#!/bin/bash
set -eou pipefail
readonly VERSION="v0.2.2"
readonly GITREPO="https://github.com/framps/raspberryTools"
readonly MYSELF="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"
readonly MYNAME=${MYSELF%.*}
readonly DELETED_KERNELS_FILENAME="$MYNAME.krnl"
function show_help() {
	echo "$MYSELF $VERSION ($GITREPO)"
	echo
	echo "Check for unnecessary kernels for the existing Raspberry hardware."
	echo "Optionally delete and save installed kernels for later reinstallation or reinstall the previously deleted kernels"
	echo
	echo "Usage: $MYSELF -i [-e] | -u [-e] | -h | -? | -v"
	echo "-e: deactivate dry run mode and modify system"
	echo "-i: reinstall kernels deleted with option -u"
	echo "-u: uninstall any unused kernels"
	echo "-h: display this help"
	echo "-v: display version"
}
function info() {
	echo "--- $@"
}
function error() {
	echo "??? $@"
}
function yesNo() {

	local answer=${1:0:1}
	answer=${1:-"n"}
	[[ "Yy" =~ $answer ]]
	return
}
function check4Pi() {
	dpkg --print-architecture | grep -q -E "arm(hf|64)"
}
function do_uninstall() {
	local availableKernels="$(dpkg --list | awk '/^ii[[:space:]]+linux-image/ { print $2 }')"
	local usedKernel="$(uname -a | awk '{ print "linux-image-" $3 }')"
	local unusedKernels="$(grep -v "$usedKernel" <<< "$availableKernels" | xargs -I {} echo "{}")"
	if [[ -z "$unusedKernels" ]]; then
		error "No unused kernels detected"
		exit 1
	fi
	local keptKernel="$(grep "$usedKernel" <<< "$availableKernels" | xargs -I {} echo "{}")"
	if [[ -z "$keptKernel" ]]; then
		error "No kernel will be kept"
		exit 1
	fi
	info "Following kernel will be kept"
	echo "$keptKernel"
	local numUnusedKernels="$(wc -l <<< "$unusedKernels")"
	info "Following $numUnusedKernels unused kernels will be deleted"
	echo "$unusedKernels"
	if (( $MODE_EXECUTE )); then
		local answer
		read -p "Are you sure to delete all $numUnusedKernels unused kernels ? (y/N) " answer
		if ! yesNo "$answer"; then
			exit 1
		fi
		read -p "Do you have a backup ? (y/N) " answer
		if ! yesNo "$answer"; then
			exit 1
		fi
		set +e
		if [[ -e /boot/$DELETED_KERNELS_FILENAME ]]; then
			sudo rm /boot/$DELETED_KERNELS_FILENAME
			(( $? )) && { error "Failure deleting /boot/$DELETED_KERNELS_FILENAME"; exit 42; }
		fi
		info "Saving $numUnusedKernels unused kernel names in /boot/$DELETED_KERNELS_FILENAME"
		echo "$unusedKernels" >> $DELETED_KERNELS_FILENAME; sudo mv $DELETED_KERNELS_FILENAME /boot
		(( $? )) && { error "Failure collecting kernels"; exit 42; }
		info "Removing $numUnusedKernels unused kernels"
		echo "$unusedKernels" | xargs sudo apt -y remove
		(( $? )) && { error "Failure removing kernels"; exit 42; }
		set -e
	fi
}
function do_install() {
	if [[ ! -e /boot/$DELETED_KERNELS_FILENAME ]]; then
		info "No unused kernels found"
		exit 0
	fi
	local numUnusedKernels=$(wc -l /boot/$DELETED_KERNELS_FILENAME | cut -f 1 -d ' ')
	if (( ! $MODE_EXECUTE )); then
		info "Following $numUnusedKernels unused kernels will be installed"
		while IFS= read -r line; do
			echo "$line"
		done < /boot/$DELETED_KERNELS_FILENAME
	else
		local errorOccured=0
		info "Installing $numUnusedKernels unused kernels"
		echo "$(</boot/$DELETED_KERNELS_FILENAME)"
		while IFS= read -r line; do
			sudo apt -y install $line
			set +e
			(( errorOccured |= $? ))
			set -e
		done < /boot/$DELETED_KERNELS_FILENAME
		if (( ! errorOccured )); then
			sudo rm /boot/$DELETED_KERNELS_FILENAME
		else
			error "Errors occured when installing kernels"
		fi
	fi
}
echo "$MYSELF $VERSION ($GITREPO)"
if ! check4Pi; then
	error "No RaspberryPi detected"
	exit 1
fi
MODE_INSTALL=0
MODE_UNINSTALL=0
MODE_EXECUTE=0
if (( $# == 0 )); then
	MODE_UNINSTALL=1
else
	while getopts ":ehiuv?" opt; do
		case "$opt" in
			e) MODE_EXECUTE=1
				;;
			h|\?)
				show_help
				exit 0
				;;
			i) MODE_INSTALL=1
				;;
			u) MODE_UNINSTALL=1
				;;
			v) echo "$MYSELF $VERSION"
				exit 0
				;;
			*) echo "Unknown option $opt"
				show_help
				exit 1
				;;
		esac
	done
fi
if (( $MODE_INSTALL )); then
	do_install
elif (( $MODE_UNINSTALL )); then
	do_uninstall
else
	show_help
fi