interval.py

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# Copyright (c) 2021-2024, Hewlett Packard Enterprise
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from __future__ import annotations

import time
import typing as t

Seconds = t.NewType("Seconds", float)


class SynchronousTimeInterval:
    """A utility class to represent and synchronously block the execution of a
    thread for an interval of time.
    """

    def __init__(self, delta: float | None, strict: bool = True) -> None:
        """Initialize a new `SynchronousTimeInterval` interval

        :param delta: The difference in time the interval represents. If
            `None`, the interval will represent an infinite amount of time in
            seconds.
        :param strict: Wether or not to raise in the case where negative time
            delta is provided. If `False`, the `SynchronousTimeInterval` and a negative `delta`
            is provided, the interval will be infinite.
        :raises ValueError: The `delta` is negative and `strict` is `True`
        """
        if delta is not None and delta < 0 and strict:
            raise ValueError("Timeout value cannot be less than 0")
        if delta is None or delta < 0:
            delta = float("inf")
        self._delta = Seconds(delta)
        """The amount of time, in seconds the interval spans."""
        self._start = time.perf_counter()
        """The time of the creation of the interval"""

    @property
    def delta(self) -> Seconds:
        """The difference in time the interval represents

        :returns: The difference in time the interval represents
        """
        return self._delta

    @property
    def elapsed(self) -> Seconds:
        """The amount of time that has passed since the interval was created

        :returns: The amount of time that has passed since the interval was
            created
        """
        return Seconds(time.perf_counter() - self._start)

    @property
    def remaining(self) -> Seconds:
        """The amount of time remaining in the interval

        :returns: The amount of time remaining in the interval
        """
        return Seconds(max(self.delta - self.elapsed, 0))

    @property
    def expired(self) -> bool:
        """The amount of time remaining in interval

        :returns: The amount of time left in the interval
        """
        return self.remaining <= 0

    @property
    def infinite(self) -> bool:
        """Is the timeout interval infinitely long.

        :returns: `True` if the delta is infinite, `False` otherwise
        """
        return self.remaining == float("inf")

    def new_interval(self) -> SynchronousTimeInterval:
        """Make a new timeout with the same interval

        :returns: The new timeout
        """
        return type(self)(self.delta)

    def wait(self) -> None:
        """Block the thread until the timeout completes

        :raises RuntimeError: The thread would be blocked forever
        """
        if self.remaining == float("inf"):
            raise RuntimeError("Cannot block thread forever")
        time.sleep(self.remaining)