import json

import etcd3 as etcd3
from retrying import retry

CLUSTER_INFO_KEY = '/syncthing_monitor/cluster_info'
DEFAULT_PORT = 2379


class EtcdClient:
    def __init__(self, host, port=DEFAULT_PORT):
        self.etcd = etcd3.client(host=host, port=port)

    def load_cluster_info(self):
        raw_value = self.etcd.get(CLUSTER_INFO_KEY)[0]
        if raw_value is None:
            return {'devices': []}
        return json.loads(raw_value)

    @retry
    def append_device_id(self, device_id, hostname):
        with self.etcd.lock('syncthing_monitor'):
            cluster_info = self.load_cluster_info()

            if any(device_id in device['id'] for device in cluster_info['devices']):
                return

            new_device = {
                'id': device_id,
                'hostname': hostname
            }

            cluster_info['devices'].append(new_device)

            print("Updating etcd value for '{0}': {1}".format(CLUSTER_INFO_KEY, json.dumps(cluster_info)))
            self.etcd.put(CLUSTER_INFO_KEY, json.dumps(cluster_info))

    @retry
    def get_device_list(self):
        device_list = self.load_cluster_info()['devices']
        print("Obtained device_list devices from etcd: {0}".format(json.dumps(device_list)))
        return device_list

    def register_device_update_handler(self, device_update_handler):
        self.etcd.add_watch_callback(CLUSTER_INFO_KEY, device_update_handler)