Improve Autoampel page fetching with retry logic and consecutive failure handling; add URL inference for pagination

src/HsnTsnScraper/Program.cs

@@ -336,16 +336,7 @@ async Task RunMergeCoreDbMode(HsnTsnClient hsnTsnClient, string? inputPath, stri
     }
 
     await BulkUpsertVehicleRowsAsync(conn, quotedTable, rowsToEnrich);
-    var autoampelUpserted = 0;
-    try
-    {
-        autoampelUpserted = await UpsertAutoampelPagesIntoDbAsync(hsnTsnClient, conn, quotedTable);
-    }
-    catch (Exception ex)
-    {
-        failed++;
-        Console.Error.WriteLine($"[warn] autoampel page-upsert failed -> {ex.Message}");
-    }
+    var autoampelUpserted = await UpsertAutoampelPagesIntoDbAsync(hsnTsnClient, conn, quotedTable);
 
     Console.Error.WriteLine($"[info] Merge-core-db finished. checked={rowsToEnrich.Count}, filled_hsntsn={filledFromHsnTsn}, autoampel_upserted={autoampelUpserted}, failed={failed}");
 }
@@ -454,12 +445,51 @@ async Task<int> UpsertAutoampelPagesIntoDbAsync(HsnTsnClient hsnTsnClient, Npgsq
     var pageUrl = hsnTsnClient.GetAutoampelFullListUrl();
     var pageIndex = 0;
     var totalUpserted = 0;
+    var consecutiveFailures = 0;
+    const int maxConsecutiveFailures = 8;
 
     while (!string.IsNullOrWhiteSpace(pageUrl))
     {
         pageIndex++;
         Console.Error.WriteLine($"[info] Processing: {pageUrl}");
-        var page = await hsnTsnClient.GetVehiclesFromAutoampelListPageAsync(pageUrl);
+        AutoampelPageResult? page = null;
+        const int maxAttempts = 7;
+        for (var attempt = 1; attempt <= maxAttempts; attempt++)
+        {
+            try
+            {
+                page = await hsnTsnClient.GetVehiclesFromAutoampelListPageAsync(pageUrl);
+                break;
+            }
+            catch (HttpRequestException ex) when (attempt < maxAttempts)
+            {
+                var delaySeconds = IsTooManyRequests(ex) ? Math.Min(90, (int)Math.Pow(2, attempt)) : Math.Min(30, attempt * 3);
+                Console.Error.WriteLine($"[warn] Autoampel page fetch failed ({ex.Message}), retry in {delaySeconds}s (attempt {attempt}/{maxAttempts})");
+                await Task.Delay(TimeSpan.FromSeconds(delaySeconds));
+            }
+        }
+
+        if (page is null)
+        {
+            consecutiveFailures++;
+            Console.Error.WriteLine($"[warn] Autoampel page skipped after retries: {pageUrl}");
+
+            if (consecutiveFailures >= maxConsecutiveFailures)
+            {
+                Console.Error.WriteLine("[warn] Too many consecutive autoampel page failures, stopping page-upsert loop.");
+                break;
+            }
+
+            pageUrl = InferNextAutoampelListUrl(pageUrl);
+            if (string.IsNullOrWhiteSpace(pageUrl))
+            {
+                break;
+            }
+
+            continue;
+        }
+
+        consecutiveFailures = 0;
         var rows = page.Vehicles
             .GroupBy(v => v.HsnTsn, StringComparer.OrdinalIgnoreCase)
             .Select(g => g.First())
@@ -495,6 +525,22 @@ async Task<int> UpsertAutoampelPagesIntoDbAsync(HsnTsnClient hsnTsnClient, Npgsq
     return totalUpserted;
 }
 
+static string? InferNextAutoampelListUrl(string currentUrl)
+{
+    var match = Regex.Match(currentUrl, @"^(?<base>https?://[^/]+/typklassen/liste/)(?<page>\d+)$", RegexOptions.IgnoreCase);
+    if (!match.Success)
+    {
+        return null;
+    }
+
+    if (!int.TryParse(match.Groups["page"].Value, out var currentPage))
+    {
+        return null;
+    }
+
+    return $"{match.Groups["base"].Value}{currentPage + 1}";
+}
+
 int FillCoreFields(CoreOutputRow target, HsnTsnVehicle source, bool fillYears)
 {
     var changes = 0;