# =================
#  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 INIT_TTY=y
        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; INIT_TTY=y" CONT
        for sig in TSTP TTIN TTOU
        do
                trap "i $sig; stop_self" $sig
        done
        for sig in INT TERM
        do
                trap "i $sig; exit" $sig
        done
}

stop_self()
{
        INIT_TTY=y
        kill -STOP $$ $BASHPID
}

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
                        stop_self
                        return
                fi
        fi

        if [ "$INIT_TTY" ]
        then
                x cfmakeraw "${readchar_termopts[@]}"
                INIT_TTY=
        fi

        if POSIXLY_CORRECT=y read -n 1 -d '' -r -s
        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
                r=$?
                if [ "$r" = 148 ]
                then
                        INIT_TTY=y
                fi
                [ $r -gt 128 ]
        fi
}

read_chars()
{
        readchar_init
        while readchar
        do
                continue
        done
}