import time
from urllib.parse import urljoin

import kubernetes.client
import kubernetes.config
import logging
import re
import requests
import tokens
from requests.auth import AuthBase

DEFAULT_CLUSTERS = 'http://localhost:8001/'
CLUSTER_ID_INVALID_CHARS = re.compile('[^a-z0-9:-]')

logger = logging.getLogger(__name__)

tokens.configure(from_file_only=True)


def generate_cluster_id(url: str):
    '''Generate some "cluster ID" from given API server URL'''
    for prefix in ('https://', 'http://'):
        if url.startswith(prefix):
            url = url[len(prefix):]
    return CLUSTER_ID_INVALID_CHARS.sub('-', url.lower()).strip('-')


class StaticTokenAuth(AuthBase):
    def __init__(self, token):
        self.token = token

    def __call__(self, request):
        request.headers['Authorization'] = 'Bearer {}'.format(self.token)
        return request


class OAuthTokenAuth(AuthBase):
    def __init__(self, token_name):
        self.token_name = token_name
        tokens.manage(token_name)

    def __call__(self, request):
        token = tokens.get(self.token_name)
        request.headers['Authorization'] = 'Bearer {}'.format(token)
        return request


class Cluster:
    def __init__(self, id, api_server_url, ssl_ca_cert=None, auth=None):
        self.id = id
        self.api_server_url = api_server_url
        self.ssl_ca_cert = ssl_ca_cert
        self.auth = auth


class StaticClusterDiscoverer:

    def __init__(self, api_server_urls: list):
        self._clusters = []

        if not api_server_urls:
            try:
                kubernetes.config.load_incluster_config()
            except kubernetes.config.ConfigException:
                # we are not running inside a cluster
                # => assume default kubectl proxy URL
                cluster = Cluster(generate_cluster_id(DEFAULT_CLUSTERS), DEFAULT_CLUSTERS)
            else:
                config = kubernetes.client.configuration
                cluster = Cluster(
                    generate_cluster_id(config.host),
                    config.host,
                    ssl_ca_cert=config.ssl_ca_cert,
                    auth=StaticTokenAuth(config.api_key['authorization'].split(' ', 1)[-1]))
            self._clusters.append(cluster)
        else:
            for api_server_url in api_server_urls:

                if 'localhost' not in api_server_url:
                    # TODO: hacky way of detecting whether we need a token or not
                    auth = OAuthTokenAuth('read-only')
                else:
                    auth = None
                self._clusters.append(Cluster(generate_cluster_id(api_server_url), api_server_url, auth=auth))

    def get_clusters(self):
        return self._clusters


class ClusterRegistryDiscoverer:

    def __init__(self, cluster_registry_url: str, cache_lifetime=60):
        self._url = cluster_registry_url
        self._cache_lifetime = cache_lifetime
        self._last_cache_refresh = 0
        self._clusters = []
        self._session = requests.Session()
        self._session.auth = OAuthTokenAuth('read-only')

    def refresh(self):
        try:
            response = self._session.get(urljoin(self._url, '/kubernetes-clusters'), timeout=10)
            response.raise_for_status()
            clusters = []
            for row in response.json()['items']:
                # only consider "ready" clusters
                if row.get('lifecycle_status', 'ready') == 'ready':
                    clusters.append(Cluster(row['id'], row['api_server_url'], auth=OAuthTokenAuth('read-only')))
            self._clusters = clusters
            self._last_cache_refresh = time.time()
        except:
            logger.exception('Failed to refresh from cluster registry {}'.format(self._url))

    def get_clusters(self):
        now = time.time()
        if now - self._last_cache_refresh > self._cache_lifetime:
            self.refresh()
        return self._clusters