Move tile logic outside calloutAnnouncer

app/callout.js

@@ -4,10 +4,6 @@
 import { enumerateTilesAround } from './tile.js'
 
 export function createCalloutAnnouncer(audioQueue, proximityThresholdMeters) {
-  // Avoid a flood of network requests, by maintaining a list of tiles already requested
-  // (handles the case where the network request is already open)
-  const seenTiles = new Set();
-
   // Avoid repeating myself, by maintaining a list of the most recent POIs announced
   const spokenRecently = {
     keys: new Set(),  // for quick lookups
@@ -85,12 +81,7 @@ export function createCalloutAnnouncer(audioQueue, proximityThresholdMeters) {
       audioQueue.updateLocation(myLocation, heading);
 
       for (const tile of tiles) {
-        //FIXME move tile logic outside of calloutAnnouncer
-        if (!seenTiles.has(tile.key)) {
-          seenTiles.add(tile.key);
-          tile.load();
-        }
-
+        tile.load();
         tile.getFeatures()
         .then(features => {
           features.forEach(feature => {

app/tile.js

@@ -8,14 +8,23 @@ import { createBoundingBox, enumerateTilesInBoundingBox } from './geospatial.js'
 const maxAge = 604800000; // 1 week, in ms
 export const zoomLevel = 16;
 
+// Track tiles that don't need to be re-requested at the moment
+const tilesInProgressOrDone = new Set();
+
 function createTile(x, y, z) {
   var tile = {
     x: x,
     y: y,
     z: z,
     key: `${z}/${x}/${y}`,
 
-    load: function() {
+    load: async function() {
+      if (tilesInProgressOrDone.has(tile.key)) {
+        // no need to request again
+        return;
+      }
+      tilesInProgressOrDone.add(tile.key);
+
       const urlToFetch = `${config.tileServer}/${tile.key}.json`;
       fetchUrlIfNotCached(urlToFetch, maxAge)
         .then((data) => {
@@ -26,6 +35,8 @@ function createTile(x, y, z) {
         })
         .catch((error) => {
           console.error(error);
+          // should be retried when next needed
+          tilesInProgressOrDone.delete(tile.key);
         });
     },