Fix latest snapshot map ranking

frontend/src/components/map/MapWorkspace.tsx

@@ -279,7 +279,7 @@ function pickThemeDataset(
       && datasetCoversSelectedArea(dataset, selectedAreaId, regionalScope),
   )
   candidates.sort((left, right) => {
-    const score = (dataset: DatasetCreateResponse) =>
+    const priorityScore = (dataset: DatasetCreateResponse) =>
       (dataset.area_id && dataset.area_id === selectedAreaId ? 10_000_000 : 0) +
       (dataset.reference_layer_name && theme.tokens.includes(dataset.reference_layer_name.toLowerCase()) ? 1_000_000 : 0) +
       (dataset.source_name === 'grb' ? 100_000 : 0) +
@@ -292,10 +292,18 @@ function pickThemeDataset(
       (dataset.source_name === 'vmm_flood_hazard' ? 5_000_000 : 0) +
       (dataset.source_metadata?.['product_key'] === 'dtm_1m' ? 1_000_000 : 0) +
       (dataset.source_metadata?.['product_key'] === 'pluviaal_current_t100' ? 1_000_000 : 0) +
-      (dataset.dataset_role === 'reference' ? 10_000 : 0) +
-      (dataset.observed_at ? new Date(dataset.observed_at).getTime() / 100_000_000 : 0) +
-      (dataset.feature_count ?? dataset.vector_summary?.feature_count ?? 0)
-    return score(right) - score(left)
+      (dataset.dataset_role === 'reference' ? 10_000 : 0)
+    const priorityDifference = priorityScore(right) - priorityScore(left)
+    if (priorityDifference !== 0) return priorityDifference
+
+    const observedAtDifference = new Date(right.observed_at ?? 0).getTime() - new Date(left.observed_at ?? 0).getTime()
+    if (observedAtDifference !== 0) return observedAtDifference
+
+    const importedAtDifference = new Date(right.imported_at ?? 0).getTime() - new Date(left.imported_at ?? 0).getTime()
+    if (importedAtDifference !== 0) return importedAtDifference
+
+    return (right.feature_count ?? right.vector_summary?.feature_count ?? 0)
+      - (left.feature_count ?? left.vector_summary?.feature_count ?? 0)
   })
   return candidates[0] ?? null
 }