1 files changed, 163 insertions, 0 deletions
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;
+                    }
+                }
+            }
+        }
+    }
+}