Add conflict notification and file update WS endpoint

5 files changed, 254 insertions, 14 deletions

diff --git a/makima/src/server/handlers/chat.rs b/makima/src/server/handlers/chat.rs
index 92c4ec8..3bdbc74 100644
--- a/makima/src/server/handlers/chat.rs
+++ b/makima/src/server/handlers/chat.rs
@@ -17,7 +17,7 @@ use crate::llm::{
     groq::{GroqClient, GroqError, Message, ToolCallResponse},
     LlmModel, ToolCall, ToolResult, AVAILABLE_TOOLS,
 };
-use crate::server::state::SharedState;
+use crate::server::state::{FileUpdateNotification, SharedState};
 
 /// Maximum number of tool-calling rounds to prevent infinite loops
 const MAX_TOOL_ROUNDS: usize = 10;
@@ -385,17 +385,43 @@ pub async fn chat_handler(
             transcript: None,
             summary: current_summary.clone(),
             body: Some(current_body.clone()),
+            version: None, // Internal update, skip version check
         };
 
-        if let Err(e) = repository::update_file(pool, id, update_req).await {
-            tracing::error!("Failed to save file changes: {}", e);
-            return (
-                StatusCode::INTERNAL_SERVER_ERROR,
-                Json(serde_json::json!({
-                    "error": format!("Failed to save changes: {}", e)
-                })),
-            )
-                .into_response();
+        match repository::update_file(pool, id, update_req).await {
+            Ok(Some(updated_file)) => {
+                // Broadcast update notification for LLM changes
+                let mut updated_fields = vec!["body".to_string()];
+                if current_summary.is_some() {
+                    updated_fields.push("summary".to_string());
+                }
+                state.broadcast_file_update(FileUpdateNotification {
+                    file_id: id,
+                    version: updated_file.version,
+                    updated_fields,
+                    updated_by: "llm".to_string(),
+                });
+            }
+            Ok(None) => {
+                // File was deleted during processing
+                return (
+                    StatusCode::NOT_FOUND,
+                    Json(serde_json::json!({
+                        "error": "File not found"
+                    })),
+                )
+                    .into_response();
+            }
+            Err(e) => {
+                tracing::error!("Failed to save file changes: {}", e);
+                return (
+                    StatusCode::INTERNAL_SERVER_ERROR,
+                    Json(serde_json::json!({
+                        "error": format!("Failed to save changes: {}", e)
+                    })),
+                )
+                    .into_response();
+            }
         }
     }
 
