#!/bin/bash

# If using normal root, avoid changing anything.

if [ -z "$RPM_BUILD_ROOT" -o "$RPM_BUILD_ROOT" = "/" ]; then

  exit 0

fi

exclude_files=""

exclude_files_from=""

exclude_shebangs=""

exclude_shebangs_from=""

usage() {

  local verbose=$1 && shift

  local outfile=$1 && shift

  local status=$1 && shift

  (

    echo 'usage: brp-mangle-shebangs [--files <regexp>] [--files-from <file>] [--shebangs <regexp>] [--shebangs-from <file>]'

    if [ "${verbose}" == "yes" ]; then

      echo '  --files: extended regexp of files to ignore'

      echo '  --files-from: file containing a list of extended regexps of files to ignore'

      echo '  --shebangs: extended regexp of shebangs to ignore'

      echo '  --shebangs-from: file containing a list of extended regexps of shebangs to ignore'

    fi

  ) >>${outfile}

  exit ${status}

}

while [ $# -gt 0 ] ; do

  case "$1" in

    --files)

      exclude_files="${2}"

      shift

      ;;

    --files=*)

      exclude_files="${1##--files=}"

      ;;

    --files-from)

      exclude_files_from="${2}"

      shift

      ;;

    --files-from=*)

      exclude_files_from="${1##--files-from=}"

      ;;

    --shebangs)

      exclude_shebangs="${2}"

      shift

      ;;

    --shebangs=*)

      exclude_shebangs="${1##--shebangs=}"

      ;;

    --shebangs-from)

      exclude_shebangs_from="${2}"

      shift

      ;;

    --shebangs-from=*)

      exclude_shebangs_from="${1##--shebangs-from=}"

      ;;

    --help|--usage|"-?"|-h)

      usage yes /dev/stdout 0

      ;;

    *)

      echo "Unknown option \"${1}\"" 1>&2

      usage no /dev/stderr 1

      ;;

  esac

  shift

done

cd "$RPM_BUILD_ROOT"

# Large packages such as kernel can have thousands of executable files.

# We take care to not fork/exec thousands of "file"s and "grep"s,

# but run just two of them.

# (Take care to exclude filenames which would mangle "file" output).

find -executable -type f ! -path '*:*' ! -path $'*\n*' \

| file -N --mime-type -f - \

| grep -P ".+(?=: text/)" \

| {

fail=0

while IFS= read -r line; do

  f=${line%%:*}

  # Remove the dot

  path="${f#.}"

  if [ -n "$exclude_files" ]; then

    echo "$path" | grep -q -E "$exclude_files" && continue

  fi

  if [ -n "$exclude_files_from" ]; then

    echo "$path" | grep -q -E -f "$exclude_files_from" && continue

  fi

  if ! read shebang_line < "$f"; then

    echo >&2 "*** WARNING: Cannot read the first line from $f, removing executable bit"

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

    chmod -x "$f"

    touch -d "$ts" "$f"

    continue

  fi

  orig_shebang="${shebang_line#\#!}"

  if [ "$orig_shebang" = "$shebang_line" ]; then

    echo >&2 "*** WARNING: $f is executable but has no shebang, removing executable bit"

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

    chmod -x "$f"

    touch -d "$ts" "$f"

    continue

  fi

  # Trim spaces

  while shebang="${orig_shebang//  / }"; [ "$shebang" != "$orig_shebang" ]; do

    orig_shebang="$shebang"

  done

  # Treat "#! /path/to " as "#!/path/to"

  orig_shebang="${orig_shebang# }"

  shebang="$orig_shebang"

  if [ -z "$shebang" ]; then

    echo >&2 "*** WARNING: $f is executable but has empty shebang, removing executable bit"

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

    chmod -x "$f"

    touch -d "$ts" "$f"

    continue

  fi

  if [ -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 python3 with the desired Python 3 shebang,

  # if passed as an non-empty environment variable PYTHON3

  if [ -n "${PYTHON3:+x}" ]; then

    shebang=$(echo "$shebang" | sed -r -e "s@/usr/bin/python3(\s|$)@${PYTHON3}\1@")

  fi

  # 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

    echo >&2 "*** ERROR: ambiguous python shebang in $path: #!$orig_shebang. Change it to python3 (or python2) explicitly."

    fail=1

  elif [ "#!$shebang" != "#!$orig_shebang" ]; then

    echo "mangling shebang in $path from $orig_shebang to #!$shebang"

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

    sed -i -e "1c #!$shebang" "$f"

    touch -d "$ts" "$f"

  fi

done

exit $fail

}