#!/bin/ksh93

integer DEFAULT_ROWS=${DEFAULT_ROWS:-24}
integer DEFAULT_COLS=${DEFAULT_COLS:-80}
# since the terminal does not take window decoration into account, we need to
# adjust reported max height and width. So you probably need to adjust these
# values wrt. window manager/theme.
integer ADJUST_ROWS=${ADJUST_ROWS:-2}
integer ADJUST_COLS=${ADJUST_COLS:-1}
SAVEOUT=""

usage() {
	printf '
Usage: %s [-h] [-v] [-a] [-V] [-H] [-F]

Toggle the size of a resizable terminal window (e.g. xterm, gnome-terminal).
Calling this script as "th" is equivalent with option "-H", calling it as
"tv" is equivalent with option "-V" and calling it as "tf" is equivalent with
option "-F". Options specified at the command line take precedence over the
script name.
NOTE: If ADJUST_* variables are not properly set or the window containing the
      terminal size has been already toggled via the window manager, one need
      to toggle the size again - otherwise the script may not work as expected!

Options:
  -h .. Print this help and exit.
  -v .. Verbose output.
  -a .. Try to find out correct values to set for ADJUST_ROWS and ADJUST_COLS.
  -V .. Toggle vertical size.
  -H .. Toggle horizontal size.
  -F .. Toggle between normal and default size.

Environment:
  ADJUST_COLS  .. Number of columns to substract from the maximum reported by
                  the terminal itself to get the usable max. column number.
  ADJUST_ROWS  .. Number of rows to substract from the maximum reported by
                  the terminal itself to get the usable max. row number.
  DEFAULT_COLS .. Number of columns to set when toggling horizontal/full size.
  DEFAULT_ROWS .. Number of rows to set when toggling vertical/full size.
' ${ basename $0;}
}

printChars() {
	STR="$1"
	for I in {0..$((${#STR}-1))}; do
		printf "%d = %c\n" "$I" "${STR:$I:$I}"
	done
	unset STR
}

readResponse() {
# Read from tty. Since it will not send a NL|CR, we need explicitly specify,
# when reading should stop (otherwise it will read forever - script will
# not terminate). Shell reads the delimiter but doesn't append it to the 
# RESPONSE. Delimiter is usually the last character of the ANSI-Escape
# sequence sent. Here 't'.
	OS=${ uname -s; }
	X=""
	if [[ $OS == "Darwin" ]]; then
		# this is buggy, the default Terminal doesn't even report a max size
		# so we need a timeout as well. However iTerm2 works. 
		LAST="@"
		while [[ "$LAST" != "t" && -n "$LAST" ]]; do
			X+="$LAST" ; LAST=""
			read -N 1 -t 1 LAST
		done
	else
		read -d t X
	fi
	RESPONSE="$X"
	if [[ "$RESPONSE" == "@" || -z "$RESPONSE" ]]; then
		print -u2 "This terminal doesn't work correctly - exiting."
		exit 2
	fi
}

# tty assigned to this terminal
TTY=${ tty; }
# read directly from the terminal input device instead of the shell's stdin
exec < $TTY
# terminal should not copy received input as well as the result to the output
stty -echo

getCurrentSize() {
# Send CSI command 18t (CSI == '\033[', \033==0x1b==27==ESC). No trailing NL!
# For more info see: http://rtfm.etla.org/xterm/ctlseq.html
	printf '\033[18t'
	readResponse
# 1st two chars of RESPONSE contain the CSI + ResponseIndicator(here '9')
#	+ ';' + height(rows) + ';' + width(columns)
#printChars "$RESPONSE"
	ROWS=${RESPONSE#*;}
	COLS=${ROWS#*;}
	ROWS=${ROWS%;*}
# as an alternative we could use:
	#COLS=${ tput cols; }
	#ROWS=${ tput lines; }
	[[ -n "$VERBOSE" ]] && SAVEOUT+="\nCurrent size: rows=$ROWS cols=$COLS"
}

getMaxSize() {
	# get max. size
	printf '\033[19t'
	readResponse
	MROWS=${RESPONSE#*;}
	MCOLS=${MROWS#*;}
	MROWS=${MROWS%;*}
	[[ -n "$VERB" ]] && SAVEOUT+="\nMax. reported size: rows=$MROWS cols=$MCOLS"
}

adjustMaxSize() {
	MROWS=$((MROWS-ADJUST_ROWS))
	MCOLS=$((MCOLS-ADJUST_COLS))
	[[ -n "$VERB" ]] && SAVEOUT+="\nMax. adjusted size: rows=$MROWS cols=$MCOLS"
}

BN=$0
BN=${BN##*/}
VERB=""

while getopts "hvaHVF" option ; do
    case "$option" in
        h) usage; exit 1;;
        a) BN="ta" ;;
		v) VERB="true" ;;
		V) BN="tv" ;;
		H) BN="th" ;;
		F) BN="tf" ;;
    esac
done
shift $((OPTIND-1))

getCurrentSize
getMaxSize

case $BN in
	tv)
		# toggle vertical size
		adjustMaxSize
		if (( $ROWS < $MROWS )); then
			printf '\033[8;%s;%st' $MROWS $COLS
		elif (( $ROWS > $DEFAULT_ROWS )); then
			printf '\033[8;%s;%st' $DEFAULT_ROWS $COLS
		fi
		;;
	th)
		# toggle horizonal size
		adjustMaxSize
		if (( $COLS < $MCOLS )); then
			printf '\033[8;%s;%st' $ROWS $MCOLS
		elif (( $COLS > $DEFAULT_COLS )); then
			printf '\033[8;%s;%st' $ROWS $DEFAULT_COLS
		fi
		;;
	tf)
		# toggle full size
		adjustMaxSize
		if (( $COLS < $MCOLS || $ROWS < $MROWS )); then
			printf '\033[8;%s;%st' $MROWS $MCOLS
		else
			printf '\033[8;%s;%st' $DEFAULT_ROWS $DEFAULT_COLS 
		fi
		;;
	ta)
		OROWS=$ROWS ; OCOLS=$COLS
		printf '\033[8;%s;%st' $MROWS $MCOLS
		resize >/dev/null
		getCurrentSize
		DIFF=$((MROWS-ROWS))
		if (( $DIFF != $ADJUST_ROWS )); then
			SAVEOUT+="\nADJUST_ROWS=$DIFF should be set."
		fi
		DIFF=$((MCOLS-COLS))
		if (( $DIFF != $ADJUST_COLS )); then
			SAVEOUT+="\nADJUST_COLS=$DIFF should be set."
		fi
		if (( $ROWS != $OROWS || $OCOLS != $COLS )); then
			printf '\033[8;%s;%st' $OROWS $OCOLS
		fi
		;;
esac

# finally re-enable input echo
stty echo
resize >/dev/null

[[ -n "$SAVEOUT" ]] && print "$SAVEOUT"