jormun-db/TODO.md

# JormunDB (Odin rewrite) — TODO

This tracks what's left to stabilize + extend the project


## 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 (config exists, need to verify enforcement path)
  - Missing/invalid headers → correct DynamoDB error types
  - Content-Type handling (be permissive but consistent)
- [x] Ensure **all request-scoped allocations** come from the request arena (no accidental long-lived allocs)
  - Verified: `handle_connection` in http.odin sets `context.allocator = request_alloc`
  - Long-lived data (table metadata, locks) explicitly uses `engine.allocator`
- [x] Standardize error responses:
  - `__type` formatting — done, uses `com.amazonaws.dynamodb.v20120810#ErrorType`
  - `message` field consistency — done
  - Status code mapping per error type — **DONE**: centralized `handle_storage_error` + `make_error_response` now maps InternalServerError→500, everything else→400
  - Missing X-Amz-Target now returns `SerializationException` (matches real DynamoDB)

### 2) Storage correctness edge cases
- [x] Table metadata durability + validation:
  - [x] Reject duplicate tables — done in `create_table` (checks existing meta key)
  - [x] Reject invalid key schema — done in `parse_key_schema` (no HASH, multiple HASH, etc.)
- [x] Item validation against key schema:
  - [x] Missing PK/SK errors — done in `key_from_item`
  - [x] Type mismatch errors (S/N/B) — **DONE**: new `validate_item_key_types` proc checks item key attr types against AttributeDefinitions
- [ ] Deterministic encoding tests:
  - [ ] Key codec round-trip
  - [ ] TLV item encode/decode round-trip (nested maps/lists/sets)

### 3) Query/Scan pagination parity
- [x] Make pagination behavior match AWS CLI expectations:
  - [x] `Limit` — done
  - [x] `ExclusiveStartKey` — done (parsed via JSON object lookup with key schema type reconstruction)
  - [x] `LastEvaluatedKey` generation — **FIXED**: now saves key of *last returned item* (not next unread item); only emits when more results exist
- [ ] Add "golden" pagination tests:
  - [ ] Query w/ sort key ranges
  - [ ] Scan limit + resume loop

### 4) Expression parsing reliability
- [x] Remove brittle string-scanning for `KeyConditionExpression` extraction:
  - **DONE**: `parse_key_condition_expression_string` uses JSON object lookup (handles whitespace/ordering safely)
- [ ] Add validation + better errors for malformed expressions
- [x] Expand operator coverage: BETWEEN and begins_with are implemented in parser
- [x] **Sort key condition filtering in query** — **DONE**: `query()` now accepts optional `Sort_Key_Condition` and applies it (=, <, <=, >, >=, BETWEEN, begins_with)

---

## Next (feature parity with Zig + API completeness)
### 5) UpdateItem / conditional logic groundwork
- [x] `UpdateItem` handler registered in router (currently returns clear "not yet supported" error)
- [x] Implement `UpdateItem` (initially minimal: SET for scalar attrs)
  - [ ] `UpdateItem` needs UPDATED_NEW/UPDATED_OLD response filtering for perfect parity with Dynamo
- [x] Add `ConditionExpression` support for Put/Delete/Update (start with simple comparisons)
- [x] Define internal "update plan" representation (parsed ops → applied mutations)

### 6) Response completeness / options
- [x] `ReturnValues` handling where relevant (NONE/ALL_OLD/UPDATED_NEW etc. — even partial support is useful)
- [x] `ProjectionExpression` (return subset of attributes)
- [x] `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
- [x] BatchWriteItem
- [x] 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
- [x] Fix TODO hygiene: keep this file short and "actionable"
  - Added "Bug Fixes Applied" section documenting what changed and why
- [ ] Add a CONTRIBUTING quick checklist (allocator rules, formatting, tests)
- [ ] Add "known limitations" section in README (unsupported DynamoDB features)