#!/bin/bash
set -Eeuo pipefail
IFS=$'\n\t'

CONFIG_FILE="/etc/ssh-monitor.conf"
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
if [ -f "$SCRIPT_DIR/ssh-monitor-perms.sh" ]; then
	# shellcheck source=ssh-monitor-perms.sh
	source "$SCRIPT_DIR/ssh-monitor-perms.sh"
fi
WATCHDOG_LOG_FILE="/var/log/ssh_monitor_watchdog.log"
LAST_HEARTBEAT_FILE="/var/log/last_heartbeat.txt"
WATCHDOG_MAX_HEARTBEAT_AGE=18000
WATCHDOG_SERVICE_NAME="ssh-monitor.service"
WATCHDOG_NOTIFY_ON_RECOVERY="0"

write_log() {
	local message="$1"
	local timestamp
	timestamp="$(date '+%Y-%m-%d %H:%M:%S')"
	echo "${timestamp} - ${message}" | tee -a "$WATCHDOG_LOG_FILE" >/dev/null
}

send_telegram_raw() {
	local message="$1"
	if [ -z "${TELEGRAM_BOT_TOKEN:-}" ] || [ -z "${TELEGRAM_CHAT_ID:-}" ]; then
		return 1
	fi

	local url="https://api.telegram.org/bot${TELEGRAM_BOT_TOKEN}/sendMessage"
	local body
	if ! body=$(curl -fsS -X POST "$url" \
		--data-urlencode "chat_id=${TELEGRAM_CHAT_ID}" \
		--data-urlencode "text=${message}" \
		--data-urlencode "parse_mode=HTML" \
		--max-time 10 2>/dev/null); then
		return 1
	fi
	if echo "$body" | grep -q '"ok":true'; then
		return 0
	fi
	return 1
}

send_backup_webhook_raw() {
	local message="$1"
	if [ -z "${BACKUP_WEBHOOK_URL:-}" ]; then
		return 1
	fi
	if ! command -v python3 >/dev/null 2>&1; then
		return 1
	fi
	local plain="$message"
	local payload
	payload="$(BACKUP_MSG="$plain" python3 - <<'PY'
import json, os
print(json.dumps({"text": os.environ.get("BACKUP_MSG", "")}))
PY
)"
	if curl -fsS -m 12 -X POST "$BACKUP_WEBHOOK_URL" \
		-H "Content-Type: application/json" \
		-d "$payload" >/dev/null 2>&1; then
		return 0
	fi
	return 1
}

notify_send() {
	local message="$1"
	if send_telegram_raw "$message"; then
		return 0
	fi
	if send_backup_webhook_raw "$message"; then
		write_log "WARN: Telegram недоступен, сообщение watchdog ушло в BACKUP_WEBHOOK_URL"
		return 0
	fi
	write_log "WARN: watchdog: не удалось отправить уведомление"
	return 1
}

load_config() {
	if [ -f "$CONFIG_FILE" ]; then
		local _strict_peek
		_strict_peek="$(ssh_monitor_config_peek CONFIG_STRICT_PERMS "$CONFIG_FILE" "0")"
		ssh_monitor_check_config_file_perms "$CONFIG_FILE" "$_strict_peek" || true
		# shellcheck disable=SC1090
		source "$CONFIG_FILE"
	fi
	if [ -n "${BACKUP_WEBHOOK_URL:-}" ]; then
		write_log "WARN: BACKUP_WEBHOOK_URL deprecated (legacy fallback); будет удалён в 2.3.x"
	fi
}

is_service_active() {
	systemctl is-active --quiet "$WATCHDOG_SERVICE_NAME"
}

heartbeat_age_seconds() {
	if [ ! -f "$LAST_HEARTBEAT_FILE" ]; then
		echo 999999
		return 0
	fi

	local hb now
	hb="$(<"$LAST_HEARTBEAT_FILE")"
	now="$(date '+%s')"
	if [[ ! "$hb" =~ ^[0-9]+$ ]]; then
		echo 999999
		return 0
	fi
	echo $((now - hb))
}

restart_monitor() {
	local reason="$1"
	write_log "Watchdog: перезапуск $WATCHDOG_SERVICE_NAME, причина: $reason"
	if systemctl restart "$WATCHDOG_SERVICE_NAME"; then
		local msg=" ⚠️ WATCHDOG: монитор перезапущен "$'\n'
		msg="${msg}Сервис: ${WATCHDOG_SERVICE_NAME}"$'\n'
		msg="${msg}Причина: ${reason}"$'\n'
		msg="${msg}Время: $(date '+%d.%m.%Y %H:%M:%S')"
		notify_send "$msg"
	else
		write_log "Watchdog: ошибка перезапуска $WATCHDOG_SERVICE_NAME"
		local msg=" ❌ WATCHDOG: не удалось перезапустить монитор "$'\n'
		msg="${msg}Сервис: ${WATCHDOG_SERVICE_NAME}"$'\n'
		msg="${msg}Причина: ${reason}"$'\n'
		msg="${msg}Время: $(date '+%d.%m.%Y %H:%M:%S')"
		notify_send "$msg"
		return 1
	fi
}

main() {
	if [ "$EUID" -ne 0 ]; then
		echo "Запустите watchdog от root"
		exit 1
	fi

	load_config
	mkdir -p "$(dirname "$WATCHDOG_LOG_FILE")"
	touch "$WATCHDOG_LOG_FILE"

	local reason=""
	if ! is_service_active; then
		reason="systemd reported inactive service"
	else
		local age
		age="$(heartbeat_age_seconds)"
		if [ "$age" -ge "${WATCHDOG_MAX_HEARTBEAT_AGE:-5400}" ]; then
			reason="stale heartbeat (${age}s)"
		fi
	fi

	if [ -n "$reason" ]; then
		restart_monitor "$reason"
	elif [ "${WATCHDOG_NOTIFY_ON_RECOVERY:-1}" = "1" ]; then
		write_log "Watchdog: OK, сервис активен и heartbeat актуален"
	fi
}

main "$@"