#!/bin/ash

DM_STATE_FILE="/run/openslx/dmsetup.state"
readonly DM_STATE_FILE

# Return the device corresponding to the given path, or
# empty if it's not mounted from a device (tmpfs, cifs, ...)
fs_path_getdev() {
	local _dev
	_dev="$( df -P "$1" | awk '$1 ~ "^/dev/" {print $1}' )"
	[ -n "$_dev" ] || return 1
	[ -b "$_dev" ] || return 1
	printf "%s" "$_dev"
}

# Return base mount point of given path
# eg. call with "/mnt/nfs/temp/data", returns "/mnt/nfs"
fs_path_getmountpoint() {
	local _mp
	_mp="$( df -P "$1" | awk '$6 ~ "^/" {print $6}' )"
	[ -n "$_mp" ] || return 1
	[ -d "$_mp" ] || return 1
	printf "%s" "$_mp"
}

# Get fstype of given directory
fs_path_gettype() {
	local _mp
	_mp="$( df -P "$1" | awk '$6 ~ "^/" {print $6}' )"
	[ -n "$_mp" ] || return 1
	[ -d "$_mp" ] || return 1
	awk '$2 == "'"$_mp"'" {print $3}' '/proc/mounts'
}

# Helper to check whether given directory resides in RAM, either
# by being mounted as tmpfs or not mounted at all in which case
# we assume the same. Returns 0 if so, 1 if otherwise backed,
# 2 when errors occur.
fs_path_isvolatile() {
	[ -z "$1" ] && return 2
	local _dev _mp
	_dev="$(fs_path_getdev "$1")"
	[ -z "$_dev" ] && return 0 # No result, assume tmpfs
	[ "$_dev" = "${_dev#/dev/zram}" ] || return 0 # zram is in RAM, like tmpfs
	[ "$_dev" != "${_dev#/dev/mapper/}" ] || return 1 # Doesn't start with /dev/mapper, assume some kind of storage
	[ -s "$DM_STATE_FILE" ] || return 2 # No point in continuing
	_mp="$(fs_path_getmountpoint "$1")"
	[ -z "$_mp" ] && return 2
	# it is a device mapper device, check if it was setup in dracut's initramfs.
	grep -qE "^$( regex_escape "${_dev}" )\s+$( regex_escape "${_mp}" )\s+type=0" "$DM_STATE_FILE"
}

# Return free/total space at given path, in KiB.
# If the given path is backed by a thin pool, snapshot, etc.
# it returns a conservative estimate, considering the remaining
# space of the backing device.
# Returns "<free> <total>"
fs_path_space() {
	[ -z "$1" ] && return 1
	local _free _total _dev _type _id _name _bs _tmp _tfree _ttotal
	_type="$( fs_path_gettype "$1" )"
	[ -z "$_type" ] && return 1
	_free="$( df -P "$1" | awk '$6 ~ "^/" {print $4 " " $2}' )"
	case "$_type" in # EASY!
		tmpfs|nfs*|cifs)
		printf "%s" "$_free"
		return
	esac
	_dev="$( fs_path_getdev "$1" )"
	if [ "$_dev" = "${_dev#/dev/mapper/}" ]; then # does *NOT* start with /dev/mapper, assume not device mapped
		# In case we start using aufs again, check if it needs special handling...
		printf "%s" "$_free"
		return
	fi
	# Split, since we might need to do Min()
	_total="${_free#* }"
	_free="${_free% *}"
	_type="$( dmsetup status "$_dev" | awk '{print $3}' )"
	_tfree=0
	_ttotal=0
	case "$_type" in
		snapshot)
			# Field 4 is used/total in sectors of 512 byte, so divide by two for KiB
			_tmp="$( dmsetup status "$_dev" | awk '{split($4, a, "/"); print (a[2] - a[1]) / 2 " " a[2] / 2}' )"
			_tfree="${_tmp% *}"
			_ttotal="${_tmp#* }"
			;;
		thin)
			# Determine matching pool
			_id="$( dmsetup table "$_dev" | awk '{print $4}' )"
			if [ -n "$_id" ]; then
				_name="$( cat "/sys/dev/block/${_id}/dm/name" )"
				if [ -n "$_name" ]; then
					# Get data block size (in sectors of 512 byte)
					_bs="$( dmsetup table "$_name" | awk '{print $6}' )"
					if [ "$_bs" -gt 0 ]; then
						# Field 6 is used/total (in data blocks), so transform into KiB
						_tmp="$( dmsetup status "$_name" | awk -v "bs=$_bs" '{split($6, a, "/"); print ((a[2] - a[1]) / 2) * bs " " (a[2] / 2) * bs}' )"
						_tfree="${_tmp% *}"
						_ttotal="${_tmp#* }"
					fi
				fi
			fi
			;;
	esac
	if [ "$_tfree" -ge 0 ] && [ "$_ttotal" -gt 0 ]; then
		[ "$_tfree" -lt "$_free" ] && _free="$_tfree"
		[ "$_ttotal" -lt "$_total" ] && _total="$_ttotal"
	fi
	printf "%s" "$_free $_total"
}