gatewayd: mm, patch_post and username

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/gatewayd/src/mm/rest.rs

@@ -30,6 +30,19 @@ struct Channel {
     id: String,
 }
 
+#[derive(Deserialize)]
+struct User {
+    username: String,
+}
+
+/// A Mattermost username: 1 to 64 characters of `a-z`, `0-9`, `.`, `-` and `_`.
+fn valid_username(name: &str) -> bool {
+    (1..=64).contains(&name.len())
+        && name.bytes().all(|b| {
+            b.is_ascii_lowercase() || b.is_ascii_digit() || matches!(b, b'.' | b'-' | b'_')
+        })
+}
+
 impl Client {
     /// `timeout` bounds connecting and each read: no bytes for that long is an error.
     pub fn new(connector: Connector, token: Secret, timeout: Duration) -> Client {
@@ -179,6 +192,42 @@ impl Client {
         }
         Ok(channel.id)
     }
+
+    /// `PUT /api/v4/posts/{post}/patch`: replace the post's text.
+    pub fn patch_post(&self, post: &str, message: &str) -> Result<(), MmError> {
+        // A post that is not `valid_id` is Json, and nothing is sent. Otherwise PUT
+        // /api/v4/posts/<post>/patch with {"message": message}, through `call`; the answer is a
+        // Post, `check`ed and dropped.
+        if !valid_id(post) {
+            return Err(MmError::Json(
+                "a post path must be a Mattermost id".to_string(),
+            ));
+        }
+        let payload = serde_json::json!({ "message": message }).to_string();
+        let body = self.call(
+            "PUT",
+            &format!("/api/v4/posts/{post}/patch"),
+            Some(payload.as_bytes()),
+        )?;
+        json::<Post>(&body)?.check().map(|_| ())
+    }
+
+    /// `GET /api/v4/users/{user}`: the user's username.
+    pub fn username(&self, user: &str) -> Result<String, MmError> {
+        // A user that is not `valid_id` is Json. Otherwise GET /api/v4/users/<user>; a username
+        // that is not `valid_username` is Json.
+        if !valid_id(user) {
+            return Err(MmError::Json(
+                "a user path must be a Mattermost id".to_string(),
+            ));
+        }
+        let body = self.call("GET", &format!("/api/v4/users/{user}"), None)?;
+        let user: User = json(&body)?;
+        if !valid_username(&user.username) {
+            return Err(MmError::Json("the user has no valid username".to_string()));
+        }
+        Ok(user.username)
+    }
 }
 
