From 5b91de6339d49ac37b5266417c0cd8885cc732cc Mon Sep 17 00:00:00 2001
From: Damocles <damocles@darkest.space>
Date: Thu, 30 Apr 2026 22:54:41 +0200
Subject: [PATCH] show others' read receipts on each message in prompt

---
 src/main.rs | 102 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 96 insertions(+), 6 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index afed561..44058b2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -638,13 +638,24 @@ async fn process_loop(state: Arc<Mutex<DaemonState>>, client: Client) {
             _ => None,
         });
 
+        // Compute who has read which message
+        let read_markers = compute_read_markers(&room, &timeline, &own_user).await;
+
         // Tell the room we're "typing" while claude thinks. Best-effort; no
         // hard fail if it doesn't go through.
         if let Err(e) = room.typing_notice(true).await {
             tracing::debug!(room = %room_id, "failed to send typing start: {e}");
         }
 
-        let invoke_result = invoke_claude(&room_id, &room_name, &timeline, seen_idx, &model).await;
+        let invoke_result = invoke_claude(
+            &room_id,
+            &room_name,
+            &timeline,
+            seen_idx,
+            &model,
+            &read_markers,
+        )
+        .await;
 
         if let Err(e) = room.typing_notice(false).await {
             tracing::debug!(room = %room_id, "failed to send typing stop: {e}");
@@ -846,9 +857,13 @@ async fn load_timeline(
 }
 
 /// Render one timeline item into the prompt.
-/// Messages: `[ts] $eid... [(you) ]@user: body`
+/// Messages: `[ts] $eid... [(you) ]@user: body [read by: ...]`
 /// Reactions: `[ts] [(you) ]@user reacted to $eid... with KEY`
-fn render_timeline_item(prompt: &mut String, item: &TimelineItem) {
+fn render_timeline_item(
+    prompt: &mut String,
+    item: &TimelineItem,
+    read_markers: &std::collections::HashMap<OwnedEventId, Vec<OwnedUserId>>,
+) {
     match item {
         TimelineItem::Message {
             event_id,
@@ -861,7 +876,20 @@ fn render_timeline_item(prompt: &mut String, item: &TimelineItem) {
             let ts_str = format_ts(*ts);
             let id = short_event_id(event_id);
             let prefix = if *is_self { "(you) " } else { "" };
-            writeln!(prompt, "[{ts_str}] {id} {prefix}{sender}: {body}").unwrap();
+            let readers_str = match read_markers.get(event_id) {
+                Some(rs) if !rs.is_empty() => {
+                    let mut sorted = rs.clone();
+                    sorted.sort();
+                    let names: Vec<String> = sorted.iter().map(|u| u.to_string()).collect();
+                    format!(" [read by: {}]", names.join(", "))
+                }
+                _ => String::new(),
+            };
+            writeln!(
+                prompt,
+                "[{ts_str}] {id} {prefix}{sender}: {body}{readers_str}"
+            )
+            .unwrap();
         }
         TimelineItem::Reaction {
             sender,
@@ -893,6 +921,67 @@ fn short_event_id(id: &OwnedEventId) -> String {
     }
 }
 
+/// For each message in the timeline, compute the list of OTHER users who
+/// have a read receipt at or after that message. Self is excluded.
+async fn compute_read_markers(
+    room: &Room,
+    timeline: &[TimelineItem],
+    own_user: &OwnedUserId,
+) -> std::collections::HashMap<OwnedEventId, Vec<OwnedUserId>> {
+    use matrix_sdk::ruma::events::receipt::ReceiptType;
+
+    // Collect unique non-self users from the timeline (senders + reactors)
+    let mut users: Vec<OwnedUserId> = timeline
+        .iter()
+        .filter(|t| !t.is_self())
+        .map(|t| t.sender().clone())
+        .collect();
+    users.sort();
+    users.dedup();
+
+    // Build position map for messages in timeline: event_id -> index
+    let positions: std::collections::HashMap<OwnedEventId, usize> = timeline
+        .iter()
+        .enumerate()
+        .filter_map(|(i, t)| match t {
+            TimelineItem::Message { event_id, .. } => Some((event_id.clone(), i)),
+            _ => None,
+        })
+        .collect();
+
+    // For each user, find their receipt position. Then for every message
+    // at or before that position, add them as a reader.
+    let mut readers: std::collections::HashMap<OwnedEventId, Vec<OwnedUserId>> =
+        std::collections::HashMap::new();
+
+    for user in &users {
+        if user == own_user {
+            continue;
+        }
+        let receipt_eid = match room
+            .load_user_receipt(ReceiptType::Read, ReceiptThread::Unthreaded, user)
+            .await
+        {
+            Ok(Some((eid, _))) => eid,
+            _ => continue,
+        };
+        let Some(&user_pos) = positions.get(&receipt_eid) else {
+            continue;
+        };
+        // Mark this user as a reader for all messages at index <= user_pos
+        for item in timeline.iter().take(user_pos + 1) {
+            if let TimelineItem::Message { event_id, .. } = item {
+                readers
+                    .entry(event_id.clone())
+                    .or_default()
+                    .push(user.clone());
+            }
+        }
+    }
+
+    readers
+}
+
 /// Resolve a (possibly shortened/ellipsized) event id to a full one by
 /// looking up against the timeline. Returns the matching message's full
 /// event id if found.
@@ -978,6 +1067,7 @@ async fn invoke_claude(
     timeline: &[TimelineItem],
     seen_idx: usize,
     model: &str,
+    read_markers: &std::collections::HashMap<OwnedEventId, Vec<OwnedUserId>>,
 ) -> anyhow::Result<Vec<ClaudeDoc>> {
     let identity_dir = paths::identity_dir();
     let identity_str = identity_dir.to_string_lossy();
@@ -1016,7 +1106,7 @@ async fn invoke_claude(
     if !old.is_empty() {
         writeln!(prompt, "\n[previously seen events — for context]").unwrap();
         for item in old {
-            render_timeline_item(&mut prompt, item);
+            render_timeline_item(&mut prompt, item, read_markers);
         }
     }
 
@@ -1025,7 +1115,7 @@ async fn invoke_claude(
         writeln!(prompt, "(none)").unwrap();
     } else {
         for item in new {
-            render_timeline_item(&mut prompt, item);
+            render_timeline_item(&mut prompt, item, read_markers);
         }
     }