#!/usr/bin/env bash
#
# Use this script to update libexpat

set -e
set -o pipefail

if [[ "${BASH_VERSINFO[0]}" -lt 4 ]]; then
  echo "A bash version >= 4 required. Got: $BASH_VERSION" >&2
  exit 1
fi

# Update this when updating to a new version after verifying that the changes
# the update brings in are good. These values are used for verifying the SBOM, too.
expected_libexpat_tag="R_2_8_5"
expected_libexpat_version="2.8.5"
expected_libexpat_sha256="920dde485e15eda0cce8d2310b41d492c534e5e3d89ad407a0b4176dd2ff88fe"

expat_dir="$(realpath "$(dirname -- "${BASH_SOURCE[0]}")")"
cd ${expat_dir}

# Step 1: download and copy files
curl --location "https://github.com/libexpat/libexpat/releases/download/${expected_libexpat_tag}/expat-${expected_libexpat_version}.tar.gz" > libexpat.tar.gz
echo "${expected_libexpat_sha256} libexpat.tar.gz" | sha256sum --check

# Step 2: Pull files from the libexpat distribution

tar xzvf libexpat.tar.gz "expat-${expected_libexpat_version}/COPYING" --strip-components 2

declare -a lib_files
lib_files=(
  ascii.h
  asciitab.h
  expat.h
  expat_external.h
  fallthrough.h
  hash_table.h
  iasciitab.h
  internal.h
  latin1tab.h
  memory_sanitizer.h
  nametab.h
  siphash.h
  utf8tab.h
  winconfig.h
  xcsinc.c
  xmlparse.c
  xmlrole.c
  xmlrole.h
  xmltok.c
  xmltok.h
  xmltok_impl.c
  xmltok_impl.h
  xmltok_ns.c
)
for f in "${lib_files[@]}"; do
  tar xzvf libexpat.tar.gz "expat-${expected_libexpat_version}/lib/${f}" --strip-components 2
done
rm libexpat.tar.gz

# Step 3: Add the namespacing include to expat_external.h
sed -i 's/#  define Expat_External_INCLUDED 1/&\n\/* Namespace external symbols to allow multiple libexpat version to\n   co-exist. \*\/\n#include "pyexpatns.h"/' expat_external.h

# Step 4: Skip the Windows rand_s entropy path in xmlparse.c when
# XML_POOR_ENTROPY is set.
sed -z -i 's|#if defined(_WIN32)\n#  include "random_rand_s\.h"\n#endif /\* defined(_WIN32) \*/|#if defined(_WIN32) \&\& ! defined(XML_POOR_ENTROPY)\n#  include "random_rand_s.h"\n#endif /* defined(_WIN32) \&\& ! defined(XML_POOR_ENTROPY) */|' xmlparse.c
sed -z -i 's|#  ifdef _WIN32\n  if (writeRandomBytes_rand_s|#  if defined(_WIN32) \&\& ! defined(XML_POOR_ENTROPY)\n  if (writeRandomBytes_rand_s|' xmlparse.c

if ! grep -q '#if defined(_WIN32) && ! defined(XML_POOR_ENTROPY)' xmlparse.c; then
  echo "
Error: rand_s gate not patched in xmlparse.c;
This may be due to source changes and will require updating this script" >&2
  exit 1
fi

echo "Updated; verify all is okay using git diff and git status."