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

# Reassemble a Git-LFS split Pi backup after `git lfs pull`.
# Usage: ./assemble-pi-backup.sh [backup-base-name]

base=${1:-pi-backup-20260714-002452.tar.zst}
shopt -s nullglob
parts=("${base}".part-*)

(( ${#parts[@]} > 0 )) || {
  printf 'No archive parts found for %s\n' "$base" >&2
  exit 1
}

for command in cat sha256sum; do
  command -v "$command" >/dev/null || {
    printf 'Required command is unavailable: %s\n' "$command" >&2
    exit 1
  }
done

cat "${parts[@]}" > "$base"
printf 'Created: %s\n' "$base"

if [[ -f "${base}.sha256" ]]; then
  sha256sum -c "${base}.sha256"
else
  printf 'Checksum file not found: %s.sha256\n' "$base" >&2
fi