Record wire-format defects and drop the dormant filters layer

AGENTS.md

@@ -27,7 +27,9 @@ These are not preferences. Breaking one is a defect.
 3. **No `error` event.** Node makes an unhandled `error` event throw, which would break rule 1.
    Sessions emit `sessionError`, servers emit `serverError`.
 4. **No casts, no non-null assertions.** `as`, `as unknown as` and `!` are all banned. Parse untyped
-   input once through a type guard at the boundary; everything past it is typed.
+   input once through a type guard at the boundary; everything past it is typed. `noUncheckedIndexedAccess`
+   is on, so every lookup into a record or buffer is `T | undefined` until you handle it — that is the
+   point, not an obstacle to route around.
 
 ## Architecture
 
@@ -40,12 +42,12 @@ src/
 	sms.ts            The live handle emitted as the 'sms' event (sendResp/sendDlr)
 	message.ts        Encoding detection, splitting, bit counting, SMPP date formatting
 	pdu.ts            pduToObj / objToPdu / pduReturn — synchronous, result-returning
+	result.ts         Result<T> — the shape every fallible call returns
 	defs/
 		commands.ts   The 33 commands, their ids and ordered parameter lists
 		constants.ts  consts + constsById (TON, NPI, ENCODING, MESSAGE_STATE, …)
-		encodings.ts  GSM 03.38, LATIN1, UCS2 and detection
+		encodings.ts  GSM 03.38, LATIN1, UCS2, detection, data_coding resolution
 		errors.ts     errors + errorsById (ESME_*)
-		filters.ts    Per-field encode/decode hooks (time, message, callback_num, …)
 		tlvs.ts       TLV definitions, tlvsById
 		types.ts      Wire types: int8/int16/int32/string/cstring/buffer/arrays
 ```
@@ -96,11 +98,16 @@ implementation (see todo.md).
 | Text-only DLRs refused | `deliver_sm` without both `message_state` and `receipted_message_id` TLVs is rejected with `ESME_RINVTLVSTREAM`, so Kannel-style receipts are unusable |
 | Unbounded reassembly | Incomplete long-SMS groups are capped by nothing and swept only when other traffic arrives, after 24 hours |
 | Dead DLR aggregation | `longSmsDlrs` is allocated to merge per-segment receipts and then never used |
+| Trailing NULL truncation | `types.buffer.size()` subtracts one whenever the value's last octet is `0x00`, so the PDU is allocated one octet short while `sm_length` still reports the full length. Any UCS2 message ending in a character like U+4E00 or U+3000 goes out corrupt |
+| Dormant filters | `defs.filters` is declared on commands and TLVs but never invoked anywhere. Dropped in the rewrite; SMPP time formatting is exported as `smppTime` instead |
+| Unchecked reads | Wire reads index straight into the buffer, so a short or malformed PDU throws out of the codec. Reads are bounds-checked and return results now |
+| Unrangechecked writes | Integer params are handed to `writeUInt8`/`writeUInt16BE` unvalidated, so an out-of-range value throws from inside Node |
 
 ## Conventions
 
-- Hard tabs. Alphabetical ordering for keys, imports and lists unless order is logic-significant
+- Hard tabs. Alphabetical ordering for keys, imports and lists unless order is logic-significant.
-  (see the wire-order note above).
+  Two deliberate exceptions: command parameters are in wire order (above), and the `errors` and TLV
+  tables are ordered by their numeric id so they can be diffed against the spec and gaps stay visible.
 - Comments are the exception, not the default — see the root `CLAUDE.md` rules. Do not write file
   preambles or restate what the code says.
 - Test data uses real randomised UUID v7 values, never `aaaa-0000` placeholders.

README.md

@@ -166,9 +166,11 @@ commands the codec knows, not just the four the session handles natively.
   `{ userData }`.
 - **Renamed options:** `enqLinkTiming` → `enquireLinkInterval`, server `timeout` → `idleTimeout`.
 - **`larvitsmpp.utils` is gone.** Its contents are named exports: `bitCount`, `decodeMessage`,
-  `encodeMessage`, `objToPdu`, `pduReturn`, `pduToObj`, `smppDate`, `splitMessage`. The PDU codec is
+  `encodeMessage`, `objToPdu`, `pduReturn`, `pduToObj`, `smppDate`, `smppTime`, `splitMessage`. The PDU codec is
   synchronous and returns `{ err, pduObj }` / `{ err, buffer }`.
 - **`pduObj.isResp()` is now the standalone `isResp(pduObj)`.**
+- **`defs.filters` is gone.** It was declared on every command and TLV but never invoked, so it did
+  nothing. SMPP time formatting, the one part worth keeping, is exported as `smppTime`.
 - **The `error` event is `sessionError`** (and `serverError` on the server handle).
 - **`log`** takes a [`@larvit/log`](https://www.npmjs.com/package/@larvit/log) instance instead of a
   `larvitutils` one, and is silent by default.
@@ -188,6 +190,10 @@ have worked around any of these, remove the workaround:
 - Alphanumeric senders were sent with TON 1 (international) instead of TON 5.
 - Delivery receipts carrying only the standard receipt text, with no TLVs — what Kannel and several
   other SMSCs send — were rejected outright. They are now parsed.
+- A message whose last octet was `0x00` was allocated one octet short while `sm_length` still
+  reported the full length, so it went out corrupt. In UCS2 that is any message ending in a
