From 60a230b2ffecffca6f3a65b64a0aa01e13e8cdcf Mon Sep 17 00:00:00 2001
From: German Khokhlov <ouchlock@gmail.com>
Date: Tue, 3 Nov 2026 20:33:13 +0400
Subject: [PATCH] Keep a bikeshare city's last known stations, marked stale,
 when it comes back into range during a source outage

---
 .../bikeshare/failureReporting.test.mjs       | 39 +++++++++++++++++++
 src/layers/bikeshare/viewport.js              |  6 +++
 2 files changed, 45 insertions(+)

diff --git a/src/layers/bikeshare/failureReporting.test.mjs b/src/layers/bikeshare/failureReporting.test.mjs
index 90c7b86f9..42efe4e0e 100644
--- a/src/layers/bikeshare/failureReporting.test.mjs
+++ b/src/layers/bikeshare/failureReporting.test.mjs
@@ -375,3 +375,42 @@ test('every status poll failing over cached points reads STALE, not fresh', asyn
   assert.equal(stats.stale, true);
   assert.equal(stats.lastUpdate, loadedAt, 'a failed poll advanced freshness');
 });
+
+test('a city that leaves range and comes back during a status outage keeps its last stations, STALE', async () => {
+  const layer = makeLiveLayer();
+  await layer.moveTo(TORONTO_ONLY);
+  await layer.enable();
+  const loadedAt = layer.stats().lastUpdate;
+  assert.equal(layer.stats().count, 1);
+
+  layer.source.deadStatus.add(TORONTO);
+  await layer.moveTo(BUFFALO_ONLY);
+  const beforeReturn = layer.stats().lastUpdate;
+  await layer.moveTo(TORONTO_ONLY);
+
+  const stats = layer.stats();
+  assert.equal(stats.count, 1, 'the last known stations stay drawn');
+  assert.equal(stats.error, undefined);
+  assert.equal(stats.stale, true, 'they are marked stale');
+  assert.equal(stats.lastUpdate, beforeReturn, 'the outage advanced freshness');
+  assert.ok(layer.state._activeCityIds.has(TORONTO), 'the city stays active');
+  const [station] = layer.state._stationRenderMap.values();
+  assert.equal(station.cityId, TORONTO);
+  assert.equal(station.bikesAvailable, 3, 'the last known status stays');
+
+  // The next poll that reaches the source clears the outage.
+  layer.source.deadStatus.delete(TORONTO);
+  await new Promise((resolve) => setTimeout(resolve, 5));
+  await layer.poll();
+  assert.equal(layer.stats().stale, undefined);
+  assert.ok(layer.stats().lastUpdate > loadedAt);
+});
+
+test('a city whose status never loaded is still removed when its status fails', async () => {
+  const layer = makeLiveLayer();
+  layer.source.deadStatus.add(TORONTO);
+  await layer.moveTo(TORONTO_ONLY);
+  await layer.enable();
+  assert.equal(layer.stats().count, 0, 'no status ever seen: nothing to keep');
+  assert.equal(layer.stats().error, 'GBFS fetch error');
+});
diff --git a/src/layers/bikeshare/viewport.js b/src/layers/bikeshare/viewport.js
index 41b7cd0e5..8bb08b859 100644
--- a/src/layers/bikeshare/viewport.js
+++ b/src/layers/bikeshare/viewport.js
@@ -94,6 +94,8 @@ export function createViewport({ state: layerState, services, parts, camera }) {
   async function activateCity(cityId, generation) {
     if (!layerState._enabled || !layerState._activeCityIds.has(cityId)) return;
 
+    // Set once the city's last known stations and status are back on the map.
+    let showingLastKnown = false;
     try {
       const stationMap = await parts.ingestion.loadCityStationInfo(
         cityId,
@@ -113,6 +115,7 @@ export function createViewport({ state: layerState, services, parts, camera }) {
       const cachedStatus = layerState._statusCache.get(cityId)?.statusMap;
       if (cachedStatus) {
         parts.rendering?.applyStatusToPoints(cityId, cachedStatus);
+        showingLastKnown = layerState._cityRuntime.has(cityId);
       }
 
       const statusMap = await parts.ingestion.loadCityStationStatus(
@@ -137,6 +140,9 @@ export function createViewport({ state: layerState, services, parts, camera }) {
         return;
       console.warn(`[Data:Bikeshare] ${cityId} activate error:`, error);
       layerState._failedCityIds.add(cityId);
+      // During a source outage a city coming back into range keeps its last
+      // known stations and status, marked stale; the status poll retries it.
+      if (showingLastKnown) return;
       deactivateCity(cityId);
       layerState._activeCityIds.delete(cityId);
     } finally {