#!/bin/sh

set -e

# get the GRUB2 boot file name
ARCH=${TARGETARCH:-`uname -m`}
case $ARCH in
x86_64)
  BOOTFILE=BOOTX64.EFI
  ;;
aarch64)
  BOOTFILE=BOOTAA64.EFI
  ;;
esac

mkdir -p /tmp/efi
cd /tmp/efi

# input is a tarball on stdin with kernel and cmdline in /boot
# output is an iso on stdout

# extract. BSD tar auto recognises compression, unlike GNU tar
# only if stdin is a tty, if so need files volume mounted...
[ -t 0 ] || bsdtar xzf -

CMDLINE="$(cat cmdline)"
rm cmdline

cp /usr/local/share/$BOOTFILE .

CFG="set timeout=0
set gfxpayload=text
menuentry 'LinuxKit ISO Image' {
	linux /kernel ${CMDLINE} text
	initrd /initrd.img
}
"

mkdir -p EFI/BOOT
printf "$CFG" > EFI/BOOT/grub.cfg

# create a ISO with a EFI boot partition
# Stuff it into a FAT filesystem, making it as small as possible.  511KiB
# headroom seems to be enough; (x+31)/32*32 rounds up to multiple of 32.
mkfs.vfat -v -C boot.img \
        $(( ($(stat -c %s "${BOOTFILE}") / 1024 + 511) \
		/ 32 * 32 )) > /dev/null
echo "mtools_skip_check=1" >> /etc/mtools.conf && \
mmd -i boot.img ::/EFI
mmd -i boot.img ::/EFI/BOOT
mcopy -i boot.img $BOOTFILE ::/EFI/BOOT/

rm $BOOTFILE

xorriso -as mkisofs \
	-R -e boot.img -hide boot.img -hide boot.catalog -no-emul-boot -o linuxkit-efi-initrd.iso .

cat linuxkit-efi-initrd.iso