#!/bin/bash
# IPC Demo using bash and terminal windows
# <C> 2019-2022 F-Hauri.ch 
# All this stuff is licensed under GPLV3+
# 	
# some command to populate both stdOut and stdErr
# > do ls -ld /t{mp,nt}
# > do date >&2
# > do date | tee /dev/stderr
# 	
# for showing XTRACE in main console, run:
# > do export BASH_XTRACEFD=$saveI;set -x
# 	

XTrm=${1:-x-terminal-emulator}

declare -A X_TERMBASE='([gnome]="gnome-terminal --geometry"
	[konsole]="konsole --geometry" [lxterm]="lxterm -geom"
	[mate]="mate-terminal --geometry" [xterm]="xterm -geom"
	[x-terminal-emulator]="x-terminal-emulator -geometry")'		
declare -A X_TERMEXEC='([gnome]="--" [mate]="--" [xterm]="-e"
	 [lxterm]="-e" [konsole]="-e" [x-terminal-emulator]="-e")'

exec {logw}<> <(:)
. <(echo "exec $logw> >("
    # To run `xterm` instead of `gnome-terminal`, you have to swap lines,
    # not only comment and uncomment! Run this sed command:
    # sed '/^#/{N;/xterm.*geom/{ s/#\(.*\)\n\(.*\)/#\2\n\1/ }}' -i filename
    #    xterm -T 'Log window...' -geom +1000 -e sh -c "
    cat <<-EOpenLog
	>/dev/null ${X_TERMBASE[$XTrm]} +1000 ${X_TERMEXEC[$XTrm]} bash -c "
	   printf '\\e];Log window...\\a\\nThis is normal OUTPUT window.\\n\\n';
	   exec stdbuf -i0 -o0 -e0 cat /proc/$$/fd/$logw"
	)
	EOpenLog
   )
sleep .2 # to ensure order of window pops
exec {errw}<> <(:)
. <(echo "exec $errw> >("
    #    xterm -T 'Error window...' -geom +1000+400 -e sh -c "
    cat <<-EOpenErr
	>/dev/null ${X_TERMBASE[$XTrm]} +1000+600 ${X_TERMEXEC[$XTrm]} bash -c "
	    printf '\\e];Error window...\\a\\nThis is ERROR window.\\n\\n';
	    exec stdbuf -i0 -o0 -e0 cat /proc/$$/fd/$errw"
	)
	EOpenErr
   )
sleep .2 # to ensure order of window pops
exec {inw}<> >(:)
. <(echo "exec $inw< <("
    #    xterm -T 'Input window...' -geom +1 -e bash -c "
    cat <<-EOpenIn
	>/dev/null ${X_TERMBASE[$XTrm]} +1 ${X_TERMEXEC[$XTrm]}  bash -c "
    	printf '\\e];Input window...\\a';
	grep '[a-z] *) *# \|^# [^ ]' '$0';
	printf '\\nThis is INPUT window, hit your commands there!\\n\\n';
        HISTFILE=/tmp/ipc_dem.hist;
        export HISTFILE;
	touch \\\$HISTFILE;
	loop=:;
	while \\\$loop && history -c && history -r \\\$HISTFILE &&
	    read -e -p '> ' foo ;do
	    tee -a <<<\"\\\$foo\" \\\$HISTFILE;
	    [[ \\\$foo == exit ]] && loop=false;
        done >/proc/$$/fd/$inw"
	)
	EOpenIn
   )
case $XTrm in  mate | gnome )
	sleep .5 # To prevent end of script before gnome-terminal hold fd.
esac

exec {saveI}>&1  # Save real STDOUT
exec {saveE}>&2  # Save real STDERR
exec 2>&$errw  # Redirect STDERR to Error window
exec 1>&$logw  # Redirect STDOUT to Log window
while [ -e /dev/fd/$inw ] && read -u $inw cmd args; do
    case $cmd in 
        free | date | df | pwd | ls | uptime ) # Simple UN*X commands
	    lastcmd=$cmd; $cmd $args;;
        top )              # 15 first lines of "top -n1"
	    lastcmd=$cmd; top -n1 | head -n 15 ;;
	help )             # Print this
	    lastcmd=$cmd; grep '[a-z] *) *# \|^# [^ ]' "$0" ;;
	do )               # Execute args via `eval`
	    lastcmd="DO $args"; eval "$args" ;;
        exit )             # Exit.       
	    exec {inw}<&-  # Close Input window
            ;;
	''|'#'* ) ;;
        *)
            echo >&2 "Error: '$cmd' not defined!" ;;
    esac
done
exec 1>&$saveI  # Restore STDOUT
exec 2>&$saveE  # Restore STDERR

exec {inw}<&-  # Close Input window
exec {logw}>&-  # Close Log window
exec {errw}>&-  # Close Err window
exec {saveI}>&-  # Release STDOUT backup
exec {saveE}>&-  # Release STDERR backup
echo "End (last command (before exit) was: '$lastcmd'".
notAcommand # This must output some error on *regular* STDERR
ls -l /dev/fd/ # Everything could be back now