Initial systant implementation in Bun/TypeScript
A lightweight system monitoring agent that: - Collects metrics via configurable shell commands - Publishes to MQTT with Home Assistant auto-discovery - Supports entity types: sensor, binary_sensor, light, switch, button - Responds to commands over MQTT for controllable entities Architecture: - src/config.ts: TOML config loading and validation - src/mqtt.ts: MQTT client with HA discovery - src/entities.ts: Entity state polling and command handling - index.ts: CLI entry point (run, check, once commands) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Claude Opus 4.5
+130
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import { parse } from "smol-toml";
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export interface SystantConfig {
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hostname: string;
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defaultInterval: number;
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}
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export interface MqttConfig {
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broker: string;
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username?: string;
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password?: string;
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clientId?: string;
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topicPrefix: string;
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}
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export type EntityType = "sensor" | "binary_sensor" | "light" | "switch" | "button";
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export interface EntityConfig {
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type: EntityType;
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state_command?: string; // for stateful entities (not button)
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on_command?: string; // for light/switch
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off_command?: string; // for light/switch
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press_command?: string; // for button
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interval?: number; // override default interval
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unit?: string; // for sensor
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device_class?: string; // for sensor (timestamp, etc.) or binary_sensor
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icon?: string;
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name?: string;
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availability?: boolean; // default true; set false to keep last value when offline
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}
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export interface HomeAssistantConfig {
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discovery: boolean;
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discoveryPrefix: string;
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}
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export interface Config {
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systant: SystantConfig;
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mqtt: MqttConfig;
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entities: Record<string, EntityConfig>;
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homeassistant: HomeAssistantConfig;
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}
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const defaults = {
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systant: {
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defaultInterval: 30,
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hostname: process.env.HOSTNAME || require("os").hostname(),
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},
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mqtt: {
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broker: "mqtt://localhost:1883",
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topicPrefix: "systant",
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},
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homeassistant: {
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discovery: true,
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discoveryPrefix: "homeassistant",
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},
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};
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export async function loadConfig(path: string): Promise<Config> {
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const file = Bun.file(path);
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if (!(await file.exists())) {
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throw new Error(`Config file not found: ${path}`);
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}
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const content = await file.text();
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const parsed = parse(content) as Record<string, unknown>;
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return buildConfig(parsed);
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}
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function buildConfig(parsed: Record<string, unknown>): Config {
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const config: Config = {
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systant: { ...defaults.systant },
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mqtt: { ...defaults.mqtt },
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entities: {},
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homeassistant: { ...defaults.homeassistant },
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};
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// MQTT settings
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if (parsed.mqtt && typeof parsed.mqtt === "object") {
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Object.assign(config.mqtt, parsed.mqtt);
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}
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// Systant settings
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if (parsed.systant && typeof parsed.systant === "object") {
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Object.assign(config.systant, parsed.systant);
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}
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// Entities
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if (parsed.entities && typeof parsed.entities === "object") {
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const entities = parsed.entities as Record<string, unknown>;
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for (const [key, value] of Object.entries(entities)) {
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if (key === "interval") continue; // skip the default interval
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if (value && typeof value === "object" && "type" in value) {
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const e = value as Record<string, unknown>;
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const entityType = String(e.type) as EntityType;
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// Buttons need press_command, others need state_command
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const hasRequiredCommand = entityType === "button"
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? "press_command" in e
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: "state_command" in e;
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if (!hasRequiredCommand) continue;
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config.entities[key] = {
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type: entityType,
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state_command: typeof e.state_command === "string" ? e.state_command : undefined,
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on_command: typeof e.on_command === "string" ? e.on_command : undefined,
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off_command: typeof e.off_command === "string" ? e.off_command : undefined,
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press_command: typeof e.press_command === "string" ? e.press_command : undefined,
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interval: typeof e.interval === "number" ? e.interval : undefined,
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unit: typeof e.unit === "string" ? e.unit : undefined,
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device_class: typeof e.device_class === "string" ? e.device_class : undefined,
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icon: typeof e.icon === "string" ? e.icon : undefined,
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name: typeof e.name === "string" ? e.name : undefined,
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availability: typeof e.availability === "boolean" ? e.availability : true,
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};
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}
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}
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}
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// Home Assistant
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if (parsed.homeassistant && typeof parsed.homeassistant === "object") {
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Object.assign(config.homeassistant, parsed.homeassistant);
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}
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return config;
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}
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+110
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import type { Config, EntityConfig } from "./config";
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import type { MqttConnection } from "./mqtt";
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export interface EntityManager {
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start(): Promise<void>;
