#!/bin/bash

#    Functions:

function makedir() {
    DIR_NAME=${1}
    if test -e "${DIR_NAME}" -a ! -d "${DIR_NAME}" ; then
        printf 'File "'"${DIR_NAME}"'" exists, but is not a directory.\n'
        while test -e "${DIR_NAME}" -a ! -d "${DIR_NAME}" ; do
            printf '\nChoose a different name: '
            read DIR_NAME
        done
        mkdir "${DIR_NAME}"
        printf 'New directory "'"${DIR_NAME}"'" created.\n'
    elif test -d "${DIR_NAME}" ; then
        printf 'Directory "'"${DIR_NAME}"'" already exists.\n[u] Use it\n[c] Create a new one'
        CHOICE='x'
        while test "${CHOICE}" != 'c' -a "${CHOICE}" != 'u' ; do
            printf '\n\tType "c" or "u": '
            read -n 1 CHOICE
        done
        if test "${CHOICE}" = 'c' ; then
            while test -d "${DIR_NAME}" -o -z "${DIR_NAME}" ; do
                printf '\n\tChoose a different name: '
                read DIR_NAME
            done
            mkdir "${DIR_NAME}"
            printf 'New directory "'"${DIR_NAME}"'" created.\n'
        else
            printf '\nUsing directory "'"${DIR_NAME}"'".\n'
        fi
    else
        mkdir "${DIR_NAME}"
        printf 'New directory "'"${DIR_NAME}"'" created.\n'
    fi
}

function makefifo() {
        FIFO_DIR=${1}
        FIFO_NAME='./'"${FIFO_DIR}"'/'"${2}"
        if test ! -p "${FIFO_NAME}" -a -e "${FIFO_NAME}" ; then
                printf 'File "'"${FIFO_NAME}"'" exists, but is not a named pipe.\n'
                while test \( ! -p "${FIFO_NAME}" -a -e "${FIFO_NAME}" \) -o -z "${FIFO_NAME}" ; do
                        printf 'Choose a different name: '
                        read FIFO_NAME
                        FIFO_NAME='./'"${FIFO_DIR}"'/'"${FIFO_NAME}"
                done
                if test -p "${FIFO_NAME}" ; then
                        printf 'Using named pipe "'"${FIFO_NAME}"'".\n'
                else
                        mkfifo "${FIFO_NAME}"
                        printf 'New named pipe "'"${FIFO_NAME}"'" created.\n'
                fi
        elif test -p "${FIFO_NAME}" ; then
                printf 'Using named pipe "'"${FIFO_NAME}"'".\n'
        else
                mkfifo "${FIFO_NAME}"
                printf 'New named pipe "'"${FIFO_NAME}"'" created.\n'
        fi
}

function keep_fifo_open() {
    INPUT=${1}
    KEEP_PAUSE=${2}
    while : ; do
        cat "${KEEP_PAUSE}"
        break
    done > "${INPUT}"
}

function listen() {
    INPUT=${1}
    FIFO=${2}
    LISTEN_PAUSE=${3}
    cat "${INPUT}" | while IFS= read -n 1 BYTE ; do
        printf "${BYTE}" > "${FIFO}"
        EXIT=`cat "${LISTEN_PAUSE}"`
        if test "${EXIT}" = '1' ; then
            break
        fi
    done
}

function yap_randomly() {
    INPUT=${1}
    SLEEP_RANGE=${2}
    while : ; do
        BYTE=`echo "ibase=10;obase=16;(${RANDOM}%256)" | bc`
        printf "\x${BYTE}"
        sleep `echo "(${RANDOM}%${SLEEP_RANGE})" | bc`
    done > "${INPUT}"
}

function grab_bytes() {
    FIFO=${1}
    LISTEN_PAUSE=${2}
    KEEP_PAUSE=${3}
    printf '[p] Print next byte\n[q] Quit\n'
    PROMPT='n'
    while test "${PROMPT}" != 'q' ; do
        printf 'Type "p" or "q": '
        read -n 1 PROMPT
        printf '\n'
        if test "${PROMPT}" = 'p' ; then
            printf 'Next byte is:\n'
            cat "${FIFO}" | xxd -cols 1
            printf '0' > "${LISTEN_PAUSE}"
        fi
    done
    cat "${FIFO}" > /dev/null
    printf '1' > "${LISTEN_PAUSE}"
    printf '1' > "${KEEP_PAUSE}"
}

#    Directories:

PIPES_DIR='pipes'

makedir "${PIPES_DIR}"

PIPES_DIR="${DIR_NAME}"

#    Named pipes:

INPUT='INPUT'
FIFO='FIFO'
KEEP_PAUSE='KEEP_PAUSE'
LISTEN_PAUSE='LISTEN_PAUSE'

makefifo "${PIPES_DIR}" "${INPUT}"
INPUT="${FIFO_NAME}"
makefifo "${PIPES_DIR}" "${FIFO}"
FIFO="${FIFO_NAME}"
makefifo "${PIPES_DIR}" "${KEEP_PAUSE}"
KEEP_PAUSE="${FIFO_NAME}"
makefifo "${PIPES_DIR}" "${LISTEN_PAUSE}"
LISTEN_PAUSE="${FIFO_NAME}"

#    Variables:

MAXDELAY=3

#    Main script:

keep_fifo_open "${INPUT}" "${KEEP_PAUSE}" &
KEEPPID="${!}"
printf '\nBackgrounded keep_fifo_open process...\n'
printf '\tkeep_fifo_open '"${INPUT}"' '"${KEEP_PAUSE}"' &\n'
printf 'PID is: '"${KEEPPID}"'\n'

listen "${INPUT}" "${FIFO}" "${LISTEN_PAUSE}" &
LISTENPID="${!}"
printf '\nBackgrounded listen process...\n'
printf '\tlisten '"${INPUT}"' '"${FIFO}"' '"${LISTEN_PAUSE}"' &\n'
printf 'PID is: '"${LISTENPID}"'\n'

yap_randomly "${INPUT}" "${MAXDELAY}" &
YAPPID="${!}"
printf '\nBackgrounded yap_randomly process...\n'
printf '\tyap_randomly '"${INPUT}"' '"${MAXDELAY}"' &\n'
printf 'PID is: '"${YAPPID}"'\n'

printf '\nBeginning byte-grabbing loop!\n'
grab_bytes "${FIFO}" "${LISTEN_PAUSE}" "${KEEP_PAUSE}"

printf '\nKilling all backgrounded processes...\n'
printf '\tkill -9 '"${KEEPPID}"' '"${LISTENPID}"' '"${YAPPID}"'\n'
kill -9 "${KEEPPID}" "${LISTENPID}" "${YAPPID}"

sleep 1

printf '\nCheck for any unterminated processes...\n'
printf '\tps -e | grep -e '"${KEEPPID}"' -e '"${LISTENPID}"' -e '"${YAPPID}"'\n'
ps -e | grep -e "${KEEPPID}" -e "${LISTENPID}" -e "${YAPPID}"

Beginning byte-grabbing loop!
[p] Print next byte
[q] Quit
Type "p" or "q": p
Next byte is:
0000000: 97  .
Type "p" or "q": p
Next byte is:
0000000: df  .
0000001: 58  X
Type "p" or "q":