108 lines
6.2 KiB
Markdown
108 lines
6.2 KiB
Markdown
# AGENTS.md
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Guidance for LLM agents working in this repository. Human-facing documentation lives in
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[README.md](README.md); the remaining work is tracked in [todo.md](todo.md).
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## What this is
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A ground-up TypeScript rewrite of `larvitsmpp` 0.4.0, published as `@larvit/smpp` 1.0.0. The branch
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started from an orphan commit — no history from 0.4.0 is carried over. The 0.4.0 source is still
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readable on the `master` branch of the same repository and is the reference for protocol behaviour,
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not for structure or style.
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The library's value is its very small API. Do not grow the public surface without being asked.
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## Hard rules
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These are not preferences. Breaking one is a defect.
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1. **Nothing throws.** Every fallible function returns (or resolves to) a DTO carrying an optional
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`err`. No `throw`, no rejected promises, no exceptions as control flow. Node APIs that throw are
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wrapped at the boundary and converted into a result. Programmer errors (bad arguments) are
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results too.
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2. **Log messages are static strings.** Every dynamic value goes into `@larvit/log` metadata. Never
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interpolate, never concatenate.
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- GOOD: `log.debug('sendSms() - splitting message', { parts: msgs.length, to });`
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- BANNED: `log.debug('sendSms() - splitting into ' + msgs.length + ' parts');`
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3. **No `error` event.** Node makes an unhandled `error` event throw, which would break rule 1.
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Sessions emit `sessionError`, servers emit `serverError`.
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4. **No casts, no non-null assertions.** `as`, `as unknown as` and `!` are all banned. Parse untyped
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input once through a type guard at the boundary; everything past it is typed.
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## Architecture
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```
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src/
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index.ts Public surface. Named exports only, no default export.
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client.ts client() -> { err, session }
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server.ts server() -> { err, server }, server owns the listener + close()
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session.ts Session: framing, sequence numbers, the send window, events
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sms.ts The live handle emitted as the 'sms' event (sendResp/sendDlr)
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message.ts Encoding detection, splitting, bit counting, SMPP date formatting
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pdu.ts pduToObj / objToPdu / pduReturn — synchronous, result-returning
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defs/
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commands.ts The 33 commands, their ids and ordered parameter lists
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constants.ts consts + constsById (TON, NPI, ENCODING, MESSAGE_STATE, …)
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encodings.ts GSM 03.38, LATIN1, UCS2 and detection
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errors.ts errors + errorsById (ESME_*)
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filters.ts Per-field encode/decode hooks (time, message, callback_num, …)
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tlvs.ts TLV definitions, tlvsById
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types.ts Wire types: int8/int16/int32/string/cstring/buffer/arrays
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```
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Dependency direction is one way: `defs` knows nothing above it, `pdu` uses `defs`, `session` uses
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`pdu`, and `client`/`server` use `session`. Nothing reaches back up.
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**Parameter order is wire order.** The key order inside `cmds.*.params` is the order the fields are
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written to and read from the buffer. Never sort those alphabetically — the alphabetical-ordering
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convention applies everywhere else, but here it corrupts every PDU.
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## Toolchain
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Run everything through the container; never invoke node or npm on the host.
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```bash
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docker compose run --rm node npm install
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docker compose run --rm node npm test
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docker compose run --rm node npm run build
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```
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- Tests are `.ts` and run directly under Node's type stripping — no build step in the dev loop.
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- Source imports use `.ts` extensions; `rewriteRelativeImportExtensions` emits `.js` into `dist`.
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- `erasableSyntaxOnly` is on, so no enums, no namespaces, no parameter properties. Use `as const`
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objects plus union types.
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- The published floor is Node 18, but the dev container runs Node 24 (type stripping needs it). CI
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compiles the tests and runs them on 18/20/22/24, so the floor is verified rather than asserted.
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- `typescript` is pinned to the 6.x line because `typescript-eslint` peer-requires `<6.1.0`. Move to
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TypeScript 7 once that constraint lifts.
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## Defects found in 0.4.0
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Confirmed by reading the 0.4.0 source. The rewrite fixes all of them; each needs a regression test
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naming the behaviour, and the wire-affecting ones are cross-checked against a reference
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implementation (see todo.md).
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| Defect | 0.4.0 behaviour |
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| --- | --- |
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| LATIN1 never decodes | `decodeMsg` loops `consts.ENCODING` without breaking, so `data_coding` 0x03 lands on the alias `ISO_8859_1`, which has no decoder, and silently falls back to ASCII |
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| Oversized segments | `splitMsg` emits 152 GSM chars + 6-byte UDH = 158 octets, over the 140-octet limit; UCS2 gets 66 chars where 67 fit |
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| DLR month off by one | `smppDate()` uses `getMonth()` (0-based) without `+1`, so January renders as `00` |
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| Non-standard DLR status | Receipts emit `stat:UNDELIVERABLE`; the spec's field is 7 characters (`UNDELIV`) |
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| Flash destroys UCS2 | `flash: true` overwrites `data_coding` with 0x10, discarding the UCS2 alphabet, which needs 0x18 |
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| Shared concat reference | The concatenation reference counter is a module-level global shared by every session in the process |
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| `send()` never times out | Each call adds a listener keyed on the sequence number; a peer that never answers leaks it and the promise never settles |
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| `tls: true` is not TLS | Constructs a bare `new tls.Socket()` with no handshake instead of `tls.connect()` |
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| Alphanumeric sender TON | `sendSms` hardcodes `source_addr_ton` to 1 (international) even for alphanumeric senders, which require TON 5 |
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| 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 |
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| Unbounded reassembly | Incomplete long-SMS groups are capped by nothing and swept only when other traffic arrives, after 24 hours |
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| Dead DLR aggregation | `longSmsDlrs` is allocated to merge per-segment receipts and then never used |
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## Conventions
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- Hard tabs. Alphabetical ordering for keys, imports and lists unless order is logic-significant
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(see the wire-order note above).
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- Comments are the exception, not the default — see the root `CLAUDE.md` rules. Do not write file
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preambles or restate what the code says.
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- Test data uses real randomised UUID v7 values, never `aaaa-0000` placeholders.
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- `message_id` values the library generates are UUID v7.
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