diff --git a/makima/src/server/handlers/file_ws.rs b/makima/src/server/handlers/file_ws.rs
new file mode 100644
index 0000000..5a44309
--- /dev/null
+++ b/makima/src/server/handlers/file_ws.rs
@@ -0,0 +1,163 @@
+//! WebSocket handler for file change subscriptions.
+//!
+//! Clients can subscribe to specific files and receive real-time notifications
+//! when those files are updated by any source (user edits, LLM modifications, etc.).
+
+use axum::{
+    extract::{ws::Message, ws::WebSocket, State, WebSocketUpgrade},
+    response::Response,
+};
+use futures::{SinkExt, StreamExt};
+use serde::{Deserialize, Serialize};
+use std::collections::HashSet;
+use uuid::Uuid;
+
+use crate::server::state::SharedState;
+
+/// Client message for file subscription management.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(tag = "type", rename_all = "camelCase")]
+pub enum FileClientMessage {
+    /// Subscribe to updates for a specific file
+    Subscribe {
+        #[serde(rename = "fileId")]
+        file_id: Uuid,
+    },
+    /// Unsubscribe from updates for a specific file
+    Unsubscribe {
+        #[serde(rename = "fileId")]
+        file_id: Uuid,
+    },
+}
+
+/// Server message for file subscription WebSocket.
+#[derive(Debug, Clone, Serialize)]
+#[serde(tag = "type", rename_all = "camelCase")]
+pub enum FileServerMessage {
+    /// Subscription confirmed
+    Subscribed {
+        #[serde(rename = "fileId")]
+        file_id: Uuid,
+    },
+    /// Unsubscription confirmed
+    Unsubscribed {
+        #[serde(rename = "fileId")]
+        file_id: Uuid,
+    },
+    /// File was updated
+    FileUpdated {
+        #[serde(rename = "fileId")]
+        file_id: Uuid,
+        version: i32,
+        #[serde(rename = "updatedFields")]
+        updated_fields: Vec<String>,
+        #[serde(rename = "updatedBy")]
+        updated_by: String,
+    },
+    /// Error occurred
+    Error { code: String, message: String },
+}
+
+/// WebSocket upgrade handler for file subscriptions.
+#[utoipa::path(
+    get,
+    path = "/api/v1/files/subscribe",
+    responses(
+        (status = 101, description = "WebSocket connection established"),
+    ),
+    tag = "Files"
+)]
+pub async fn file_subscription_handler(
+    ws: WebSocketUpgrade,
+    State(state): State<SharedState>,
+) -> Response {
+    ws.on_upgrade(|socket| handle_file_subscription(socket, state))
+}
+
+async fn handle_file_subscription(socket: WebSocket, state: SharedState) {
+    let (mut sender, mut receiver) = socket.split();
+
+    // Set of file IDs this client is subscribed to
+    let mut subscriptions: HashSet<Uuid> = HashSet::new();
+
+    // Subscribe to the broadcast channel
+    let mut broadcast_rx = state.file_updates.subscribe();
+
+    loop {
+        tokio::select! {
+            // Handle incoming WebSocket messages from client
+            msg = receiver.next() => {
+                match msg {
+                    Some(Ok(Message::Text(text))) => {
+                        match serde_json::from_str::<FileClientMessage>(&text) {
+                            Ok(FileClientMessage::Subscribe { file_id }) => {
+                                subscriptions.insert(file_id);
+                                let response = FileServerMessage::Subscribed { file_id };
+                                let json = serde_json::to_string(&response).unwrap();
+                                if sender.send(Message::Text(json.into())).await.is_err() {
+                                    break;
+                                }
+                                tracing::debug!("Client subscribed to file {}", file_id);
+                            }
+                            Ok(FileClientMessage::Unsubscribe { file_id }) => {
+                                subscriptions.remove(&file_id);
+                                let response = FileServerMessage::Unsubscribed { file_id };
+                                let json = serde_json::to_string(&response).unwrap();
+                                if sender.send(Message::Text(json.into())).await.is_err() {
+                                    break;
+                                }
+                                tracing::debug!("Client unsubscribed from file {}", file_id);
+                            }
+                            Err(e) => {
+                                let response = FileServerMessage::Error {
+                                    code: "PARSE_ERROR".into(),
+                                    message: e.to_string(),
+                                };
+                                let json = serde_json::to_string(&response).unwrap();
+                                let _ = sender.send(Message::Text(json.into())).await;
+                            }
+                        }
+                    }
+                    Some(Ok(Message::Close(_))) | None => {
+                        tracing::debug!("Client disconnected from file subscription");
+                        break;
+                    }
+                    Some(Err(e)) => {
+                        tracing::warn!("WebSocket error: {}", e);
+                        break;
+                    }
+                    _ => {}
+                }
+            }
+
+            // Handle broadcast notifications
+            notification = broadcast_rx.recv() => {
+                match notification {
+                    Ok(notification) => {
+                        // Only forward if client is subscribed to this file
+                        if subscriptions.contains(&notification.file_id) {
+                            let response = FileServerMessage::FileUpdated {
+                                file_id: notification.file_id,
+                                version: notification.version,
+                                updated_fields: notification.updated_fields,
+                                updated_by: notification.updated_by,
+                            };
+                            let json = serde_json::to_string(&response).unwrap();
+                            if sender.send(Message::Text(json.into())).await.is_err() {
+                                break;
+                            }
+                        }
+                    }
+                    Err(tokio::sync::broadcast::error::RecvError::Lagged(n)) => {
+                        // Client is too slow, skip some messages
+                        tracing::warn!("File subscription client lagged, skipped {} messages", n);
+                    }
+                    Err(tokio::sync::broadcast::error::RecvError::Closed) => {
+                        // Channel closed, exit
+                        break;
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/makima/src/server/handlers/files.rs b/makima/src/server/handlers/files.rs
index 746d66b..c65eed5 100644
--- a/makima/src/server/handlers/files.rs
+++ b/makima/src/server/handlers/files.rs
@@ -9,9 +9,9 @@ use axum::{
 use uuid::Uuid;
 
