#!/bin/sh

[ 0 = "`id -u`" ] || exec sudo http_proxy="$http_proxy" "$0" "$@"

SOURCE_BASE_DIR=/usr/src
SOURCE_BASE_URI=http://www.kernel.org/pub/linux/kernel/v3.x/

usage() {
	echo "Usage: $0 $(help | sed -ne '3,$s/^\([^'"`printf '\t'`"']*\)'"`printf '\t'`"'.*$/\1/p' | tr '\n' '|' | sed -e 's/|/ | /g;s/ | $//')"
}

help() {
	cat <<EOH
$0 Command
possible commands:
help			Print this help message
latest_stable		prints the latest stable available version on kernel.org
latest_fetched		prints the latest fetched version
update_available	prints the latest stable available version on kernel.org if it isn't fetched yet
fetched			prints all fetched versions
download_uri [V]	prints the uri of V (default: latest_stable)
download [V]		downloads the kernel of V (default: latest_stable)
unpack			simple unpack with unxz and tar in \$SOURCE_BASE_DIR (default: $SOURCE_BASE_DIR)
fetch [V]		downloads and unpack the kernel of V (default: latest_stable)
update			downloads and unpack the latest_stable kernel if it isn't fetched yet
EOH
}

cache() {
	eval "$1() { echo '$(echo "$2" | sed -e 's/'\''/'"'\\\''"'/g')'; }"
	$1
}

_latest_stable() {
	curl -s http://www.kernel.org/kdist/finger_banner | sed -E -ne 's/^The latest stable .* version of the Linux kernel is: *([0-9.]*).*/\1/p' | head -1
}

latest_stable() {
	cache latest_stable "`_latest_stable`"
}

print_version() {
	while read v d
	do
		echo "$v"
	done
}

print_dir() {
	while read v d
	do
		echo "$d"
	done
}

kernelversion_of() {
	make -isC "$1" kernelversion
}

fetched() {
	for d in "${SOURCE_BASE_DIR}"/linux-*
	do
		v="`kernelversion_of "$d"`"
		if [ "$v" ]
		then
			echo "$v $d"
		fi
	done
}

latest_version() {
	sort -rV | head -1
}

latest_fetched() {
	fetched | latest_version
}

is_listed() {
	awk \""${1}"'"==$1{print$0;exit}'
}

latest_stable_is_fetched() {
	fetched | is_listed "`latest_stable`"
}

update_available() {
	[ -z "`latest_stable_is_fetched`" ]
}

download_uri() {
	echo "${SOURCE_BASE_URI}/linux-${1:-`latest_stable`}.tar.xz"
}

download() {
	curl `download_uri "${1}"`
}

unpack() {
	unxz | tar -C "${SOURCE_BASE_DIR}" -xf -
}

fetch() {
	download | unpack
}

update() {
	if update_available
	then
		echo Update available: `latest_stable`
		fetch
	else
		echo "Upto date."
		return 1
	fi
}

configs() {
	fetched | while read v d
	do
		[ -e "$d/.config" ] && echo "$v $d"
	done
}

has_config() {
	configs | is_listed "$2"
}

latest_config() {
	configs | latest_version
}

copy_to_dir_config() {
	cp "${2:-`latest_config | print_dir`}/.config" "${1:-`latest_fetched | print_dir`}"
}

install_config() {
	d="${1:-`latest_fetched | print_dir`}"
	s="${2:-`latest_config | print_dir`}"
	[ -e "$d/.config" ] || copy_to_dir_config "${d}" "${s}"
}

oldconfig() {
	d="${1:-`latest_fetched | print_dir`}"
	install_config "$d" && make -C "$d" oldconfig
}

install_all() {
	d="${1:-`latest_fetched | print_dir`}"
	oldconfig && make -C "$d" all modules_install install
}

cmd="$1"
shift

case "$cmd" in
latest_stable) latest_stable ;;
fetched) fetched ;;
latest_fetched) latest_fetched ;;
update_available) update_available ;;
fetch) fetch "$@" ;;
download_uri) download_uri "$@" ;;
download) download "$@" ;;
unpack) unpack ;;
update) update ;;
help|--help|-h) help ;;
usage) usage ;;
latest_stable_is_fetched) latest_stable_is_fetched ;;
oldconfig) oldconfig "$@" ;;
configs) configs ;;
install) install_all ;;
all) update && install_all ;;
*)
	usage >&2
	exit 1
	;;
esac