Split the session, gate optional parameters on the peer version, own the SMPP version in defs

src/reconnect-loop.ts

@@ -0,0 +1,86 @@
+import type { LogInt } from '@larvit/log';
+import type { Result, VoidResult } from './result.ts';
+import type { Socket } from 'node:net';
+
+export type ReconnectLoopOptions = {
+	connect: () => Promise<Result<{ sock: Socket }>>;
+	log: LogInt;
+	maxDelay: number;
+	minDelay: number;
+	/** Brings the owner back up on a freshly opened socket. An err means try again. */
+	onConnected: (sock: Socket) => Promise<VoidResult>;
+};
+
+/** Reopens a dropped connection, backing off between attempts until it is told to stop. */
+export class ReconnectLoop {
+	private readonly options: ReconnectLoopOptions;
+	private delay: number;
+	private halted = false;
+	private timer: NodeJS.Timeout | undefined;
+
+	constructor(options: ReconnectLoopOptions) {
+		this.options = options;
+		this.delay = options.minDelay;
+	}
+
+	/** Read through a method: stop() can land while an attempt is awaiting. */
+	isStopped(): boolean {
+		return this.halted;
+	}
+
+	schedule(): void {
+		if (this.timer || this.isStopped()) return;
+
+		const delay = this.delay;
+
+		this.options.log.info('reconnect - retrying after a drop', { delay });
+
+		this.timer = setTimeout(() => {
+			this.timer = undefined;
+			void this.run();
+		}, delay);
+		this.timer.unref();
+
+		this.delay = Math.min(delay * 2, this.options.maxDelay);
+	}
+
+	stop(): void {
+		this.halted = true;
+
+		if (this.timer) clearTimeout(this.timer);
+
+		this.timer = undefined;
+	}
+
+	private async run(): Promise<void> {
+		if (this.isStopped()) return;
+
+		const opened = await this.options.connect();
+
+		if (opened.err) {
+			this.options.log.warn('reconnect - could not open a socket', {
+				message: opened.err.message,
+			});
+			this.schedule();
+
+			return;
+		}
+
+		if (this.isStopped()) {
+			opened.sock.destroy();
+
+			return;
+		}
+
+		const up = await this.options.onConnected(opened.sock);
+
+		if (up.err) {
+			this.options.log.warn('reconnect - could not come back up', { message: up.err.message });
+			this.schedule();
+
+			return;
+		}
+
+		this.delay = this.options.minDelay;
+	}
+}