#!/bin/bash
set -eo pipefail

# Banner
echo "   _     _                   _                        _                   _   _           _             _ "
echo "  (_)___| |_ _ __ ___       | | _____ _ __ _ __   ___| |       ___  _ __ | |_(_)_ __ ___ (_)_______  __| |"
echo "  | / __| __| '_ \` _ \\ _____| |/ / _ \\ '__| '_ \\ / _ \\ |_____ / _ \\| '_ \\| __| | '_ \` _ \\| |_  / _ \\/ _\` |"
echo "  | \\__ \\ |_| | | | | |_____|   <  __/ |  | | | |  __/ |_____| (_) | |_) | |_| | | | | | | |/ /  __/ (_| |"
echo " _/ |___/\\__|_| |_| |_|     |_|\\_\\___|_|  |_| |_|\\___|_|      \\___/| .__/ \\__|_|_| |_| |_|_/___\\___|\\__,_|"
echo "|__/                                                               |_|"
echo ""

# Variables
export "BUILDTOOL_REPOSITORY=https://git.staropensource.de/JeremyStarTM/kernel-optimized.git"
export "BUILDTOOL_PACKAGES=base-devel git rustup"
export "BUILDTOOL_BUILDCMDLINE=nice -20 env MAKEFLAGS=-j$(nproc)"
export "BUILDTOOL_CLONEDIR=jstm-kernel-optimized"

# Checks
## Check for Arch Linux
(
	# shellcheck disable=SC1091
	source "/etc/os-release"
	if [ "${NAME}" != "Arch Linux" ] || [ "${PRETTY_NAME}" != "Arch Linux" ] || [ "${ID}" != "arch" ]; then
		if [ "${BUILDTOOL_COMPILE_NONARCH}" != "true" ]; then
			echo ":: Error: Not running on Arch Linux."
			echo "          This kernel can only compile on Arch Linux."
			echo "          If you are sure that you want to compile this kernel on other distributions"
			echo "          set the \$BUILDTOOL_COMPILE_NONARCH environment variable to \"true\""
			exit 1
		else
			echo ":: Warning: Compiling on a non-arch distribution. This may lead to unexpected errors!"
		fi
	fi
)
## Check for root
if [ "${UID}" == "0" ]; then
	echo ":: Error: Can't build kernel as root."
	echo "          Please create a new user for building the kernel."
	exit 1
fi
## Check for sudo
if ! which sudo &> /dev/null; then
	echo ":: Error: Could not find sudo in \$PATH."
	echo "          Please ensure that you have sudo installed."
	exit 1
fi

