#!/bin/bash

# Fail early
set -e
set -o nounset
set -o pipefail

# Devices
USB_DEV="/dev/serial/by-id/usb-FTDI_FT232R_USB_UART_AL0287C1-if00-port0"
TAPE1_DEV="/dev/tape/by-id/scsi-35000000000000000-nst"
TAPE2_DEV="/dev/tape/by-id/scsi-30000000000000000-nst"
TAPE_COOL="60"

# Mail parameters for tape alerts (cleaning etc.)
MAIL_SENDER="Backup"
MAIL_FROM="bareos@example.com"
MAIL_TO="operator@example.com"
HOST_NAME=$(hostname -f)

# Misc
umask 002
LOGGER="logger -i -t $(basename $0)"

# USB needs serialization
readonly LOCK_ROOT_DIR="/run/bareos"
readonly LOCK_DIR="$LOCK_ROOT_DIR/.tape-helper-lock"
readonly LOCK_TIMEOUT=50

#
# Lock
#
lock()
{
	if ! [ -w "$LOCK_ROOT_DIR" ]; then
		echo "Warning: Lock directory $LOCK_ROOT_DIR is not writable." | $LOGGER
		return
	fi

	for i in $(seq 1 $LOCK_TIMEOUT); do
		if mkdir "${LOCK_DIR}" 2>/dev/null; then
			break
		else
			if [ $i -eq $LOCK_TIMEOUT ]; then
				echo "Warning: Lock held for too long, trying to break it and continuing anyway." | $LOGGER
				unlock
				break
			else
				sleep 0.2
			fi
		fi
	done
}

#
# Unlock
#
unlock()
{
	if [ -d "$LOCK_DIR" ] && [ -w "$LOCK_DIR" ]; then
		rmdir "$LOCK_DIR" 
	fi
}

#
# Set parameters
#
set_params()
{
	# LTO-5 and LTO-6 have differing startup times
    case "$1" in
        1|LTO-6*|"$TAPE1_DEV")
			ON="\xFF\x01\x01"
			OFF="\xFF\x01\x00"
			TAPE_DEV=$TAPE1_DEV
            TAPE_WAIT="180"
            ;;
        2|LTO-5*|LTO-4*|"$TAPE2_DEV")
			ON="\xFF\x02\x01"
			OFF="\xFF\x02\x00"
			TAPE_DEV=$TAPE2_DEV
            TAPE_WAIT="90"
            ;;
        *)
			echo "Sorry, I don't know a drive called $1." | $LOGGER
			exit 1
            ;;
    esac
}

#
# Push the button
#
toggle_relais()
{
    if [ -w "$USB_DEV" ]; then
		lock
        echo -e $ON > $USB_DEV
        sleep 0.5
        echo -e $OFF > $USB_DEV
		unlock
	    # Wait for drive to fully boot
		sleep $TAPE_WAIT
	elif ! [ -r "$USB_DEV" ]; then
		echo "Warning: USB relais box not found." | $LOGGER
    else
        echo "Not enough rights to write to $USB_DEV, aborting." | $LOGGER
        exit 1
    fi
}

#
# Help
#
print_help()
{
    echo "tape-helper [tape drive] [on|off|health|mam]"
    echo "            [create-snapshot|delete-snapshot] snapshot-name zfs-datasets..."
    echo ""
    echo "Valid tape drives: 1 (LTO-6), 2 (LTO-5)"
    echo ""
    echo "on .......... Turn on tape drive"
    echo "off ......... Turn off tape drive"
    echo "health ...... Print health stats to stdout"
    echo "mam ......... Read cartridge MAM and print contents"
    echo ""
}

tape_on()
{
	# Do nothing if device already present
	if [ -e "$TAPE_DEV" ]; then
		:
		#echo "Warning: Tape drive already present." | $LOGGER
	else
	    # Turn on drive
	    toggle_relais
    fi
    # If tape device present, try to load tape
    if [ -w "$TAPE_DEV" ]; then
        mt -f "$TAPE_DEV" load 2>/dev/null || true
    fi
}

