3 files changed, 81 insertions, 11 deletions

diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 0ebfd641d..8cfb6a192 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -31,10 +31,10 @@ use crate::{
 pub fn handle_analyzer_status(world: ServerWorld, _: ()) -> Result<String> {
     let mut buf = world.status();
     writeln!(buf, "\n\nrequests:").unwrap();
-    let requests = world.latest_completed_requests.read();
-    for (idx, r) in requests.iter().enumerate() {
-        let current = if idx == world.request_idx { "*" } else { " " };
-        writeln!(buf, "{:4}{}{:<36}{}ms", r.id, current, r.method, r.duration.as_millis()).unwrap();
+    let requests = world.latest_requests.read();
+    for (is_last, r) in requests.iter() {
+        let mark = if is_last { "*" } else { " " };
+        writeln!(buf, "{}{:4} {:<36}{}ms", mark, r.id, r.method, r.duration.as_millis()).unwrap();
     }
     Ok(buf)
 }
diff --git a/crates/ra_lsp_server/src/main_loop/pending_requests.rs b/crates/ra_lsp_server/src/main_loop/pending_requests.rs
new file mode 100644
index 000000000..741770e45
--- /dev/null
+++ b/crates/ra_lsp_server/src/main_loop/pending_requests.rs
@@ -0,0 +1,72 @@
+use std::time::{Duration, Instant};
+
+use rustc_hash::FxHashMap;
+
+#[derive(Debug)]
+pub struct CompletedRequest {
+    pub id: u64,
+    pub method: String,
+    pub duration: Duration,
+}
+
+#[derive(Debug)]
+pub(crate) struct PendingRequest {
+    pub(crate) id: u64,
+    pub(crate) method: String,
+    pub(crate) received: Instant,
+}
+
+impl From<PendingRequest> for CompletedRequest {
+    fn from(pending: PendingRequest) -> CompletedRequest {
+        CompletedRequest {
+            id: pending.id,
+            method: pending.method,
+            duration: pending.received.elapsed(),
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+pub(crate) struct PendingRequests {
+    map: FxHashMap<u64, PendingRequest>,
+}
+
+impl PendingRequests {
+    pub(crate) fn start(&mut self, request: PendingRequest) {
+        let id = request.id;
+        let prev = self.map.insert(id, request);
+        assert!(prev.is_none(), "duplicate request with id {}", id);
+    }
+    pub(crate) fn cancel(&mut self, id: u64) -> bool {
+        self.map.remove(&id).is_some()
+    }
+    pub(crate) fn finish(&mut self, id: u64) -> Option<CompletedRequest> {
+        self.map.remove(&id).map(CompletedRequest::from)
+    }
+}
+
+const N_COMPLETED_REQUESTS: usize = 10;
+
+#[derive(Debug, Default)]
+pub struct LatestRequests {
+    // hand-rolling VecDeque here to print things in a nicer way
+    buf: [Option<CompletedRequest>; N_COMPLETED_REQUESTS],
+    idx: usize,
+}
+
+impl LatestRequests {
+    pub(crate) fn record(&mut self, request: CompletedRequest) {
+        // special case: don't track status request itself
+        if request.method == "rust-analyzer/analyzerStatus" {
+            return;
+        }
+        let idx = self.idx;
+        self.buf[idx] = Some(request);
+        self.idx = (idx + 1) % N_COMPLETED_REQUESTS;
+    }
+
+    pub(crate) fn iter(&self) -> impl Iterator<Item = (bool, &CompletedRequest)> {
+        let idx = self.idx;
+        self.buf.iter().enumerate().filter_map(move |(i, req)| Some((i == idx, req.as_ref()?)))
+    }
+}
diff --git a/crates/ra_lsp_server/src/main_loop/subscriptions.rs b/crates/ra_lsp_server/src/main_loop/subscriptions.rs
index 11bd952d9..470bc1205 100644
--- a/crates/ra_lsp_server/src/main_loop/subscriptions.rs
+++ b/crates/ra_lsp_server/src/main_loop/subscriptions.rs
@@ -1,21 +1,19 @@
 use ra_ide_api::FileId;
 use rustc_hash::FxHashSet;
 
-pub struct Subscriptions {
+#[derive(Default)]
+pub(crate) struct Subscriptions {
     subs: FxHashSet<FileId>,
 }
 
 impl Subscriptions {
-    pub fn new() -> Subscriptions {
-        Subscriptions { subs: FxHashSet::default() }
-    }
-    pub fn add_sub(&mut self, file_id: FileId) {
+    pub(crate) fn add_sub(&mut self, file_id: FileId) {
         self.subs.insert(file_id);
     }
-    pub fn remove_sub(&mut self, file_id: FileId) {
+    pub(crate) fn remove_sub(&mut self, file_id: FileId) {
         self.subs.remove(&file_id);
     }
-    pub fn subscriptions(&self) -> Vec<FileId> {
+    pub(crate) fn subscriptions(&self) -> Vec<FileId> {
         self.subs.iter().cloned().collect()
     }
 }