# M4b task 05: `[gateway]` in `brokerd.toml`

**Branch:** `m4b` (run `git switch m4b`; `git status --short` must be empty, otherwise stop)
**Commit subject:** `brokerd: config, [gateway] socket for Mattermost approvals`

## Goal

`brokerd` carries pending approvals to `gatewayd` only when `brokerd.toml` says where (M4b spec,
section 3):

```toml
[gateway]                     # absent: Mattermost approvals are off, as in M3
socket = ""                   # empty: <home>/run/gateway/gateway.sock
```

## Files

- Copy: `crates/brokerd/tests/config_gateway.rs`, and a **new version** of the given
  `crates/brokerd/tests/support/rig.rs` (its `Config` gains `gateway: None,`)
- Modify: `crates/brokerd/src/config.rs`, `docs/implementer-log.md`

## The changes, exactly

In `crates/brokerd/src/config.rs`:

1. Before `fn default_podman`, the section:

```rust
/// `[gateway]`: where `gatewayd` takes approvals to post in Mattermost. Without the section,
/// Mattermost approvals are off and only `bxctl` answers. An empty path means the default.
#[derive(Debug, Clone, PartialEq, Eq, Deserialize, Default)]
#[serde(deny_unknown_fields, default)]
pub struct Gateway {
    pub socket: PathBuf,
}
```

2. In `struct Config`, after `pub runner: Option<Runner>,`:

```rust
    #[serde(default)]
    pub gateway: Option<Gateway>,
```

3. In `impl Config`, before `audit_dir`:

```rust
    /// `gateway.sock`, when `[gateway]` is set.
    pub fn gateway_socket(&self) -> Option<PathBuf> {
        let gateway = self.gateway.as_ref()?;
        if gateway.socket.as_os_str().is_empty() {
            Some(self.paths.home.join("run/gateway/gateway.sock"))
        } else {
            Some(gateway.socket.clone())
        }
    }
```

## Steps

- [ ] **1. Copy.** `git switch m4b`, then
  `cp docs/plans/M4b/files/crates/brokerd/tests/config_gateway.rs crates/brokerd/tests/ && cp docs/plans/M4b/files/crates/brokerd/tests/support/rig.rs crates/brokerd/tests/support/`
- [ ] **2. See it fail.** `cargo test -p brokerd --test config_gateway`. Expected: it does not
  compile.
- [ ] **3. Make the three changes.** Run `cargo fmt --all`.
- [ ] **4. See it pass.** `cargo test -p brokerd`. Expected: every suite passes; `config_gateway`
  4 passed.
- [ ] **5. Run the gate.** `make gate`. Expected last line: `gate: ok`.
- [ ] **6. Log and commit.** `git add crates/brokerd docs/implementer-log.md Cargo.lock && git commit`

## Done when

- `cargo test -p brokerd` passes; `make gate` prints `gate: ok`.