events.py

import numpy as np


def _smooth(values: np.ndarray, k: int = 3) -> np.ndarray:
    """Moving average over the sampled motion. Kills 1-frame spikes."""
    if k < 2 or len(values) < k:
        return values
    return np.convolve(values, np.ones(k) / k, mode="same")


def pick_key_events(motion: dict, fps: float, max_events: int = 10,
                    min_gap_sec: float = 1.5, pct_floor: float = 60.0) -> list[float]:
    """motion: {frame_idx: score}. Returns sorted list of timestamps (sec).

    pct_floor: only frames above this percentile of (smoothed) motion can be
    events — tune up for "only the biggest moments", down for "more chatter".
    """
    if not motion:
        return [0.5]

    frames = sorted(motion)
    scores = _smooth(np.array([motion[f] for f in frames], dtype=float))
    total_sec = frames[-1] / fps if fps else 0.0

    # how many events does a clip this long deserve?
    cap = max(1, min(max_events, int(total_sec / min_gap_sec) or 1))

    floor = np.percentile(scores, pct_floor)

    # local maxima above the floor = genuine "moments"
    peaks = []
    n = len(frames)
    for i in range(n):
        s = scores[i]
        if s < floor:
            continue
        left  = scores[i - 1] if i > 0 else -np.inf
        right = scores[i + 1] if i < n - 1 else -np.inf
        if s >= left and s >= right:
            peaks.append((frames[i], s))

    if not peaks:                                   # flat clip -> evenly spaced
        if total_sec <= 0:
            return [0.5]
        return [round((i + 0.5) * total_sec / cap, 2) for i in range(cap)]

    # strongest first, then suppress neighbours within min_gap (spread them out)
    peaks.sort(key=lambda kv: kv[1], reverse=True)
    min_gap_frames = int(min_gap_sec * fps)
    chosen: list[int] = []
    for frame_idx, _ in peaks:
        if all(abs(frame_idx - c) >= min_gap_frames for c in chosen):
            chosen.append(frame_idx)
        if len(chosen) >= cap:
            break

    chosen.sort()
    return [round(c / fps, 2) for c in chosen]


def events_to_frames(timestamps: list[float], fps: float) -> list[int]:
    return [int(round(ts * fps)) for ts in timestamps]