Add PDU framing and delivery receipt parsing

src/dlr.ts

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+import type { MessageState } from './defs/constants.ts';
+import type { PduObject } from './pdu.ts';
+import { consts, constsById } from './defs/constants.ts';
+
+/**
+ * The seven-character status codes carried in a receipt's `stat:` field, mapped to the
+ * message_state values they correspond to.
+ */
+const receiptStates: Record<string, MessageState> = {
+	ACCEPTD: 'ACCEPTED',
+	DELETED: 'DELETED',
+	DELIVRD: 'DELIVERED',
+	ENROUTE: 'ENROUTE',
+	EXPIRED: 'EXPIRED',
+	REJECTD: 'REJECTED',
+	UNDELIV: 'UNDELIVERABLE',
+	UNKNOWN: 'UNKNOWN',
+};
+
+/** message_state values as the seven-character codes a receipt's `stat:` field must carry. */
+export const receiptCodes: Record<MessageState, string> = {
+	ACCEPTED: 'ACCEPTD',
+	DELETED: 'DELETED',
+	DELIVERED: 'DELIVRD',
+	ENROUTE: 'ENROUTE',
+	EXPIRED: 'EXPIRED',
+	REJECTED: 'REJECTD',
+	SCHEDULED: 'ENROUTE',
+	SKIPPED: 'UNKNOWN',
+	UNDELIVERABLE: 'UNDELIV',
+	UNKNOWN: 'UNKNOWN',
+};
+
+export type Receipt = {
+	doneDate: string | undefined;
+	dlvrd: number | undefined;
+	err: string | undefined;
+	id: string | undefined;
+	stat: string | undefined;
+	sub: number | undefined;
+	submitDate: string | undefined;
+	text: string | undefined;
+};
+
+export type Dlr = {
+	doneDate: Date | undefined;
+	errorCode: string | undefined;
+	receipt: Receipt | undefined;
+	smsId: string;
+	statusId: number;
+	statusMsg: string;
+};
+
+const field = (name: string) => new RegExp(`\\b${name}:([^ ]*)`, 'i');
+
+const patterns = {
+	dlvrd: field('dlvrd'),
+	doneDate: /\bdone date:([^ ]*)/i,
+	err: field('err'),
+	id: field('id'),
+	stat: field('stat'),
+	sub: field('sub'),
+	submitDate: /\bsubmit date:([^ ]*)/i,
+	text: /\btext:(.*)$/i,
+};
+
+function toNumber(value: string | undefined): number | undefined {
+	if (value === undefined) return undefined;
+
+	const parsed = Number(value);
+
+	return Number.isFinite(parsed) ? parsed : undefined;
+}
+
+/** Delivery receipt dates are YYMMDDhhmm, sometimes with seconds. */
+function receiptDate(value: string | undefined): Date | undefined {
+	if (value === undefined) return undefined;
+
+	const match = /^(\d\d)(\d\d)(\d\d)(\d\d)(\d\d)(\d\d)?$/.exec(value);
+
+	if (!match) return undefined;
+
+	const [, years, months, days, hours, minutes, seconds] = match;
+	const century = Math.floor(new Date().getUTCFullYear() / 100) * 100;
+
+	return new Date(Date.UTC(
+		century + Number(years),
+		Number(months) - 1,
+		Number(days),
+		Number(hours),
+		Number(minutes),
+		Number(seconds ?? 0),
+	));
+}
+
+/**
+ * Parses the standard receipt body, as in
+ * `id:0123 sub:001 dlvrd:001 submit date:2508251430 done date:2508251431 stat:DELIVRD err:000 text:…`
+ */
+export function parseReceipt(message: string): Receipt {
+	const read = (pattern: RegExp): string | undefined => pattern.exec(message)?.[1];
+
+	return {
+		dlvrd: toNumber(read(patterns.dlvrd)),
+		doneDate: read(patterns.doneDate),
+		err: read(patterns.err),
+		id: read(patterns.id),
+		stat: read(patterns.stat),
+		sub: toNumber(read(patterns.sub)),
+		submitDate: read(patterns.submitDate),
+		text: read(patterns.text),
+	};
+}
+
+/**
+ * Builds a delivery report from a deliver_sm. The message_state and receipted_message_id TLVs are
+ * authoritative when present; otherwise the receipt text is parsed, which is the only thing Kannel
+ * and several other SMSCs send. 0.4.0 required the TLVs and rejected everything else.
+ */
+export function dlrFromPdu(pduObj: PduObject): Dlr | undefined {
+	const message = pduObj.params.short_message;
+	const receipt = typeof message === 'string' ? parseReceipt(message) : undefined;
+
+	const tlvState = pduObj.tlvs.message_state?.tagValue;
+	const tlvId = pduObj.tlvs.receipted_message_id?.tagValue;
+
+	const smsId = typeof tlvId === 'string' && tlvId !== ''
+		? tlvId
+		: receipt?.id;
+
+	if (smsId === undefined || smsId === '') return undefined;
+
+	const statusMsg = typeof tlvState === 'number'
+		? constsById.MESSAGE_STATE?.[tlvState]
+		: receiptStates[receipt?.stat?.toUpperCase() ?? ''];
+
+	if (statusMsg === undefined) return undefined;
+
+	const statusId = typeof tlvState === 'number'
+		? tlvState
+		: consts.MESSAGE_STATE[receiptStates[receipt?.stat?.toUpperCase() ?? ''] ?? 'UNKNOWN'];
+
+	return {
+		doneDate: receiptDate(receipt?.doneDate),
+		errorCode: receipt?.err,
+		receipt,
+		smsId,
+		statusId,
+		statusMsg,
+	};
+}

