#!/bin/sh

## SPDX-FileCopyrightText: 2024 Benjamin Grande M. S. <ben.grande.b@gmail.com>
##
## SPDX-License-Identifier: GFDL-1.3-or-later
##
## Credits: https://wiki.archlinux.org/title/Working_with_the_serial_console#Resizing_a_terminal
##
## Resize terminal columns and lines to current window size.
## Useful for terminals over link (serial console, socat's pty etc).

test -t 0 || exit

## If argument is provided, allow user to bypass tty check.
if test "${#}" -eq 0; then
  ## Shells on graphical sessions (terminal emulators) are skipped.
  test "${XDG_SESSION_TYPE:-}" = "tty" || exit
  ## Serial ports and devices are desired.
  term_file="$(tty)"
  term_file_wanted="ttyUSB ttyS"
  ## Consoles are desired.
  if test -r /sys/class/tty/console/active; then
    term_file_wanted="${term_file_wanted} $(cat /sys/class/tty/console/active)"
  fi
  term_file_active=0
  for tf in $(printf %s"${term_file_wanted}"); do
    case "${term_file}" in
      *"/${tf}"*) term_file_active=1;;
      *) ;;
    esac
  done
  unset tf term_file term_file_wanted
  ## Terminal can handle screen resizing by itself.
  if test "${term_file_active}" = "0"; then
    unset term_file_active
    exit
  fi
  unset term_file_active
fi

## POSIX compliant.
# shellcheck disable=SC3045
if ! echo R | read -r -t 1 -sd R 2>/dev/null; then
  ## Fast but depends on XTerm.
  if has resize; then
    eval "$(resize)" >/dev/null
    exit
  fi
  ## Slow due to heavy stty calls.
  termios="$(stty -g)"
  stty raw -echo min 0 time 1
  printf '\0337\033[r\033[99999;99999H\033[6n\0338' >/dev/tty
  IFS='[;R' read -r _ rows cols _ </dev/tty
  stty "$termios" cols "$cols" rows "$rows"
  unset termios
  exit
fi

## Non-POSIX compliant and fast.
stty -echo
printf '\e7\e[r\033[99999;99999H\e[6n\e8' >/dev/tty
# shellcheck disable=3045,SC2034
IFS='[;R' read -r -t 1 -s -d R _ rows cols _ </dev/tty || {
  echo "error: cannot resize screen: unsupported terminal emulator" >&2
  stty echo
  unset rows cols
  exit 1
}

if test ${COLUMNS} -eq "${cols}" && test ${LINES} -eq "${rows}";then
  stty echo
  unset rows cols
  exit
elif test "${rows}" -gt 0 && test "${cols}" -gt 0;then
  stty echo cols "${cols}" rows "${rows}"
  unset rows cols
  exit
fi

echo "error: cannot resize screen: unsupported terminal emulator" >&2
stty echo
unset rows cols
exit 1