from threading import Lock
import typing
import time
import abc

from .path import Path


class Now(typing.NamedTuple):
    def time(self) -> int:
        return round(time.time() * 1000)


NOW = Now()


class MetricValue(typing.NamedTuple):
    value: float
    timestamp: typing.Optional[int]


_NAN = float('nan')


class MetricMutableValue:
    # global lock for metrics by default
    DEFAULT_LOCK: typing.ClassVar[Lock] = Lock()

    def __init__(self, value: float = _NAN, timestamp: typing.Optional[int] = None, lock: Lock = DEFAULT_LOCK):
        self._lock = lock
        self._value = MetricValue(value, timestamp)

    def set_no_lock(self, value: float, timestamp: typing.Optional[int]):
        self._value = MetricValue(value, timestamp)

    def set(self, value: float, timestamp: typing.Union[int, None, Now] = NOW):
        if isinstance(timestamp, Now):
            timestamp = timestamp.time()
        with self._lock:
            self.set_no_lock(value, timestamp)

    def inc_no_lock(self, add: float, timestamp: typing.Optional[int]):
        self._value = MetricValue(self._value.value + add, timestamp)

    def inc(self, add: float = 1, timestamp: typing.Union[int, None, Now] = NOW):
        if isinstance(timestamp, Now):
            timestamp = timestamp.time()
        with self._lock:
            self.inc_no_lock(add, timestamp)

    def get(self) -> MetricValue:
        with self._lock:
            return self._value


class MetricBase(MetricMutableValue):
    metric_type: typing.ClassVar[str]
    help_text: typing.Optional[str] = None

    def __init__(self, value: float = _NAN, timestamp: typing.Optional[int] = None, help: typing.Optional[str] = None):
        super().__init__(value, timestamp)
        self.help_text = help


class MetricGroupDefinition(typing.NamedTuple):
    reserved_suffixes: typing.FrozenSet[str]
    reserved_labels: typing.FrozenSet[str]


EMPTY_GROUP_DEFINITION = MetricGroupDefinition(frozenset(), frozenset())


class MetricGroupBase(abc.ABC):
    metric_type: typing.ClassVar[str]
    group_definition: typing.ClassVar[MetricGroupDefinition]
    help_text: typing.Optional[str] = None

    def __init__(self, help: typing.Optional[str] = None):
        self.help_text = help

    @abc.abstractmethod
    def metrics(self) -> typing.Iterator[typing.Tuple[(Path, MetricMutableValue)]]:
        pass