#!/bin/bash -i
set -m
[ "${BASH_LOADABLES_PATH:=/lib/bash:/usr/lib/bash}" ]

cfmakeraw()
{
        cmd=(stty -ignbrk -brkint -parmrk -istrip -inlcr -igncr -icrnl
        -ixon -opost -echo -echonl -icanon -isig -iexten -parenb cs8)
        "${cmd[@]}" "$@" >/dev/null
}

readchar_reset()
{
        :
}

i()
{
        if [ "$DEBUG" ]
        then
                printf 'I: %s\n' "$*" >&2
        fi
}

x()
{
        if [ "$DEBUG" ]
        then
                printf '+ %s\n' "${*@Q}" >&2
        fi
        "$@"
}

readchar_init()
{
        [ $$ != $BASHPID ] || return

        declare -g SOCAT= SOCAT_PID=
        declare -g t
        declare -g -a readchar_termopts

        [ -t 1 ] && t=y || t=
        readchar_termopts=(
                opost onlcr isig
                intr undef
                quit undef
        )

        trap "i CONT; readchar_SIGCONT" CONT
        for sig in TSTP TTIN TTOU
        do
                trap "i $sig; x kill -STOP \$BASHPID \$SOCAT_PID" $sig
        done
}

DEBUG=y

readchar_SIGCONT()
{
        if check_foreground
        then
                if [ -t 0 ]
                then
                        cfmakeraw "${readchar_termopts[@]}"
                fi
                x kill -CONT $SOCAT_PID 2>/dev/null
        else
                x kill -STOP $BASHPID $SOCAT_PID 2>/dev/null
        fi
}

check_foreground()
{
        read _pid _comm _state _ppid pgrp _session _tty_nr tpgid _rest < /proc/self/stat
        [ "$tpgid" = "$pgrp" ]
}

readchar()
{
        declare -n REPLY="${1:-CHARACTER}"

        if [ -t 0 ]
        then
                if check_foreground
                then
                        if ! [ "$SOCAT_PID" ]
                        then
                                cfmakeraw "${readchar_termopts[@]}"
                        fi
                else
                        sleep .25
                        return
                fi
        fi

        if ! [ "$SOCAT_PID" ]
        then
                exec {SOCAT}< <(trap 'sleep .25' SIGTSTP; socat - -)
                SOCAT_PID=$!
        fi

        if read -n 1 -d '' -r -s -u "$SOCAT"
        then
                if [ "$t" ]
                then
                        printf -v quoted_reply "%s" "${REPLY@Q}"
                        if (( (count += 1 + ${#quoted_reply}) < COLUMNS - 10 ))
                        then
                                seperate=' '
                        else
                                seperate=$'\n'
                                count=0
                        fi
                        printf "%s" "$seperate" "$quoted_reply"
                else
                        if [ "$REPLY" ]
                        then
                                printf "%s" "$REPLY"
                        else
                                printf "\0"
                        fi
                fi
        else
                [ $? -gt 128 ]
        fi
}

read_char()
{
        readchar_init
        t=
        c=
        count=0
        while ! [ "$c" ]
        do
                readchar c
        done
        readchar_reset
        if [ -t 1 ]
        then
                printf '%s\n' "${c@Q}"
        else
                printf %s "$c"
        fi
}

read_chars()
{
        readchar_init
        while readchar
        do
                continue
        done
        readchar_reset
}

reader_process()
{
        enable -f sleep sleep
        if [ "$SHLVL" = 1 -a -t 1 ]
        then
                (read_chars)
        else
                read_chars
        fi
}

run_test()
{
        reader_process &
        kill -TSTP %reader_process
        bg %reader_process
        kill -TSTP %reader_process
        bg %reader_process
        kill -TSTP %reader_process
        bg %reader_process
        kill -TSTP %reader_process
        bg %reader_process
        kill -TSTP %reader_process
        fg %reader_process
}