src/pdu-framer.ts

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+import type { Result } from './result.ts';
+import { maxPduLength } from './pdu.ts';
+
+/**
+ * Cuts a byte stream into whole PDUs.
+ *
+ * Chunks are held in a list and only joined when a complete PDU is available, so a peer dribbling
+ * bytes cannot make this quadratic the way concatenating the whole queue on every chunk does.
+ */
+export class PduFramer {
+	private chunks: Buffer[] = [];
+	private length = 0;
+
+	get buffered(): number {
+		return this.length;
+	}
+
+	push(chunk: Buffer): void {
+		if (chunk.length === 0) return;
+
+		this.chunks.push(chunk);
+		this.length += chunk.length;
+	}
+
+	/**
+	 * Every complete PDU buffered so far. An error means the stream is unusable — the peer sent a
+	 * command length that cannot be honoured — and the caller should close the connection.
+	 */
+	next(): Result<{ pdus: Buffer[] }> {
+		const pdus: Buffer[] = [];
+
+		while (this.length >= 16) {
+			const cmdLength = this.join(16).readUInt32BE(0);
+
+			if (cmdLength < 16 || cmdLength > maxPduLength) {
+				return { err: new Error(`Refusing a cmd_length of ${String(cmdLength)}`) };
+			}
+
+			if (this.length < cmdLength) break;
+
+			pdus.push(this.take(cmdLength));
+		}
+
+		return { pdus };
+	}
+
+	/** Makes sure the first chunk holds at least `size` octets, then returns it. */
+	private join(size: number): Buffer {
+		const first = this.chunks[0];
+
+		if (first && first.length >= size) return first;
+
+		const joined = Buffer.concat(this.chunks, this.length);
+
+		this.chunks = [joined];
+
+		return joined;
+	}
+
+	private take(size: number): Buffer {
+		const source = this.join(size);
+		const pdu = source.subarray(0, size);
+		const rest = source.subarray(size);
+
+		this.chunks[0] = rest;
+		if (rest.length === 0) this.chunks.shift();
+		this.length -= size;
+
+		return pdu;
+	}
+}