tape_eject()
{
    if ! [ -e "$TAPE_DEV" ]; then
        echo "Tape drive not detected, doing nothing." | $LOGGER
        exit 0
    fi
    # If tape online with tape loaded, rewind and unload
    ONLINE=$(mt -f "$TAPE_DEV" status 2>/dev/null | awk '
        BEGIN { go=0; }
        /^General status bits on/ { go=1; }
        /ONLINE/ {
            for (i=1;i<=NF; i++) {
                if (go==1 && $i=="ONLINE")
                    printf "%s",$i;
            }
        }')
    if [ -n "$ONLINE" ]; then
        mt -f "$TAPE_DEV" rewoffl 2>/dev/null || true
    fi
}

tape_off()
{
	# Eject tape
	tape_eject
    # Wait a little for drive to cool
    sleep "$TAPE_COOL"
    # Turn off drive
    toggle_relais
}

sg_from_nst()
{
    # Figure out sg device from nst device
    local NST=$(readlink -m $TAPE_DEV 2>/dev/null || true)
    NST=${NST/\/dev\/nst/\/dev\/st}
    SG=$(lsscsi -g | awk -v nst=$NST '
        {
            i=NF-1
            if ($i == nst) {
                printf "%s", $NF
                exit
            }
        }')
    if [ -z "$SG" ]; then
        echo "Error: Cannot find tape drive $TAPE_DEV to show health information." | $LOGGER
		exit 1
	fi
}

#TapeAlert Errors (C=Critical, W=Warning, I=Informational):
#[0x15] W: The tape drive is due for routine cleaning:
#  1. Wait for the current operation to finish.
#  2. The use a cleaning cartridge.
#  Check the tape drive users manual for device specific cleaning instructions.
show_health()
{
	sg_from_nst
	F="/run/bareos/tape-health-"$(basename $SG|tr -dc [a-z0-9])".txt"
	smartctl -H -H -i -l error -l tapedevstat $SG 2>&1 | tee "$F" || true
	if ! grep "^TapeAlert: OK" "$F" >/dev/null; then
		(
			echo "To: ${MAIL_TO}"
			echo "Subject: Backup alert on host ${HOST_NAME}"
			echo "Content-Transfer-Encoding: quoted-printable"
			echo "Content-Type: text/plain; charset=\"utf-8\""
			echo ""
			cat "$F"
			echo ""
		) | sendmail -i -t -F "${MAIL_SENDER}" -f "${MAIL_FROM}"
	fi
	rm -f "$F"
}

read_mam()
{
	sg_from_nst
	sg_raw -o - -r 1024 -t 60 -v $TAPE_DEV \
		8c 00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 2>/dev/null | \
			/etc/bareos/read_attribute.pl
}

#
# Main
#
[ $# -eq 0 ] && { print_help; exit 1; }
case "$1" in
	create-snapshot|delete-snapshot)
		[ $# -lt 3 ] && { print_help; exit 1; }
		[ "$1" = "create-snapshot" ] && mode="Create" || mode="Delete"
		snapshot_name=$(echo "$2" | tr -dc [a-zA-Z0-9-_])
		shift 2
		for d in $*; do
			dataset="$d"
			snapshot="$dataset@$snapshot_name"
			if zfs list -H -t snapshot -o name "$dataset" >/dev/null 2>&1; then
				if zfs list -H -t snapshot -o name "$snapshot" >/dev/null 2>&1; then
					[ "$mode" = "Create" ] && echo "Warning: Snapshot $snapshot exists, destroying and re-creating" | $LOGGER
					zfs destroy -d "$snapshot"
				else
					[ "$mode" = "Delete" ] && echo "Error: Cannot destroy snapshot $snapshot, does not exist" | $LOGGER
				fi
				[ "$mode" = "Create" ] && {
					zfs snapshot "$snapshot" || exit 1
				}
			else
				echo "$mode snapshot error: Dataset $dataset does not exist" | $LOGGER
			fi
		done
		;;
	*)
		[ $# -lt 2 ] && { print_help; exit 1; }
		set_params "$1"
		case "$2" in
			"on") tape_on ;;
			"off") tape_off ;;
			"eject") tape_eject ;;
			"health") show_health ;;
			"mam") read_mam ;;
			*) print_help ; exit 1 ;;
		esac
		;;
esac

exit 0