#!/bin/sh
set -eu

if [ "$#" -lt 1 ]; then
  echo "usage: $0 ROOT [ROOT ...]" >&2
  exit 2
fi

manifest_file="$(mktemp)"
trap 'rm -f "$manifest_file"' EXIT INT TERM

root_index=0
file_count=0
for root in "$@"; do
  if [ ! -d "$root" ]; then
    echo "library root is unavailable: $root" >&2
    exit 3
  fi
  root_index=$((root_index + 1))
  count="$(find "$root" -type f -printf . | wc -c)"
  file_count=$((file_count + count))
  (cd "$root" && find . -type f -printf "${root_index}\t%P\t%s\t%T@\0") >> "$manifest_file"
done

digest="$(LC_ALL=C sort -z "$manifest_file" | sha256sum | cut -d ' ' -f 1)"
printf 'sha256=%s files=%s roots=%s\n' "$digest" "$file_count" "$#"