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stop(): void;
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}
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export function createEntityManager(config: Config, mqtt: MqttConnection): EntityManager {
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const timers: Timer[] = [];
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async function setupStatefulEntity(id: string, entity: EntityConfig): Promise<void> {
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const interval = entity.interval ?? config.systant.defaultInterval;
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const isControllable = entity.type === "light" || entity.type === "switch";
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if (!entity.state_command) return;
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// State polling
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const pollState = async () => {
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try {
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const output = await Bun.$`sh -c ${entity.state_command}`.text();
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const value = output.trim();
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console.debug(`[${id}] state: ${value}`);
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await mqtt.publish(`${id}/state`, value, true); // retain state
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} catch (err) {
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console.error(`[${id}] state poll failed:`, err instanceof Error ? err.message : err);
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}
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};
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// Initial state poll
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await pollState();
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// Schedule periodic polling
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const timer = setInterval(pollState, interval * 1000);
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timers.push(timer);
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// Command subscription for controllable entities
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if (isControllable && (entity.on_command || entity.off_command)) {
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await mqtt.subscribe(`${id}/set`, async (_topic, payload) => {
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const command = payload.toString().toUpperCase();
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console.log(`[${id}] received command: ${command}`);
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try {
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if (command === "ON" && entity.on_command) {
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await Bun.$`sh -c ${entity.on_command}`;
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console.log(`[${id}] executed on_command`);
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} else if (command === "OFF" && entity.off_command) {
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await Bun.$`sh -c ${entity.off_command}`;
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console.log(`[${id}] executed off_command`);
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} else {
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console.warn(`[${id}] unknown command or no handler: ${command}`);
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return;
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}
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// Re-poll state after command execution
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await new Promise((r) => setTimeout(r, 500)); // brief delay for state to settle
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await pollState();
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} catch (err) {
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console.error(`[${id}] command failed:`, err instanceof Error ? err.message : err);
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}
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});
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}
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const typeLabel = isControllable ? `${entity.type} (controllable)` : entity.type;
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console.log(` ${id}: ${typeLabel}, poll every ${interval}s`);
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}
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async function setupButton(id: string, entity: EntityConfig): Promise<void> {
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if (!entity.press_command) return;
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await mqtt.subscribe(`${id}/press`, async (_topic, _payload) => {
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console.log(`[${id}] button pressed`);
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try {
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await Bun.$`sh -c ${entity.press_command}`;
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console.log(`[${id}] executed press_command`);
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} catch (err) {
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console.error(`[${id}] press_command failed:`, err instanceof Error ? err.message : err);
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}
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});
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console.log(` ${id}: button`);
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}
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return {
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async start(): Promise<void> {
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const entityCount = Object.keys(config.entities).length;
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if (entityCount === 0) {
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console.log("No entities configured");
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return;
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}
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console.log(`Starting ${entityCount} entity manager(s):`);
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for (const [id, entity] of Object.entries(config.entities)) {
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if (entity.type === "button") {
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await setupButton(id, entity);
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} else {
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await setupStatefulEntity(id, entity);
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}
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}
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},
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stop(): void {
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for (const timer of timers) {
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clearInterval(timer);
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}
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timers.length = 0;
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},
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};
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}
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+177
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import mqtt, { type MqttClient, type IClientOptions } from "mqtt";
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import type { Config, EntityConfig } from "./config";
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export interface MqttConnection {
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client: MqttClient;
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publish(topic: string, payload: string | object, retain?: boolean): Promise<void>;
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subscribe(topic: string, handler: (topic: string, payload: Buffer) => void): Promise<void>;
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disconnect(): Promise<void>;
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}
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export async function connect(config: Config, hostname: string): Promise<MqttConnection> {
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const options: IClientOptions = {
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clientId: config.mqtt.clientId || `systant-${hostname}`,
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username: config.mqtt.username,
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password: config.mqtt.password,
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will: {
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topic: `${config.mqtt.topicPrefix}/${hostname}/status`,
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payload: Buffer.from("offline"),
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qos: 1,
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retain: true,
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},
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};
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const client = mqtt.connect(config.mqtt.broker, options);
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const handlers = new Map<string, (topic: string, payload: Buffer) => void>();
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await new Promise<void>((resolve, reject) => {
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client.on("connect", () => {
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console.log(`Connected to MQTT broker: ${config.mqtt.broker}`);
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resolve();
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});
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client.on("error", reject);
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});
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client.on("message", (topic, payload) => {
