#!/bin/bash

function install_dependencies() {
	echo "Installing dependencies..."
	sudo apt -qq update
	sudo apt -qq install -y curl git wget
	sudo apt -qq install -y bison flex kernel-package libelf-dev libssl-dev
}

function init() {
	echo "Initializing..."

	kernel_config=$(ls /boot/config-* | grep generic | sort -Vr | head -n 1)
	grub_config="/etc/default/grub"

	current_dir=$(pwd)
	working_dir=$(mktemp -d)
	cd "${working_dir}" || exit

	install_dependencies
}

function get_newest_versions() {
	echo "Retrieving newest version information..."

	stable_releases_3x_url="https://mirrors.edge.kernel.org/pub/linux/kernel/v3.x/"
	stable_releases_4x_url="https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/"
	stable_releases_5x_url="https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/"

	stable_releases_3x_html=$(curl -s "${stable_releases_3x_url}")
	stable_releases_4x_html=$(curl -s "${stable_releases_4x_url}")
	stable_releases_5x_html=$(curl -s "${stable_releases_5x_url}")

	stable_releases_combined_html="${stable_releases_3x_html}${stable_releases_4x_html}${stable_releases_5x_html}"
	stable_version=$(echo "${stable_releases_combined_html}" | grep -E -o 'linux-([0-9]{1,}\.)+[0-9]{1,}' | sort -Vru | head -n 1 | cut -d '-' -f 2)

	mainline_link=$(curl -s https://www.kernel.org/ | grep https://git.kernel.org/torvalds/t/linux- | grep -Po '(?<=href=")[^"]*')
	if ! [ -z "${mainline_link}" ]
	then
		mainline_version=$(echo "${mainline_link}" | cut -d '-' -f 2,3 | cut -d '.' -f 1,2)
	else
		mainline_version="unavailable"
	fi

	repo_pkg=$(apt search 'linux-source-' | grep 'linux-source' | cut -d '/' -f 1 | awk -F- 'NF<=3' | sort -Vr | head -n 1)
	#repo_version=$(echo "${repo_pkg}" | cut -d '-' -f 3)
	repo_version=$(apt search 'linux-source-' | grep 'linux-source' | sort -Vr | head -n 1 | cut -d ' ' -f 2)
}

function stable_or_mainline_or_repo() {
	get_newest_versions
	echo "Newest stable version is: ${stable_version}"
	echo "Mainline version is:      ${mainline_version}"
	echo "Repository version is:    ${repo_version}"
	echo -n "Do you want to get a [s]table, the newest [m]ainline release candidate or the newest kernel from your [r]epositories? [S/m/r] "
	read -r s_or_m_or_r

	echo -n "Do you want to apply the acs override patch? Kernels below 4.10 are not supported. [Y/n] "
	read -r acso

	echo -n "Do you want to apply the experimental AMD AGESA patch to fix VFIO setups on AGESA 0.0.7.2 and newer? [y/N] "
	read -r agesa

	echo -n "Do you want to apply the experimental AMD Vega PCI reset patch? [y/N] "
	read -r vega

	echo -n "Do you want to install the kernel and its headers after compilation? [Y/n] "
	read -r install

	if [ -z "${install}" ] || [ "${install}" == "y" ]
	then
		echo -n "Do you want to make this kernel the new default? [Y/n] "
		read -r default
	fi

	if [ -z "${s_or_m_or_r}" ] || [ "${s_or_m_or_r}" == "s" ]
	then
		stable_preparations
	else
		if [ "${s_or_m_or_r}" == "m" ]
		then
			if [ "${mainline_version}" == "unavailable" ]
			then
				echo "Mainline version currently unavailable. Exiting."
				exit
			else
				mainline_preparations
			fi
		else
			if [ "${s_or_m_or_r}" == "r" ]
			then
				repo_preparations
			else
				echo "Not a valid option. Exiting."
				exit
			fi
		fi
	fi
}

