from __future__ import annotations
import time

class ETA:
    def __init__(self, total: int, smoothing: float = 0.95):
        self.total = max(1, total)
        self.smoothing = smoothing
        self.start = time.time()
        self.last = self.start
        self.avg = None
        self.n = 0

    def step(self, count: int = 1):
        now = time.time()
        dt = (now - self.last) / max(1, count)
        self.last = now
        self.n += count
        if self.avg is None:
            self.avg = dt
        else:
            self.avg = self.smoothing * self.avg + (1 - self.smoothing) * dt

    def eta_seconds(self) -> float:
        rem = max(0, self.total - self.n)
        return rem * (self.avg or 0.0)

    @staticmethod
    def fmt(seconds: float) -> str:
        seconds = int(seconds)
        h = seconds // 3600
        m = (seconds % 3600) // 60
        s = seconds % 60
        if h > 0:
            return f"{h:d}h {m:02d}m {s:02d}s"
        if m > 0:
            return f"{m:d}m {s:02d}s"
        return f"{s:d}s"