# =================
#  read_chars.bash
# =================
#
# Bash library for reading from tty and writing to standard out.
# Can be suspended and resumed from bash (or with unix job control in
# any shell).
#
# exporting for users:
#
# read_chars()    <-- calls readchar in a loop
#
# readchar()      <-- reads one character
#
# readchar_init() <-- must be called before readchar() in the same subshell
#
# The function read_chars is also available as the executable read-tty

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

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

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

readchar_init()
{
        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 EXIT; kill $SOCAT_PID 2>/dev/null; kill -CONT $SOCAT_PID 2>/dev/null" EXIT
        trap "i CONT; readchar_SIGCONT" CONT
        for sig in TSTP TTIN TTOU
        do
                trap "i $sig; x kill -STOP \$BASHPID \$SOCAT_PID 2>/dev/null" $sig
        done
        for sig in INT TERM
        do
                trap "i $sig; exit" $sig
        done
}

readchar_SIGCONT()
{
        if check_foreground
        then
                if [ -t 0 ]
                then
                        x 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" ]
}

SOCAT()
{
        #BASH_ARGV0=socat-tty-sleeper
        #echo -n "$0" >/proc/$BASHPID/comm
        #trap 'sleep .25' SIGTSTP
        #trap 'kill -INT $BASHPID 0' SIGTTIN SIGTTOU
        exec -a user-ended-connection socat - -
}

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

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

        if ! [ "$SOCAT_PID" ]
        then
                exec {SOCAT}< <(SOCAT)
                SOCAT_PID=$!
        fi

        if POSIXLY_CORRECT=y read -n 1 -d '' -r -s -u "$SOCAT"
        then
                if [ "$t" ]
                then
                        printf -v quoted_reply "%s" "${REPLY@Q}"
                        if (( (count += 1 + ${#quoted_reply}) < ${COLUMNS:-80} - 10 ))
                        then
                                seperate=' '
                        else
                                seperate=$'\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_chars()
{
        readchar_init
        while readchar
        do
                continue
        done
}