#!/usr/bin/env python3
"""Library re-encode driver: same look, SMALLER file, playable on iPad + Android.

Policy (see references/hevc-conversion-policy.md):
  * classify each source by `bpp` and pick the cheapest tier that keeps the quality:
      lean  (bpp < 0.025) -> `-c:v copy`            video bit-identical, nothing to gain
      mid   (0.025-0.040) -> hevc_nvenc cq 30       ~6.4x realtime
      fat   (> 0.040)     -> libx265 crf 24         ~3x realtime, 9-16% more efficient
  * `-maxrate` = 1.0x the source's **video** bitrate (never the file's total) and a
    post-encode assertion that the output video bitrate did not exceed it
  * quality pinned to a measured number: per-frame SSIM of a sampled window vs the source
  * audio: copy when already AAC, else AAC at the SOURCE's own bitrate (never a fixed 256k)
  * `-fps_mode cfr` + `-pix_fmt yuv420p` + `-tag:v hvc1` on every re-encode

Per file, in order:
  1. copy the source OFF the network share to LOCAL staging (never encode over SMB/WebDAV)
  2. encode locally (tier above)
  3. structural gate + full decode pass + SSIM-vs-source + size assertion, all on the LOCAL output
  4. copy the verified output to the share as <name>.new.mp4
  5. read the share copy back end-to-end and compare SHA-256 with the local file
  6. ONLY then rename it over the original, and re-probe the result on the share
A file that fails at any step leaves the original untouched and is retried next run.
"""
import argparse
import csv
import ctypes
import hashlib
import json
import os
import re
import shutil
import subprocess
import sys
import time

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import transcode as T  # noqa: E402

FFMPEG = T.FFMPEG
FFPROBE = T.FFPROBE
# A console-less parent (the queues run the engines under pythonw.exe) makes every console-subsystem
# child - ffmpeg, ffprobe - allocate a NEW console and SHOW it: measured 2026-10-11, one visible
# Windows Terminal window per spawned child while two encodes ran. CREATE_NO_WINDOW suppresses that
# (0 on POSIX, where the flag does not exist).
NOWIN = getattr(subprocess, "CREATE_NO_WINDOW", 0)
ROOT = r"Z:\Class\樊登读书\樊登读书会（每周更新）"
WORK = r"C:\AI\transcode-run"
STAGE = os.path.join(WORK, "stage")
LEDGER = os.path.join(WORK, "ledger.jsonl")
LOCKF = os.path.join(WORK, "run.lock")
VIDEO_EXT = {".mkv", ".mp4", ".mov", ".avi", ".webm", ".flv", ".ts", ".m4v", ".wmv",
             ".mpg", ".mpeg", ".m2ts", ".3gp", ".ogv", ".vob", ".rmvb", ".rm", ".divx"}
DECODE_CHECK = True

# ---- policy (all numbers measured; see references/hevc-conversion-policy.md §10) ----------
CQ_NVENC = 31            # measured: min SSIM 0.989-0.994 at 43-74% of the source video bitrate
CRF_X265 = 26            # measured: min SSIM 0.988-0.993 at 34-67% -- 10-22% smaller than NVENC
                         # at matched SSIM. crf24 = the conservative option (min 0.990-0.994, 43-84%)
NVENC_PRESET = "p6"
X265_PRESET = "medium"
X265_POOLS = 10          # E-cores only (affinity 0x3FF0000)
E_CORE_MASK = 0x3FF0000
SSIM_TARGET = 0.985      # per-frame floor vs the source window (480x270 comparison)
SSIM_WINDOW = 60         # seconds sampled for the SSIM gate
BAD_FRAME_SSIM = 0.85    # a frame this far below the source is 'bad' for the share test
MAX_BAD_SHARE = 0.01     # ... and more than this share of them means a systematic defect, not fades
FLAT_LUMA_STD = 3.0      # a source frame flatter than this: SSIM on it means nothing
ALIGN_FINE = 6           # fine offset search STEP: 1 frame, over +-ALIGN_FINE frames. A cfr
                         # duplicate (inserted wherever the encoder dropped a frame) displaces the
                         # whole window by EXACTLY one frame - measured 2026-10-11 on two installed
                         # outputs: 1499/1500 and 1495/1500 frames needed off=-1, which a step-10
                         # sweep cannot see (it cost 1.5-1.7 mean points and refused 14 healthy
                         # encodes in 9.6 h).
ALIGN_PERFRAME = 2       # last resort: score every frame against the best of its +-N neighbours
                         # (the TubeSync engine's CONTENT_SHIFT discriminator), for a window whose
                         # displacement varies instead of being one constant shift.


def _flat_frames(raw_path, n, w=480, h=270, thresh=FLAT_LUMA_STD):
    """Indices of near-flat source frames (fades, black, plain titles) in a raw YUV window.

    SSIM collapses on such frames - two nearly black frames score ~0.25 while their neighbours
    score 0.998 - so a minimum taken over every frame condemns perfectly good encodes (measured on
    this library: the file that failed had 5 of 1500 frames below 0.85, all isolated, at a 0.98
    mean, while the genuine decoder-defect files had 44 of 1499).
    """
    import numpy as np
    fsz = w * h * 3 // 2
    flat = set()
    with open(raw_path, "rb") as f:
        for i in range(n):
            luma = f.read(w * h)
            if len(luma) < w * h:
                break
            if float(np.frombuffer(luma, dtype=np.uint8).std()) < thresh:
                flat.add(i)
            f.seek(fsz - w * h, 1)
    return flat


SIZE_CEIL = 1.0          # output video bitrate must not exceed the source's
QUALITY_STEPS = 2        # on a quality-gate failure, retry with the quality raised this many
                         # steps (cq -2 / crf -2) before giving up; the retry only fires on a
                         # file the cheaper setting could not carry
SSIM_MEAN_MIN = 0.995    # the window-mean bar for a normal encode (owner decision 2026-10-11).
# Measured basis: the aligned means of healthy encodes on this library land at 0.9960-0.9978 (the
# canary plus two x265 items); the pre-fix distribution had 41% of items below 0.995, which is
# pessimistic - the old index pairing depressed every mean by 1.5-1.7 points.
SSIM_MEAN_MIN_REDO = 0.990   # ... and for a RE-DO of a file that already plays everywhere
                         # (HEVC hvc1 + AAC). Owner decision 2026-10-08: measured on this library,
                         # 11 of a pass's attempts died on a mean of 0.9655-0.9795 while files with
                         # WORSE frame minima (0.33-0.90) passed - the bar was splitting a
                         # continuum, not separating defects (0718 马斯克原理 failed with 0.00% of
                         # frames below 0.85 and min 0.887). A re-do's only job is to reclaim the
                         # old settings' bloat, so it must not be stranded with the bigger file for
                         # ever; 0.990 still rejects the genuine stragglers (0.9655, 0.9739).
SSIM_MEAN_MIN_FALLBACK = 0.990   # the SECOND tier, for an item the owner has released from the first
                         # (the accept list): the frame-share test stays the verdict that catches a
                         # defect, but the mean is now enforced here instead of being ignored
                         # entirely. This IS the owner's ladder from 2026-10-11 - a bar of 0.995 for
                         # a normal encode and 0.990 once an item has been released - rather than a
                         # hidden retry counter: after "park after 2 failed rounds" an item stops and
                         # waits for that explicit decision.
VMAF_OBSERVE = True      # compute VMAF inside the gate and PRINT it - never gate on it (owner
                         # decision 2026-10-11). The evidence base is two items (aligned mean 95.85 /
                         # 96.00, min 93.76 / 94.10 against a proposed 95/93: ~zero margin), so this
                         # runs observe-only and accumulates the distribution the bar can be picked
                         # from. See docs/QUALITY-POLICY-PLAN.md 2.4.


def log(*a):
    print(time.strftime("%H:%M:%S") + " " + " ".join(str(x) for x in a), flush=True)


def disp(p):
    """Path for logs/ledger: relative to the library when possible.