 use crate::db::models::{CreateFileRequest, FileListResponse, FileSummary, UpdateFileRequest};
-use crate::db::repository;
+use crate::db::repository::{self, RepositoryError};
 use crate::server::messages::ApiError;
-use crate::server::state::SharedState;
+use crate::server::state::{FileUpdateNotification, SharedState};
 
 /// List all files for the current owner.
 #[utoipa::path(
@@ -148,6 +148,7 @@ pub async fn create_file(
     responses(
         (status = 200, description = "File updated", body = crate::db::models::File),
         (status = 404, description = "File not found", body = ApiError),
+        (status = 409, description = "Version conflict", body = ApiError),
         (status = 503, description = "Database not configured", body = ApiError),
         (status = 500, description = "Internal server error", body = ApiError),
     ),
@@ -166,14 +167,62 @@ pub async fn update_file(
             .into_response();
     };
 
+    // Collect which fields are being updated for broadcast
+    let mut updated_fields = Vec::new();
+    if req.name.is_some() {
+        updated_fields.push("name".to_string());
+    }
+    if req.description.is_some() {
+        updated_fields.push("description".to_string());
+    }
+    if req.transcript.is_some() {
+        updated_fields.push("transcript".to_string());
+    }
+    if req.summary.is_some() {
+        updated_fields.push("summary".to_string());
+    }
+    if req.body.is_some() {
+        updated_fields.push("body".to_string());
+    }
+
     match repository::update_file(pool, id, req).await {
-        Ok(Some(file)) => Json(file).into_response(),
+        Ok(Some(file)) => {
+            // Broadcast update notification
+            state.broadcast_file_update(FileUpdateNotification {
+                file_id: id,
+                version: file.version,
+                updated_fields,
+                updated_by: "user".to_string(),
+            });
+            Json(file).into_response()
+        }
         Ok(None) => (
             StatusCode::NOT_FOUND,
             Json(ApiError::new("NOT_FOUND", "File not found")),
         )
             .into_response(),
-        Err(e) => {
+        Err(RepositoryError::VersionConflict { expected, actual }) => {
+            tracing::info!(
+                "Version conflict on file {}: expected {}, actual {}",
+                id,
+                expected,
+                actual
+            );
+            (
+                StatusCode::CONFLICT,
+                Json(serde_json::json!({
+                    "code": "VERSION_CONFLICT",
+                    "message": format!(
+                        "File was modified by another user. Expected version {}, actual version {}",
+                        expected, actual
+                    ),
+                    "expectedVersion": expected,
+                    "actualVersion": actual,
+                })),
+            )
+                .into_response()
+        }
+        Err(RepositoryError::Database(e)) => {
             tracing::error!("Failed to update file {}: {}", id, e);
             (
                 StatusCode::INTERNAL_SERVER_ERROR,
diff --git a/makima/src/server/handlers/listen.rs b/makima/src/server/handlers/listen.rs
index 5fc5cea..a26c208 100644
--- a/makima/src/server/handlers/listen.rs
+++ b/makima/src/server/handlers/listen.rs
@@ -467,6 +467,7 @@ async fn handle_socket(socket: WebSocket, state: SharedState) {
                 transcript: Some(final_entries.clone()),
                 summary: None,
                 body: None,
+                version: None, // Internal update, skip version check
             }).await {
                 Ok(_) => {
                     tracing::info!(
diff --git a/makima/src/server/handlers/mod.rs b/makima/src/server/handlers/mod.rs
index b13668a..c08f1bd 100644
--- a/makima/src/server/handlers/mod.rs
+++ b/makima/src/server/handlers/mod.rs
@@ -1,5 +1,6 @@
 //! HTTP and WebSocket request handlers.
 
 pub mod chat;
+pub mod file_ws;
 pub mod files;
 pub mod listen;