#!/usr/bin/env bash
set -euo pipefail

INPUT=""
OUTDIR=""
COUNT="14"

while [[ $# -gt 0 ]]; do
  case "$1" in
    --input)
      INPUT="$2"
      shift 2
      ;;
    --outdir)
      OUTDIR="$2"
      shift 2
      ;;
    --count)
      COUNT="$2"
      shift 2
      ;;
    *)
      echo "Unknown arg: $1" >&2
      exit 1
      ;;
  esac
done

if [[ -z "$INPUT" || -z "$OUTDIR" ]]; then
  echo "Usage: $0 --input <video.mp4> --outdir <dir> [--count 14]" >&2
  exit 1
fi

if [[ ! -f "$INPUT" ]]; then
  echo "Input file not found: $INPUT" >&2
  exit 1
fi

mkdir -p "$OUTDIR"
rm -f "$OUTDIR"/frame_*.jpg

DURATION="$(ffprobe -v error -show_entries format=duration -of default=nokey=1:noprint_wrappers=1 "$INPUT")"

python3 - "$INPUT" "$OUTDIR" "$COUNT" "$DURATION" <<'PY'
import os
import subprocess
import sys

inp, outdir, count_s, dur_s = sys.argv[1:]
count = max(1, int(count_s))
duration = float(dur_s)

if duration <= 0:
    print("Invalid duration", file=sys.stderr)
    sys.exit(1)

# Centered uniform sampling across full duration.
step = duration / count
times = [min(duration - 0.01, (i + 0.5) * step) for i in range(count)]

for idx, t in enumerate(times, start=1):
    out = os.path.join(outdir, f"frame_{idx:02d}.jpg")
    cmd = [
        "ffmpeg", "-y",
        "-ss", f"{t:.6f}",
        "-i", inp,
        "-frames:v", "1",
        "-q:v", "2",
        out,
    ]
    subprocess.run(cmd, check=True, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)

print(f"Extracted {count} frames to {outdir}")
PY

ls -1 "$OUTDIR"/frame_*.jpg