    A single-file run can point anywhere (measured: os.path.relpath raises ValueError when the file
    is on D: and the library on Z:), so fall back to the absolute path.
    """
    try:
        return os.path.relpath(p, ROOT)
    except ValueError:
        return p


# ---- owner gate policy (2026-10-10) -----------------------------------------------------------
# Two settings, both owner decisions, kept OUT of the code so they can be changed without touching
# the pipeline:
#
#  * accept  - items for which the FRAME-SHARE test is the verdict and the mean bar is only a
#              warning. The bar was splitting a continuum rather than separating defects: on
#              2026-10-10 eight items failed by 0.2-1.7 thousandths of mean while keeping
#              0.20-0.93 % of frames below the floor, and only one of them (0912 洞见, 1.33 %)
#              actually tripped the frame-share test that is documented as the real defect test.
#              An item that fails the frame-share test is refused even when listed here.
#  * park    - {item: failed quality ROUNDS}. A round is an initial attempt plus its quality+2
#              retry. At PARK_AFTER rounds the item is skipped instead of re-encoded: without this
#              the same eight items burned ~3.3 GPU-hours every pass, forever, and never converted.
POLICY = os.path.join(WORK, "gate_policy.json")
PARK_AFTER = 2


def load_policy():
    """{"accept": set(disp keys), "park": {disp key: failed rounds}} - missing file means neither."""
    try:
        with open(POLICY, encoding="utf-8") as fh:
            d = json.load(fh)
        return {"accept": set(d.get("accept") or []), "park": dict(d.get("park") or {})}
    except (OSError, ValueError):
        return {"accept": set(), "park": {}}


def save_policy(p):
    try:
        with open(POLICY, "w", encoding="utf-8") as fh:
            json.dump({"accept": sorted(p["accept"]), "park": p["park"]}, fh,
                      ensure_ascii=False, indent=1)
    except OSError as e:
        log("   ! could not save %s: %s" % (POLICY, e))


POLICY_CACHE = load_policy()


def probe(p, tries=3):
    """T.probe with retries: this share times a probe out (measured: 120 s for a 30 MB read), and
    one hiccup must not fail an item that is otherwise fine. The per-item try/except in the main
    loop would have turned a hiccup into a FAIL, leaving the file unconverted."""
    last = None
    for a in range(1, tries + 1):
        try:
            v = T.probe(p)
            if v:
                return v
            last = "no streams"
        except Exception as e:
            last = e
        log("   ! probe attempt %d/%d failed (%s) - retrying" % (a, tries, last))
        time.sleep(5 * a)
    raise IOError("could not probe %s after %d attempts: %s" % (p, tries, last))


def run(cmd, timeout=86400, **kw):
    kw.setdefault("creationflags", NOWIN)      # never a visible console per call
    return subprocess.run(cmd, capture_output=True, text=True, encoding="utf-8",
                          errors="replace", timeout=timeout, **kw)


STALL_S = 900   # an encode with no output growth for this long is wedged, not slow
# ... and the SSIM window decodes get a longer one: the trim filter writes nothing until the window
# starts, so decoding the file's first half is legitimate silence (see ssim_vs_source).
GATE_STALL_S = 3600


def run_watched(cmd, watch, stall_s=STALL_S, timeout=86400):
    """run() with a STALL WATCHDOG on the file the command writes.

    Measured: a hevc_nvenc encode sat FROZEN for 1.5 hours with its output unchanged - the user had
    updated the NVIDIA driver while it was running, which wedges in-flight GPU work without any
    error. A multi-day unattended run must recover from that by itself: no output growth for
    `stall_s` -> kill the command and report a failure the normal retry path can pick up.

    NB the child's stderr goes to a FILE, never a pipe. ffmpeg with `-stats` writes a line every
    0.5 s, which fills a 64 KB pipe within minutes; a blocked ffmpeg stops writing its output, so
    the watchdog then kills a perfectly healthy encode (measured: ~270 kills in one night, almost no
    work done, while the encoder sat idle in write() on stderr).
    """
    errf = watch + ".err"
    err = ""
    with open(errf, "wb") as ferr:
        p = subprocess.Popen(cmd, stdout=subprocess.DEVNULL, stderr=ferr, creationflags=NOWIN)
        last, last_t, t0 = -1, time.time(), time.time()
        while p.poll() is None:
            time.sleep(30)
            if time.time() - t0 > timeout:
                p.kill()
                p.wait()
                err = "timeout after %d s" % timeout
                break
            try:
                sz = os.path.getsize(watch) if os.path.exists(watch) else 0
            except OSError:
                sz = last
            if sz != last:
                last, last_t = sz, time.time()
            elif time.time() - last_t > stall_s:
                p.kill()
                p.wait()
                log("   !! STALL: no output growth for %d s - killed the wedged encode" % stall_s)
                err = "killed: wedged (no growth for %ds)" % stall_s
                break
    try:
        with open(errf, "rb") as f:
            data = f.read()
        tail = data[-4000:].decode("utf-8", "replace")
        err = (tail + "\n" + err).strip()
        os.remove(errf)
    except OSError:
        pass
    rc = p.returncode if p.returncode is not None else -9
    return subprocess.CompletedProcess(cmd, rc, "", err)


# ---------------------------------------------------------------- integrity

def _sha_local(path, label="local"):
    h = hashlib.sha256()
    n = 0
    with open(path, "rb") as f:
        while True:
            b = f.read(8 << 20)
            if not b:
                break
            h.update(b)
            n += len(b)
    return h.hexdigest(), n


def _sha_remote(path, label="remote", tries=3):
    """Hash a file over the network. getsize() lies on RaiDrive/Dokan, so the byte
    count here is what was actually read, never a metadata figure."""
    last = None
    for attempt in range(1, tries + 1):
        try:
            h = hashlib.sha256()
            n = 0
            with open(path, "rb") as f:
                while True:
                    b = f.read(8 << 20)
                    if not b:
                        break
                    h.update(b)
                    n += len(b)
            return h.hexdigest(), n
        except (OSError, MemoryError) as e:
            last = e
            log("   ! %s read attempt %d failed: %s" % (label, attempt, e))
            time.sleep(5 * attempt)
    raise last


def copy_remote_to_local(remote, local, expect_size=None, tries=5):
    """Network -> local. Retried; a short read is a failure, never a silent pass.

    Measured on this host: RaiDrive/Dokan throws `[Errno 9] Bad file descriptor` on a 1 GB read
    when three jobs hammer the share at once (the user sees RaiDrive's own upload-failure toasts at
    the same time). Smaller chunks, more attempts and a longer backoff ride those hiccups out
    instead of losing the file - and each failed attempt costs minutes on a 1 GB source, so the
    point is to stop retrying as fast as we can.
    """
    for attempt in range(1, tries + 1):
        try:
            n = 0
            with open(remote, "rb") as fi, open(local, "wb") as fo:
                while True:
                    b = fi.read(4 << 20)
                    if not b:
                        break
                    fo.write(b)
                    n += len(b)
                fo.flush()
                os.fsync(fo.fileno())
            if expect_size and n != expect_size:
                raise IOError("short read: got %d, container says %d" % (n, expect_size))
            # A read of the RIGHT LENGTH can still be wrong on this share: RaiDrive reports stale
            # sizes, and a listing read here stopped halfway with no error at all (it looked like a
            # truncated file and was not). A corrupt staged source would be encoded into a corrupt
            # output, so pay for one more pass and compare hashes of what we wrote against a fresh
            # read of the share copy.
            if n > (64 << 20):
                a = _sha_local(local, "staged source")
                b = _sha_remote(remote, "share source")
                if a != b:
                    raise IOError("staged source hash mismatch (local %s.. != share %s..)"
                                  % (a[:12], b[:12]))
            return n
        except (OSError, MemoryError) as e:
            log("   ! source copy attempt %d/%d failed: %s" % (attempt, tries, e))
            time.sleep(15 * attempt)
    raise IOError("could not copy source off the share after %d attempts" % tries)


def copy_local_to_remote(local, remote_tmp, tries=4):
    """Local -> network temp name. Chunked; never writes the final name.