function try_acso_patch() {
	acso_patch_5_6_12="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/5.6.12/acso.patch"
	acso_patch_5_4="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/5.4/acso.patch"
	acso_patch_4_18="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/4.18/acso.patch"
	acso_patch_4_17="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/4.17/acso.patch"
	acso_patch_4_14="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/4.14/acso.patch"
	acso_patch_4_10="https://gitlab.com/Queuecumber/linux-acs-override/raw/master/workspaces/4.10/acso.patch"
	acso_patch_4_18_ubuntu="https://gist.github.com/mdPlusPlus/bb3df6248ffc7c6b3772ae0901659966/raw/acso_4_18_ubuntu.patch"

	echo "Trying to apply acs override patch for 5.6.12+."
	wget -O ../acso_5_6_12.patch "${acso_patch_5_6_12}"
	if $(git apply --check ../acso_5_6_12.patch)
	then
		echo "Applying acs override patch for 5.6_12+."
		git apply ../acso_5_4.patch
	else
		echo "Trying to apply acs override patch for 5.4+."
		wget -O ../acso_5_4.patch "${acso_patch_5_4}"
		if $(git apply --check ../acso_5_4.patch)
		then
			echo "Applying acs override patch for 5.4+."
			git apply ../acso_5_4.patch
		else
			echo "Trying to apply acs override patch for 4.18+."
			wget -O ../acso_4_18.patch "${acso_patch_4_18}"
			if $(git apply --check ../acso_4_18.patch)
			then
				echo "Applying acs override patch for 4.18+."
				git apply ../acso_4_18.patch
			else
				echo "Trying to apply acs override patch for 4.17+."
				wget -O ../acso_4_17.patch "${acso_patch_4_17}"
				if $(git apply --check ../acso_4_17.patch)
				then
					echo "Applying acs override patch for 4.17+."
					git apply ../acso_4_17.patch
				else
					echo "Trying to apply acs override patch for 4.14+."
					wget -O ../acso_4_14.patch "${acso_patch_4_14}"
					if $(git apply --check ../acso_4_14.patch)
					then
						echo "Applying acs override patch for 4.14+."
						git apply ../acso_4_14.patch
					else
						echo "Trying to apply acs override patch for 4.10+."
						wget -O ../acso_4_10.patch "${acso_patch_4_10}"
						if $(git apply --check ../acso_4_10.patch)
						then
							echo "Applying acs override patch for 4.10+."
							git apply ../acso_4_10.patch
						else
							echo "Last resort: Trying to apply acs override patch for Ubuntu repository kernel source."
							wget -O ../acso_4_18_ubuntu.patch "${acso_patch_4_18_ubuntu}"
							if $(git apply --check ../acso_4_18_ubuntu.patch)
							then
								echo "Applying acs override patch for Ubuntu repository kernel source."
								git apply ../acso_4_18_ubuntu.patch
							else
								echo "[ERROR]: Failed to apply acs override patch. Exiting."
								exit
							fi
							rm -f ../acso_4_18_ubuntu.patch
						fi
						rm -f ../acso_4_10.patch
					fi
					rm -f ../acso_4_14.patch
				fi
				rm -f ../acso_4_17.patch
			fi
			rm -f ../acso_4_18.patch
		fi
		rm -f ../acso_5_4.patch
	fi
	rm -f ../acso_5_6_12.patch

	kernel_localversion+="-acso"
}

function try_agesa_patch() {
	##by reddit user https://www.reddit.com/user/hansmoman/
	##https://www.reddit.com/r/VFIO/comments/bqeixd/apparently_the_latest_bios_on_asrockmsi_boards/eo4neta
	agesa_patch="https://clbin.com/VCiYJ"
	agesa_patch_filename="agesa.patch"

	echo "Trying to apply AMD AGESA patch."
	wget -O ../${agesa_patch_filename} "${agesa_patch}"
	if $(git apply --check ../${agesa_patch_filename})
	then
		echo "Applying AMD AGESA patch."
		git apply ../${agesa_patch_filename}
	else
		echo "[ERROR]: Failed to apply AMD AGESA patch. Exiting."
		exit
	fi

