#!/usr/bin/bash

# needed configuration values
# BOOTSTRAP_HOSTNAME=
# BOOTSTRAP_ROOTFS=
# BOOTSTRAP_IFNAME=
# BOOTSTRAP_IFADDR=
# BOOTSTRAP_IFGW=
# BOOTSTRAP_DNS=
# BOOTSTRAP_ALPINE_VERSION=

# Must be root
notroot() {
    echo "You must be root to run this script"
    exit 1
}
[ `id -u` -eq 0 ] || notroot

# Set the variable in the environment or give a file defining them as an argument
if [ $# -ge 1 ];
then
    source $1
fi

echo "Starting to bootstrap an Alpine Linux OS with the following configuration:"
echo BOOTSTRAP_HOSTNAME=$BOOTSTRAP_HOSTNAME
echo BOOTSTRAP_ROOTFS=$BOOTSTRAP_ROOTFS
echo BOOTSTRAP_IFNAME=$BOOTSTRAP_IFNAME
echo BOOTSTRAP_IFADDR=$BOOTSTRAP_IFADDR
echo BOOTSTRAP_IFGW=$BOOTSTRAP_IFGW
echo BOOTSTRAP_DNS=$BOOTSTRAP_DNS
echo BOOTSTRAP_ALPINE_VERSION=$BOOTSTRAP_ALPINE_VERSION

echo "confirm (y/n)"
read confirm

[ "$confirm" != "y" ] && exit 0

APK_BINARY=
TARGET_MNT=`mktemp -d`

error_mount() {
    echo "Cannot mount $BOOTSTRAP_ROOTFS to $TARGET_MNT"
    exit 1
}
mount_rootfs() {
     mount -t ext4 $BOOTSTRAP_ROOTFS $TARGET_MNT || error_mount
}

error_download_apk() {
    echo "Cannot download apk binary file"
    exit 1
}
download_apk() {
    APK_BINARY=`mktemp` 
    curl https://gitlab.alpinelinux.org/api/v4/projects/5/packages/generic/v2.14.6/x86_64/apk.static > $APK_BINARY || error_download_apk
    chmod +x $APK_BINARY
}

error_bootstrap() {
    echo "Cannot bootstrap alpine"
    exit 1
}
bootstrap() {
    REPO=https://dl-cdn.alpinelinux.org/alpine/v$BOOTSTRAP_ALPINE_VERSION/main/
    $APK_BINARY --arch x86_64 \
        -X $REPO \
        -U --allow-untrusted --initdb \
        --root $TARGET_MNT \
        add alpine-base agetty || error_bootstrap
}

genfstab() {
    echo "UUID=`blkid -s UUID -o value $BOOTSTRAP_ROOTFS`   /   ext4 defaults,errors=remount-ro,discard,noatime  0   1"
}

# geninittab() {
# }

geninterfaces() {
    cat << EOF
auto lo
iface lo inet loopback

auto $BOOTSTRAP_IFNAME
iface $BOOTSTRAP_IFNAME inet static
    address $BOOTSTRAP_IFADDR
    gateway $BOOTSTRAP_IFGW
EOF
}

genresolvconf() {
    cat << EOF
nameserver $BOOTSTRAP_DNS
search `echo $BOOTSTRAP_HOSTNAME|cut -d. -f2-`
EOF
}

genapkrepo() {
    cat << EOF
https://dl-cdn.alpinelinux.org/alpine/v$BOOTSTRAP_ALPINE_VERSION/main
https://dl-cdn.alpinelinux.org/alpine/v$BOOTSTRAP_ALPINE_VERSION/community
EOF
}

chrooting() {
    for dir in /proc /sys /dev;
    do
        mount -o bind $dir $TARGET_MNT$dir
    done
}

unchroot() {
    for dir in /proc /sys /dev;
    do
        umount $TARGET_MNT$dir
    done
}

exit_clean() {
    unchroot
    umount $TARGET_MNT
    rmdir $TARGET_MNT
    rm $APK_BINARY
}

echo "Installing"

mount_rootfs

[ ! -x "$APK_BINARY" ] && download_apk

bootstrap
echo $BOOTSTRAP_HOSTNAME > $TARGET_MNT/etc/hostname
genfstab > $TARGET_MNT/etc/ftsab
# geninittab > $TARGET_MNT/etc/inittab
geninterfaces > $TARGET_MNT/etc/network/interfacces
genresolvconf > $TARGET_MNT/etc/resolv.conf
genapkrepo > $TARGET_MNT/etc/apk/repositories
chrooting

CHROOT_CMD="chroot $TARGET_MNT"
(
PATH=/sbin:/bin:/usr/sbin:/usr/bin 

# Install packages
$CHROOT_CMD apk update
$CHROOT_CMD apk add linux-virt linux-firmware-none acpi mkinitfs vim screen qemu-guest-agent openssh-server

# Enable services
for svc in seedrng swap networking modules hostname hwclock bootmisc;
do
    $CHROOT_CMD rc-update add $svc boot;
done;
for svc in acpid crond qemu-guest-agent sshd;
do
    $CHROOT_CMD rc-update add $svc default;
done;
for svc in devfs dmesg mdev hwdrivers;
do
    $CHROOT_CMD rc-update add $svc sysinit;
done;
for svc in killprocs mount-ro savecache;
do
    $CHROOT_CMD rc-update add $svc shutdown;
done;
)
exit_clean