#!/usr/bin/env bash
# le-lab: set up, grade and reset LINUXexpert practice labs on a throwaway VM.
# Run "le-lab help" for usage.

set -uo pipefail

ROOT=$(cd "$(dirname "$(readlink -f "$0")")" && pwd)
. "$ROOT/lib/lab.sh"

MARKER=/etc/le-lab/throwaway-vm
CURRENT=$LE_STATE/current

usage() {
	cat <<EOF
Usage: sudo ./le-lab COMMAND [LAB]

  list [GUIDE]   show the labs (all, or one guide's, such as lfcs)
  start LAB      set up a lab, such as lfcs/5-1-user-group-accounts
  tasks          show the tasks of the lab you're working on
  check          grade your work so far (as often as you like)
  reset          undo the lab's setup and your work on its files
  status         show which lab is set up

Run it only on a throwaway VM: labs change system settings on purpose.
Take a snapshot of the VM first so you can roll back.
EOF
}

need_root() { [ "$(id -u)" -eq 0 ] || die "run it as root: sudo $0 $*"; }

lab_dir() {
	local id=${1%/}
	id=${id#labs/}
	[ -f "$ROOT/labs/$id/lab.conf" ] || die "no lab called $id (try: le-lab list)"
	printf '%s\n' "$ROOT/labs/$id"
}

lab_id() { printf '%s\n' "${1#"$ROOT"/labs/}"; }

# Labs change the system on purpose, so refuse anything that isn't a VM,
# and ask once before the first lab on this one.
confirm_vm() {
	[ -f "$MARKER" ] && return 0
	local virt
	virt=$(systemd-detect-virt 2>/dev/null) || virt=none
	if systemd-detect-virt --container >/dev/null 2>&1; then
		die "this is a container ($virt); labs need a full virtual machine"
	fi
	if [ "$virt" = none ]; then
		die "this doesn't look like a virtual machine; labs only run on a throwaway VM"
	fi
	cat <<EOF
${C_B}Practice labs change this system on purpose.${C_0} They add users, disks,
services and firewall rules, and some tasks break the boot for you to fix.
Use a throwaway VM ($virt detected) and take a snapshot first.

EOF
	if [ "${LE_LAB_YES:-}" != 1 ]; then
		local reply
		read -r -p 'Type "throwaway" to continue: ' reply
		[ "$reply" = throwaway ] || die "stopped; nothing was changed"
	fi
	mkdir -p "${MARKER%/*}"
	printf 'Confirmed %s\n' "$(date -Is)" >"$MARKER"
}

# Attaches the spare disks again at boot; installed once, harmless when
# there are none.
install_disk_unit() {
	local unit=/etc/systemd/system/le-lab-disks.service old=''
	[ -f "$unit" ] && old=$(cat "$unit")
	cat >"$unit" <<EOF
[Unit]
Description=Attach LINUXexpert practice lab disks
DefaultDependencies=no
After=systemd-udevd.service
Before=local-fs-pre.target lvm2-activation-early.service
Wants=local-fs-pre.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/bin/bash -c '. $LE_LIB && disks_attach'

[Install]
WantedBy=local-fs-pre.target
EOF
	[ "$old" = "$(cat "$unit")" ] && return 0
	systemctl daemon-reload
	systemctl enable --quiet le-lab-disks.service
}

conf_get() { (. "$1/lab.conf" && eval "printf '%s' \"\${$2:-}\""); }

cmd_list() {
	local filter=${1:-} conf dir id title
	for conf in "$ROOT"/labs/*/*/lab.conf; do
		[ -e "$conf" ] || continue
		dir=${conf%/lab.conf}; id=$(lab_id "$dir")
		[ -z "$filter" ] || [ "${id%%/*}" = "$filter" ] || continue
		title=$(conf_get "$dir" TITLE)
		printf '  %-42s %s\n' "$id" "$title"
	done
}

