jormun-db/TODO.md

# JormunDB (Odin rewrite) — TODO

This tracks the rewrite from Zig (ZynamoDB) → Odin (JormunDB), and what’s left to stabilize + extend.

## Status Snapshot

### ✅ Ported / Working (core)
- [x] Project layout + Makefile targets (build/run/test/fmt)
- [x] RocksDB bindings / integration
- [x] Core DynamoDB types (AttributeValue / Item / Key / TableDescription, etc.)
- [x] Binary key codec (varint length-prefixed segments)
- [x] Binary item codec (TLV encoding / decoding)
- [x] Storage engine: tables + CRUD + scan/query plumbing
- [x] Table-level RW locks (read ops shared / write ops exclusive)
- [x] HTTP server + request routing via `X-Amz-Target`
- [x] DynamoDB JSON (parse + serialize)
- [x] Expression parsing for Query key conditions (basic support)

---

## Now (MVP correctness + polish)
Goal: “aws cli works reliably for CreateTable/ListTables/PutItem/GetItem/DeleteItem/Scan/Query” with correct DynamoDB-ish responses.

### 1) HTTP + routing hardening
- [ ] Audit request parsing boundaries:
  - Max body size enforcement
  - Missing/invalid headers → correct DynamoDB error types
  - Content-Type handling (be permissive but consistent)
- [ ] Ensure **all request-scoped allocations** come from the request arena (no accidental long-lived allocs)
- [ ] Standardize error responses:
  - `__type` formatting
  - `message` field consistency
  - status code mapping per error type

### 2) Storage correctness edge cases
- [ ] Table metadata durability + validation:
  - reject duplicate tables
  - reject invalid key schema (no HASH, multiple HASH, etc.)
- [ ] Item validation against key schema:
  - missing PK/SK errors
  - type mismatch errors (S/N/B)
- [ ] Deterministic encoding tests:
  - key codec round-trip
  - TLV item encode/decode round-trip (nested maps/lists/sets)

### 3) Query/Scan pagination parity
- [ ] Make pagination behavior match Zig version + AWS CLI expectations:
  - `Limit`
  - `ExclusiveStartKey`
  - `LastEvaluatedKey` generation (and correct key-type reconstruction)
- [ ] Add “golden” pagination tests:
  - query w/ sort key ranges
  - scan limit + resume loop

### 4) Expression parsing reliability
- [ ] Remove brittle string-scanning for `KeyConditionExpression` extraction:
  - Parse expression fields via JSON object lookup (handles whitespace/ordering safely)
- [ ] Add validation + better errors for malformed expressions
- [ ] Expand operator coverage as needed (BETWEEN/begins_with already planned)

---

## Next (feature parity with Zig + API completeness)
### 5) UpdateItem / conditional logic groundwork
- [ ] Implement `UpdateItem` (initially minimal: SET for scalar attrs)
- [ ] Add `ConditionExpression` support for Put/Delete/Update (start with simple comparisons)
- [ ] Define internal “update plan” representation (parsed ops → applied mutations)

### 6) Response completeness / options
- [ ] `ReturnValues` handling where relevant (NONE/ALL_OLD/UPDATED_NEW etc. — even partial support is useful)
- [ ] `ProjectionExpression` (return subset of attributes)
- [ ] `FilterExpression` (post-query filter for Scan/Query)

### 7) Test coverage / tooling
- [ ] Add integration tests mirroring AWS CLI script flows:
  - create table → put → get → scan → query → delete
- [ ] Add fuzz-ish tests for:
  - JSON parsing robustness
  - expression parsing robustness
  - TLV decode failure cases (corrupt bytes)

---

## Later (big features)
These align with the “Future Enhancements” list in ARCHITECTURE.md.

### 8) Secondary indexes
- [ ] Global Secondary Indexes (GSI)
- [ ] Local Secondary Indexes (LSI)
- [ ] Index backfill + write-path maintenance

### 9) Batch + transactions
- [ ] BatchWriteItem
- [ ] BatchGetItem
- [ ] Transactions (TransactWriteItems / TransactGetItems)

### 10) Performance / ops
- [ ] Connection reuse / keep-alive tuning
- [ ] Bloom filters / RocksDB options tuning for common patterns
- [ ] Optional compression policy (LZ4/Zstd knobs)
- [ ] Parallel scan (segment scanning)

---

## Replication / WAL
(There is a C++ shim stubbed out for WAL iteration and applying write batches.)
- [ ] Implement WAL iterator: `latest_sequence`, `wal_iter_next` returning writebatch blob
- [ ] Implement apply-writebatch on follower
- [ ] Add a minimal replication test harness (leader generates N ops → follower applies → compare)

---

## Housekeeping
- [ ] Fix TODO hygiene: keep this file short and “actionable”
- [ ] Add a CONTRIBUTING quick checklist (allocator rules, formatting, tests)
- [ ] Add “known limitations” section in README (unsupported DynamoDB features)