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

# Restore dataset from split archives created by pack_upload.sh.
# Supports both .tar.gz.part-* and .tar.zst.part-* archives.

ARCHIVE_DIR="${ARCHIVE_DIR:-.}"
RESTORE_BASE="${RESTORE_BASE:-./data_restored}"
MAX_JOBS="${MAX_JOBS:-1}"
ONLY_GROUP="${ONLY_GROUP:-}"  # optional: e.g. packed__frames or packed__jsonl

if ! [[ "$MAX_JOBS" =~ ^[1-9][0-9]*$ ]]; then
  echo "MAX_JOBS must be a positive integer, got: $MAX_JOBS" >&2
  exit 1
fi

mkdir -p "$RESTORE_BASE"

wait_for_slot() {
  while true; do
    local running
    running=$(jobs -rp | wc -l)
    if [ "$running" -lt "$MAX_JOBS" ]; then
      break
    fi
    wait -n
  done
}

restore_one_prefix() {
  local prefix="$1"

  # prefix format: packed__frames__seed_101 (without .tar.*.part-*)
  local group seed rel_dir out_dir
  group="${prefix%%__seed_*}"
  seed="${prefix##*__}"

  if [ -n "$ONLY_GROUP" ] && [ "$group" != "$ONLY_GROUP" ]; then
    echo "[SKIP] $prefix (group mismatch: $group)"
    return 0
  fi

  # Map packed__vision_cache__frames -> vision_cache/frames, etc.
  rel_dir="${group#packed__}"
  rel_dir="${rel_dir//__//}"
  out_dir="$RESTORE_BASE/$rel_dir"
  mkdir -p "$out_dir"

  local zst_parts=()
  local gz_parts=()

  # Use find instead of globstar to avoid shell-option dependent misses.
  while IFS= read -r p; do
    zst_parts+=("$p")
  done < <(find "$ARCHIVE_DIR" -type f -name "$prefix.tar.zst.part-*" | sort)

  while IFS= read -r p; do
    gz_parts+=("$p")
  done < <(find "$ARCHIVE_DIR" -type f -name "$prefix.tar.gz.part-*" | sort)

  if [ "${#zst_parts[@]}" -gt 0 ]; then
    if ! command -v zstd >/dev/null 2>&1; then
      echo "[ERROR] zstd archives found for $prefix but 'zstd' is not installed." >&2
      return 1
    fi
    echo "[UNPACK] $prefix (.tar.zst) -> $out_dir/$seed"
    cat "${zst_parts[@]}" | tar --use-compress-program=unzstd -xf - -C "$out_dir"
    return 0
  fi

  if [ "${#gz_parts[@]}" -gt 0 ]; then
    echo "[UNPACK] $prefix (.tar.gz) -> $out_dir/$seed"
    cat "${gz_parts[@]}" | tar -xzf - -C "$out_dir"
    return 0
  fi

  echo "[WARN] no archive parts found for $prefix"
  return 0
}

# Discover restore units from archive parts (works for downloaded HF datasets).
prefixes=()
declare -A seen_prefixes
while IFS= read -r part; do
  [ -f "$part" ] || continue
  base="$(basename "$part")"
  case "$base" in
    *.tar.zst.part-*) prefix="${base%.tar.zst.part-*}" ;;
    *.tar.gz.part-*)  prefix="${base%.tar.gz.part-*}" ;;
    *) continue ;;
  esac

  if [ -z "${seen_prefixes[$prefix]:-}" ]; then
    seen_prefixes[$prefix]=1
    prefixes+=("$prefix")
  fi
done < <(find "$ARCHIVE_DIR" -type f \( -name '*.tar.zst.part-*' -o -name '*.tar.gz.part-*' \) | sort)

if [ "${#prefixes[@]}" -eq 0 ]; then
  echo "No archive parts found under $ARCHIVE_DIR. Nothing to restore." >&2
  exit 1
fi

echo "[INFO] Restore base: $RESTORE_BASE"
echo "[INFO] Archive dir : $ARCHIVE_DIR"
echo "[INFO] Units       : ${#prefixes[@]}"

for prefix in "${prefixes[@]}"; do
  wait_for_slot
  restore_one_prefix "$prefix" &
done

wait

echo "[DONE] Restore completed."