#!/bin/sh
# Notes {{{
#		Mount or extract
#			At the end, mounting or extracting the iso use the same disk space, but
#			mount require root permissions, so i choose to extract the iso.
# }}}

# Vars {{{
DEBIAN_VERSION_NAME="stretch"
DEBIAN_VERSION_NB="9.6.0"

DEBIAN_ISO_DVD_URL="https://cdimage.debian.org/debian-cd/current/amd64/iso-dvd/debian-${DEBIAN_VERSION_NB}-amd64-DVD-1.iso"
DEBIAN_ISO_NETINST_URL="https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-${DEBIAN_VERSION_NB}-amd64-netinst.iso"
DEBIAN_ISO_MINI_URL="http://ftp.nl.debian.org/debian/dists/${DEBIAN_VERSION_NAME}/main/installer-amd64/current/images/netboot/mini.iso"

TEMP_DIR=$(mktemp -d -t new-preseed-debian-iso-XXXXXX.tmp)
TEMP_ISO_DIR="${TEMP_DIR}/extracted-iso"
TEMP_INITRD_DIR="${TEMP_DIR}/initrd"

DEBIAN_DL_ISO_PATH="${TEMP_DIR}/debian.iso"
DEBIAN_PRESEED_ISO_PATH="$(dirname ${TEMP_DIR})/preseed-debian-${DEBIAN_VERSION_NB}-amd64.iso"
# }}}

#USE_DEBIAN_ISO="${DEBIAN_ISO_DVD_URL}"
USE_DEBIAN_ISO="${DEBIAN_ISO_NETINST_URL}"
#USE_DEBIAN_ISO="${DEBIAN_ISO_MINI_URL}"

# Pre-requisites {{{
if [ ! $(command -v 7z) ]; then
	printf '%b\n' "ERROR : Please install '7z' bin :\\nsudo apt install p7zip-full"
	exit 1
fi
if [ ! $(command -v gzip) ]; then
	printf '%b\n' "ERROR : Please install 'gzip' bin :\\nsudo apt install gzip"
	exit 1
fi
if [ ! $(command -v xorriso) ]; then
	printf '%b\n' "ERROR : Please install 'xorriso' bin :\\nsudo apt install xorriso"
	exit 1
fi
if [ ! -f /usr/lib/ISOLINUX/isohdpfx.bin ]; then
	printf '%b\n' "ERROR : Please install 'isolinux' package :\\nsudo apt install isolinux"
	exit 1
fi
# }}}

# Test vars {{{
case $# in
	1 )
		PRESEED_FILE="${1}"
	;;
	2 )
		PRESEED_FILE="${1}"
		USER_TEMP_DIR="${2}"
		## Check user temp dir argument
		if [ ! -d "${USER_TEMP_DIR}" ]; then
			printf '%b\n' "ERROR : The first argument should be the path to a directory."
			exit 1
		fi
		TEMP_DIR=$(mktemp -d -t debian-iso-XXXXXX.tmp -p "${USER_TEMP_DIR}")
	;;
	* )
		printf '%b\n' "Usage :"
		printf '%b\n' "$(basename ${0}) PRESEED_FILE_PATH [TEMP_DIR]"
		printf '%b\n' "-------"
		printf '%b\n' "PRESEED_FILE_PATH : Required"
		printf '%b\n' "Should be the absolut path to the preseed file you want to add to the ISO."
		printf '%b\n' "-------"
		printf '%b\n' "TEMP_DIR : Optionnal"
		printf '%b\n' "If you want to store temporary files and final ISO in a specific directory."
		printf '%b\n' "Note : This script require ISO size × 2 (eg for DVD. 3.4GB × 2)."
		printf '%b\n' "Otherwise \$TMPDIR will be used."
	;;
esac

## Check preseed argument
if [ ! -f "${PRESEED_FILE}" ]; then
	printf '%b\n' "ERROR : The first argument should be the path to preseed file to add."
	exit 1
fi
# }}}

# Download and extract ISO {{{
wget -q "${USE_DEBIAN_ISO}" -O "${DEBIAN_DL_ISO_PATH}"
command 7z x -o"${TEMP_ISO_DIR}" -- "${DEBIAN_DL_ISO_PATH}" > /dev/null
rm -rf -- "${DEBIAN_DL_ISO_PATH}"
## Ensure to have the write permission on the extracted folder
chmod 0700 -- "${TEMP_ISO_DIR}"
# }}}
# Manage initrd.gz file {{{
mkdir -- "${TEMP_INITRD_DIR}"
## Exclude initrd.gz files from xen and gtk directories
INITRD_GZ_PATH=$(find "${TEMP_ISO_DIR}" -type f \( -path '*xen*' -o -path '*gtk*' \) -prune -o -name "initrd.gz" -print -quit)

## Copy it to a directory
cp -- "${INITRD_GZ_PATH}" "${TEMP_INITRD_DIR}" || exit 2

cd -- "${TEMP_INITRD_DIR}" > /dev/null || exit 2
## Uncompress initrd.gz then delete it
gunzip < initrd.gz | cpio --extract --quiet --make-directories --no-absolute-filenames >> /dev/null
rm -f -- initrd.gz

## Add preseed file
cp -- "${PRESEED_FILE}" preseed.cfg || exit 2

## Recompress to initrd.gz and move it back to the extracted files for ISO
find . -not -name initrd.gz | cpio --format=newc --create --quiet | gzip --best > initrd.gz
cp -- initrd.gz "${INITRD_GZ_PATH}" || exit 2

## Go back to previous directory and remove no longer useful files
cd - > /dev/null || exit 2
rm -rf -- "${TEMP_INITRD_DIR}"

## Fix permissions in install directory
chmod -w -R -- $(dirname -- "${INITRD_GZ_PATH}")
# }}}
# Generate new md5sum {{{
## Ensure to have the write permission on the iso folder
chmod 0700 -- "${TEMP_ISO_DIR}"
cd -- "${TEMP_ISO_DIR}" > /dev/null || exit 2
## Exclude some unwanted files
find . -follow -type f -not \( -name "md5sum.txt" -o -name 'mkisofs' -o -name 'Bootable_NoEmulation.img' -o -path '*isolinux*' \) -exec md5sum {} \; > ./md5sum.txt
## Fix md5sum.txt permissions
chmod -w -- md5sum.txt
cd - > /dev/null || exit 2
# }}}
# Generate new bootable iso {{{
if [ -d "${TEMP_ISO_DIR}/isolinux" ] ; then
	xorriso -as mkisofs -o "${DEBIAN_PRESEED_ISO_PATH}" \
-quiet -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
-c isolinux/boot.cat -b isolinux/isolinux.bin -no-emul-boot \
-boot-load-size 4 -boot-info-table "${TEMP_ISO_DIR}"
else
	## For mini.iso creation
	xorriso -as mkisofs -o "${DEBIAN_PRESEED_ISO_PATH}" \
-quiet -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
-c boot.cat -b isolinux.bin -no-emul-boot \
-boot-load-size 4 -boot-info-table "${TEMP_ISO_DIR}"
fi

## Then remove temp iso directory
chmod u+w -R -- "${TEMP_ISO_DIR}"
rm -rf -- "${TEMP_ISO_DIR}"

# }}}

rmdir -- "${TEMP_DIR}"

printf '%b\n' "The new ISO image is available : ${DEBIAN_PRESEED_ISO_PATH}"

exit 0