    Measured failure mode on this host: RaiDrive/Dokan aborts a ~500 MB write with
    "the operation didn't complete within specific time limit" (and leaves a partial `.new.mp4`),
    which the user sees as an upload-failed toast. Three jobs reading/writing the share at once is
    what provokes it. So: smaller chunks, a periodic flush so nothing huge sits in a buffer, more
    attempts, and a longer backoff. A partial file is always deleted before retrying (never resumed
    from `os.path.getsize()` on the share - RaiDrive reports stale sizes, so an offset taken from it
    would silently corrupt the upload).
    """
    for attempt in range(1, tries + 1):
        try:
            written = 0
            with open(local, "rb") as fi, open(remote_tmp, "wb") as fo:
                while True:
                    b = fi.read(4 << 20)
                    if not b:
                        break
                    fo.write(b)
                    written += len(b)
                    if written % (32 << 20) < (4 << 20):
                        fo.flush()
                        os.fsync(fo.fileno())
                fo.flush()
                os.fsync(fo.fileno())
            return True
        except (OSError, MemoryError) as e:
            log("   ! upload attempt %d/%d failed after %.0f MB: %s" % (
                attempt, tries, written / 1e6, e))
            try:
                os.remove(remote_tmp)
            except (OSError, MemoryError):
                pass
            time.sleep(20 * attempt)
    return False


def probe_ok(path, info, vcodec="hevc"):
    """Structural gate on any path (local or share)."""
    return T.verify(info, path, vcodec, "copy" if info["acodec"] in ("aac", "mp4a", "") else "aac",
                    check_decode=False)


# ---------------------------------------------------------------- encode

def src_bitrate(info):
    if info["dur"] > 0 and info["size"] > 0:
        return info["size"] * 8 / info["dur"]
    return 0


def match_audio_kbps(path, floor=96, ceil=256, fallback=192):
    """AAC at the SOURCE's own bitrate, not a fixed 256k.

    Measured on this library: the weekly series ships mp3 at 128 kbps, so a fixed
    -b:a 256k added ~128 kbps for no audible gain - about +10% file size on a
    1.3 Mbps file, which by itself cancels the video savings. AAC is more efficient
    than mp3, so matching the bitrate is already a quality upgrade, never a loss.
    """
    r = run([FFPROBE, "-v", "error", "-select_streams", "a:0",
             "-show_entries", "stream=bit_rate", "-of", "csv=p=0", path], timeout=120)
    try:
        b = int((r.stdout or "").strip().splitlines()[0].split(",")[0])
    except Exception:
        return fallback
    return max(floor, min(ceil, round(b / 1000)))


def src_video_bps(path, info):
    """The SOURCE's video-stream bitrate. Never the file's total: mixing them turned a 109%
    (grow) into a false 86% (shrink) in one analysis, because the total carries the audio."""
    r = run([FFPROBE, "-v", "error", "-select_streams", "v:0", "-show_entries", "stream=bit_rate",
             "-of", "csv=p=0", path], timeout=180)
    try:
        v = int((r.stdout or "").strip().splitlines()[0].split(",")[0])
        if v > 0:
            return v
    except Exception:
        pass
    tot = info["size"] * 8 / info["dur"] if info.get("dur") else 0
    return max(0, int(tot - (info.get("abps") or 0)))


def src_fps(info):
    """transcode.probe() exposes rfps/afps, not `fps`."""
    return info.get("rfps") or info.get("afps") or 0


def bpp_of(info, vbps):
    """bits per pixel per frame: how much fat the source still carries."""
    d = (info.get("w") or 0) * (info.get("h") or 0) * src_fps(info)
    return (vbps / d) if d else 0.0


def tier_for_bpp(b):
    if b < 0.025:
        return "copy"
    return "nvenc" if b <= 0.040 else "x265"


def out_video_bps(path, dur):
    r = run([FFPROBE, "-v", "error", "-select_streams", "v:0", "-show_entries", "stream=bit_rate",
             "-of", "csv=p=0", path], timeout=180)
    try:
        v = int((r.stdout or "").strip().splitlines()[0].split(",")[0])
        if v > 0:
            return v
    except Exception:
        pass
    return int(os.path.getsize(path) * 8 / dur) if dur else 0


def ssim_vs_source(src_local, out_local, info, workdir, tag, dur=SSIM_WINDOW):
    """Per-frame SSIM of a sampled window: the OUTPUT against the SOURCE.

    The comparison is done at 480x270 (a wrong/scaled picture is obvious at that size and the
    decode stays cheap). NB the stats file must be a BARE name inside workdir - a Windows path
    inside `-lavfi` has its backslashes eaten by the filter parser, which silently yields zero
    frames and 0.0000 SSIM.

