Source code for faust.windows

"""Window Types."""
from typing import List
from mode import Seconds, want_seconds
from .types import WindowRange, WindowT

__all__ = [
    'Window',
    'HoppingWindow',
    'TumblingWindow',
    'SlidingWindow',
]


class Window(WindowT):
    ...


class HoppingWindow(Window):
    """Hopping window type.

    Fixed-size, overlapping windows.
    """

    size: float
    step: float

    def __init__(self, size: Seconds, step: Seconds,
                 expires: Seconds = None) -> None:
        self.size = want_seconds(size)
        self.step = want_seconds(step)
        self.expires = want_seconds(expires) if expires else None

    def ranges(self, timestamp: float) -> List[WindowRange]:
        curr = self._timestamp_window(timestamp)
        earliest = curr.start - self.size + self.step
        return [
            WindowRange.from_start(float(start), self.size)
            for start in range(int(earliest), int(curr.end), int(self.step))
        ]

    def stale(self, timestamp: float, latest_timestamp: float) -> bool:
        return (timestamp <= self._stale_before(latest_timestamp, self.expires)
                if self.expires else False)

    def current(self, timestamp: float) -> WindowRange:
        return self._timestamp_window(timestamp)

    def delta(self, timestamp: float, d: Seconds) -> WindowRange:
        return self._timestamp_window(timestamp - want_seconds(d))

    def _timestamp_window(self, timestamp: float) -> WindowRange:
        start = (timestamp // self.step) * self.step
        return WindowRange.from_start(start, self.size)

    def _stale_before(self, latest_timestamp: float, expires: float) -> float:
        return self._timestamp_window(latest_timestamp - expires).start


class TumblingWindow(HoppingWindow):
    """Tumbling window type.

    Fixed-size, non-overlapping, gap-less windows.
    """

    def __init__(self, size: Seconds, expires: Seconds = None) -> None:
        super(TumblingWindow, self).__init__(size, size, expires)


class SlidingWindow(Window):
    """Sliding window type.

    Fixed-size, overlapping windows that work on differences between
    record timestamps
    """

    before: float
    after: float

    def __init__(self, before: Seconds, after: Seconds,
                 expires: Seconds) -> None:
        self.before = want_seconds(before)
        self.after = want_seconds(after)
        self.expires = want_seconds(expires)

    def ranges(self, timestamp: float) -> List[WindowRange]:
        """Return list of windows from timestamp.

        Notes:
            .. sourcecode:: sql

                SELECT * FROM s1, s2
                WHERE
                    s1.key = s2.key
                AND
                s1.ts - before <= s2.ts AND s2.ts <= s1.ts + after
        """
        return [
            WindowRange(
                start=timestamp - self.before, end=timestamp + self.after),
        ]

    def stale(self, timestamp: float, latest_timestamp: float) -> bool:
        return (timestamp <= self._stale_before(self.expires, latest_timestamp)
                if self.expires else False)

    def _stale_before(self, expires: float, latest_timestamp: float) -> float:
        return latest_timestamp - expires