OpenFUT/openfut-blaze-host/README.md

# openfut-blaze-host

A deliberately thin TCP host for the FIFA 17 Blaze RPC surface. Runs **beside**
the working Python backend, never instead of it.

```
  listener → Fire2 stream framing → per-connection Session
                                         │
                             openfut-adapter-fifa17::dispatch
                                         │
                             write returned frames, in order
```

## Scope

Owns: a socket, a read buffer, one `Session` per connection, diagnostics.
That is the complete list.

Must never acquire: coins, club state, packs, profiles, market state, UTAS
logic. Those belong to OpenFUT Core, reached later through the adapter. A
transport host that starts holding game state becomes a second backend — the
architecture this migration exists to avoid.

## No TLS

The Blaze main port is **plaintext**. Verified against the running Python
backend by sending a raw Fire2 `Util::ping` and getting a plaintext
`PingResponse` back; `blaze_responder_v3b.py::blaze_handle` uses the raw socket
and only `redir_handle` wraps `ssl`. TLS belongs to the redirector phase.

## Running it

Both critical settings are required — there is no default port anywhere in this
crate, so it cannot silently collide with the Python container.

```bash
cargo build -p openfut-blaze-host

OPENFUT_ADVERTISE=<backend LAN ip> \
OPENFUT_BIND=0.0.0.0 \
POW_CONTENT_HOST=<backend LAN ip>:8085 \
OPENFUT_BLAZE_HOST_BIND=0.0.0.0 \
OPENFUT_BLAZE_HOST_PORT=<free port> \
OPENFUT_BLAZE_TRACE=/tmp/rust-blaze.trace \
  ./target/debug/openfut-blaze-host
```

`OPENFUT_BIND` is the **advertised-config** bind, not the listener's. The
adapter derives `nucleusConnect` from it (reproducing the oracle — see the
adapter README and the vault's known-issue entry), so it must mirror whatever
the Python container runs with, or the two will not compare. The listener has
its own `OPENFUT_BLAZE_HOST_BIND`.

For a FIFA test from another machine, `OPENFUT_BLAZE_HOST_BIND` must be `0.0.0.0`
(or the LAN address); the default follows `OPENFUT_BIND`.

## Live A/B against Python

```bash
./check-live-parity.sh 127.0.0.1:42130 127.0.0.1:<rust port>
```

Replays the recorded conversations against both endpoints over real sockets and
diffs the normalized traces. Session keys and server timestamps are masked, so
anything that differs is a real behavioural difference.

**The diff is the test, not the probe's exit code.** The probe only detects
anomalies visible live — missing frames, an early close. A same-length content
change deep inside a notification body shows up *only* as a digest difference in
the trace. Both cases were verified by mutation.

For the comparison to mean anything both servers must run the same config —
same `OPENFUT_ADVERTISE`, `OPENFUT_BIND`, `POW_CONTENT_HOST` and active persona
— or legitimate config differences read as parity failures.

Current result against the live container:

```
  main:      IDENTICAL (82 frames)
  fallbacks: IDENTICAL (12 frames)
  locale:    IDENTICAL (7 frames)
  LIVE PARITY OK — 101 frames, identical normalized traces.
```

## Tests

`cargo test -p openfut-blaze-host` — 18 tests. The integration suite runs the
real host on an ephemeral port and replays the recorded conversations over TCP,
covering what fixtures cannot:

* byte-for-byte replay over a socket
* requests dribbled **one byte at a time** (fragmentation)
* several requests in **one write** (coalescing)
* the four-frame login burst arriving in order on the wire
* session state persisting across frames, and *not* leaking between connections
* an absurd payload length closing the connection instead of allocating
* an undecodable body still getting a reply

Byte-exactness is possible only because `Hooks` injects the session key and
clock — they appear inside response bodies, so with the real ones no live run
could reproduce a recording. That is the crate's only test seam.

## Promotion gates

Automated, re-runnable now:

1. ✅ All migration tests pass (116 across the three crates).
2. ✅ Python contract suite still 446/446.
3. ✅ Scripted connection to the Rust host succeeds.
4. ✅ Recorded conversations work through the real TCP host, and the live A/B
   against Python is identical over 101 frames.

Requiring a FIFA client on the game machine — **not yet done**:

5. ⬜ FIFA reaches FUT with Rust Blaze.
6. ⬜ Close FIFA completely.
7. ⬜ FIFA reaches FUT a second time.
8. ⬜ Restore Python Blaze and confirm rollback works.
9. ⬜ Switch back to Rust and confirm again.
10. ⬜ Only then is Rust Blaze a viable runtime replacement.

Gates 8 and 9 matter as much as 5: `Python → Rust → Python → Rust` proves the
rollback path rather than asserting one exists.

### Running gate 5

Keep the Python container exactly as it is. On the game machine, redirect **only
the Blaze destination** to the sidecar's port; the redirector, Nucleus, roster,
UTAS and POW keep hitting Python. The single changed variable is then Python
Blaze vs Rust Blaze.

The redirector is what tells the client where Blaze lives, so the cleanest
switch is to point the Python redirector's advertised Blaze port at the sidecar
rather than reconfiguring the client.

## Diagnostics

The log mirrors the Python responder's shape so the two can be read side by
side: connection id, peer, frame number, route, msgType, msgNum, userIndex,
options, payload and metadata sizes, every response emitted, and a close reason.

`OPENFUT_BLAZE_TRACE=<path>` additionally writes the normalized structural
trace — the same format the probe emits, so a live FIFA session against Rust can
be diffed against one against Python.

No credential or token is logged. Volatile values are replaced before they reach
the line, not truncated after, and a test asserts a known secret never appears
in trace output.