    Both sides are decoded with `-fps_mode passthrough` so the frame counts are the REAL ones. If
    they differ by more than 1% the source's timeline is irregular (measured on this library: a
    source with a 1.7 s hole - 1459 frames where 1500 belong - while the CFR encode fills it with
    duplicated frames), and a frame-by-frame comparison is *meaningless*: after the hole every
    frame pairs with the wrong one and SSIM collapses to 0.25 while the encode is perfectly good.
    In that case the picture gate is skipped (reported, not silently) and the caller's other
    assertions - structure, full decode, frame count not lower than the source, size ceiling -
    carry the verdict.
    """
    start = max(0.0, (info["dur"] / 2) - dur / 2)
    cmp_scale = "480:270"
    # The raw frame files MUST be per-run: the tiers run side by side (by design - copy is I/O,
    # x265 is CPU, nvenc is the GPU ASIC) and they share this stage directory, so fixed names let
    # two concurrent gates overwrite each other's decodes. Measured: a comparison came out with
    # 100% of frames below 0.85 (a convincing-looking 'systematic defect') that was nothing but two
    # runs writing ssim_ref.yuv at the same time.
    ref = os.path.join(workdir, "ssim_%d_%s_ref.yuv" % (os.getpid(), tag))
    out = os.path.join(workdir, "ssim_%d_%s_out.yuv" % (os.getpid(), tag))
    counts = []
    # Decode WITHOUT an input seek, and cut the window with the trim filter on absolute PTS.
    #
    # Two traps live here, both measured on real files in this library:
    #   1. An input seek snaps to a keyframe, and it snaps to a DIFFERENT keyframe for the source
    #      and for the encode (two 1500-frame decodes whose start times differed by ~10 s), so the
    #      frames met the wrong partners and a good encode scored mean 0.45.
    #   2. Worse, on an H.264 source with open GOPs an input seek decodes the frames after the
    #      landing point differently from a sequential decode: the SAME file compared with itself,
    #      once seeked and once decoded in order, scored min 0.25 / mean 0.82. A seek-based
    #      reference therefore condemns perfectly good encodes.
    # Sequential decoding costs a pass over the file up to the window at 480x270 - small next to the
    # encode it is judging, and it is the only decode that is guaranteed to match what the encoder
    # itself saw.
    vf = ("trim=start=%.3f:end=%.3f,setpts=PTS-STARTPTS,scale=%s:flags=bilinear,format=yuv420p"
          % (start, start + dur, cmp_scale))
    decode_err = None
    for path, dstp in ((src_local, ref), (out_local, out)):
        # Retry once, and KEEP the reason. Measured 2026-10-11: a window decode failed outright on a
        # 53-minute source (the run died 16.7 min in with "FAIL ssim: no frames compared" and the
        # next attempt of the same file passed at 0.9960) - and because this path discarded the
        # ffmpeg stderr, there was nothing to diagnose it with. The retry costs a 480x270 decode;
        # discarding a finished encode over a transient decode does not.
        # NB the stall window is deliberately much longer than an encode's: the trim filter writes
        # NOTHING until the window starts, so a sequential decode of the file's first half is
        # legitimate silence and must not be read as a wedge.
        for attempt in (1, 2):
            r = run_watched([FFMPEG, "-y", "-v", "error", "-i", path,
                             "-map", "0:v:0", "-an", "-vf", vf,
                             "-fps_mode", "passthrough", "-f", "rawvideo", dstp], dstp,
                            stall_s=GATE_STALL_S, timeout=7200)
            if r.returncode == 0 and os.path.exists(dstp) and os.path.getsize(dstp):
                decode_err = None
                break
            decode_err = ("window decode of %s failed (rc=%s, %s): %s"
                          % (os.path.basename(path), r.returncode,
                             "empty output" if not (os.path.exists(dstp) and os.path.getsize(dstp))
                             else "nonzero rc", (r.stderr or "").strip()[-500:]))
            if attempt == 1:
                log("   ! %s - retrying the decode once" % decode_err[:200])
                time.sleep(5)
        if decode_err:
            for f in (ref, out):
                try:
                    os.remove(f)
                except OSError:
                    pass
            return None, None, 0, None, {"decode_error": decode_err}
        counts.append(os.path.getsize(dstp) // (480 * 270 * 3 // 2))
    n_src, n_out = counts
    if n_src and abs(n_out - n_src) / float(n_src) > 0.01:
        for f in (ref, out):
            try:
                os.remove(f)
            except OSError:
                pass
        return None, None, 0, ("source timeline irregular: %d frames vs %d in the sampled window "
                               "(%.1f%% difference) - the CFR encode fills the source's holes, so a "
                               "frame-by-frame comparison is not applicable" % (n_src, n_out,
                                                                               100.0 * (n_out - n_src) / n_src)), {}
    try:
        subprocess.run([FFMPEG, "-y", "-v", "error", "-f", "rawvideo", "-pix_fmt", "yuv420p", "-s", cmp_scale,
                        "-i", ref, "-f", "rawvideo", "-pix_fmt", "yuv420p", "-s", cmp_scale, "-i", out,
                        "-lavfi", "ssim=stats_file=ssim_%s.log" % tag, "-f", "null", "-"],
                       capture_output=True, cwd=workdir, timeout=900,
                       creationflags=NOWIN)
    except subprocess.TimeoutExpired:
        # A wedged ffmpeg must not hang the item forever: without this the lane would sit on a dead
        # filtergraph until a human noticed (measured outside the engine 2026-10-11: a stalled
        # helper burned 4500 s of CPU over an hour and nobody was watching).
        log("   ! ssim filter timed out after 900 s - no picture verdict from this attempt")
        decode_err = "ssim filter timed out after 900 s"
    vals = []
    p = os.path.join(workdir, "ssim_%s.log" % tag)
    if os.path.exists(p):
        with open(p, encoding="utf-8", errors="replace") as fh:
            for line in fh:
                m = re.search(r"All:([0-9.]+)", line)
                if m:
                    vals.append(float(m.group(1)))
    n = len(vals)
    # SSIM is meaningless on a nearly flat frame: two almost-black frames of a fade scored 0.25
    # while their neighbours scored 0.998, so a MINIMUM over every frame condemns good encodes.
    # Measure the source frames' flatness and drop them from the verdict (reported, not hidden).
    flat = set()
    try:
        flat = _flat_frames(ref, n)
    except Exception as e:  # numpy missing / unreadable raw: fall back to using every frame
        log("   ! flat-frame scan skipped: %s" % e)
    if flat and len(flat) < n * 0.5:
        vals = [v for i, v in enumerate(vals) if i not in flat]
        log("   %d near-flat source frame(s) excluded from the picture verdict (SSIM is "
            "meaningless on them)" % len(flat))
    n = len(vals)
    lo = min(vals) if vals else None
    mean = (sum(vals) / len(vals)) if vals else None
    bad = sum(1 for v in vals if v < BAD_FRAME_SSIM)
    stats = {"below": bad, "flat": len(flat), "total": n}
    if decode_err:
        # carry the reason out: `process()` puts it in the FAIL message so a gate that could not run
        # is diagnosable instead of a bare "no frames compared"
        stats["decode_error"] = decode_err
    note = None
    # If the direct pairing looks bad, try to EXPLAIN the mismatch as a timeline offset before
    # condemning the file: a source whose timeline drifts (or had a hole earlier) makes the encode
    # lag it by a fixed number of frames, and a wrong-picture defect can NOT be fixed by any single
    # shift. Requiring a good score at some offset is therefore a sound discriminator.
    #
    # Three stages, cheapest first, and the note says which one carried the verdict:
    #   1. fine, STEP 1 over +-ALIGN_FINE - the measured failure mode (a cfr duplicate displaces the
    #      whole window by exactly one frame; a step-10 sweep cannot see it);
    #   2. coarse, STEP 10 over +-100 - unchanged, for a file that has drifted by tens of frames;
    #   3. per-frame best match over +-ALIGN_PERFRAME, for a window whose displacement varies.
    used_off = 0            # the alignment the VMAF observation below is measured at
    if n and (lo is None or lo < SSIM_TARGET or mean is None or mean < SSIM_MEAN_MIN):
        best = None
        nf = min(n, 1200)
        pid = os.getpid()          # two lanes share the stage dir: a fixed tag let them overwrite
        for stage, offs in (("fine", range(-ALIGN_FINE, ALIGN_FINE + 1)),
                            ("coarse", range(-100, 101, 10))):
            for off in offs:
                if off == 0:
                    continue
                mn, mm, k = _paired_ssim(ref, out, off, nf, workdir, "%d%s%d" % (pid, stage, abs(off)))
                if mn is not None and (best is None or mn > best[0]):
                    best = (mn, mm, k, off, stage)
            if best and best[0] >= 0.90 and best[1] >= 0.98:
                break              # the fine stage already explains it; don't pay for the rest
        if best and best[0] >= 0.90 and best[1] >= 0.98:
            # NB this is INFORMATION, not a reason to skip the verdict: it goes into stats (the
            # caller logs it and still applies the mean / frame-share bars at these aligned
            # numbers). The 4th return value stays reserved for the one case where a frame-by-frame
            # comparison genuinely cannot be made (an irregular source timeline), because that is
            # the only case where the caller must fall back to structure/decode/size alone.
            stats["align_note"] = ("timeline offset of %+d frames between source and encode "
                                   "(%s search) - pictures verified at that alignment"
                                   % (best[3], best[4]))
            lo, mean, n = best[0], best[1], best[2]
            used_off = best[3]
        else:
            per = _perframe_best(ref, out, nf, workdir, "%d" % pid)
            if per and per[1] >= 0.90 and per[2] >= 0.98:
                stats["align_note"] = ("per-frame best match (+-%d frames) - displacement varies "
                                       "inside the window" % ALIGN_PERFRAME)
                lo, mean, n = per[1], per[2], per[0]
            else:
                log("   no alignment explains the mismatch (best constant offset %s,"
                    " per-frame best-match %s) - keeping the direct-pairing verdict"
                    % (("min %.4f" % best[0]) if best else "none",
                       ("min %.4f mean %.4f" % (per[1], per[2])) if per else "none"))
    if VMAF_OBSERVE and n:
        # An observation, never a verdict - if it cannot be computed the item is judged without it.
        stats["vmaf"] = vmaf_of_pair(ref, out, used_off, min(n, 1200), workdir, "%d" % os.getpid())
    for f in (ref, out):
        try:
            os.remove(f)
        except OSError:
            pass
    return lo, mean, n, note, stats


def _copy_frames(src, dst, start_frame, nframes, fs=480 * 270 * 3 // 2, chunk=48):
    """Copy `nframes` frames from `start_frame` of a raw 480x270 yuv420p file into `dst`.

    Chunked on purpose: a 1200-frame slice is ~233 MB, and this host has thrown MemoryError on a
    single read that size while the lanes were running.
    """
    left = nframes * fs
    with open(src, "rb") as f, open(dst, "wb") as g:
        f.seek(start_frame * fs)
        while left > 0:
            b = f.read(min(left, chunk * fs))
            if not b:
                break
            g.write(b)
            left -= len(b)
    return nframes * fs - left


def _ssim_series(ref_raw, out_raw, off, nf, workdir, tag):
    """Per-frame SSIM of `out_raw` against `ref_raw` displaced by `off` frames.