 fn status_error(status: u16, body: &[u8]) -> MmError {

crates/gatewayd/tests/mm_edit.rs

@@ -0,0 +1,129 @@
+//! Editing a post and looking up a username, against a scripted server (M4b spec, sections 6 and
+//! 7). Do not edit.
+
+#[path = "support/http_server.rs"]
+mod http_server;
+#[path = "support/tls_server.rs"]
+mod tls_server;
+
+use std::net::SocketAddr;
+use std::time::Duration;
+
+use gatewayd::config::ServerUrl;
+use gatewayd::mm::MmError;
+use gatewayd::mm::rest::Client;
+use gatewayd::net::Connector;
+use gatewayd::secrets::Secret;
+use http_server::{reply, serve_http};
+use serde_json::json;
+
+const BOT: &str = "b0000000000000000000000000";
+const KYLE: &str = "k0000000000000000000000000";
+const DM: &str = "d0000000000000000000000000";
+const POST: &str = "p0000000000000000000000001";
+const WAIT: Duration = Duration::from_secs(5);
+
+fn client(addr: SocketAddr) -> Client {
+    let url = ServerUrl {
+        tls: false,
+        host: "localhost".to_string(),
+        port: addr.port(),
+    };
+    Client::new(
+        Connector::new(url, None).unwrap(),
+        Secret::new("TOKEN".to_string()),
+        WAIT,
+    )
+}
+
+#[test]
+fn a_post_is_patched_with_its_new_text() {
+    let (addr, rx) = serve_http(None, |_, r| {
+        let text = r.json()["message"].as_str().unwrap().to_string();
+        let post = json!({"id": POST, "user_id": BOT, "channel_id": DM, "root_id": "", "message": text, "create_at": 5, "is_pinned": false});
+        reply(200, "", &post.to_string())
+    });
+    client(addr)
+        .patch_post(
+            POST,
+            "**Approval 42**\n✅ Approved by @kyle: the call runs.",
+        )
+        .unwrap();
+    let r = rx.recv_timeout(WAIT).unwrap();
+    assert_eq!(
+        (r.method.as_str(), r.path.as_str()),
+        ("PUT", format!("/api/v4/posts/{POST}/patch").as_str())
+    );
+    assert!(
+        r.head.contains("Authorization: Bearer TOKEN\r\n"),
+        "{}",
+        r.head
+    );
+    assert_eq!(
+        r.json(),
+        json!({"message": "**Approval 42**\n✅ Approved by @kyle: the call runs."})
+    );
+}
+
+#[test]
+fn a_post_that_is_not_an_id_is_never_sent() {
+    let (addr, rx) = serve_http(None, |_, _| reply(200, "", "{}"));
+    for bad in ["../users/me", "", "P0000000000000000000000001"] {
+        assert!(
+            matches!(client(addr).patch_post(bad, "x"), Err(MmError::Json(_))),
+            "{bad:?}"
+        );
+        assert!(
+            matches!(client(addr).username(bad), Err(MmError::Json(_))),
+            "{bad:?}"
+        );
+    }
+    std::thread::sleep(Duration::from_millis(100));
+    assert!(rx.try_recv().is_err(), "nothing was sent");
+}
+
+#[test]
+fn a_refused_edit_is_an_error() {
+    let (addr, _rx) = serve_http(None, |_, _| {
+        reply(
+            403,
+            "",
+            r#"{"id":"api.post.update_post.permissions_details.app_error"}"#,
+        )
+    });
+    assert!(matches!(
+        client(addr).patch_post(POST, "x"),
+        Err(MmError::Auth(403))
+    ));
+}
+
+#[test]
+fn the_username_of_a_user() {
+    let (addr, rx) = serve_http(None, |_, _| {
+        reply(
+            200,
+            "",
+            &json!({"id": KYLE, "username": "kyle", "first_name": "K", "roles": "system_user"})
+                .to_string(),
+        )
+    });
+    assert_eq!(client(addr).username(KYLE).unwrap(), "kyle");
+    let r = rx.recv_timeout(WAIT).unwrap();
+    assert_eq!(
+        (r.method.as_str(), r.path.as_str()),
+        ("GET", format!("/api/v4/users/{KYLE}").as_str())
+    );
+    for bad in [
+        json!({"id": KYLE}),
+        json!({"id": KYLE, "username": ""}),
+        json!({"id": KYLE, "username": "Kyle\n@channel"}),
+        json!({"id": KYLE, "username": "x".repeat(65)}),
+    ] {
+        let body = bad.to_string();
+        let (addr, _rx) = serve_http(None, move |_, _| reply(200, "", &body));
+        assert!(
+            matches!(client(addr).username(KYLE), Err(MmError::Json(_))),
+            "{bad}"
+        );
+    }
+}

docs/implementer-log.md

@@ -6,6 +6,7 @@ reviewer adds findings under "Reviews" once per milestone.
 
