gatewayd: a turn's speaker, the username of the one person who wrote its burst

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/gatewayd/src/sessions.rs

@@ -39,6 +39,8 @@ pub struct Message {
     pub text: String,
     /// A thread in a channel or group message that this Boxmaker now takes part in.
     pub joins_thread: bool,
+    /// Who wrote it: the post's `user_id`, a Mattermost user id.
+    pub user: String,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -245,6 +247,7 @@ impl Router {
                 resume: !post.root_id.is_empty(),
                 text: format!("!{rest}"),
                 joins_thread: channel_type != "D",
+                user: post.user_id.clone(),
             });
         }
         if let Some(command) = approval_command(message) {
@@ -269,6 +272,7 @@ impl Router {
             resume: !post.root_id.is_empty(),
             text: message.to_string(),
             joins_thread: channel_type != "D",
+            user: post.user_id.clone(),
         })
     }
 }
@@ -280,6 +284,22 @@ pub struct Batch {
     pub thread: Thread,
     pub resume: bool,
     pub text: String,
+    /// Who wrote each message of `text`, in order: Mattermost user ids.
+    pub senders: Vec<String>,
+}
+
+impl Batch {
+    /// The one user who wrote every message of the batch. `None` when two or more people did, or
+    /// when it names nobody: a burst joined from several people has no speaker (M5c spec,
+    /// section 4).
+    pub fn sender(&self) -> Option<&str> {
+        let first = self.senders.first()?;
+        if self.senders.iter().all(|user| user == first) {
+            Some(first.as_str())
+        } else {
+            None
+        }
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -295,6 +315,8 @@ pub enum Pushed {
 struct Pending {
     thread: Thread,
     waiting: Vec<String>,
+    /// The author of each message in `waiting`, in the same order.
+    senders: Vec<String>,
 }
 
 /// The sessions with a turn running, and the messages waiting for each.
@@ -323,6 +345,7 @@ impl Queues {
                 return Pushed::Full(pending.thread.clone());
             }
             pending.waiting.push(message.text.clone());
+            pending.senders.push(message.user.clone());
             return Pushed::Waiting;
         }
         let batch = Batch {
@@ -330,12 +353,14 @@ impl Queues {
             thread: message.thread.clone(),
             resume: message.resume,
             text: message.text.clone(),
+            senders: vec![message.user.clone()],
         };
         self.running.insert(
             message.session,
             Pending {
                 thread: message.thread.clone(),
                 waiting: Vec::new(),
+                senders: Vec::new(),
             },
         );
         Pushed::Start(batch)
@@ -354,6 +379,7 @@ impl Queues {
             thread: pending.thread.clone(),
             resume: true,
             text: pending.waiting.join("\n\n"),
+            senders: std::mem::take(&mut pending.senders),
         };
         pending.waiting.clear();
         self.running.insert(session.clone(), pending);