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for (const [pattern, handler] of handlers) {
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if (topicMatches(pattern, topic)) {
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handler(topic, payload);
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}
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}
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});
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// Publish online status
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await publishAsync(client, `${config.mqtt.topicPrefix}/${hostname}/status`, "online", true);
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// Publish HA discovery if enabled
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if (config.homeassistant.discovery) {
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await publishDiscovery(client, config, hostname);
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}
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return {
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client,
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async publish(topic: string, payload: string | object, retain = false): Promise<void> {
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const fullTopic = `${config.mqtt.topicPrefix}/${hostname}/${topic}`;
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const data = typeof payload === "object" ? JSON.stringify(payload) : payload;
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await publishAsync(client, fullTopic, data, retain);
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},
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async subscribe(topic: string, handler: (topic: string, payload: Buffer) => void): Promise<void> {
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const fullTopic = `${config.mqtt.topicPrefix}/${hostname}/${topic}`;
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handlers.set(fullTopic, handler);
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await new Promise<void>((resolve, reject) => {
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client.subscribe(fullTopic, { qos: 1 }, (err) => {
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if (err) reject(err);
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else resolve();
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});
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});
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console.log(`Subscribed to: ${fullTopic}`);
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},
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async disconnect(): Promise<void> {
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await publishAsync(client, `${config.mqtt.topicPrefix}/${hostname}/status`, "offline", true);
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await new Promise<void>((resolve) => client.end(false, {}, () => resolve()));
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},
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};
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}
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function publishAsync(client: MqttClient, topic: string, payload: string, retain: boolean): Promise<void> {
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return new Promise((resolve, reject) => {
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client.publish(topic, payload, { qos: 1, retain }, (err) => {
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if (err) reject(err);
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else resolve();
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});
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});
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}
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function topicMatches(pattern: string, topic: string): boolean {
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if (pattern === topic) return true;
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if (pattern.endsWith("#")) {
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return topic.startsWith(pattern.slice(0, -1));
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}
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return false;
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}
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async function publishDiscovery(client: MqttClient, config: Config, hostname: string): Promise<void> {
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const prefix = config.homeassistant.discoveryPrefix;
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const topicPrefix = config.mqtt.topicPrefix;
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const entityCount = Object.keys(config.entities).length;
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if (entityCount === 0) {
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console.log("No entities configured, skipping HA discovery");
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return;
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}
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for (const [id, entity] of Object.entries(config.entities)) {
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const payload = buildDiscoveryPayload(id, entity, hostname, topicPrefix);
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const discoveryTopic = `${prefix}/${entity.type}/${hostname}_${id}/config`;
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await publishAsync(client, discoveryTopic, JSON.stringify(payload), true);
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}
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console.log(`Published Home Assistant discovery for ${entityCount} entity/entities`);
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}
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function buildDiscoveryPayload(
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id: string,
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entity: EntityConfig,
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hostname: string,
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topicPrefix: string
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): Record<string, unknown> {
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const displayName = entity.name || id.replace(/_/g, " ");
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const payload: Record<string, unknown> = {
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name: displayName,
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unique_id: `systant_${hostname}_${id}`,
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device: {
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identifiers: [`systant_${hostname}`],
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name: `${hostname}`,
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manufacturer: "Systant",
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},
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};
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// Stateful entities have a state_topic (buttons don't)
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if (entity.type !== "button") {
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payload.state_topic = `${topicPrefix}/${hostname}/${id}/state`;
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}
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// Add availability tracking unless explicitly disabled
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if (entity.availability !== false) {
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payload.availability_topic = `${topicPrefix}/${hostname}/status`;
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payload.payload_available = "online";
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payload.payload_not_available = "offline";
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}
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// Common optional fields
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if (entity.icon) payload.icon = entity.icon;
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// Type-specific fields
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switch (entity.type) {
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case "sensor":
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if (entity.unit) payload.unit_of_measurement = entity.unit;
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if (entity.device_class) payload.device_class = entity.device_class;
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break;
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case "binary_sensor":
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payload.payload_on = "ON";
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payload.payload_off = "OFF";
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if (entity.device_class) payload.device_class = entity.device_class;
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break;
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case "light":
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case "switch":
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payload.command_topic = `${topicPrefix}/${hostname}/${id}/set`;
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payload.payload_on = "ON";
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payload.payload_off = "OFF";
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payload.state_on = "ON";
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payload.state_off = "OFF";
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break;
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case "button":
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payload.command_topic = `${topicPrefix}/${hostname}/${id}/press`;
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payload.payload_press = "PRESS";
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break;
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}
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return payload;
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}
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