# Questions
## Ask if mold should replace ld/lld
function ask_mold() {
	read -rp ":: Do you want to use mold as your linker (much faster) [Y/n]? " BUILDTOOL_MOLD
	case "${BUILDTOOL_MOLD}" in
		"y"|"Y"|"")
			export "BUILDTOOL_PACKAGES=${BUILDTOOL_PACKAGES} mold"
			export "BUILDTOOL_BUILDCMDLINE=${BUILDTOOL_BUILDCMDLINE} LDFLAGS=-fuse-ld=mold RUSTFLAGS=\"-C link-arg=-fuse-ld=mold\""
			;;
		"n"|"N") ;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_mold
	esac
}
## Ask if the governor should be adjusted
function ask_cpupower() {
	read -rp ":: Do you want to adjust the cpu governor (improves build performance) [Y/n]? " BUILDTOOL_CPUPOWER
	case "${BUILDTOOL_CPUPOWER}" in
		"y"|"Y"|"")
			export "BUILDTOOL_PACKAGES=${BUILDTOOL_PACKAGES} cpupower"
			;;
		"n"|"N") ;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_cpupower
	esac
}
## Ask for building in tmpfs
function ask_tmpfs() {
	read -rp ":: Do you want to build in a tmpfs (improves build performance, protects your disk from wearing out faster, ~32 GiB memory required) [Y/n]? " BUILDTOOL_TMPFS
	case "${BUILDTOOL_TMPFS}" in
		"y"|"Y"|"")
			export "BUILDTOOL_CLONEDIR=/tmp/${BUILDTOOL_CLONEDIR}"
			;;
		"n"|"N")
			export "BUILDTOOL_CLONEDIR=$(pwd)/${BUILDTOOL_CLONEDIR}"
			;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_tmpfs
	esac
}
## Ask for kernel config modification using xconfig
function ask_xconfig() {
	read -rp ":: Do you want to configure the kernel using xconfig before build [y/N]? " BUILDTOOL_XCONFIG
	case "${BUILDTOOL_XCONFIG}" in
		"y"|"Y")
			export "BUILDTOOL_PKGBUILD_XCONFIG=_makexconfig=SET"
			;;
		"n"|"N"|"")
			export "BUILDTOOL_PKGBUILD_XCONFIG=_makexconfig="
			;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_xconfig
	esac
}
## Ask for kernel config modification using xconfig
function ask_nconfig() {
	read -rp ":: Do you want to configure the kernel using nconfig before build [y/N]? " BUILDTOOL_NCONFIG
	case "${BUILDTOOL_NCONFIG}" in
		"y"|"Y")
			export "BUILDTOOL_PKGBUILD_NCONFIG=_makenconfig=SET"
			;;
		"n"|"N"|"")
			export "BUILDTOOL_PKGBUILD_NCONFIG=_makenconfig="
			;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_nconfig
	esac
}
## Ask if the final kernel configuration should be copied
function ask_cpfinalconfig() {
	read -rp ":: Do you want to copy the final kernel configuration before build [y/N]? " BUILDTOOL_CPFINALCONFIG
	case "${BUILDTOOL_CPFINALCONFIG}" in
		"y"|"Y")
			export "BUILDTOOL_PKGBUILD_CPFINALCONFIG=_copyfinalconfig=SET"
			;;
		"n"|"N"|"")
			export "BUILDTOOL_PKGBUILD_CPFINALCONFIG=_copyfinalconfig="
			;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_cpfinalconfig
	esac
}
## Ask if only active modules should be compiled into the kernel
function ask_modprobeddb() {
	read -rp ":: Do you want to only build active kernel modules (modprobed-db must be installed, read \"https://wiki.archlinux.org/index.php/Modprobed-db\" first) [y/N]? " BUILDTOOL_MODPROBEDDB
	case "${BUILDTOOL_MODPROBEDDB}" in
		"y"|"Y")
			if ! which modprobed-db &> /dev/null; then
				echo ":: Error: Could not find modprobed-db in \$PATH."
				echo "          Please ensure that you have modprobed-db installed."
				ask_modprobeddb
				return 1
			fi
			export "BUILDTOOL_PACKAGES=${BUILDTOOL_PACKAGES} modprobed-db"
			export "BUILDTOOL_PKGBUILD_MODPROBEDDB=_localmodcfg=SET"
			;;
		"n"|"N"|"")
			export "BUILDTOOL_PKGBUILD_MODPROBEDDB=_localmodcfg="
			;;
		*)
			echo "Invalid answer. Please answer with Y or N."
			ask_modprobeddb
	esac
}
## Ask for sub architecture
function ask_subarchitecture() {
  echo ":: Displaying sub architecture list"
	echo "    1. AMD Opteron/Athlon64/Hammer/K8 (MK8)"
	echo "    2. AMD Opteron/Athlon64/Hammer/K8 with SSE3 (MK8SSE3)"
	echo "    3. AMD 61xx/7x50/PhenomX3/X4/II/K10 (MK10)"
	echo "    4. AMD Barcelona (MBARCELONA)"
	echo "    5. AMD Bobcat (MBOBCAT)"
	echo "    6. AMD Jaguar (MJAGUAR)"
