William Valentin
108 lines
2.8 KiB
TypeScript
108 lines
2.8 KiB
TypeScript
import { spawn, type ChildProcess } from 'child_process';
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export interface GatewayDiscoveryConfig {
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serviceName: string;
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serviceType: string;
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port: number;
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txtRecord?: Record<string, string>;
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}
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export interface GatewayDiscoveryHandle {
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stop(): Promise<void>;
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}
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function toTxtArgs(txtRecord?: Record<string, string>): string[] {
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if (!txtRecord) {
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return [];
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}
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return Object.entries(txtRecord).map(([key, value]) => `${key}=${value}`);
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}
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async function spawnAdvertiser(command: string, args: string[]): Promise<ChildProcess> {
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return new Promise((resolve, reject) => {
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const child = spawn(command, args, { stdio: 'ignore' });
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const onError = (error: Error): void => {
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cleanup();
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reject(error);
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};
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const onExit = (code: number | null, signal: NodeJS.Signals | null): void => {
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cleanup();
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reject(new Error(`${command} exited early (code=${code ?? 'null'}, signal=${signal ?? 'null'})`));
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};
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const onSpawn = (): void => {
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setTimeout(() => {
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cleanup();
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resolve(child);
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}, 100);
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};
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const cleanup = (): void => {
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child.off('error', onError);
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child.off('exit', onExit);
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child.off('spawn', onSpawn);
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};
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child.once('error', onError);
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child.once('exit', onExit);
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child.once('spawn', onSpawn);
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});
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}
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async function stopChild(child: ChildProcess): Promise<void> {
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if (child.exitCode !== null || child.killed) {
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return;
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}
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await new Promise<void>((resolve) => {
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const timeout = setTimeout(() => {
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child.kill('SIGKILL');
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resolve();
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}, 1000);
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child.once('exit', () => {
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clearTimeout(timeout);
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resolve();
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});
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child.kill('SIGTERM');
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});
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}
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/**
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* Starts LAN discovery using best-effort host tools.
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* Priority: avahi-publish-service (Linux) -> dns-sd (macOS).
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*/
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export async function startGatewayDiscovery(config: GatewayDiscoveryConfig): Promise<GatewayDiscoveryHandle> {
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const txtArgs = toTxtArgs(config.txtRecord);
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const attempts: Array<{ command: string; args: string[] }> = [
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{
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command: 'avahi-publish-service',
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args: [config.serviceName, config.serviceType, String(config.port), ...txtArgs],
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},
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{
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command: 'dns-sd',
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args: ['-R', config.serviceName, config.serviceType, 'local', String(config.port), ...txtArgs],
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},
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];
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let lastError: Error | null = null;
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for (const attempt of attempts) {
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try {
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const child = await spawnAdvertiser(attempt.command, attempt.args);
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child.unref();
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return {
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stop: async () => {
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await stopChild(child);
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},
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};
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} catch (error) {
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lastError = error instanceof Error ? error : new Error(String(error));
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}
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}
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throw new Error(
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`Failed to start mDNS advertiser (tried avahi-publish-service and dns-sd): ${lastError?.message ?? 'unknown error'}`,
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);
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}
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