Declare the alphabet a GSM message is actually written in (#100)

* Regression tests for the alphabet a GSM message declares

* Declare the alphabet a GSM message is actually written in

* Reflow the composing-by-hand paragraph

* Drop the ASCII alias SMPP's flat table shares with the option's own

* Bound the receipt test's wait and tighten the notes around it

src/defs/constants.ts

@@ -22,7 +22,6 @@ export const consts = {
 		YEARS: 0x0E,
 	},
 	ENCODING: {
-		ASCII: 0x01,
 		BINARY: 0x04,
 		CYRILLIC: 0x06,
 		EXTENDED_KANJI_JIS: 0x0D,

src/defs/encodings.ts

@@ -188,3 +188,13 @@ export function encodingByDataCoding(dataCoding: number): EncodingName {
 	// 0x02 and 0x04 are 8-bit binary, 0x03 is Latin-1.
 	return dataCoding >= 0x02 && dataCoding <= 0x04 ? 'LATIN1' : 'ASCII';
 }
+
+/**
+ * The `data_coding` an alphabet is written under, the mirror of `encodingByDataCoding()`. GSM 03.38
+ * takes 0x00, the SMSC default alphabet, rather than SMPP 3.4 5.2.19's 0x01, which is IA5.
+ */
+export const dataCodingByEncoding: Readonly<Record<EncodingName, number>> = {
+	ASCII: 0x00,
+	LATIN1: 0x03,
+	UCS2: 0x08,
+};

src/index.ts

@@ -4,7 +4,7 @@ export { Session } from './session.ts';
 
 export { cmds, cmdsById, commandNameById, isCommandName } from './defs/commands.ts';
 export { consts, constsById } from './defs/constants.ts';
-export { detect, encodingByDataCoding, encodings, isEncodingName, messageClassOf, unencodable } from './defs/encodings.ts';
+export { dataCodingByEncoding, detect, encodingByDataCoding, encodings, isEncodingName, messageClassOf, unencodable } from './defs/encodings.ts';
 export { errorNameById, errors, errorsById, isErrorName } from './defs/errors.ts';
 export { tlvs, tlvsById } from './defs/tlvs.ts';
 export { types } from './defs/types.ts';

src/message.ts

@@ -1,7 +1,7 @@
 import type { Result } from './result.ts';
 import type { EncodingName } from './defs/encodings.ts';
-import { detect, encodingByDataCoding, encodings, unencodable, unencodableText } from './defs/encodings.ts';
-import { consts, hasUdh } from './defs/constants.ts';
+import { dataCodingByEncoding, detect, encodingByDataCoding, encodings, unencodable, unencodableText } from './defs/encodings.ts';
+import { hasUdh } from './defs/constants.ts';
 import { udhLength } from './udh.ts';
 
 /** A single SMS carries 1120 bits, whatever the alphabet. */
@@ -35,7 +35,7 @@ export function encodeBody(
 	if (dataCoding === undefined) {
 		const detected = encodeMessage(text);
 
-		return { buffer: detected.buffer, dataCoding: consts.ENCODING[detected.encoding] };
+		return { buffer: detected.buffer, dataCoding: dataCodingByEncoding[detected.encoding] };
 	}
 
 	const encoding = encodingByDataCoding(dataCoding);

src/send-sms.ts

@@ -7,7 +7,7 @@ import type { SmppLog } from './log.ts';
 import type { SmsIdNotation } from './sms-id.ts';
 import { UnansweredError } from './unanswered-error.ts';
 import { consts, defaultMessagingMode, isMessagingMode, isSubmitMessagingMode, submitMessagingModes } from './defs/constants.ts';
-import { detect, encodingNames, isEncodingName, unencodable, unencodableText } from './defs/encodings.ts';
+import { dataCodingByEncoding, detect, encodingNames, isEncodingName, unencodable, unencodableText } from './defs/encodings.ts';
 import { namedValue } from './error-from.ts';
 import { normaliseSmsId } from './sms-id.ts';
 import { paramText } from './defs/types.ts';
@@ -89,7 +89,7 @@ function addressTon(address: string): number {
 }
 
 function dataCodingFor(encoding: EncodingName, flash: boolean): number {
-	if (!flash) return consts.ENCODING[encoding];
+	if (!flash) return dataCodingByEncoding[encoding];
 
 	// Message class present (0x10) plus the alphabet bits, so flash survives UCS2.
 	return encoding === 'UCS2' ? 0x18 : 0x10;