cmd_start() {
	[ $# -eq 1 ] || die "usage: le-lab start LAB"
	need_root start
	local dir id systems
	dir=$(lab_dir "$1"); id=$(lab_id "$dir")
	systems=$(conf_get "$dir" SYSTEMS)
	case " $systems " in
	*" $OS_FAMILY "*) ;;
	*) die "$id runs on: $systems (this is $OS_NAME)" ;;
	esac
	if [ -f "$CURRENT" ]; then
		local cur; cur=$(cat "$CURRENT")
		[ "$cur" = "$id" ] && die "$id is already set up; use le-lab reset to start over"
		die "$cur is still set up; run le-lab reset first"
	fi
	confirm_vm
	mkdir -p "$LE_STATE"
	install_disk_unit
	export LAB_DIR=$dir LAB_STATE=$LE_STATE/labs/${id//\//_}
	rm -rf "$LAB_STATE"; mkdir -p "$LAB_STATE" /root/lab-answers
	say "${C_B}Setting up $id: $(conf_get "$dir" TITLE)${C_0} on $OS_NAME"
	bash -c '. "$1/lib/lab.sh"; set -e; . "$2/setup.sh"' _ "$ROOT" "$dir"
	case $? in
	0) ;;
	3) rm -rf "$LAB_STATE"; exit 1 ;;
	*)
		warn "Setup failed. Run le-lab reset, then try again."
		printf '%s\n' "$id" >"$CURRENT"
		exit 1
		;;
	esac
	printf '%s\n' "$id" >"$CURRENT"
	say ''
	cmd_tasks
	say ''
	say "When you're ready: ${C_B}sudo $0 check${C_0}"
}

current_dir() {
	[ -f "$CURRENT" ] || die "no lab is set up (try: le-lab list, then le-lab start LAB)"
	lab_dir "$(cat "$CURRENT")"
}

cmd_tasks() {
	local dir; dir=$(current_dir)
	# Print the README's "Before you start" and "Tasks" sections as plain
	# text.
	awk '/^## /{p = ($0 ~ /^## (Before you start|Tasks)/); if (p) print toupper(substr($0, 4)); next} p' "$dir/README.md"
	local url; url=$(conf_get "$dir" CHAPTER)
	[ -n "$url" ] && say "Study guide chapter: https://linuxexpert.net$url"
	true
}

cmd_check() {
	need_root check
	local dir id
	dir=$(current_dir); id=$(lab_id "$dir")
	export LAB_DIR=$dir LAB_STATE=$LE_STATE/labs/${id//\//_}
	say "${C_B}$id: $(conf_get "$dir" TITLE)${C_0} on $OS_NAME"
	say ''
	bash -c '. "$1/lib/lab.sh"; . "$2/check.sh"; grade_report' _ "$ROOT" "$dir"
}

cmd_reset() {
	need_root reset
	local dir id
	dir=$(current_dir); id=$(lab_id "$dir")
	export LAB_DIR=$dir LAB_STATE=$LE_STATE/labs/${id//\//_}
	say "Resetting $id..."
	if [ -f "$dir/reset.sh" ]; then
		bash -c '. "$1/lib/lab.sh"; . "$2/reset.sh"' _ "$ROOT" "$dir" || warn "Some of the reset failed; see above."
	fi
	bash -c '. "$1/lib/lab.sh"; users_remove; disks_remove; peer_down; nodes_down' _ "$ROOT"
	rm -rf "$LAB_STATE" "$CURRENT" /root/lab-answers
	say "Done. Anything you changed outside the lab's own files is still there;"
	say "roll back to your snapshot for a completely clean VM."
}

cmd_status() {
	if [ -f "$CURRENT" ]; then
		local dir; dir=$(lab_dir "$(cat "$CURRENT")")
		say "Set up: $(cat "$CURRENT") ($(conf_get "$dir" TITLE))"
		[ -f "$LE_STATE/last-score" ] && say "Last check: $(cut -d' ' -f2 "$LE_STATE/last-score") tasks"
	else
		say "No lab is set up."
	fi
}

case ${1:-help} in
list) shift; cmd_list "$@" ;;
start) shift; cmd_start "$@" ;;
tasks) cmd_tasks ;;
check) cmd_check ;;
reset) cmd_reset ;;
status) cmd_status ;;
help | -h | --help) usage ;;
*) usage >&2; exit 2 ;;
esac