#!/bin/sh

DAEMON=/usr/bin/tera-seriald
PIDFILE=/run/tera-seriald/tera-seriald.pid
ENVFILE=/etc/tera/tera-seriald.env
RUN_AS=tera:tera

ensure_account() {
	if ! grep -q '^tera:' /etc/group; then
		addgroup -S tera || return 1
	fi
	if ! id tera >/dev/null 2>&1; then
		adduser -S -D -H -s /bin/false -G tera tera || return 1
	fi
	normalize_service_account_password || return 1
}

normalize_service_account_password() {
	shadow_value="$(awk -F: '$1 == "tera" { print $2 }' /etc/shadow)" || return 1
	case "$shadow_value" in
		""|!*) ;;
		\**) ;;
		*) return 0 ;;
	esac

	command -v mkpasswd >/dev/null 2>&1 || return 1
	random_secret="$(dd if=/dev/urandom bs=48 count=1 2>/dev/null | sha256sum | cut -d' ' -f1)" || return 1
	password_hash="$(mkpasswd -m sha-256 "$random_secret")" || return 1
	unset random_secret
	temporary_shadow="/etc/.shadow.tera.$$"
	trap 'rm -f "$temporary_shadow"' EXIT HUP INT TERM
	awk -F: -v OFS=: -v replacement="$password_hash" '
		$1 == "tera" { $2 = replacement; found = 1 }
		{ print }
		END { if (!found) exit 1 }
	' /etc/shadow >"$temporary_shadow" || return 1
	chown 0:0 "$temporary_shadow" || return 1
	chmod 0600 "$temporary_shadow" || return 1
	mv -f "$temporary_shadow" /etc/shadow || return 1
	trap - EXIT HUP INT TERM
}

wait_for_mapped_devices() {
	mapping="${TERA_SERIALD_MAPPING:-/etc/tera/serial-map.json}"
	[ -r "$mapping" ] || { echo "missing serial mapping $mapping" >&2; return 1; }
	devices="$(sed -n 's/.*"device":[[:space:]]*"\([^"]*\)".*/\1/p' "$mapping")" || return 1
	[ "$(printf '%s\n' "$devices" | grep -c '^/dev/ttyWCH[0-9][0-9]*$')" -eq 48 ] || {
		echo "serial mapping must contain exactly 48 WCH devices" >&2
		return 1
	}
	attempt=0
	while [ "$attempt" -lt 100 ]; do
		missing=0
		for device in $devices; do
			[ -c "$device" ] || { missing=1; break; }
		done
		[ "$missing" -eq 0 ] && return 0
		attempt=$((attempt + 1))
		sleep 0.1
	done
	echo "mapped WCH devices did not appear within 10 seconds" >&2
	return 1
}

prepare_runtime() {
	ensure_account || return 1
	wait_for_mapped_devices || return 1
	mkdir -p /run/tera-seriald /var/log/tera || return 1
	chown tera:tera /run/tera-seriald /var/log/tera || return 1
	for device in /dev/ttyWCH*; do
		[ -c "$device" ] || continue
		chgrp tera "$device" || return 1
		chmod 0660 "$device" || return 1
	done
}

load_environment() {
	if [ -r "$ENVFILE" ]; then
		set -a
		. "$ENVFILE"
		set +a
	fi
}

is_running() {
	[ -r "$PIDFILE" ] || return 1
	pid="$(cat "$PIDFILE" 2>/dev/null)"
	[ -n "$pid" ] && kill -0 "$pid" 2>/dev/null
}

start_service() {
	if is_running; then
		echo "tera-seriald is already running"
		return 0
	fi
	rm -f "$PIDFILE"
	[ -x "$DAEMON" ] || { echo "missing $DAEMON" >&2; return 1; }
	load_environment
	prepare_runtime || return 1
	start-stop-daemon -S -q -b -m -p "$PIDFILE" -c "$RUN_AS" -x "$DAEMON"
}

stop_service() {
	if ! is_running; then
		rm -f "$PIDFILE"
		return 0
	fi
	start-stop-daemon -K -q -p "$PIDFILE" -x "$DAEMON"
	rm -f "$PIDFILE"
}

case "$1" in
	start) start_service ;;
	stop) stop_service ;;
	restart) stop_service && start_service ;;
	status) is_running ;;
	*) echo "Usage: $0 {start|stop|restart|status}" >&2; exit 1 ;;
esac