import etcd3
import json
import signal

from dataclasses import dataclass
from collections import namedtuple

PseudoEtcdMeta = namedtuple("PseudoEtcdMeta", ["key"])


@dataclass(init=False)
class EtcdEntry:
    def __init__(self, meta, value, value_in_json=False):
        self.key = meta.key.decode("utf-8")

        self.value = value.decode("utf-8")
        
        if value_in_json:
            self.value = json.loads(self.value)

    key: str
    value: str


class Etcd3Wrapper(object):
    def __init__(self, *args, **kwargs):
        self.client = etcd3.client(*args, **kwargs)
    
    def get(self, *args, value_in_json=False, **kwargs):   
        _value, _key = self.client.get(*args, **kwargs)
        if _key is None:
            return None
        return EtcdEntry(_key, _value, value_in_json=value_in_json)
    
    def put(self, *args, value_in_json=False, **kwargs):
        _key, _value = args
        if value_in_json:
            _value = json.dumps(_value)

        if not isinstance(_key, str):
            _key = _key.decode("utf-8")

        return self.client.put(_key, _value, **kwargs)

    def get_prefix(self, *args, value_in_json=False, **kwargs):
        r = self.client.get_prefix(*args, **kwargs)
        for entry in r:
            yield EtcdEntry(*entry[::-1], value_in_json=value_in_json)

    def watch_prefix(self, *args, timeout=0, value_in_json=False, **kwargs):
        if timeout > 0:
            signal.signal(signal.SIGALRM, raise_timeout)
        while True:
            try:
                if timeout > 0:
                    signal.alarm(timeout)
                r, _ = self.client.watch_prefix(*args, **kwargs)

                for event in r:
                    # if e.value is None don't propagate its value
                    if event.value is None:
                        continue
                    event = EtcdEntry(event, event.value, value_in_json=value_in_json)
                    yield event
            except TimeoutError:
                _value = {"status": "TIMEOUT"}
                yield EtcdEntry(PseudoEtcdMeta(key=b"TIMEOUT"), value=str.encode(json.dumps(_value)))


def raise_timeout(signum, frame):
    _ = signum, frame
    raise TimeoutError()