Read an intermediate delivery notification as a report, and keep it out of the merge

src/dlr-merger.ts

@@ -41,7 +41,8 @@ const severity: Record<MessageState, number> = {
  * Merges the per-segment receipts of a multipart message into one report, but only when the peer
  * numbered its ids `<base>-<n>` off one base — the convention this library's own server follows. An
  * SMSC that hands out unrelated ids per segment cannot be merged, so nothing is reported for it.
- * A base is merged at most once: a reused id cannot be told apart from a straggler.
+ * A base is merged at most once: a reused id cannot be told apart from a straggler, and a report the
+ * peer marked intermediate is never counted — it would fill a slot before the real receipt arrives.
  */
 export class DlrMerger {
 	private readonly groups: ExpiringGroups<Group>;
@@ -95,7 +96,7 @@ export class DlrMerger {
 	collect(dlr: Dlr): MessageDlr | undefined {
 		this.sweep();
 
-		if (dlr.smsId === undefined) return undefined;
+		if (dlr.intermediate || dlr.smsId === undefined) return undefined;
 
 		const match = numbered.exec(dlr.smsId);
 		const base = match?.[1];

src/dlr.ts

@@ -50,6 +50,7 @@ export type Receipt = {
 export type Dlr = {
 	doneDate: Date | undefined;
 	errorCode: string | undefined;
+	intermediate: boolean;
 	receipt: Receipt | undefined;
 	smsId: string | undefined;
 	statusId: number;
@@ -127,13 +128,12 @@ export function parseReceipt(message: string): Receipt {
 	};
 }
 
-type MessageType = 'other' | 'receipt' | 'unmarked';
+type MessageType = 'intermediate' | 'other' | 'receipt' | 'unmarked';
 
-/** The message types the spec names that are not receipts. It reserves the remaining ten. */
-const notReceiptTypes: number[] = [
+/** The types the far-end SME writes, rather than the MC reporting. The spec reserves the remaining ten. */
+const smeMessageTypes: number[] = [
 	consts.ESM_CLASS.CONVERSATION_ABORT,
 	consts.ESM_CLASS.DELIVERY_ACKNOWLEDGEMENT,
-	consts.ESM_CLASS.INTERMEDIATE_DELIVERY,
 	consts.ESM_CLASS.USER_ACKNOWLEDGEMENT,
 ];
 
@@ -145,7 +145,8 @@ function messageType(pduObj: PduObject): MessageType {
 	const type = messageTypeOf(paramNumber(pduObj.params.esm_class, 0));
 
 	if (type === consts.ESM_CLASS.MC_DELIVERY_RECEIPT) return 'receipt';
-	if (notReceiptTypes.includes(type)) return 'other';
+	if (type === consts.ESM_CLASS.INTERMEDIATE_DELIVERY) return 'intermediate';
+	if (smeMessageTypes.includes(type)) return 'other';
 
 	return nonEmptyText(pduObj.tlvs.receipted_message_id?.tagValue) === undefined ? 'unmarked' : 'receipt';
 }
@@ -214,6 +215,7 @@ export function dlrFromPdu(pduObj: PduObject, format: SmsIdFormat = {}): Dlr | u
 	return {
 		doneDate: receiptDate(receipt?.doneDate),
 		errorCode: receipt?.err,
+		intermediate: type === 'intermediate',
 		receipt,
 		smsId,
 		statusId,