    BOTH directions are real. The previous version only ever advanced the *reference*
    (`f.seek(max(0, off) * fs)`) and read the output from frame 0, so every negative offset scored
    exactly the same as 0: the negative half of the search was a no-op, and a "verified at -100
    frames" note in the log was really the unshifted pairing again (measured 2026-10-11).
    A positive `off` = the reference is ahead (the output lags it); negative = the output is ahead.
    """
    fs = 480 * 270 * 3 // 2
    k = nf - abs(off)
    if k < 1:
        return []
    pa = os.path.join(workdir, "pair_a_%s.yuv" % tag)
    pb = os.path.join(workdir, "pair_b_%s.yuv" % tag)
    _copy_frames(ref_raw, pa, max(0, off), k, fs)
    _copy_frames(out_raw, pb, max(0, -off), k, fs)
    log = os.path.join(workdir, "pair_%s.log" % tag)
    try:
        subprocess.run([FFMPEG, "-y", "-v", "error", "-f", "rawvideo", "-pix_fmt", "yuv420p", "-s", "480:270",
                        "-i", pa, "-f", "rawvideo", "-pix_fmt", "yuv420p", "-s", "480:270", "-i", pb,
                        "-lavfi", "ssim=stats_file=%s" % os.path.basename(log), "-f", "null", "-"],
                       capture_output=True, cwd=workdir, timeout=900,
                       creationflags=NOWIN)
    except subprocess.TimeoutExpired:
        # one offset that cannot be scored is data we do not have - never a hang and never a verdict
        log("   ! pair ssim at off %+d timed out after 900 s - skipping this offset" % off)
        for f in (pa, pb):
            try:
                os.remove(f)
            except OSError:
                pass
        return []
    vals = []
    if os.path.exists(log):
        with open(log, encoding="utf-8", errors="replace") as fh:
            for line in fh:
                m = re.search(r"All:([0-9.]+)", line)
                if m:
                    vals.append(float(m.group(1)))
    for f in (pa, pb, log):
        # the stats log goes too: the alignment search writes one per offset (13 for the fine stage
        # alone) and nothing prunes them, so a full pass over the library would leave tens of
        # thousands of 80 KB files behind. The verdict is already in the run log.
        try:
            os.remove(f)
        except OSError:
            pass
    return vals


def vmaf_of_pair(ref_raw, out_raw, off, nf, workdir, tag):
    """VMAF of the output window against the source window at the alignment the SSIM search found.

    Observe-only (see VMAF_OBSERVE). libvmaf takes the DISTORTED stream first and the reference
    second; both sides are sliced out of the window's raw frames so the number is measured at exactly
    the alignment the SSIM verdict used - VMAF on misaligned frames reads 75-87 for a healthy encode
    (measured), so measuring at offset 0 unconditionally would produce noise, not evidence.
    Never raises into the gate: a VMAF that cannot be computed is an absent observation.
    """
    fs = 480 * 270 * 3 // 2
    k = nf - abs(off)
    if k < 1:
        return None
    pa = os.path.join(workdir, "vmaf_a_%s.yuv" % tag)      # reference (source)
    pb = os.path.join(workdir, "vmaf_b_%s.yuv" % tag)      # distorted (the encode)
    log = os.path.join(workdir, "vmaf_%s.json" % tag)
    raw = ["-f", "rawvideo", "-pix_fmt", "yuv420p", "-s", "480:270", "-framerate", "25"]
    try:
        _copy_frames(ref_raw, pa, max(0, off), k, fs)
        _copy_frames(out_raw, pb, max(0, -off), k, fs)
        subprocess.run([FFMPEG, "-y", "-v", "error"] + raw + ["-i", pb] + raw + ["-i", pa,
                        "-lavfi", "libvmaf=log_path=%s:log_fmt=json" % os.path.basename(log),
                        "-f", "null", "-"], capture_output=True, cwd=workdir, timeout=900,
                       creationflags=NOWIN)
        with open(log, encoding="utf-8", errors="replace") as fh:
            m = json.load(fh)["pooled_metrics"]["vmaf"]
        return {"mean": float(m["mean"]), "min": float(m["min"]), "frames": k}
        # SCALE MATTERS: this is a 480x270 comparison because that is the window the SSIM gate
        # already decoded. Measured on one item (危机领导力, aligned): 480p reads mean 98.27 /
        # min 96.97 where the SAME window at native resolution reads 95.85 / 93.76 - i.e. +2.4 /
        # +3.2 points. So the number is reported as `vmaf480`, and a bar picked from it is a 480p
        # bar. Native-scale calibration is the separate one-off run (plan 2.4, item 2).
    except Exception as e:                                  # noqa: BLE001
        log("   vmaf observation unavailable: %s" % str(e)[:160])
        return None
    finally:
        for f in (pa, pb, log):
            try:
                os.remove(f)
            except OSError:
                pass


def _paired_ssim(ref_raw, out_raw, off, nf, workdir, tag):
    """(min, mean, frames) for one constant offset - see `_ssim_series` for the sign convention."""
    vals = _ssim_series(ref_raw, out_raw, off, nf, workdir, tag)
    return (min(vals), sum(vals) / len(vals), len(vals)) if vals else (None, None, 0)


def _perframe_best(ref_raw, out_raw, nf, workdir, tag):
    """(frames, min, mean) where each frame scores against the best of its +-ALIGN_PERFRAME
    neighbours.

    For a window whose displacement is not one constant shift. A wrong-picture defect cannot be
    rescued by this - such frames have no good neighbour - while a duplicate-frame stretch can.
    """
    per = {}
    for off in range(-ALIGN_PERFRAME, ALIGN_PERFRAME + 1):
        vals = _ssim_series(ref_raw, out_raw, off, nf, workdir, "%sp%+d" % (tag, off))
        base = max(0, off)
        for i, v in enumerate(vals):
            j = base + i
            if v > per.get(j, -1.0):
                per[j] = v
    if not per:
        return None
    s = [per[k] for k in sorted(per)]
    return len(s), min(s), sum(s) / len(s)


def pin_to_e_cores():
    """x265 tiers: keep the P-cores free for the desktop (measured 3.51x vs 4.37x realtime)."""
    try:
        ctypes.windll.kernel32.SetProcessAffinityMask(
            ctypes.windll.kernel32.GetCurrentProcess(), ctypes.c_size_t(E_CORE_MASK))
        return True
    except Exception:
        return False


def encode(src_local, dst_local, info, args, tier, vbps, q_off=0):
    cmd = [FFMPEG, "-y", "-hide_banner", "-loglevel", "warning", "-stats",
           "-i", src_local, "-map", "0:v:0", "-map", "0:a:0?", "-map_metadata", "0"]
    if tier == "copy":
        # Nothing to win: the video is copied bit-for-bit, which is the strongest possible
        # answer to "same picture quality" and the smallest file that still plays everywhere.
        cmd += ["-c:v", "copy"]
    elif tier == "nvenc":
        cmd += ["-c:v", "hevc_nvenc", "-preset", args.nvenc_preset, "-tune", "hq", "-rc", "vbr",
                "-cq", str(max(1, args.cq - q_off)), "-b:v", "0",
                # efficiency knobs verified accepted by this build (multipass 2pass-full and
                # weighted_pred are REJECTED here)
                "-spatial-aq", "1", "-temporal-aq", "1", "-rc-lookahead", "32",
                "-b_ref_mode", "middle", "-bf", "4", "-g", "240"]
    else:
        cmd += ["-c:v", "libx265", "-preset", args.x265_preset, "-crf", str(max(1, args.crf - q_off)),
                "-x265-params", "pools=%d" % args.pools]
    if tier != "copy" and vbps > 0:
        # Hard ceiling at the source's own video bitrate: the output physically cannot grow.
        cmd += ["-maxrate", str(int(vbps * SIZE_CEIL)), "-bufsize", str(int(vbps * SIZE_CEIL * 2.5))]
    if tier != "copy":
        cmd += ["-profile:v", "main", "-pix_fmt", "yuv420p", "-tag:v", "hvc1", "-fps_mode", "cfr"]
    if info["acodec"] in ("aac", "mp4a", ""):
        cmd += ["-c:a", "copy"]
    else:
        # AAC at the SOURCE's own bitrate: a fixed 256k added ~128 kbps for no audible gain on
        # this library's 128k mp3 sources, which by itself cancelled the video saving.
        abr = args.audio or ("%dk" % match_audio_kbps(src_local))
        cmd += ["-c:a", "aac", "-b:a", abr, "-ac", "2"]
    cmd += ["-movflags", "+faststart", dst_local]
    t0 = time.time()
    r = run_watched(cmd, dst_local)
    return r, time.time() - t0



def decode_check(path):
    """Full decode pass. The only check that proves the payload is not truncated/corrupt."""
    r = run([FFMPEG, "-v", "error", "-i", path, "-f", "null", "-"], timeout=14400)
    return r.returncode == 0, (r.stderr or "").strip()[:300]


