#!/bin/bash -eu

# If using normal root, avoid changing anything.
if [ -z "$RPM_BUILD_ROOT" -o "$RPM_BUILD_ROOT" = "/" ]; then
  exit 0
fi

exclude_files="${1:-}"
exclude_shebangs="${2:-}"

cd "$RPM_BUILD_ROOT"

trim() {
  printf '%s' "$*"
}

fail=0
while IFS= read -r -d $'\0' f; do
  file -N --mime-type "$f" | grep -q -P ".+(?=: text/)" || continue

  # Remove the dot
  path="${f#.}"

  if [ -n "$exclude_files" ]; then
    echo "$path" | grep -q -E "$exclude_files" && continue
  fi

  ts=$(stat -c %y "$f")

  read shebang_line < "$f" || :
  orig_shebang=$(trim $(echo "$shebang_line" | grep -Po "#!\K.*" || echo))
  shebang="$orig_shebang"
  if [ -n "$exclude_shebangs" ]; then
    echo "$shebang" | grep -q -E "$exclude_shebangs" && continue
  fi

  if [ -z "$shebang" ]; then
    echo >&2 "*** WARNING: $f is executable but has empty or no shebang, removing executable bit"
    chmod -x "$f"
    touch -d "$ts" "$f"
    continue
  elif [ -n "${shebang##/*}" ]; then
    echo >&2 "*** ERROR: $f has shebang which doesn't start with '/' ($shebang)"
    fail=1
    continue
  fi

  if ! { echo "$shebang" | grep -q -P "^/(?:usr/)?(?:bin|sbin)/"; }; then
    continue
  fi

  # Replace "special" env shebang:
  # /whatsoever/env /whatever/foo → /whatever/foo
  shebang=$(echo "$shebang" | sed -r -e 's@^(.+)/env /(.+)$@/\2@')
  # /whatsoever/env foo → /whatsoever/foo
  shebang=$(echo "$shebang" | sed -r -e 's@^(.+/)env (.+)$@\1\2@')

  # Replace ambiguous python with python2
  py_shebang=$(echo "$shebang" | sed -r -e 's@/usr/bin/python(\s|$)@/usr/bin/python2\1@')

  if [ "$shebang" != "$py_shebang" ]; then
    sed -i -e "1c #!$py_shebang" "$f"
    echo >&2 "*** WARNING: mangling shebang in $path from #!$orig_shebang to #!$py_shebang. This will become an ERROR, fix it manually!"
  elif [ "#!$shebang" != "#!$orig_shebang" ]; then
    sed -i -e "1c #!$shebang" "$f"
    echo "mangling shebang in $path from $orig_shebang to #!$shebang"
  fi

  touch -d "$ts" "$f"
done < <(find -executable -type f -print0)

exit $fail