	rm -f ../${agesa_patch_filename}

	kernel_localversion+="-agesa"
}

function try_vega_patch() {
	##Original by github user https://gist.github.com/numinit

	vega_patch_new="https://gist.github.com/mdPlusPlus/1754d82b53269ead770133829874fbfd/raw/"
	vega_patch="https://gist.github.com/numinit/1bbabff521e0451e5470d740e0eb82fd/raw"
	vega_patch_filename="fix-vega-reset.patch"

	echo "Trying to apply AMD Vega reset patch."
	wget -O ../${vega_patch_filename} "${vega_patch_new}"

	if $(git apply --check ../${vega_patch_filename})
	then
		echo "Applying AMD Vega reset patch."
		git apply ../${vega_patch_filename}
	else
		rm -f ../${vega_patch_filename}
		wget -O ../${vega_patch_filename} "${vega_patch}"

		if $(git apply --check ../${vega_patch_filename})
		then
			echo "Applying AMD Vega reset patch."
			git apply ../${vega_patch_filename}
		else
			echo "[ERROR]: Failed to apply AMD Vega reset patch. Exiting."
			exit
		fi
	fi

	rm -f ../${vega_patch_filename}

	kernel_localversion+="-vega"
}

function stable_preparations() {
	echo "The newest available stable kernel version is ${stable_version}. Kernels below 4.10 are not supported."
	echo -n "Which version do you want to download? [${stable_version}] "
	read -r user_version

	if  ! [ -z "${user_version}" ]
	then
		stable_version="${user_version}"
	fi

	kernel_version="${stable_version}"
	kernel_name="linux-${kernel_version}"


	##Test whether the version string starts with 3, 4, or 5 and sets the URL accordingly
	if [[ $stable_version == 5* ]]
	then
		stable_link="${stable_releases_5x_url}linux-${stable_version}.tar.xz"
	else
		if [[ $stable_version == 4* ]]
		then
			stable_link="${stable_releases_4x_url}linux-${stable_version}.tar.xz"
		else
			if [[ $stable_version == 3* ]]
			then
				stable_link="${stable_releases_3x_url}linux-${stable_version}.tar.xz"
			else
				echo "${stable_version} is not a vaild version number. Exiting."
				exit
			fi
		fi
	fi

	wget "${stable_link}"
	tar xf "${kernel_name}.tar.xz"
	cd "${kernel_name}" || exit

	independent_code
}

function mainline_preparations() {
	kernel_version="${mainline_version}"
	kernel_name="linux-${kernel_version}"

	wget "${mainline_link}"
	tar xf "${kernel_name}.tar.gz"
	cd "${kernel_name}" || exit

	independent_code
}

function repo_preparations() {
	kernel_name="${repo_pkg}"

	sudo apt install "${repo_pkg}"
	tar xf "/usr/src/${kernel_name}.tar.bz2"
	cd "${kernel_name}" || exit

	makefile_version=$(grep "^VERSION" Makefile |  tr -d '[:space:]' | cut -d '=' -f 2)
	makefile_patchlevel=$(grep "^PATCHLEVEL" Makefile|  tr -d '[:space:]' | cut -d '=' -f 2)
	makefile_sublevel=$(grep "^SUBLEVEL" Makefile |  tr -d '[:space:]' | cut -d '=' -f 2)
	#makefile_extraversion=$(grep "^EXTRAVERSION" Makefile|  tr -d '[:space:]' | cut -d '=' -f 2)

	if ! [ -z "${makefile_version}" ]
	then
		kernel_version="${makefile_version}"
		if ! [ -z "${makefile_patchlevel}" ]
		then
			kernel_version="${makefile_version}.${makefile_patchlevel}"
			if ! [ -z "${makefile_sublevel}" ]
			then
				kernel_version="${makefile_version}.${makefile_patchlevel}.${makefile_sublevel}"
			fi
		fi
	fi

