from __future__ import annotations

import time
from collections import deque

from PySide6.QtCore import QObject
from PySide6.QtMultimedia import QVideoFrame


class TelemetryCollector(QObject):
    def __init__(self, parent: QObject | None = None) -> None:
        super().__init__(parent)
        self._timestamps: deque[float] = deque(maxlen=500)

    def on_frame(self, frame: QVideoFrame) -> None:
        self._timestamps.append(time.perf_counter())

    def metrics(self) -> dict[str, float | int]:
        if not self._timestamps:
            return {"fps": 0, "frame_time_ms": 0.0, "frame_count": 0}

        now = time.perf_counter()
        cutoff = now - 1.0
        recent = [t for t in self._timestamps if t >= cutoff]
        fps = len(recent)

        frame_time_ms = 0.0
        if len(self._timestamps) >= 2:
            diffs = [
                self._timestamps[i] - self._timestamps[i - 1]
                for i in range(1, len(self._timestamps))
            ]
            frame_time_ms = (sum(diffs) / len(diffs)) * 1000 if diffs else 0.0

        return {
            "fps": fps,
            "frame_time_ms": round(frame_time_ms, 2),
            "frame_count": len(self._timestamps),
        }