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

root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
cd "${root}"

input=""
seconds="6"
chunk_ms="2000"

usage() {
  cat >&2 <<'EOF'
usage:
  scripts/determinism-cmaf.sh --input <TS_FILE_OR_URL> [--seconds N] [--chunk-ms MS]

what it does:
  - runs the CMAF (HLS fMP4) encoder/segmenter twice with the deterministic x264 profile
  - compares sha256 of init + segments to check byte-for-byte determinism

notes:
  - requires `ffmpeg` on PATH
EOF
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --input)
      input="${2:-}"
      shift 2
      ;;
    --seconds)
      seconds="${2:-}"
      shift 2
      ;;
    --chunk-ms)
      chunk_ms="${2:-}"
      shift 2
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "error: unknown arg: $1" >&2
      usage
      exit 2
      ;;
  esac
done

if [[ -z "${input}" ]]; then
  echo "error: --input is required" >&2
  usage
  exit 2
fi

tmp="$(mktemp -d)"
trap 'rm -rf "$tmp"' EXIT

ts="$input"
if [[ "${input}" == http://* || "${input}" == https://* ]]; then
  ts="$tmp/in.ts"
  ffmpeg -hide_banner -loglevel error -nostdin -y \
    -t "${seconds}" -i "${input}" -c copy -f mpegts "${ts}"
fi

seg_secs="$(python3 - <<PY
ms=int("${chunk_ms}")
print(f"{ms/1000:.3f}")
PY
)"

run_one() {
  out="$1"
  rm -rf "$out"
  mkdir -p "$out"
  (cd "$out" && ffmpeg -hide_banner -loglevel error -nostdin -y \
    -i "pipe:0" \
    -map 0:v:0 -map 0:a:0? -sn -dn -map_metadata -1 \
    -c:v libx264 \
    -c:a aac -b:a 128k -ac 2 -ar 48000 \
    -pix_fmt yuv420p -g 60 -keyint_min 60 -sc_threshold 0 -bf 0 \
    -threads 1 \
    -fflags +bitexact -flags:v +bitexact -flags:a +bitexact \
    -f hls \
    -hls_time "${seg_secs}" \
    -hls_list_size 0 \
    -hls_segment_type fmp4 \
    -hls_flags independent_segments \
    -hls_fmp4_init_filename init.mp4 \
    -hls_segment_filename segment_%06d.m4s \
    index.m3u8 < "$ts")
}

run_one "$tmp/a"
run_one "$tmp/b"

(cd "$tmp/a" && shasum -a 256 init.mp4 segment_*.m4s | sort) > "$tmp/a.sha"
(cd "$tmp/b" && shasum -a 256 init.mp4 segment_*.m4s | sort) > "$tmp/b.sha"

if diff -u "$tmp/a.sha" "$tmp/b.sha" >/dev/null; then
  echo "OK: deterministic (init + segments match)"
else
  echo "DIFF: non-deterministic output"
  diff -u "$tmp/a.sha" "$tmp/b.sha" || true
  exit 1
fi