#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
lum_scan.py —— 全片逐帧亮度扫描（单次解码，流式）

为什么要全量而不是抽样：后面三件事都依赖逐帧亮度
  1. 对齐：传送时「掉黑」那一帧是把日志 vt 钉到视频时间轴的信号
  2. D2：帧均值 < 6 的低照度过滤
  3. 传送窗口复核：确认固定余量 [leg_end-1.0, leg_start+1.5] 真的盖住了黑屏+加载页

度量必须与交付规格一致：`scale=64:36` + bicubic + gray，然后取整帧均值。
换成别的缩放尺寸/插值，暗场景的读数会系统性偏移，D2 的阈值 6 就不再是同一个 6。

产出 <out>/<session>/lum.npz：
    mean  float32[N]  逐帧 64x36 灰度均值 (0-255)
    p95   float32[N]  逐帧 64x36 灰度 95 分位（配合 max 判「真·全黑」）
    mx    uint8[N]     逐帧最大值
    diff  float32[N]  与前一帧的平均绝对差（diff[0]=nan），粗粒度重复帧信号
    fps, n_frames
"""
from __future__ import annotations

import argparse
import json
import os
import subprocess
import sys
import time

import numpy as np

W, H = 64, 36
FRAME_BYTES = W * H


def probe(path: str) -> dict:
    out = subprocess.run(
        ["ffprobe", "-v", "error", "-print_format", "json",
         "-show_streams", "-show_format", path],
        capture_output=True, text=True, check=True).stdout
    info = json.loads(out)
    v = next(s for s in info["streams"] if s["codec_type"] == "video")
    num, den = (v.get("r_frame_rate") or "30/1").split("/")
    return dict(width=int(v["width"]), height=int(v["height"]),
                fps=float(num) / float(den or 1),
                nb_frames=int(v.get("nb_frames") or 0),
                duration=float(info["format"].get("duration", 0) or 0))


def scan(path: str, threads: int = 8, chunk_frames: int = 512, report_every: int = 60.0):
    info = probe(path)
    fps = info["fps"]
    est = info["nb_frames"] or int(info["duration"] * fps)
    cmd = ["ffmpeg", "-v", "error", "-threads", str(threads), "-i", path,
           "-vf", f"scale={W}:{H}:flags=bicubic,format=gray",
           "-f", "rawvideo", "-pix_fmt", "gray", "-"]
    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=FRAME_BYTES * chunk_frames)

    means, p95s, mxs, diffs = [], [], [], []
    prev = None
    t0 = time.time()
    last_report = t0
    n = 0
    want = FRAME_BYTES * chunk_frames
    buf = b""
    while True:
        block = p.stdout.read(want)
        if not block:
            break
        buf += block
        k = len(buf) // FRAME_BYTES
        if k == 0:
            continue
        arr = np.frombuffer(buf[:k * FRAME_BYTES], np.uint8).reshape(k, H * W)
        buf = buf[k * FRAME_BYTES:]
        a = arr.astype(np.float32)
        means.append(a.mean(1))
        p95s.append(np.percentile(a, 95, axis=1).astype(np.float32))
        mxs.append(arr.max(1))
        d = np.empty(k, np.float32)
        if prev is None:
            d[0] = np.nan
            if k > 1:
                d[1:] = np.abs(np.diff(a, axis=0)).mean(1)
        else:
            d[0] = np.abs(a[0] - prev).mean()
            if k > 1:
                d[1:] = np.abs(np.diff(a, axis=0)).mean(1)
        diffs.append(d)
        prev = a[-1]
        n += k
        now = time.time()
        if now - last_report >= report_every:
            el = now - t0
            pct = 100.0 * n / est if est else 0.0
            eta = (est - n) / max(n / el, 1e-9) if est else 0.0
            print(f"    {n:,}/{est:,} 帧 ({pct:.1f}%) · {n/el:.0f} fps · 已用 {el/60:.1f} min"
                  f" · 剩 {eta/60:.1f} min", flush=True)
            last_report = now
    p.stdout.close()
    rc = p.wait()
    if rc != 0:
        print(f"  [警告] ffmpeg 退出码 {rc}（多半是文件尾损坏，前面的帧仍然有效）", file=sys.stderr)
    return dict(
        mean=np.concatenate(means) if means else np.zeros(0, np.float32),
        p95=np.concatenate(p95s) if p95s else np.zeros(0, np.float32),
        mx=np.concatenate(mxs) if mxs else np.zeros(0, np.uint8),
        diff=np.concatenate(diffs) if diffs else np.zeros(0, np.float32),
    ), fps, rc


def main():
    ap = argparse.ArgumentParser(description="全片逐帧亮度扫描")
    ap.add_argument("--raw", default="/data/zhiyangdeng/EYBXROAM")
    ap.add_argument("--out", default="/data/zhiyangdeng/data_eybx/logs")
    ap.add_argument("--sessions", nargs="*", default=None)
    ap.add_argument("--threads", type=int, default=8)
    args = ap.parse_args()

    sessions = args.sessions or sorted(
        d for d in os.listdir(args.raw)
        if os.path.isdir(os.path.join(args.raw, d)) and d[0].isdigit())
    for sid in sessions:
        vid = os.path.join(args.raw, sid, "video.mp4")
        dst = os.path.join(args.out, sid)
        os.makedirs(dst, exist_ok=True)
        print(f"== {sid}  {os.path.getsize(vid)/1e9:.1f} GB")
        t0 = time.time()
        d, fps, rc = scan(vid, threads=args.threads)
        n = d["mean"].size
        np.savez_compressed(os.path.join(dst, "lum.npz"), fps=np.float64(fps),
                            n_frames=np.int64(n), ffmpeg_rc=np.int32(rc), **d)
        el = time.time() - t0
        m = d["mean"]
        print(f"   {n:,} 帧 @ {fps:.4f} fps = {n/fps/3600:.2f} h · 用时 {el/60:.1f} min "
              f"({n/el:.0f} fps)")
        print(f"   亮度 中位 {np.median(m):.1f} · <6 占 {100*(m<6).mean():.2f}% · "
              f"<10 占 {100*(m<10).mean():.2f}% · <20 占 {100*(m<20).mean():.2f}%")
    print("DONE")


if __name__ == "__main__":
    main()