+  character like 一 (U+4E00), which made the bug routine for CJK text.
+- Short or malformed PDUs threw out of the codec instead of being reported as a parse failure.
 
 ## Development
 

todo.md

@@ -107,7 +107,8 @@ smpp.on('session', session => {
 - **Named exports only.** No default export. `defs` stays as a grouped export alongside the
   individual tables (`cmds`, `consts`, `encodings`, `errors`, `tlvs`, `types`, and the `*ById` maps).
 - **`utils` is gone.** Its contents are named exports: `bitCount`, `decodeMessage`, `encodeMessage`,
-  `objToPdu`, `pduReturn`, `pduToObj`, `smppDate`, `splitMessage`.
+  `objToPdu`, `pduReturn`, `pduToObj`, `smppDate`, `smppTime`, `splitMessage`.
+- **`defs.filters` is gone** — it never did anything. `smppTime` replaces the one useful part.
 - **The PDU codec is synchronous** and returns `{ err?, pduObj? }` / `{ err?, buffer? }`.
 - **Low-level surface stays public**, including `session.sock`, `session.send()` and
   `session.sendReturn()` — that is how the other 29 commands are reached.
@@ -117,29 +118,32 @@ smpp.on('session', session => {
 
 ### 1. Definition tables — `src/defs/`
 
+All done, with tests in `test/encodings.test.ts`, `test/types.test.ts` and `test/commands.test.ts`.
+
 - [x] `constants.ts` — `consts` + `constsById`.
-- [x] `errors.ts` — all `ESME_*` codes plus `errorsById`.
+- [x] `errors.ts` — all `ESME_*` codes plus `errorsById`, `isErrorName`, `errorNameById`.
-- [ ] `types.ts` — wire types `int8`, `int16`, `int32`, `string`, `cstring`, `buffer`,
+- [x] `types.ts` — wire types. `read` is bounds-checked and reports `bytesRead`, so no caller has to
-      `dest_address_array`, `unsuccess_sme_array`, and the `tlv` variants. Each is
+      re-derive a length that could disagree with what was written. `size` and `write` validate their
-      `{ default, read(buffer, offset, length?), size(value), write(value, buffer, offset) }`.
+      input and return results.
-      `read` must be bounds-checked and return a result rather than throwing.
+- [x] `encodings.ts` — GSM 03.38, LATIN1, UCS2, FLASH, `detect` and `encodingByDataCoding`.
-- [ ] `encodings.ts` — GSM 03.38 (`ASCII`), `LATIN1`, `UCS2`, `FLASH` (alias of ASCII) and `detect`.
+      `iconv-lite` is gone; Buffer does it natively.
-      Drop `iconv-lite`: LATIN1 is `Buffer.from(str, 'latin1')`, UCS2 is `Buffer.from(str,
+- [x] `tlvs.ts` — 67 TLV definitions, `tlvsById`, and the two aliases.
-      'utf16le').swap16()` (copy before swapping, and reject odd-length input on decode).
+- [x] `commands.ts` — all 33 commands, wire-ordered, plus `cmdsById` and the `PduParams<C>` /
-- [ ] `filters.ts` — `time`, `message`, `billing_identification`, `broadcast_area_identifier`,
+      `PduParamsInput<C>` per-command types.
-      `broadcast_content_type`, `broadcast_frequency_interval`, `callback_num`, `callback_num_atag`.
+- [x] `filters.ts` — **not ported.** `defs.filters` was declared on commands and TLVs but never
-- [ ] `tlvs.ts` — the 67 TLV definitions plus `tlvsById` and the two aliases
+      invoked anywhere in 0.4.0. The one piece that is genuinely needed, SMPP time formatting, is
-      (`alert_on_msg_delivery`, `failed_broadcast_area_identifier`).
+      task 2's `smppTime`.
-- [ ] `commands.ts` — all 33 commands with ids and **wire-ordered** parameter lists, plus `cmdsById`.
 
 ### 2. Message helpers — `src/message.ts`
 
 - [ ] `bitCount(msg, encoding?)`, `encodeMessage`, `decodeMessage`, `smppDate`, `splitMessage`.
+- [ ] `smppTime.encode(value)` / `smppTime.decode(value)` — absolute and relative SMPP time formats,
+      replacing the dormant `filters.time`. Used by `validityPeriod` and `scheduleDeliveryTime`.
 - [ ] **Fix:** segments are 134 GSM characters or 67 UCS2 characters, so that segment + 6-byte UDH
       is exactly 140 octets. 0.4.0 produces 152/66.
 - [ ] **Fix:** `smppDate` must add 1 to `getMonth()` and zero-pad correctly.
-- [ ] **Fix:** LATIN1 must actually decode — resolve `data_coding` to a concrete encoding, not to
+- [ ] **Fix:** `decodeMessage` must resolve the alphabet through `encodingByDataCoding` (already
-      whichever alias happens to sort last.
+      written and tested) rather than scanning the alias table, which is what broke LATIN1.
 - [ ] The concatenation reference counter is per session, not module-global. `splitMessage` therefore
       takes the reference as an argument instead of owning a counter.
 
@@ -148,6 +152,8 @@ smpp.on('session', session => {
 - [ ] `pduToObj(buffer)` → `{ err?, pduObj? }`, `objToPdu(obj)` → `{ err?, buffer? }`,
       `pduReturn(pdu, status?, params?, tlvs?)` → `{ err?, buffer? }`, `isResp(pduObj)`.
 - [ ] Keep the trailing-NULL-octet retry for `short_message` that 0.4.0 has — real peers send it.
+      It is now an explicit decision in the parser: `types.buffer.size()` no longer silently drops a
+      trailing `0x00`, because that corrupted every UCS2 message ending in one (see AGENTS.md).
 - [ ] Guard `cmdLength` against a maximum before allocating, so a hostile peer cannot ask for a 4 GiB
       buffer. 0.4.0 has no such guard.
 - [ ] Per-command typed params: `pduToObj` returns a union discriminated on `cmdName`, and