Wait out the messages the application holds before shutting a session down

src/sms.ts

@@ -1,6 +1,6 @@
 import type { ErrorName } from './defs/errors.ts';
 import type { MessageState } from './defs/constants.ts';
-import type { PduObject, TlvInput } from './pdu.ts';
+import type { PduObject, PduObjectInput, TlvInput } from './pdu.ts';
 import type { Result, VoidResult } from './result.ts';
 import type { Session } from './session.ts';
 import { consts } from './defs/constants.ts';
@@ -43,12 +43,18 @@ export type SmsInput = {
 	to: string;
 };
 
+/** What the session's incoming side gives a message so it can be answered and accounted for. */
+export type SmsHandlers = {
+	onAnswered: () => void;
+	send: (input: PduObjectInput) => Promise<Result<{ pduObj: PduObject }>>;
+};
+
 /** Each segment of a multipart message gets its own message_id, as a separate submit_sm must. */
 function segmentId(smsId: string, index: number, total: number): string {
 	return total === 1 ? smsId : `${smsId}-${String(index + 1)}`;
 }
 
-export function createSms(input: SmsInput): Sms {
+export function createSms(input: SmsInput, handlers: SmsHandlers): Sms {
 	const first = input.pduObjs[0];
 	const registered = first?.params.registered_delivery;
 	const dataCoding = first?.params.data_coding;
@@ -60,8 +66,8 @@ export function createSms(input: SmsInput): Sms {
 		from: input.from,
 		message: input.message,
 		pduObjs: input.pduObjs,
-		sendDlr: status => sendDlr(sms, status),
-		sendResp: options => sendResp(sms, answered, options ?? {}),
+		sendDlr: status => sendDlr(sms, handlers.send, status),
+		sendResp: options => sendResp(sms, answered, options ?? {}).finally(handlers.onAnswered),
 		session: input.session,
 		get smsId(): string {
 			return answered.smsId;
@@ -124,6 +130,7 @@ function receiptTlvs(smsId: string, status: MessageState): Record<string, TlvInp
 
 async function sendDlr(
 	sms: Sms,
+	send: SmsHandlers['send'],
 	status: MessageState = 'DELIVERED',
 ): Promise<Result<{ pduObjs: PduObject[] }>> {
 	if (!sms.session.bindAllows('deliver_sm')) {
@@ -135,7 +142,7 @@ async function sendDlr(
 
 	for (let index = 0; index < total; index++) {
 		const smsId = segmentId(sms.smsId, index, total);
-		const sent = await sms.session.send({
+		const sent = await send({
 			cmdName: 'deliver_sm',
 			params: {
 				destination_addr: sms.from,