# ---------------------------------------------------------------- per file

def dst_path_for(src):
    """In-place: the SAME name for an existing .mp4/.MP4 (the share is case-sensitive),
    <stem>.mp4 for anything else."""
    if os.path.splitext(src)[1].lower() == ".mp4":
        return src
    return os.path.splitext(src)[0] + ".mp4"


def already_hevc(src, info):
    """Self-describing resume test: the share copy is already HEVC hvc1 and matches."""
    if info["vcodec"] != "hevc" or info["tag"] != "hvc1":
        return False
    return True


def process(src, args, dest=None, origin=None):
    info = probe(src)
    if not info:
        return "FAIL unreadable", None
    if info["dur"] < 1.0:
        return "FAIL stub (%.1fs) - needs a re-download, not a transcode" % info["dur"], None
    live = dest or dst_path_for(src)
    redo_playable = False    # True once we know this run is re-doing a file that ALREADY plays

    if info["vcodec"] == "hevc" and info["tag"] == "hvc1" and info["pix"] in ("yuv420p",) \
            and not T.unusable_timeline(info, src)[0]:
        # Already converted. Only worth touching if the ORIGINAL is available and the current
        # file is BIGGER than it: that is precisely the old settings' damage (a fixed cq27 above
        # the source's own quality plus a fixed 256k audio). A file that is already smaller than
        # its original is left alone, which makes the whole run naturally idempotent.
        if not (origin and os.path.exists(origin)):
            return "SKIP already HEVC hvc1", None
        o_size = os.path.getsize(origin)
        if info["size"] <= o_size * 0.99:
            return "SKIP already HEVC hvc1 (%.0f MB <= original %.0f MB)" % (
                info["size"] / 1e6, o_size / 1e6), None
        log("   re-doing from the original: live %.0f MB > original %.0f MB" % (
            info["size"] / 1e6, o_size / 1e6))
        # A re-do replaces a file that already plays on iPad + Android; its only purpose is to
        # reclaim the old settings' bloat, so it earns the relaxed mean bar (owner decision,
        # SSIM_MEAN_MIN_REDO) - but only when the live file really is playable end to end
        # (HEVC hvc1 video, which the branch above guarantees, plus AAC audio).
        redo_playable = info["acodec"] in ("aac", "mp4a")
        if not redo_playable:
            log("   re-do of a file whose audio is %s (not playable) - the normal bar applies"
                % (info["acodec"] or "none"))
        src, info = origin, probe(origin)
        if not info:
            return "FAIL original unreadable", None

    # ---- policy: classify the source, then work only on the requested tier (if any) ----------
    vbps = src_video_bps(src, info)
    bpp = bpp_of(info, vbps)
    tier = tier_for_bpp(bpp)
    forced = getattr(args, "force_tier", None)
    if forced:
        # An explicit override, but never a silent one, and never one that breaks playability:
        #   * copy on a VP9/AV1 source would ship an MP4 whose video iOS cannot decode;
        #   * a re-encode of a file that already plays (HEVC hvc1) is the `--overwrite` decision.
        if forced == "copy" and info["vcodec"] not in ("h264", "avc1", "hevc"):
            return "SKIP force-tier copy refused: %s source cannot play on iOS" % info["vcodec"], None
        if forced != "copy" and info["vcodec"] == "hevc" and info["tag"] == "hvc1"                 and not T.unusable_timeline(info, src)[0]:
            return "SKIP force-tier re-encode refused: already HEVC hvc1 (use --overwrite)", None
        log("   force-tier %s (bpp rule said %s)" % (forced, tier))
        tier = forced
    elif args.tier and args.tier != tier:
        return "SKIP classified %s (run wants %s)" % (tier, args.tier), None
    expect_vc = "hevc" if tier != "copy" else (info["vcodec"] or "h264")
    log("   tier=%s bpp=%.4f src_video=%.0f kbps %sx%s@%.0f %s" % (
        tier, bpp, vbps / 1000, info["w"], info["h"], src_fps(info), os.path.basename(src)[:46]))

    os.makedirs(STAGE, exist_ok=True)
    tag = hashlib.sha1(src.encode("utf-8")).hexdigest()[:12]
    loc_src = os.path.join(STAGE, tag + "_src" + os.path.splitext(src)[1].lower())
    loc_out = os.path.join(STAGE, tag + "_out.mp4")
    remote_tmp = live + ".new.mp4"
    for p in (loc_src, loc_out):
        if os.path.exists(p):
            os.remove(p)
    origin_used = bool(origin and os.path.abspath(src) == os.path.abspath(origin))
    try:
        if os.path.exists(remote_tmp):
            os.remove(remote_tmp)

