#!/bin/bash
set -e

function usage {
    echo "Script usage:"
    echo ""
    echo "${0} list                                 Lists all printers"
    echo "${0} duplicate <printer-name>             Duplicates a printer"
    echo "${0} dup <printer-name>                   Alias of 'duplicate'"
    echo "${0} rename <printer-name> <new-name>     Renames a printer internally"
    echo "${0} ren <printer-name> <new-name>        Alias of 'rename'"
    echo "${0} clear-queue <printer-name>           Clears the current queue of a printer"
    echo "${0} cq <printer-name>                    Alias of 'clear-queue'"
}

##
# Ensures the 'uuid' command is installed
##
function ensure_uuid_command {
    if ! which uuid >/dev/null; then
        echo "Installing required 'uuid' package via apt-get..."
        DEBIAN_FRONTEND=noninteractive apt-get install -q --yes uuid >/dev/null
        echo "OK"
    fi
}

##
# Lists all internal names of available printers
#
# @echo List of all available printers
##
function list {
    echo "Available printers:"
    lpstat -v | awk '!/ iserv:/{ gsub(":", "", $3); print $3 }'
}

##
# Creates a duplicate of an existing printer
#
# @param $1 Internal name of the printer
##
function printer_duplicate {
    ensure_uuid_command

    PRINTER=${1}
    echo "Duplicating printer '${PRINTER}'..."

    if [ "${PRINTER}" = "" ]; then
        echo "No printer specified!"
        exit 1
    elif [ "${PRINTER}" = "iserv" ]; then
        echo "IServ built-in printer 'iserv' cannot be duplicated!"
        exit 1
    fi

    TEMP_CONF_FILE=$(mktemp)
    sed -n '/<Printer '${PRINTER}'>/,/<\/Printer>/p' /etc/cups/printers.conf > ${TEMP_CONF_FILE}

    if (( $(stat --printf="%s" ${TEMP_CONF_FILE}) == 0 )); then
        echo "Printer not found!"
        rm ${TEMP_CONF_FILE}
        exit 1
    fi

    NEXT_ID=$(next_printer_id)

    # Set printer ID
    sed -i 's/^PrinterId [0-9]\+/PrinterId '${NEXT_ID}'/' ${TEMP_CONF_FILE}

    # Change printer UUID
    sed -i 's/^UUID urn:uuid:.\+$/UUID urn:uuid:'$(uuid)'/' ${TEMP_CONF_FILE}

    # Append '_duplicate' to printer name
    sed -i 's/^<Printer \(.\+\)>$/<Printer \1_duplicate>/' ${TEMP_CONF_FILE}

    # Update printer description
    sed -i 's/^Info \(.\+\),/Info Duplicate of \1,/' ${TEMP_CONF_FILE}

    # Change ConfigTime to now
    sed -i 's/^ConfigTime [0-9]\+/ConfigTime '$(date +%s)'/' ${TEMP_CONF_FILE}

    # Change StateTime to now
    sed -i 's/^StateTime [0-9]\+/StateTime '$(date +%s)'/' ${TEMP_CONF_FILE}

    # Set printer state to idle
    sed -i 's/^State .\+$/State Idle/' ${TEMP_CONF_FILE}
    sed -i 's/^StateMessage .\+$//' ${TEMP_CONF_FILE}
    sed -i 's/^Reason .\+$//' ${TEMP_CONF_FILE}

    # Add new configuration to CUPS
    systemctl stop cups
    cat ${TEMP_CONF_FILE} >> /etc/cups/printers.conf
    systemctl start cups

    rm "${TEMP_CONF_FILE}"
    echo "OK"
}

##
# Renames a printer internally
#
# @param $1 Current internal name of the printer
# @param $2 New internal name of the printer
##
function printer_rename {
    PRINTER=${1}
    NEW_NAME=${2}
    echo "Renaming printer '${PRINTER}' to '${NEW_NAME}'..."

    if [ "${PRINTER}" = "" ]; then
        echo "No printer specified!"
        exit 1
    elif [ "${NEW_NAME}" = "" ]; then
        echo "No new name specified!"
        exit 1
    elif [ "${PRINTER}" = "iserv" ]; then
        echo "IServ built-in printer 'iserv' cannot be renamed!"
        exit 1
    fi

    if grep -qE '[ \/'\''"?#]' <<< "${NEW_NAME}"; then
        echo "Invalid characters in new name '${NEW_NAME}'!"
        echo "Valid characters are anything except \" ' \\ / ? # and spaces"
        exit 1
    fi

    if ! grep -qE "^<Printer ${PRINTER}>" /etc/cups/printers.conf; then
        echo "Printer not found!"
        exit 1
    fi

    echo "Renaming the printer will drop all current pages in the queue!"
    echo -n "Continue <y/n>? "
    read CHOICE

    if [ "${CHOICE}" != "y" ]; then
        echo "Operation cancelled"
        exit 1
    fi

    cp /etc/cups/printers.conf /etc/cups/printers.conf.ren_bak

    # Stop CUPS, rename, restart CUPS
    systemctl stop cups
    sed -i 's/<Printer '${PRINTER}'>$/<Printer '${NEW_NAME}'>/' /etc/cups/printers.conf
    systemctl start cups

    echo "OK"
}

##
# Clears the printing queue of a printer
#
# @param $1 Internal name of the printer
##
function printer_clear_queue {
    PRINTER=${1}
    echo "Clearing printing queue of '${PRINTER}'..."

    if [ "${PRINTER}" = "" ]; then
        echo "No printer specified!"
        exit 1
    fi

    if ! lpstat -e | grep -q "${PRINTER}"; then
        echo "Printer not found!"
        exit 1
    fi

    lprm -P "${PRINTER}" -
    echo "OK"
}

##
# Fetches the next free printer ID
#
# @echo Next available printer ID
##
function next_printer_id {
    HIGHEST_ID=-1

    while read LINE; do
        if grep -qE "^PrinterId" <<< "${LINE}"; then
            PRINTER_ID=$(awk '/PrinterId/{ print $2 }' <<< "${LINE}")

            if (( PRINTER_ID > HIGHEST_ID )); then
                HIGHEST_ID=${PRINTER_ID}
            fi
        fi
    done < /etc/cups/printers.conf

    (( HIGHEST_ID++ ))
    echo ${HIGHEST_ID}
}

case "$1" in
    duplicate|dup)
        shift
        printer_duplicate $@
        ;;
    rename|ren)
        shift
        printer_rename $@
        ;;
    clear-queue|cq)
        shift
        printer_clear_queue $@
        ;;
    list)
        list
        ;;
    *)
        usage
        exit 1
        ;;
esac