#!/bin/bash

# Usage:
# ./is-perl-object /path/to/file
#
# Returns a zero status code and prints the object's identity if the file can
# be identified as a self-modifying Perl script, and returns a status code of
# 1 otherwise.

# Identity retrieval is optimized, but will query the Perl object directly if
# the optimistic lookup fails. If the Perl object is unidentified, this may
# cause an ID to be generated for that object, in which case it will rewrite
# itself if possible.

# To prevent this script from querying the object, you can use the --no-query
# or -n arguments.

if [[ $1 == '-n' || $1 == '--no-query' ]]; then
  no_query=$1
  shift
fi

magic=$(head -c64 "$1" | tail -n1 | awk '{print $2}')
if [[ $magic == '99aeabc9ec7fe80b1b39f5e53dc7e49e' ]]; then
  identity_line="$(grep "^meta::data('permanent-identity'" "$1")"

  if [[ $? == 0 ]]; then
    echo "$identity_line" | tail -c36 | head -c32
    echo
    exit 0
  elif [[ ! "$no_query" ]]; then
    "./$1" identity
    exit 0
  else
    exit 2
  fi
else
  exit 1
fi