	echo "    7. AMD Bulldozer (MBULLDOZER)"
	echo "    8. AMD Piledriver (MPILEDRIVER)"
	echo "    9. AMD Steamroller (MSTEAMROLLER)"
	echo "   10. AMD Excavator (MEXCAVATOR)"
	echo "   11. AMD Zen (MZEN)"
	echo "   12. AMD Zen 2 (MZEN2)"
	echo "   13. AMD Zen 3 (MZEN3)"
	echo "   14. AMD Zen 4 (MZEN4)"
	echo "   15. Intel P4 / older Netburst based Xeon (MPSC)"
	echo "   16. Intel Core 2 (MCORE2)"
	echo "   17. Intel Atom (MATOM)"
	echo "   18. Intel Nehalem (MNEHALEM)"
	echo "   19. Intel Westmere (MWESTMERE)"
	echo "   20. Intel Silvermont (MSILVERMONT)"
	echo "   21. Intel Goldmont (MGOLDMONT)"
	echo "   22. Intel Goldmont Plus (MGOLDMONTPLUS)"
	echo "   23. Intel Sandy Bridge (MSANDYBRIDGE)"
	echo "   24. Intel Ivy Bridge (MIVYBRIDGE)"
	echo "   25. Intel Haswell (MHASWELL)"
	echo "   26. Intel Broadwell (MBROADWELL)"
	echo "   27. Intel Skylake (MSKYLAKE)"
	echo "   28. Intel Skylake X (MSKYLAKEX)"
	echo "   29. Intel Cannon Lake (MCANNONLAKE)"
	echo "   30. Intel Ice Lake (MICELAKE)"
	echo "   31. Intel Cascade Lake (MCASCADELAKE)"
	echo "   32. Intel Cooper Lake (MCOOPERLAKE)"
	echo "   33. Intel Tiger Lake (MTIGERLAKE)"
	echo "   34. Intel Sapphire Rapids (MSAPPHIRERAPIDS)"
	echo "   35. Intel Rocket Lake (MROCKETLAKE)"
	echo "   36. Intel Alder Lake (MALDERLAKE)"
	echo "   37. Intel Raptor Lake (MRAPTORLAKE)"
	echo "   38. Intel Meteor Lake (MMETEORLAKE)"
	echo "   39. Intel Emerald Rapids (MEMERALDRAPIDS)"
	echo "   40. Generic-x86-64 (GENERIC_CPU)"
	echo "   41. Generic-x86-64-v2 (GENERIC_CPU2)"
	echo "   42. Generic-x86-64-v3 (GENERIC_CPU3)"
	echo "   43. Generic-x86-64-v4 (GENERIC_CPU4)"
	echo "   44. Intel-Native optimizations autodetected by the compiler (MNATIVE_INTEL)"
	echo "   45. AMD-Native optimizations autodetected by the compiler (MNATIVE_AMD)"
	read -rp ":: Which sub architecture do you want to build Linux for (see above, enter 40 if unsure) [40]? " BUILDTOOL_SUBARCHITECTURE
	case "${BUILDTOOL_SUBARCHITECTURE}" in
		"")
			export "BUILDTOOL_PKGBUILD_SUBARCHITECTURE=_subarch=40"
			;;
		*[!0-9]*)
			echo ":: Error: Invalid subarchitecture"
			ask_subarchitecture
			return 1
			;;
		*)
			if [ ! "${BUILDTOOL_SUBARCHITECTURE}" -gt 0 ] || [ ! "${BUILDTOOL_SUBARCHITECTURE}" -lt 46 ]; then
				echo ":: Error: Invalid subarchitecture."
				ask_subarchitecture
			else
				export "BUILDTOOL_PKGBUILD_SUBARCHITECTURE=_subarch=${BUILDTOOL_SUBARCHITECTURE}"
			fi
			;;
	esac
}
## Ask for kernel debug mode
function ask_debug() {
	read -rp ":: Do you want to enable kernel debug mode [y/N/i(gnore)]? " BUILDTOOL_DEBUG
	case "${BUILDTOOL_DEBUG}" in
		"y"|"Y")
			export "BUILDTOOL_PKGBUILD_DEBUG=_debug=y"
			;;
		"n"|"N"|"")
			export "BUILDTOOL_PKGBUILD_DEBUG=_debug=n"
			;;
		"i"|"I")
			export "BUILDTOOL_PKGBUILD_DEBUG=_debug="
			;;
		*)
			echo "Invalid answer. Please answer with Y, N or I."
			ask_debug
	esac
}
## Ask for clone directory conflict resolution (includes check)
function ask_clonedir_conflictresolution() {
	if [ ! -d "${BUILDTOOL_CLONEDIR}" ]; then
		return
	elif [ -a "${BUILDTOOL_CLONEDIR}" ] && [ ! -d "${BUILDTOOL_CLONEDIR}" ]; then
		echo ":: Warning: Something that isn't a directory exists at location \"${BUILDTOOL_CLONEDIR}\""
	fi
	read -rp ":: Warning: \"${BUILDTOOL_CLONEDIR}\" already exists. What should be done to resolve the conflict [A(bort)/r(ecompile)/f(resh)]? " BUILDTOOL_CLONEDIR_CONFLICT
	case "${BUILDTOOL_CLONEDIR_CONFLICT}" in
		"a"|"A"|"")
			echo ":: Error: Conflict resolution failed."
			exit 1
			;;
		"r"|"R") ;;
		"f"|"F")
			echo ":: Removing existing \$BUILDTOOL_CLONEDIR directory"
			#rm -rf "${BUILDTOOL_CLONEDIR}"
			;;
		*)
			echo "Invalid answer. Please answer with Y, N or I."
			ask_debug
	esac
}
ask_mold
ask_cpupower
ask_tmpfs
ask_xconfig
ask_nconfig
ask_cpfinalconfig
ask_modprobeddb
ask_subarchitecture
ask_debug
ask_clonedir_conflictresolution

