import {platform} from "node:os";
import type {UnixDgramSocket} from "unix-dgram";

import logger from "./logger";

/**
 * Handle sd_notify protocol, @see https://www.freedesktop.org/software/systemd/man/latest/sd_notify.html
 * No-op if running on unsupported platforms or without Type=notify
 * Soft-fails if improperly setup (this is not necessary for Zigbee2MQTT to function properly)
 */
export async function initSdNotify(): Promise<{notifyStopping: () => void; stop: () => void} | undefined> {
    if (!process.env.NOTIFY_SOCKET) {
        return;
    }

    let socket: UnixDgramSocket | undefined;

    try {
        const {createSocket} = await import("unix-dgram");
        socket = createSocket("unix_dgram");
    } catch (error) {
        if (platform() !== "win32" || process.env.WSL_DISTRO_NAME) {
            // not on plain Windows
            logger.error(`Could not init sd_notify: ${(error as Error).message}`);
            // biome-ignore lint/style/noNonNullAssertion: always Error
            logger.debug((error as Error).stack!);
        } else {
            // this should not happen
            logger.warning(`NOTIFY_SOCKET env is set: ${(error as Error).message}`);
        }

        return;
    }

    const sendToSystemd = (msg: string): void => {
        const buffer = Buffer.from(msg);

        // biome-ignore lint/style/noNonNullAssertion: valid from start of function
        socket.send(buffer, 0, buffer.byteLength, process.env.NOTIFY_SOCKET!, (err) => {
            if (err) {
                logger.warning(`Failed to send "${msg}" to systemd: ${err.message}`);
            }
        });
    };
    const notifyStopping = (): void => sendToSystemd("STOPPING=1");

    sendToSystemd("READY=1");

    const wdUSec = process.env.WATCHDOG_USEC !== undefined ? Math.max(0, Number.parseInt(process.env.WATCHDOG_USEC, 10)) : -1;

    if (wdUSec > 0) {
        // Convert us to ms, send twice as frequently as the timeout
        const watchdogInterval = setInterval(() => sendToSystemd("WATCHDOG=1"), wdUSec / 1000 / 2);

        return {
            notifyStopping,
            stop: (): void => clearInterval(watchdogInterval),
        };
    }

    if (wdUSec !== -1) {
        logger.warning(`WATCHDOG_USEC invalid: "${process.env.WATCHDOG_USEC}", parsed to "${wdUSec}"`);
    }

    return {
        notifyStopping,
        stop: (): void => {},
    };
}