	##linux-hwe (5.0.0-25.26~18.04.1) bionic; urgency=medium
	##->
	##5.0.0-25.26~18.04.1
	#kernel_version=$(head -n 1 debian/changelog | cut -d '(' -f 2 | cut -d ')' -f 1)
	##This somehow comes out empty when run in the script, but is successful when issued manually

	independent_code
}

function independent_code() {
	kernel_localversion=""

	if [ -z "${acso}" ] || [ "${acso}" != "n" ]
	then
		try_acso_patch
	fi

	if [ "${agesa}" == "y" ]
	then
		try_agesa_patch
	fi

	if [ "${vega}" == "y" ]
	then
		try_vega_patch
	fi

	##temporary
	#fix_steam

	cp "${kernel_config}" .config
	yes '' | make oldconfig

	##set xhci_hcd to load as a module instead of including it directly into the kernel
	##results in vfio_pci being able to grab usb controllers before xhci_hcd is able to
	sed -i -e 's/^CONFIG_USB_XHCI_HCD=y/CONFIG_USB_XHCI_HCD=m/g' .config

	##Enable AMD's HSA driver for ROCm support. Thanks at https://github.com/jfturcot
	sed -i -e 's/^#\ CONFIG_HSA_AMD\ is\ not\ set/CONFIG_HSA_AMD=y/g' .config

	##Disable debug builds
	sed -i -e 's/^CONFIG_DEBUG_INFO=y/CONFIG_DEBUG_INFO=n/g' .config
	sed -i -e 's/^CONFIG_DEBUG_KERNEL=y/CONFIG_DEBUG_KERNEL=n/g' .config

	##check for versions containing only a single dot instead of two
	##but only when not choosing the repo source
	if [ "${s_or_m_or_r}" != "r" ]
	then
		dots=$(echo "${kernel_version}" | awk -F "." '{print NF-1}')
		dashes=$(echo "${kernel_version}" | awk -F "-" '{print NF-1}')
		if [ "${dots}" -lt 2 ]
		then
			if [ "${dashes}" -lt 1 ]
			then
				##5.1 -> 5.1.0
				kernel_version="${kernel_version}.0"
			else
				##5.1-rc1 -> 5.1.0-rc1
				kernel_version="$(echo "${kernel_version}" | sed 's/-/.0-/')"
			fi
			kernel_name="linux-${kernel_version}"
		fi
	fi

	make clean
	make -j "$(nproc)" bindeb-pkg LOCALVERSION="${kernel_localversion}" || exit


	if [ -z "${install}" ] || [ "${install}" == "y" ]
	then
		sudo dpkg -i ../linux-image-${kernel_version}${kernel_localversion}*.deb ../linux-headers-${kernel_version}${kernel_localversion}*.deb
		if [ -z "${default}" ] || [ "${default}" == "y" ]
		then
			if [ "$(lsb_release -s -d | cut -d ' ' -f 1)" == "Ubuntu" ]
			then
				##removing previous commented line
				sudo sed -i -e 's/^#GRUB_DEFAULT=.*//g' "${grub_config}"

				##commenting current line
				sudo sed -i 's/^GRUB_DEFAULT=/#GRUB_DEFAULT=/' "${grub_config}"

				##adding line
				## TODO multilanguage! only works for en-US (and other en-*) right now!
				grub_line="GRUB_DEFAULT=\"Advanced options for Ubuntu>Ubuntu, with Linux ${kernel_version}${kernel_localversion}\""
				sudo sed -i -e "s/^#GRUB_DEFAULT=.*/\0\n${grub_line}/" "${grub_config}"

				sudo update-grub
			fi
		fi
	fi


	cd "${current_dir}" || exit
	rm -rf "${working_dir}"
}

##actual logic
init
stable_or_mainline_or_repo