"""Build the narration track from recorded beat marks and mux it onto the video."""
import json, subprocess, sys
from pathlib import Path

SP = Path(__file__).parent
VO = SP / "vo"
take = sys.argv[1] if len(sys.argv) > 1 else "win1"
video = SP / f"{take}.mp4"
out = SP / f"{take}_narrated.mp4"

marks = [json.loads(l) for l in (SP / "marks.jsonl").read_text().splitlines() if l.strip()]
dur = json.loads((VO / "durations.json").read_text())
vlen = float(subprocess.run(["ffprobe", "-v", "error", "-show_entries", "format=duration",
                             "-of", "default=nw=1:nk=1", str(video)],
                            capture_output=True, text=True).stdout.strip())

inputs, filters, labels = [], [], []
for i, m in enumerate(marks):
    wav = VO / f"{m['key']}.wav"
    if not wav.exists():
        print(f"  missing {wav.name}, skipping"); continue
    delay_ms = int(m["t"] * 1000)
    inputs += ["-i", str(wav)]
    filters.append(f"[{i}:a]adelay={delay_ms}|{delay_ms},apad[a{i}]")
    labels.append(f"[a{i}]")
    end = m["t"] + dur.get(m["key"], 0)
    flag = "" if end <= vlen + 0.5 else "  <-- OVERRUNS VIDEO"
    print(f"  {m['key']:9} start {m['t']:7.2f}s  len {dur.get(m['key'],0):5.2f}s  end {end:7.2f}s{flag}")

mix = "".join(labels) + f"amix=inputs={len(labels)}:normalize=0,atrim=0:{vlen},asetpts=N/SR/TB[a]"
cmd = (["ffmpeg", "-y", "-loglevel", "error"] + inputs + ["-i", str(video),
       "-filter_complex", ";".join(filters) + ";" + mix,
       "-map", f"{len(labels)}:v", "-map", "[a]",
       "-c:v", "copy", "-c:a", "aac", "-b:a", "160k", "-shortest", str(out)])
r = subprocess.run(cmd, capture_output=True, text=True)
if r.returncode != 0:
    print("ffmpeg failed:\n", r.stderr[-1500:]); sys.exit(1)
print(f"\n  video {vlen:.1f}s | narration ends {max(m['t']+dur.get(m['key'],0) for m in marks):.1f}s")
print(f"  -> {out}")