#!/bin/sh

MIN_DISK_SPACE_MB=1000

list_disks() {
    lsblk -o NAME -r -d -n
}

main() {
    local disks=$(list_disks)

    local found_free_space=0
    local found_device=""

    for device_name in ${disks}; do
        local device="/dev/${device_name}"
        echo "Checking disk '$device'..."
        
        local disk_free_space="$(parted $device unit MB print free 2>/dev/null | grep 'Free Space' | tail -n1 | awk '{ print $3 }')"
        disk_free_space=${disk_free_space%MB}
        disk_free_space=$(printf '%.0f' "${disk_free_space:-0}")
        
        echo "Free space on disk: ${disk_free_space}"

        if [ ! -z "${disk_free_space}" ]; then
            if [ ${disk_free_space} -gt ${found_free_space} ]; then
                found_free_space=${disk_free_space}
                found_device=${device}
            fi
        fi
    done

    if [ -z "${found_device}" ] || [ ${MIN_DISK_SPACE_MB} -gt ${found_free_space} ]; then
        echo "No device with sufficient remaining disk space, exiting."
        exit 1
    fi

    echo "Creating new partition on '${found_device}' with remaining disk free space"

    local last_partition_end_mb=$(parted "$found_device" unit MB print | awk '/^ [0-9]+ / {start=$3} END {print int(start)}')
    
    if [ "${last_partition_end_mb}" != "0" ]; then
        parted -s "${found_device}" -f -a opt mkpart primary "${last_partition_end_mb}MB" '100%'
    else
        parted -s "${found_device}" -f -a opt mkpart primary '0%' '100%'
    fi

    sync

    local last_partition_number=$(parted ${found_device} print | grep -o -e '^ [0-9]*' | awk '{print $1}' | tail -n 1)
    local new_partition_device=$(lsblk -r -n -o PARTN,NAME ${found_device} | awk -v partition_number="${last_partition_number}" '$1 == partition_number {print $2}')

    mkfs.ext4 -F /dev/${new_partition_device}
    if [ $? -ne 0 ]; then
        echo "Could not initialize filesystem on new partition !"
        exit 1
    fi
    
    local new_partition_uuid=$(lsblk -r -n -o PARTN,UUID ${found_device} | awk -v partition_number="${last_partition_number}" '$1 == partition_number {print $2}')

    if [ -z "${new_partition_uuid}" ]; then
        echo "Could not find partition with number '${last_partition_number}' !"
        exit 1
    fi

    umount -f /data
    rm -rf /data
    mkdir -p /data

    uci add fstab mount
    uci set fstab.@mount[-1].target='/data'
    uci set fstab.@mount[-1].uuid=${new_partition_uuid}
    uci set fstab.@mount[-1].enabled='1'
    uci commit fstab

    reload_config
}

main