#!/bin/bash
#
# prl_fstat - gather mounted filesystems statistics
#
# (c) 2015. Parallels IP Holdings GmbH. All rights reserved.

# SCSI host index -> bus name mapping
declare -a HOST_BUS_MAP 
# SCSI bus name -> starting host offset mapping
declare -A BUS_OFFSET_MAP

init_scsi_disk_types() {
	for host in $(find /sys/class/scsi_host/ -type l); do
		local bus_type="-"
		local tmp="$(basename "$(readlink "$host")")"
		local index=${tmp#host}

		case "$(cat "$host"/proc_name)" in
		BusLogic)
			# only BusLogic SCSI interface is available for
			# Linux guests
			bus_type="scsi"
			;;
		ata*)
			bus_type="ide"
			;;
		sata|ahci)
			bus_type="sata"
			;;
		esac

		HOST_BUS_MAP[$index]="$bus_type"
	done
	
	BUS_OFFSET_MAP[ide]=${#HOST_BUS_MAP[@]}
	BUS_OFFSET_MAP[sata]=${#HOST_BUS_MAP[@]}
	BUS_OFFSET_MAP[scsi]=${#HOST_BUS_MAP[@]}
	BUS_OFFSET_MAP[-]=${#HOST_BUS_MAP[@]}
	for host in "${!HOST_BUS_MAP[@]}"; do
		bus=${HOST_BUS_MAP[$host]}
		[[ ${BUS_OFFSET_MAP[$bus]} -gt $host ]] \
			&& BUS_OFFSET_MAP[$bus]=$host
	done
}

get_disk_interface() {
	IFS=: read -a hctl <<< \
		"$(basename "$(readlink /sys/block/"$1"/device)")"
	local bus="${HOST_BUS_MAP[${hctl[0]}]}"
	local offset="${BUS_OFFSET_MAP[$bus]}"
	local position=""

	case $bus in
	sata)
		position="$((${hctl[0]}-$offset))"
		;;
	scsi)
		position="${hctl[2]}"
		;;
	ide)
		position="$(((${hctl[0]} - $offset) * 2 + ${hctl[2]}))"
	esac

	echo -n "$bus$position"
}

get_swap_stats() {
	echo "$(cat /proc/swaps | tail -n +2 | awk '{print $1,$3,$4}')" | \
	while read dev total used; do
		local name="$(lsblk --output NAME --nodeps --noheadings --raw \
			"$dev" 2>/dev/null)"
		[[ $? -ne 0 ]] && exit 2
		if [ "$name" == "$1" ]; then
			echo "$total $(($total - $used))"
			break
		fi
	done
}

get_excluded_block_devices() {
	local excluded=""
	local block=0
	while read major name; do
		if [[ $major == Block ]]; then
			block=1
			continue
		fi
		if [[ $block -eq 1 && -n $name && $name != sd ]]; then
			[[ -n $excluded ]] && excluded+=","
			excluded+="$major"
		fi
		[[ $major == Character ]] && block=0
	done <<< "$(cat /proc/devices)"
	echo "$excluded"
}

get_fs_statistics() {
	LANG=C
	
	local -A mounted # device -> mountpoint
	local -A disks # mountpoint -> "disk1 disk2 disk3"

	init_scsi_disk_types &>/dev/null

	local output="$(lsblk --exclude "$(get_excluded_block_devices)"\
		--output NAME,MOUNTPOINT --noheadings --raw 2>/dev/null)"
	[[ $? -ne 0 ]] && exit 1
	local cur=""
	while read name mountpoint; do
		if [[ $name =~ ^sd[[:alpha:]]{1,2}$ ]]; then
			cur="$name"
		fi
		if [[ -n "$mountpoint" ]]; then
			mounted[$name]="$mountpoint"
			local iface="$(get_disk_interface $cur)"
			[[ "$iface" != - ]] && \
				disks[$mountpoint]+="$iface "
		fi
	done <<< "$output"
	
	for device in ${!mounted[@]}; do
		local stats="0 0"
		if [ "${mounted[$device]}" == "[SWAP]" ]; then
			stats="$(get_swap_stats "$device")"
		else
			local tmp="$(stat --file-system --printf="%s %b %f" \
				"${mounted[$device]}")"
			read -a usage <<< "$tmp"
			stats="$((${usage[0]}*${usage[1]}/1024)) \
				$((${usage[0]}*${usage[2]}/1024))"
		fi
		tmp=${disks[${mounted[$device]}]}
		[[ -n "$tmp" ]] && echo $device $stats $tmp
	done	
}

[[ -z "$(which lsblk)" ]] && exit 3
[[ -z "$(ls /sys/block/)" ]] && exit 4

get_fs_statistics
exit 0