        # 1. fetch the source to local disk
        n_in = copy_remote_to_local(src, loc_src, expect_size=info["size"] or None)
        # 2. encode (with a bounded quality ladder: if the sampled window cannot clear the SSIM
        #    bar at the tier's default setting, raise the quality and try once more)
        attempt, q_off, el = 0, 0, 0.0
        while True:
            attempt += 1
            r, el = encode(loc_src, loc_out, info, args, tier, vbps, q_off)
            if r.returncode != 0 or not os.path.exists(loc_out):
                return "FAIL ffmpeg rc=%s %s" % (r.returncode, (r.stderr or "").strip()[-300:]), None
            # 3. verify the LOCAL output (structural + full decode)
            ok, msg = T.verify(info, loc_out, expect_vc, "aac", check_decode=False)
            if not ok:
                return "FAIL verify: %s" % msg, None
            if DECODE_CHECK and not args.no_decode_check:
                ok, msg = decode_check(loc_out)
                if not ok:
                    return "FAIL decode pass: %s" % msg, None
            # 3b. the two policy gates that make "same look, never bigger" a fact and not a hope:
            #     a per-frame SSIM of a sampled window against the source, and a hard assertion
            #     that the output video bitrate did not exceed the source's.
            ssim_note, growth = "copy (video bit-identical)", 100.0
            if tier != "copy":
                lo, mean, nfr, irreg, sstat = ssim_vs_source(loc_src, loc_out, info, STAGE, tag)
                obps = out_video_bps(loc_out, info["dur"])
                growth = 100.0 * obps / vbps if vbps else 0.0
                if irreg:
                    # The source's timeline is irregular: frame pairing is meaningless, so there is
                    # no picture verdict to apply. Reported, not swallowed, and the other gates
                    # (structure, full decode, frame count, size ceiling) still carry the item.
                    ssim_note = irreg
                    log("   NOTE: %s" % ssim_note)
                    if vbps and obps > vbps * SIZE_CEIL:
                        return "FAIL size: output %.0f kbps > source %.0f kbps (%.1f%%)" % (
                            obps / 1000, vbps / 1000, growth), None
                    break
                if not nfr:
                    derr = (sstat or {}).get("decode_error")
                    return "FAIL ssim: no frames compared%s" % (
                        " - " + derr[:300] if derr else ""), None
                ssim_note = "ssim min %.4f mean %.4f (%d frames)%s" % (
                    lo, mean, nfr, "" if not q_off else " at quality+%d" % q_off)
                if (sstat or {}).get("align_note"):
                    # Information only - the bars below are applied AT THESE ALIGNED NUMBERS. This
                    # used to arrive in the `irreg` slot and therefore skip the whole picture verdict
                    # (measured 2026-10-11: the canary and two x265 items were accepted that way
                    # with the mean bar never enforced at all).
                    log("   NOTE: %s" % sstat["align_note"])
                    ssim_note += " ; " + sstat["align_note"]
                if (sstat or {}).get("vmaf"):
                    v = sstat["vmaf"]
                    log("   vmaf480 (observe-only, no verdict): mean %.2f min %.2f (%d frames)"
                        % (v["mean"], v["min"], v["frames"]))
                    ssim_note += " ; vmaf480 mean %.2f min %.2f (observe-only)" % (v["mean"], v["min"])
                # The verdict is a DEFECT SHAPE, not a single frame. A systematic mismatch drops the
                # mean and puts a real share of frames below the floor; a handful of scattered low
                # frames at a healthy mean is what fades, black frames and hard cuts do to SSIM.
                # Measured on this library: good encodes 0 of 1500 frames below 0.95; the file that
                # triggered this rule 5 of 1500 below 0.85 (0.33%) at 0.98 mean; the genuine
                # decoder-defect files 44 of 1499 (2.9%) with the mean falling too.
                # The MEAN bar is 0.975 instead of 0.98 when this is a re-do of a file that already
                # plays (SSIM_MEAN_MIN_REDO) - the frame-share test below is unchanged and is what
                # actually catches a defect.
                bad_share = (sstat.get("below", 0) / float(nfr)) if nfr else 0.0
                mean_min = SSIM_MEAN_MIN_REDO if redo_playable else SSIM_MEAN_MIN
                # Owner decision 2026-10-11: the accept list releases an item from the FIRST tier to
                # the SECOND (a mean bar of 0.990) - it used to switch the mean test off entirely, so
                # an approved file could be filed at any mean whatsoever. The frame-share test is
                # still the verdict that actually catches a defect, and it applies to every item.
                approved = disp(src) in POLICY_CACHE["accept"]
                if approved and mean_min > SSIM_MEAN_MIN_FALLBACK:
                    log("   owner-released item: mean bar is the second tier %.3f (normal bar %.3f)"
                        % (SSIM_MEAN_MIN_FALLBACK, mean_min))
                    mean_min = SSIM_MEAN_MIN_FALLBACK
                systematic = bad_share > MAX_BAD_SHARE or (
                    mean is not None and mean < mean_min)
                if systematic:
                    if q_off < QUALITY_STEPS and (attempt == 1):
                        q_off = QUALITY_STEPS
                        log("   quality gate: mean %.4f < bar %.3f, %d of %d frames below %.2f "
                            "(%.2f%%) - retrying at quality+%d" % (
                                mean, mean_min, sstat.get("below", 0), nfr,
                                BAD_FRAME_SSIM, 100.0 * bad_share, q_off))
                        continue
                    return ("FAIL quality: %s - systematic: mean %.4f < bar %.3f, %.2f%% of frames "
                            "below %.2f%s"
                            % (ssim_note, mean, mean_min, 100.0 * bad_share, BAD_FRAME_SSIM,
                               " (re-do of an already playable file)" if redo_playable else "")), None
                if lo is not None and lo < SSIM_TARGET:
                    log("   %d scattered frame(s) below %.2f (%.2f%% of the window) with a healthy "
                        "mean - treated as fades/black, not a defect"
                        % (sstat.get("below", 0), BAD_FRAME_SSIM, 100.0 * bad_share))
                if vbps and obps > vbps * SIZE_CEIL:
                    return "FAIL size: output %.0f kbps > source %.0f kbps (%.1f%%)" % (
                        obps / 1000, vbps / 1000, growth), None
                log("   %s  %.1f%% of source video" % (ssim_note, growth))
            break
        # 4. upload under a temp name
        if args.keep_local:
            return "ok", {"sha256": "", "bytes": os.path.getsize(loc_out), "src_bytes": n_in,
                          "src_mb": round(info["size"] / 1e6, 1),
                          "out_mb": round(os.path.getsize(loc_out) / 1e6, 1),
                          "ratio": round(100.0 * os.path.getsize(loc_out) / max(info["size"], 1), 1),
                          "tier": tier, "bpp": round(bpp, 4), "video_pct": round(growth, 1),
                          "ssim": ssim_note + " [LOCAL ONLY - not uploaded]", "encode_s": round(el, 1)}
        # 4-5. upload under a temp name, then read the share copy back and compare.
        # The read-back is not ceremony: RaiDrive can return from a write with NO error while the
        # remote file is a fraction of the local one (measured: 12.5 MB of 403 MB), and its own
        # "operation didn't complete within specific time limit" toast arrives afterwards. So a
        # mismatch is retried rather than reported straight away.
        h_loc, n_loc = _sha_local(loc_out)
        last = ""
        for up in range(1, 3):
            if not copy_local_to_remote(loc_out, remote_tmp):
                last = "FAIL upload"
                time.sleep(10 * up)
                continue
            h_rem, n_rem = _sha_remote(remote_tmp)
            if (h_loc, n_loc) == (h_rem, n_rem):
                break
            last = "FAIL read-back mismatch local=%s/%d remote=%s/%d" % (
                h_loc[:12], n_loc, h_rem[:12], n_rem)
            log("   ! %s (upload %d) - retrying" % (last, up))
            try:
                os.remove(remote_tmp)
            except (OSError, MemoryError):
                pass
            time.sleep(10 * up)
        else:
            return last, None
        # 6. atomic replace, then confirm on the share
        os.replace(remote_tmp, live)
        # NEVER delete the source when it came from the snapshot origin: that is the archive of
        # the originals, and removing it would destroy the only clean copy of the library.
        if not origin_used and not getattr(args, "keep_source", False) \
                and os.path.abspath(live) != os.path.abspath(src):
            os.remove(src)
        back = probe(live)
        tag_needed = (tier != "copy")
        if not back or back["vcodec"] != expect_vc \
                or (tag_needed and back["tag"] != "hvc1") \
                or abs(back["dur"] - info["dur"]) > max(1.0, info["dur"] * 0.01):
            return "FAIL read-back probe: %s" % (back and (back["vcodec"], back["tag"], back["dur"]),), None
        ok, msg = probe_ok(live, info, expect_vc)
        if not ok:
            return "FAIL post-replace gate on share: %s" % msg, None
        # Metadata can lie on this share. RaiDrive/Dokan serves CACHED attributes, and a rename did
        # not actually land for one file while every metadata probe insisted it had: the run
        # reported "ok 1085 MB -> 478 MB" and the live file was still the H.264 original afterwards,
        # with nothing anywhere reporting an error. So read the installed file back and compare its
        # hash with what we encoded - the only check that cannot be served from a cache.
        try:
            h_back, n_back = _sha_remote(live)
        except OSError as e:
            return "FAIL install verify: cannot read the installed file back: %s" % e, None
        if (h_back, n_back) != (h_loc, n_loc):
            return ("FAIL install verify: the live file is NOT the encode we made "
                    "(live %s/%d bytes vs ours %s/%d) - the replace did not land"
                    % (h_back[:12], n_back, h_loc[:12], n_loc)), None
        return "ok", {"sha256": h_loc, "bytes": n_loc, "src_bytes": n_in,
                      "src_mb": round(info["size"] / 1e6, 1),
                      "out_mb": round(n_loc / 1e6, 1),
                      "ratio": round(100.0 * n_loc / max(info["size"], 1), 1),
                      "tier": tier, "bpp": round(bpp, 4), "video_pct": round(growth, 1),
                      "ssim": ssim_note, "encode_s": round(el, 1)}
    finally:
        for p in (loc_src, loc_out):
            try:
                if os.path.exists(p):
                    os.remove(p)
            except OSError:
                pass


def collect(root):
    out = []
    for dp, _, fn in os.walk(root):
        for f in fn:
            if os.path.splitext(f)[1].lower() in VIDEO_EXT and ".part." not in f \
                    and "_src" not in f and ".new." not in f:
                out.append(os.path.join(dp, f))
    return sorted(out)