# Pre-building
## Install dependencies
echo ":: Installing dependencies"
if ! sudo pacman -Syu --asdeps --needed ${BUILDTOOL_PACKAGES}; then
	echo ":: Error: Installing dependencies failed: pacman returned with non-zero exit code"
	exit 1
fi
if ! rustup default nightly; then
	echo ":: Error: Installing dependencies failed: rustup returned with non-zero exit code"
	exit 1
fi
## Adjust cpu governor
case "${BUILDTOOL_CPUPOWER}" in
	"y"|"Y"|"")
		echo ":: Adjusting cpu governor"
		if ! sudo cpupower frequency-set -g performance; then
			echo ":: Error: Adjusting cpu governor failed: cpupower returned with non-zero exit code"
			return 1
		fi
		;;
	"n"|"N") ;;
	*)
		echo ":: Error: Internal inconsistency detected: Value of \$BUILDTOOL_CPUPOWER is not a valid boolean answer"
		exit 2
		;;
esac

# Clone repository
echo ":: Cloning repository"
git clone "${BUILDTOOL_REPOSITORY}" "${BUILDTOOL_CLONEDIR}"
cd "${BUILDTOOL_CLONEDIR}"

# Print debug information
if [ "${BUILDTOOL_DEBUG}" == "true" ]; then
	echo ":: Printing debug information"
	echo "++ env ++"
	env|grep "BUILDTOOL_"|sort
	echo "++ env ++"
	echo "build cmdline: ${BUILDTOOL_BUILDCMDLINE} "${BUILDTOOL_PKGBUILD_XCONFIG}" "${BUILDTOOL_PKGBUILD_NCONFIG}" "${BUILDTOOL_PKGBUILD_CPFINALCONFIG}" "${BUILDTOOL_PKGBUILD_MODPROBEDDB}" "${BUILDTOOL_PKGBUILD_SUBARCHITECTURE}" "${BUILDTOOL_PKGBUILD_DEBUG}" makepkg --syncdeps -p PKGBUILD.buildtool"
fi

# Build kernel
echo ":: Building kernel"
${BUILDTOOL_BUILDCMDLINE} "${BUILDTOOL_PKGBUILD_XCONFIG}" "${BUILDTOOL_PKGBUILD_NCONFIG}" "${BUILDTOOL_PKGBUILD_CPFINALCONFIG}" "${BUILDTOOL_PKGBUILD_MODPROBEDDB}" "${BUILDTOOL_PKGBUILD_SUBARCHITECTURE}" "${BUILDTOOL_PKGBUILD_DEBUG}" makepkg --syncdeps -p PKGBUILD.buildtool