#!/bin/sh

function generate_hostname() {
    mac=$( ifconfig |grep eth0 | grep -io '[0-9a-f:]\{15\}[0-9a-f]\{2\}' )
    mac=${mac//:}
    nic=${mac:6}
    nic=$(( 16#$nic ))
    let length=32

    for i in 4 3 2 1 0; do
        let div=$length**$i
        let idx=$nic/$div
        let nic=$nic%$div

        if [ $idx = 0 ] ; then
            res=a
        elif [ $idx = 1 ] ; then
            res=b
        elif [ $idx = 2 ] ; then
            res=c
        elif [ $idx = 3 ] ; then
            res=d
        elif [ $idx = 4 ] ; then
            res=e
        elif [ $idx = 5 ] ; then
            res=f
        elif [ $idx = 6 ] ; then
            res=g
        elif [ $idx = 7 ] ; then
            res=h
        elif [ $idx = 8 ] ; then
            res=i
        elif [ $idx = 9 ] ; then
            res=j
        elif [ $idx = 10 ] ; then
            res=k
        elif [ $idx = 11 ] ; then
            res=m
        elif [ $idx = 12 ] ; then
            res=n
        elif [ $idx = 13 ] ; then
            res=p
        elif [ $idx = 14 ] ; then
            res=q
        elif [ $idx = 15 ] ; then
            res=r
        elif [ $idx = 16 ] ; then
            res=s
        elif [ $idx = 17 ] ; then
            res=t
        elif [ $idx = 18 ] ; then
            res=u
        elif [ $idx = 19 ] ; then
            res=v
        elif [ $idx = 20 ] ; then
            res=w
        elif [ $idx = 21 ] ; then
            res=x
        elif [ $idx = 22 ] ; then
            res=y
        elif [ $idx = 23 ] ; then
            res=z
        elif [ $idx = 24 ] ; then
            res=2
        elif [ $idx = 25 ] ; then
            res=3
        elif [ $idx = 26 ] ; then
            res=4
        elif [ $idx = 27 ] ; then
            res=5
        elif [ $idx = 28 ] ; then
            res=6
        elif [ $idx = 29 ] ; then
            res=7
        elif [ $idx = 30 ] ; then
            res=8
        elif [ $idx = 31 ] ; then
            res=9
        fi
        basex="$basex${res}"
    done

    old_hostname=$( cat /etc/hostname )
    new_hostname=unknown-$basex

    if [ $old_hostname = raspberrypi3-64 ]
    then
        new_hostname=rpi3-$basex
    fi

    if [ $old_hostname = raspberrypi4-64 ]
    then
        new_hostname=rpi4-$basex
    fi

    echo $new_hostname > /etc/hostname
}

FLAG="/var/local/firstboot.log"

if [ ! -f $FLAG ]; then
    echo "First boot"
    touch $FLAG

    generate_hostname
    generate_avahi_service

    
    reboot
fi