#!/bin/bash

IMAGE_ARCH="e2kv6" # possible values are e2k, e2kv4, e2kv5, e2kv6
IMAGE_VERSION="20240705"
IMAGE_PATH="/ALTLinux/images/Sisyphus/docker/docker-$IMAGE_VERSION-$IMAGE_ARCH.tar.xz"
MIRRORS=("http://elbrus.ivk.ru/pub" "http://setwd.ws/altlinux")

QEMU_BUILD_FLAGS="--disable-werror --disable-pie"
QEMU_BRANCH="e2k-v8.1.3"

CHROOT_DIR="chroot-$IMAGE_ARCH"

BINFMT_REGISTER_FLAGS=""

# this is taken from qemu's binfmt set up script because I don't want to pollute
# binfmt_misc with unrelated stuff
e2k_magic='\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xaf\x00'
e2k_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'
e2k_old_magic='\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x31\x00'
e2k_old_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'
qemu_target_list="e2k e2k_old"

if ! command -v git > /dev/null; then
	echo "To build qemu-e2k, we need to clone git repository. Install git."
	exit 1
fi

if ! command -v xz > /dev/null; then
	echo "To unpack ALTLinux Docker image, we need xz. Install it."
	exit 1
fi

if ! command -v wget > /dev/null; then
	echo "To download ALTLinux Docker image, we need wget. Install it."
	exit 1
fi

if [ "$(uname -m)" == "e2k" ]; then
	echo "This script is for emulating Elbrus and you're already running on this architecture"
	exit 1
fi

echo "WARNING: this script just set ups basic chroot to play with."
echo "Do not use this in production!\n"
echo "During installation, you will be asked for root access to properly"
echo "unpack image and install binfmt_misc rule\n"
read -p "Did you read and understood the message above? [Yn] " yn

case $yn in
	[yY|""] ) echo "Continuing..."; ;;
	[nN] ) echo "Exiting"; exit 0;;
	[*] ) echo "Unrecognized answer"; exit 1;;
esac

set -x

git clone https://git.mentality.rip/OpenE2K/qemu-e2k -b $QEMU_BRANCH --depth=1 || exit 2
pushd qemu-e2k || exit 2
./configure --target-list=e2k-linux-user --static $QEMU_BUILD_FLAGS || exit 2
make -j$(nproc) || exit 2
popd || exit 2

for i in "${MIRRORS[@]}"; do
	echo -n "Probing mirror $i..."
	if wget -q -O/dev/null "$i"; then
		SELECTED_MIRROR=$i

		echo "OK"
		break;
	else
		echo "BAD"
	fi
done

if [ -z "$SELECTED_MIRROR" ]; then
	echo "Can't find working mirror, exiting..."
	exit 2
fi

qemu_register_interpreter() {
	echo "Setting $qemu as binfmt interpreter for $cpu"
	qemu_generate_register | sudo tee /proc/sys/fs/binfmt_misc/register || exit 2
}

qemu_generate_register() {
	flags="${BINFMT_REGISTER_FLAGS}"

	echo ":qemu-$cpu:M::$magic:$mask:$qemu:$flags"
}

wget -Odocker.txz "$SELECTED_MIRROR$IMAGE_PATH"
mkdir -p $CHROOT_DIR || exit 2
pushd $CHROOT_DIR
sudo tar -xJf ../docker.txz || exit 2
sudo cp ../qemu-e2k/build/qemu-e2k usr/bin || exit 2

# Change default mirror in case if ivk is unreachable (it's kinda stupid to block non-Russian IP addresses, isn't it?)
if [ "$SELECTED_MIRROR" != "http://elbrus.ivk.ru/pub" ]; then
	sed "s|http://elbrus.ivk.ru/pub|$SELECTED_MIRROR|g" etc/apt/sources.list.d/ivk.list | sudo tee etc/apt/sources.list.d/mirror.list

	sudo mv etc/apt/sources.list.d/ivk.list etc/apt/sources.list.d/ivk.list.disabled
fi

sudo cp /etc/resolv.conf etc/resolv.conf

for cpu in ${qemu_target_list} ; do
	qemu="/usr/bin/qemu-e2k"
	magic=$(eval echo \$${cpu}_magic)
	mask=$(eval echo \$${cpu}_mask)
	qemu_register_interpreter
done
popd || exit 2

set +x

echo "All done."
echo "Keep in mind, it's up to you to set up binfmt_misc so it doesn't get lost between reboots"
echo "Now you can do 'sudo chroot $CHROOT_DIR /bin/bash' and have some fun!"