 | Task | Date | Status | Gate runs | First gate | Deviations | Notes | Model |
 |---|---|---|---|---|---|---|---|
+| M4b/09-gatewayd-mm-edit | 2026-09-24 | done | 1 | pass | none | Copied `docs/plans/M4b/files/crates/gatewayd/tests/mm_edit.rs` into `crates/gatewayd/tests/`. In `rest.rs`: added the `User { username: String }` struct and `valid_username` (1..=64 bytes of a-z, 0-9, `.`, `-` and `_`) after `Channel`, then `patch_post` (a `post` that is not `valid_id` is `Json` and nothing is sent; otherwise PUT `/api/v4/posts/{post}/patch` with `{"message": message}` through `call`, the answer a `Post` `check`ed and dropped) and `username` (a `user` that is not `valid_id` is `Json`; GET `/api/v4/users/{user}`, a username that is not `valid_username` is `Json`, else the name) at the end of `impl Client`. `cargo fmt --all` then `cargo test -p gatewayd --test mm_edit --test mm_rest` green (4 and 10 passed); `make gate` prints `gate: ok` on the first run. | ? |
 | M4b/08-gatewayd-mention-commands | 2026-09-24 | done | 1 | pass | none | Copied `sessions_mention.rs` into `crates/gatewayd/tests/`, the new `sessions.rs` (commands now route to `Approval`, the mention stripped) and `serve.rs` (from `serve.rs-task08`, the turn's text is `start`). In `sessions.rs`: added `Route::Approval { thread, command, user, post, at }` after `Queue(Message)`; added the given `ApprovalCommand` enum, `MAX_REASON = proto::MAX_REASON`, and `approval_command` (returns `None` for text that is not a `!` command, else `Approve`/`Deny`/`Malformed`); wrote `strip_mention` (the five steps: strip a leading `@`, take the longest name run, trim a trailing dot, match `me` case-insensitively, return the message when the remainder is empty); in `route` bound `message` from `strip_mention(&post.message, &self.me_name)`, replaced the `!` command block with `approval_command` → Approval then any other `!` → Reply UNKNOWN_COMMAND, and changed the final Queue's `text: message.clone()` to `message.to_string()` since `message` is now `&str`; updated the step comment. In `handle.rs` `handle_post` added the `Route::Approval` arm posting M4B_COMMAND (approvals module wired in task 15) and `M4B_COMMAND` to the `use`. All three suites pass (serve 6, sessions 8, sessions_mention 4); `make gate` prints `gate: ok` on the first run. | ? |
 | M4b/07-gatewayd-config-approvals | 2026-09-24 | done | 1 | pass | none | Copied `docs/plans/M4b/files/crates/gatewayd/tests/config_approvals.rs` into `crates/gatewayd/tests/`. In `config.rs`: added `#[serde(default)] pub approvals: ApprovalsConfig,` after `pub limits: Limits,` in `Config`, the `ApprovalsConfig { users: Vec<String>, socket: PathBuf }` struct (`#[serde(deny_unknown_fields, default)]`, with the doc comments) after `struct Config`, the `[approvals] users` check in `problem` right before the `[limits] queue` check (each id must be in `allow.users`), and the three methods before `state_path`: `approvers` (`&self.approvals.users`, or `&self.allow.users` when empty), `first_approver` (`.first().map(String::as_str)`), and `gateway_socket` (`self.approvals.socket`, or `<home>/run/gateway/gateway.sock` when `as_os_str().is_empty()`). The `ApprovalsConfig` derives `Default` so the empty `socket` deserialises from an absent field; `PathBuf`'s default is empty, matching the runbook's "empty" rule. `cargo fmt --all` then `cargo test -p gatewayd --test config_approvals --test config` green (4 and 7 passed); `make gate` prints `gate: ok` on the first run. | ? |
 | M4b/06-brokerd-courier | 2026-09-24 | done | 1 | pass | none | Filled the four `todo!()`s in the copied `courier.rs`: `finished` (`stop.load(SeqCst) || !broker.table().contains(id)`); `pause` (a `while Instant::now() < until && !finished` loop sleeping `timing.tick.min(until.saturating_duration_since(now))`); `frames` (`try_clone` the stream, spawn a reader thread that hands whole frames over an mpsc channel so the courier can `recv_timeout` without losing half a frame, `Ok(rx)`); `answer` (`take` the entry → `Gone {}` if gone, build the `Answer` from `reply.approved`, call `admin::answer`, map the returned `DecisionRecord` through the five-arm match to `Runs`/`Denied`/`Refused`/`Denied`/`Refused`). The four `broker.rs` changes: `RecvTimeoutError` import widened to include `Receiver`, `use crate::courier;` after the `config` use, `let shown = info.clone();` before the insert, step 4 replaced by `courier::alongside(broker, &shown, || wait_for_verdict(...))` matching `Waited`, and the old step 4 moved to `wait_for_verdict` (with the `Waited` enum) before `pub fn alive`. `cargo build -p brokerd` clean; courier test went 1 pass/9 fail then 10 passed three times running; full brokerd suite green; `cargo fmt --all` then `make gate` prints `gate: ok` on the first run. | ? |