#!/bin/bash

## FORSTWOOF UBUNTU PRESEED :: BUILD SCRIPT

# Quit on first error
set -e

# Temporary directory for the build
TMP="/var/tmp/ubuntu-build"


# Cleanup function
cleanup () {
    echo "Cleaning up"
    umount "${TMP}/files" || true
    umount "${TMP}/mnt" || true
    rm -r "${TMP}"
}

# Clean up on SIGINT
trap "cleanup" INT

# Get the script's running directory
SCRDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

# Directory from where script was started
CURDIR="$(pwd)"

# Preseed file
SEED="${SCRDIR}/preseed.cfg"

# Source and destination files
SRC="${1}"
DST="${2}"

echo "Performing file presence checks"

# Check if the source file exists
[ -f "${SRC}" ] || {
    echo "The source file does not exist!"
    exit 1
}

# Check if the source file is of an appropriate type
TYPE=$(file "${SRC}" | tail -c 16)
[ "${TYPE}" != "x86 boot sector" ] && {
    echo "The source file is not a valid bootable ISO file!"
    exit 3
}

# Check if the preseed file exists
[ -f "${SEED}" ] || {
    echo "The preseed file does not exist!"
    exit 2
}

# Check if the destination file exists and offer to delete it
[ -e "${DST}" ] && {
    echo -n "The destination file already exists! Do you want to remove it? [y/N] "
    read ANS

    ([ "${ANS}" == "y" ] || [ "${ANS}" == "Y" ]) || {
        echo "Build cancelled."
        exit 4
    }

    rm -r "${DST}"
}

# Create the temporary directory
echo "Creating a temporary directory"
[ -e "${TMP}" ] && cleanup
mkdir "${TMP}"

# Mount the source ISO image
echo "Mounting the source image"
mkdir "${TMP}/mnt"
mount -o ro "${SRC}" "${TMP}/mnt"

# Create an overlay file system
echo "Creating an overlay file system"
mkdir "${TMP}/files"
mkdir "${TMP}/overlay"
mkdir "${TMP}/work"
mount -t overlayfs -o lowerdir="${TMP}/mnt",upperdir="${TMP}/overlay",workdir="${TMP}/work" overlayfs "${TMP}/files"

# Enable serial console for EFI boot entries
echo "Enabling serial console for EFI boot entries (grub)"
cat <<EOF >"${TMP}/files/boot/grub/grub.cfg"
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal_input console serial
terminal_output console serial

menuentry "Install Ubuntu Server (automated)" {
    linux   /install/vmlinuz file=/cdrom/preseed/ubuntu-server.seed text console=ttyS0,115200n8 ---
    initrd  /install/initrd.gz
}
menuentry "Check disc for defects" {
    linux   /install/vmlinuz MENU=/bin/cdrom-checker-menu text console=ttyS0,115200n8 ---
    initrd  /install/initrd.gz
}
menuentry "Rescue a broken system" {
    linux   /install/vmlinuz rescue/enable=true text console=ttyS0,115200n8 ---
    initrd  /install/initrd.gz
}
EOF

# Enable serial console for legacy boot entries
echo "Enabling serial console for legacy boot entries (syslinux)"
cat <<EOF >"${TMP}/isolinux.cfg"
serial 0 115200 0x003
EOF
cat "${TMP}/files/isolinux/isolinux.cfg" >>"${TMP}/isolinux.cfg"
sed -i 's/default vesamenu.c32//g' "${TMP}/isolinux.cfg"
sed -i 's/ui gfxboot bootlogo//g' "${TMP}/isolinux.cfg"
mv "${TMP}/isolinux.cfg" "${TMP}/files/isolinux/isolinux.cfg"
sed -i 's/---/console=ttyS0,115200n8 ---/g' "${TMP}/files/isolinux/txt.cfg"

# Rebuilding initrd
echo "Rebuilding initrd for CD booting"
mkdir "${TMP}/initrd"
cd "${TMP}/initrd"
gzip -d < "${TMP}/files/install/initrd.gz" | cpio --extract --make-directories --no-absolute-filenames --quiet
rm "${TMP}/files/install/initrd.gz"
cp "${SEED}" "${TMP}/initrd"
find . | cpio -H newc --create --quiet | gzip -9 > "${TMP}/files/install/initrd.gz"

echo "Rebuilding initrd for network booting"
rm -r *
ARCH=$(ls "${TMP}/files/install/netboot/ubuntu-installer")
gzip -d < "${TMP}/files/install/netboot/ubuntu-installer/${ARCH}/initrd.gz" | cpio --extract --make-directories --no-absolute-filenames --quiet
rm "${TMP}/files/install/netboot/ubuntu-installer/${ARCH}/initrd.gz"
cp "${SEED}" "${TMP}/initrd"
find . | cpio -H newc --create --quiet | gzip -9 > "${TMP}/files/install/netboot/ubuntu-installer/${ARCH}/initrd.gz"
rm -r "${TMP}/initrd"

# Recreate the md5sum.txt file
echo "Calculating MD5 checksums for the image"
cd "${TMP}/files"
md5sum -b $(find -type f) > md5sum.txt

OPTS=""
[ -f "${TMP}/files/boot/grub/efi.img" ] && OPTS="-eltorito-alt-boot -e boot/grub/efi.img -no-emul-boot"

# Build the ISO image
echo "Building the new ISO image"
cd "${CURDIR}"
mkisofs -r -V "UBUNTUSEED" \
        -cache-inodes \
        -J -l -b isolinux/isolinux.bin \
        -c isolinux/boot.cat -no-emul-boot \
        -boot-load-size 4 -boot-info-table \
        ${OPTS} \
	-input-charset utf-8 -quiet \
        -o "${DST}" "${TMP}/files"

# Clean up the mess
cleanup