#!/bin/sh
set -eu


usage() {
	cat <<-'EOF'
		Usage:
		  vm ACTION [OS]
		  vm -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  ACTION        one of:
		                - up
		                - down
		                - status
		  OS            the name of the OS to be acted upon


		Manage the state of known virtual machines.

		The VM QCOW2 images are stored under
		$XDG_STATE_HOME/euandreh/qemu/, as "$OS.qcow2" files.  The PIDs
		of the running images are stored in individual files under
		$XDG_RUNTIME_DIR/vm-pids/, as "$OS.pid" files.

		It also generates an SSH configuration file to bu `Included`
		by the main $XDG_CONFIG_HOME/ssh/config file, which contains
		one alias entry for each VM, so that one can do a combination
		of `vm up alpine && ssh alpine`.


		Examples:

		  Start the VM for Alpine:

		    $ vm up alpine


		  Stop the VM for Slackware, which was already down

		    $ vm down slackware
		    The VM for "slackware" is not running, already.


		  List the available VMs, and their current state:

		    $ vm status
		    alpine:up
		    slackware:down
		    freebsd:up
	EOF
}


for flag in "$@"; do
	case "$flag" in
		--)
			break
			;;
		--help)
			usage
			help
			exit
			;;
		*)
			;;
	esac
done

while getopts 'h' flag; do
	case "$flag" in
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


ACTION="${1:-}"
OS="${2:-}"

eval "$(assert-arg "$ACTION" 'ACTION')"


VMS='
alpine:60022
'

for vm in $VMS; do
	NAME="$(echo "$vm" | cut -d: -f1)"
	PORT="$(echo "$vm" | cut -d: -f2)"
	cat <<-EOF
		Host $NAME
		  HostName localhost
		  Port $PORT

	EOF
done > "$XDG_DATA_HOME"/euandreh/vm-ssh.conf

PIDS_DIR="${XDG_RUNTIME_DIR:-${TMPDIR:-/tmp}}/vm-pids"
PID_F="$PIDS_DIR/$OS.pid"
mkdir -p "$PIDS_DIR"


port_for_os() {
	_OS="$1"
	_PORT="$(echo "$VMS" | awk -F: -vOS="$_OS" '$1 == OS { print $2 }')"
	if [ -z "$_PORT" ]; then
		printf 'Unknown OS: "%s".\n\n' "$_OS" >&2
		usage >&2
		exit 2
	fi
	printf '%s' "$_PORT"
}

case "$ACTION" in
	status)
		echo "$VMS" | awk -F: '$0=$1' | while read -r vm; do
			if [ -e "$PIDS_DIR/$vm.pid" ]; then
				STATUS=up
			else
				STATUS=down
			fi
			printf '%s:%s\n' "$vm" "$STATUS"
		done
		;;
	up)
		eval "$(assert-arg "$OS" 'OS')"
		PORT="$(port_for_os "$OS")"

		if [ -e "$PID_F" ]; then
			printf 'The VM for "%s" is already running with PID %s.\n' \
				"$OS" "$(cat "$PID_F")" >&2
		else
			QCOW="$XDG_STATE_HOME"/euandreh/qemu/"$OS".qcow2
			qemu-system-x86_64 \
				-m 1G                                           \
				-nic user,model=virtio,hostfwd=tcp::"$PORT"-:22 \
				-drive file="$QCOW",media=disk,if=virtio        \
				-enable-kvm                                     \
				-nographic 1>/dev/null 2>&1 &
			printf '%s' $! > "$PID_F"
		fi
		;;
	down)
		eval "$(assert-arg "$OS" 'OS')"
		PORT="$(port_for_os "$OS")"

		if [ ! -e "$PID_F" ]; then
			printf 'The VM for "%s" is not running, already.\n' "$OS" >&2
		else
			# shellcheck disable=2064
			trap "rm -f $PID_F" EXIT
			kill "$(cat "$PID_F")"
		fi
		;;
	*)
		printf 'Unrecognized action: "%s".\n\n' "$ACTION" >&2
		usage >&2
		exit 2
esac