refactor: streamline client import pipeline

src/client/app.ts

@@ -26,6 +26,7 @@ const state = {
 };
 let activeImportController = null;
 const IMPORT_RENDER_INTERVAL_MS = 180;
+const IMPORT_CONCURRENCY = 2;
 let scheduledRenderFrame = null;
 let scheduledRenderTimer = null;
 let scheduledRenderOptions = { fitMap: false };
@@ -908,14 +909,19 @@ async function readRemoteImage(entry, shareUrlValue, signal) {
   const capturedAt =
     normalizeExifDate(tags?.DateTimeOriginal?.value ?? tags?.DateTimeOriginal) ||
     parseDateOrNull(entry.lastModified);
+
+  if (gps?.latitude === undefined || gps?.longitude === undefined) {
+    return null;
+  }
+
   const thumbUrl = await createThumbnailObjectUrl(blob);
   state.objectUrls.push(thumbUrl);
 
   return {
     id: entry.href,
     name: entry.name,
-    latitude: gps?.latitude ?? null,
-    longitude: gps?.longitude ?? null,
+    latitude: gps.latitude,
+    longitude: gps.longitude,
     capturedAt,
     thumbUrl,
     fullUrl,
@@ -923,6 +929,50 @@ async function readRemoteImage(entry, shareUrlValue, signal) {
   };
 }
 
+async function processImportEntries(listing, shareUrlValue, signal) {
+  let loaded = 0;
+  let skipped = 0;
+  let processed = 0;
+  let nextIndex = 0;
+
+  async function importWorker() {
+    while (nextIndex < listing.length) {
+      if (signal.aborted) {
+        throw signal.reason ?? new Error("Import canceled");
+      }
+
+      const entry = listing[nextIndex];
+      nextIndex += 1;
+
+      try {
+        const photo = await readRemoteImage(entry, shareUrlValue, signal);
+        if (photo) {
+          appendPhoto(photo);
+          loaded += 1;
+        } else {
+          skipped += 1;
+        }
+      } catch (error) {
+        if (signal.aborted) {
+          throw signal.reason ?? error;
+        }
+        skipped += 1;
+        console.error(error);
+      }
+
+      processed += 1;
+      setProgress(processed, listing.length, "processed " + processed + " / " + listing.length);
+      setImportStatus("Importing: " + loaded + " shown, " + skipped + " skipped.");
+      await new Promise((resolve) => setTimeout(resolve, 0));
+    }
+  }
+
+  const workerCount = Math.min(IMPORT_CONCURRENCY, listing.length);
+  await Promise.all(Array.from({ length: workerCount }, () => importWorker()));
+
+  return { loaded, skipped };
+}
+
 async function importFromShare() {
   if (activeImportController) {
     return;
@@ -945,32 +995,7 @@ async function importFromShare() {
 
     setProgress(0, listing.length, "checking files");
 
-    let loaded = 0;
-    let skipped = 0;
-    let processed = 0;
-
-    for (const entry of listing) {
-      if (controller.signal.aborted) {
-        throw controller.signal.reason ?? new Error("Import canceled");
-      }
-
-      try {
-        const photo = await readRemoteImage(entry, importUrlInput.value, controller.signal);
-        if (photo.latitude !== null && photo.longitude !== null) {
-          appendPhoto(photo);
-          loaded += 1;
-        } else {
-          skipped += 1;
-        }
-      } catch (error) {
-        skipped += 1;
-        console.error(error);
-      }
-
-      processed += 1;
-      setProgress(processed, listing.length, "processed " + processed + " / " + listing.length);
-      setImportStatus("Importing: " + loaded + " shown, " + skipped + " skipped.");
-    }
+    const { loaded, skipped } = await processImportEntries(listing, importUrlInput.value, controller.signal);
 
     if (!loaded) {
       throw new Error("No images with GPS data found.");