.randrange(256) for _ in range(num)]


def generate_mac(uaa=False, multicast=False, oui=None, separator=':', byte_fmt='%02x'):
    mac = random_bytes()
    if oui:
        if type(oui) == str:
            oui = [int(chunk) for chunk in oui.split(separator)]
        mac = oui + random_bytes(num=6-len(oui))
    else:
        if multicast:
            mac[0] |= 1 # set bit 0
        else:
            mac[0] &= ~1 # clear bit 0
        if uaa:
            mac[0] &= ~(1 << 1) # clear bit 1
        else:
            mac[0] |= 1 << 1 # set bit 1
    return separator.join(byte_fmt % b for b in mac)


def get_ip_addr(mac_address, device):
    """Return IP address of a device provided its mac address / link local address
       and the device with which it is connected.
       
       For Example, if we call get_ip_addr(mac_address="52:54:00:12:34:56", device="br0")
       the following two scenarios can happen
       1. It would return None if we can't be able to find device whose mac_address is equal
          to the arg:mac_address or the mentioned arg:device does not exists or the ip address
          we found is local.
       2. It would return ip_address of device whose mac_address is equal to arg:mac_address
          and is connected/neighbor of arg:device       
    """
    try:
        output = sp.check_output(['ip','-6','neigh', 'show', 'dev', device], stderr=sp.PIPE)
    except sp.CalledProcessError:
        return None
    else:
        result = []
        output = output.strip().decode("utf-8")
        output = output.split("\n")
        for entry in output:
            entry = entry.split()
            if entry:
                ip = ipaddress.ip_address(entry[0])
                mac = entry[2]
                if ip.is_global and mac_address == mac:
                    result.append(ip)
        return result


def increment_etcd_counter(etcd_client, key):
    kv = etcd_client.get(key)
    
    if kv:
        counter = int(kv.value)
        counter = counter + 1
    else:
        counter = 1
    
    etcd_client.put(key, str(counter))
    return counter


def get_etcd_counter(etcd_client, key):
    kv = etcd_client.get(key)
    if kv:
        return int(kv.value)
    return None