Answer every segment of an inbound concatenated message as it arrives (#83)

* Regression tests for answering every inbound segment as it arrives

* Answer every segment of an inbound concatenated message as it arrives

* Record the segment-by-segment answer in AGENTS.md and README

* Regression tests for an empty message_id on deliver_sm_resp

* Answer a deliver_sm with the empty message_id SMPP 3.4 makes it

* Record Jasmin's refusal of a deliver_sm_resp message_id

* Mark the Jasmin multipart deadlock fixed

* Regression tests for the architecture review's findings

* Give the segment id notation an owner, and every segment a status

* Correct what the ids reach and what a lost group tells the application

* Regression tests for a group lost to its own octet overrun

* Report a group lost to its own overrun, and refuse by the command it arrived on

* Keep the docs true about what a segment is answered with

* Count only the answered segments of a group lost to an overrun

* Report only what a lost group cost, and say which cap bit

src/sms-id.ts

@@ -1,3 +1,6 @@
+import type { CommandName } from './defs/commands.ts';
+import type { ParamValue } from './defs/types.ts';
+
 const notations = {
 	decimal: { digits: /^[0-9]+$/, prefix: '' },
 	hex: { digits: /^[0-9a-f]+$/i, prefix: '0x' },
@@ -33,3 +36,26 @@ export function normaliseSmsId(id: string, notation: SmsIdNotation | undefined):
 
 	return digits.test(id) ? BigInt(`${prefix}${id}`).toString(10) : id;
 }
+
+const numbered = /^(.*)-(\d+)$/;
+
+/** Each segment of a multipart message gets its own message_id, as a separate submit_sm must. */
+export function segmentId(smsId: string, index: number, total: number): string {
+	return total === 1 ? smsId : `${smsId}-${String(index + 1)}`;
+}
+
+/** The message and the part an id names, or nothing where `segmentId()` did not write it. */
+export function parseSegmentId(smsId: string): { base: string; part: number } | undefined {
+	const match = numbered.exec(smsId);
+	const base = match?.[1];
+	const part = match?.[2];
+
+	if (base === undefined || part === undefined) return undefined;
+
+	return { base, part: Number(part) };
+}
+
+/** SMPP 3.4 4.6.2 makes `deliver_sm_resp`'s `message_id` unused, and Jasmin FINs the link over one. */
+export function respIdParams(cmdName: CommandName, smsId: string): Record<string, ParamValue> {
+	return cmdName === 'deliver_sm' ? {} : { message_id: smsId };
+}