def main():
    global DECODE_CHECK
    ap = argparse.ArgumentParser()
    ap.add_argument("--cq", type=int, default=CQ_NVENC, help="nvenc tier quality (measured default 30)")
    ap.add_argument("--crf", type=int, default=CRF_X265, help="x265 tier quality (measured default 24)")
    ap.add_argument("--x265-preset", default=X265_PRESET)
    ap.add_argument("--pools", type=int, default=X265_POOLS, help="x265 threads (match the E-core mask)")
    ap.add_argument("--tier", choices=["copy", "nvenc", "x265"],
                    help="only touch files classified into this tier (run tiers separately)")
    ap.add_argument("--force-tier", choices=["copy", "nvenc", "x265"], default=None,
                    help="override the bpp classification for this run instead of skipping the "
                         "file (the control plane needs it: an owner decision can say a LEAN "
                         "source is still worth re-encoding, and `--tier x265` would otherwise "
                         "refuse every lean file it disagrees about). Two guards stay in place: "
                         "copy is refused for a source iOS cannot play (VP9/AV1), and a re-encode "
                         "is refused for a file that is already HEVC hvc1.")
    ap.add_argument("--origin-root", default=None,
                    help="tree holding the PRE-CONVERSION originals (e.g. a snapshot); a file that "
                         "is already HEVC and BIGGER than its original is re-done from that "
                         "original, and the original is never modified or deleted")
    ap.add_argument("--audio", default=None,
                    help="audio bitrate; default = the SOURCE's own bitrate (never a fixed 256k)")
    ap.add_argument("--nvenc-preset", default=NVENC_PRESET)
    ap.add_argument("--limit", type=int, default=0)
    ap.add_argument("--only", default=None, help="substring filter")
    ap.add_argument("--path", default=None,
                    help="convert this ONE file instead of the library tree (its tier is still "
                         "chosen by the same bpp rule); pair with --dest to install it elsewhere")
    ap.add_argument("--dest", default=None,
                    help="install the result at this exact path (default: next to the source)")
    ap.add_argument("--keep-source", action="store_true",
                    help="never delete the source file after a verified install")
    ap.add_argument("--reverse", action="store_true")
    ap.add_argument("--dry-run", action="store_true")
    ap.add_argument("--no-decode-check", action="store_true")
    ap.add_argument("--overwrite", action="store_true", help="re-do files already HEVC")
    ap.add_argument("--keep-local", action="store_true",
                    help="pilot mode: encode + verify + gate locally and report the numbers, then "
                         "THROW THE OUTPUT AWAY - nothing is uploaded and nothing is replaced")
    args = ap.parse_args()
    DECODE_CHECK = not args.no_decode_check

    os.makedirs(STAGE, exist_ok=True)
    if args.path:
        files = [args.path]
        if not os.path.exists(args.path):
            log("!!! no such file: %s" % args.path)
            return
    else:
        files = collect(ROOT)
    if args.only:
        files = [f for f in files if args.only in f]
    if args.reverse:
        files = list(reversed(files))
    if args.limit:
        files = files[:args.limit]
    if args.tier == "x265":
        # x265 is CPU: pin it to the E-cores so the P-cores stay free (children inherit the mask).
        log("=== E-core pinning: %s" % ("on" if pin_to_e_cores() else "FAILED (running unpinned)"))
    # One lock PER TIER, not one global lock: the copy tier uses no encoder, the x265 tier is CPU
    # and the nvenc tier is the GPU ASIC, so they are safe to run side by side whereas two runs of
    # the same tier would race on dst and starve a shared unit.
    lockf = os.path.join(WORK, "run-%s.lock" % (args.tier or ("single" if args.path else "all")))
    log("=== %d file(s)  tier=%s cq=%d crf=%d audio=%s decode_check=%s lock=%s" %
        (len(files), args.tier or "auto", args.cq, args.crf, args.audio or "source-matched",
         DECODE_CHECK, os.path.basename(lockf)))

    if args.dry_run:
        plan = {}
        for f in files:
            info = probe(f)
            if not info:
                log("PLAN %s -> UNREADABLE" % disp(f))
                continue
            vbps = src_video_bps(f, info)
            b = bpp_of(info, vbps)
            t = tier_for_bpp(b)
            plan[t] = plan.get(t, 0) + 1
            log("PLAN %-5s bpp=%.4f %sx%s@%.0f %6.0f kbps %7.1f MB %s" % (
                t, b, info["w"], info["h"], src_fps(info), vbps / 1000, info["size"] / 1e6,
                disp(f)[:60]))
        log("=== plan: %s" % plan)
        return

    POLICY_CACHE.update(load_policy())      # pick up an edited gate_policy.json between runs
    with T.Lock(lockf):
        stats = {"ok": 0, "skip": 0, "fail": 0}
        ledger = open(LEDGER, "a", encoding="utf-8")
        for i, f in enumerate(files, 1):
            free = shutil.disk_usage(STAGE).free / 2 ** 30
            if free < 8:
                log("!!! ABORT: only %.1f GB free on C: - stopping" % free)
                break
            log("--- %d/%d %s" % (i, len(files), disp(f)))
            t0 = time.time()
            origin = None
            parked = POLICY_CACHE["park"].get(disp(f), 0)
            if parked >= PARK_AFTER:
                # Parked: it has failed this many quality rounds already and every further attempt
                # costs an encode (plus its quality+2 retry) without ever converting. Recorded as a
                # SKIP so it is visible, not silent; clear its entry in gate_policy.json to retry.
                status = ("SKIP parked: %d quality round(s) already failed - not re-encoding "
                          "(clear the entry in %s to retry)" % (parked, os.path.basename(POLICY)))
                extra = None
            else:
                if args.origin_root:
                    try:
                        cand = os.path.join(args.origin_root, os.path.relpath(f, ROOT))
                    except ValueError:
                        cand = None
                    origin = cand if cand and os.path.exists(cand) else None
                try:
                    status, extra = process(f, args, dest=args.dest or dst_path_for(f), origin=origin)
                except Exception as e:
                    status, extra = "FAIL %s: %s" % (type(e).__name__, e), None
                    # Any failure raised out of process() may leave the staged upload target on the
                    # share. Measured 2026-10-09: the host ran out of memory/commit while installing
                    # the largest output of the batch, `MemoryError` came out of a Dokan write, and
                    # the complete 493 MB `.new.mp4` stayed next to the live file (8 such orphans had
                    # piled up). Delete it unconditionally - a metadata check on this share can serve
                    # a stale answer, so "not found" is the only outcome that is ignored.
                    try:
                        staged = (args.dest or dst_path_for(f)) + ".new.mp4"
                        os.remove(staged)
                        log("   ! removed the orphaned staging file %s" % staged)
                    except FileNotFoundError:
                        pass
                    except (OSError, MemoryError) as ex:
                        log("   ! could not remove the staging file: %s" % ex)
            el = time.time() - t0
            if status == "ok":
                stats["ok"] += 1
                log("   ok %.0f MB -> %.0f MB (%.0f%%) video %.1f%% enc %.0fs tot %.0fs | %s | %s" % (
                    extra["src_mb"], extra["out_mb"], extra["ratio"], extra["video_pct"],
                    extra["encode_s"], el, extra["tier"], extra["ssim"]))
            elif status.startswith("SKIP"):
                stats["skip"] += 1
                log("   %s" % status)
            else:
                stats["fail"] += 1
                log("   !! %s" % status)
                if status.startswith("FAIL quality"):
                    # Count the round so a repeat offender stops consuming the encoder. The counter
                    # is persisted: without it every pass re-encoded the same eight items forever.
                    k = disp(f)
                    POLICY_CACHE["park"][k] = POLICY_CACHE["park"].get(k, 0) + 1
                    save_policy(POLICY_CACHE)
                    log("   -> quality round %d/%d failed for this item%s"
                        % (POLICY_CACHE["park"][k], PARK_AFTER,
                           (" - PARKED, skipped from now on (clear its entry in %s)"
                            % os.path.basename(POLICY))
                           if POLICY_CACHE["park"][k] >= PARK_AFTER else ""))
            ledger.write(json.dumps({"t": time.strftime("%Y-%m-%dT%H:%M:%S"),
                                     "path": disp(f), "status": status,
                                     "secs": round(el, 1), "extra": extra},
                                    ensure_ascii=False) + "\n")
            ledger.flush()
            if i % 10 == 0:
                log("   [progress] ok=%d skip=%d fail=%d" % (stats["ok"], stats["skip"], stats["fail"]))
        ledger.close()
        log("=== done: ok=%d skipped=%d failed=%d" % (stats["ok"], stats["skip"], stats["fail"]))
        if stats["fail"]:
            sys.exit(1)


if __name__ == "__main__":
    main()