# erldistpy roadmap

Phases below are sized to land as discrete commits. Each phase ends with
`make all` green and a real-VM interop test where applicable.

## Phase 0 — Repo bones ✅

- LICENSE, README, .gitignore, Makefile, pyproject.toml
- Package skeleton, ruff config matches unfeed
- `make bootstrap test lint` works on a fresh checkout

## Phase 1 — ETF codec ✅

- Subset of External Term Format we need for gen_call to Elixir:
  small_int, int, big_int, atom_utf8 (legacy atom_ext on decode), binary,
  nil, list, tuple (small + large), pid (new_pid), ref (newer_reference)
- Booleans and `None` ride as atoms `true` / `false` / `nil`
- Golden vectors decoded from real `term_to_binary/1` output
- Round-trip tests for the encoder
- Generator script committed at `docs/etf_vectors.erl`

## Phase 2 — EPMD client

EPMD (Erlang Port Mapper Daemon) maps node names to TCP ports.
Tiny synchronous TCP client.

- Connect `epmd_host:4369` (configurable)
- `PORT_PLEASE2_REQ` (113) → port + dist version range
- Return `EpmdNodeInfo(port, lo_ver, hi_ver, node_type, proto)`
- Tests: live EPMD on localhost (skip if not running), unit tests
  against a recorded byte stream

## Phase 3 — Distribution handshake

- TCP connect to the resolved port
- `send_name` / `recv_status` / `recv_challenge` / `send_challenge_reply`
  / `recv_challenge_ack`
- Cookie digest via `erlang:phash2`-equivalent (md5-based per spec)
- Version 6 ("v6") handshake, the modern one Elixir 1.15+ uses
- Tests: handshake against a live Erlang node started in conftest

## Phase 4 — Distribution channel

- After handshake, the socket carries control + payload messages framed
  by a 4-byte length prefix
- Send `SEND_TT` / `REG_SEND` for outgoing messages
- Receive replies, route by ref
- Tick loop for keepalive (60s default per OTP)

## Phase 5 — gen_call convenience layer

- `Node.call(name_or_pid, request, timeout=5.0)` → reply term
- Wraps the `$gen_call` protocol used by `:gen_server`
- Idempotency-key handling lives in the caller; we just pass the term

## Phase 6 — TLS dist

- Wrap the post-EPMD socket in TLS
- Match `inet_tls_dist` config on the Erlang side (cert + key + ca paths)
- Same handshake, just runs inside the TLS tunnel

## Phase 7 — unfeed integration

- `ErlangDistTransport` implementing unfeed's `WalletTransport` Protocol
- Maps `/v1/health`, `/v1/address`, ... to gen_call requests
- `unfeed` deploys with a config switch: `wallet_transport = http | erldist`
- Cutover after a soak period on staging