[AZ-359] Refactor C07: collapse RegionService catch ladder via RegionFailureClassifier

Replace 9 nearly-identical catch blocks in RegionService.ProcessRegionAsync with a single catch (Exception ex) that delegates to RegionFailureClassifier.Classify, returning a typed (category, errorMessage) pair. Preserves all original error messages stored in region summary files; failure-path call into HandleProcessingFailureAsync is unchanged. Net source delta: -38 lines in RegionService, +71 lines in new RegionFailureClassifier (pure static), +10 unit tests covering each category, precedence, status-code propagation, null guard. Tests: 68 unit (was 58) + 5 smoke + 3 stub-contract integration tests pass. Co-authored-by: Cursor <cursoragent@cursor.com>
2026-06-21 12:11:14 +00:00 · 2026-05-11 00:07:31 +03:00
parent 1d89cd9997
commit 5a28f67d33
8 changed files with 312 additions and 48 deletions
@@ -0,0 +1,70 @@
+using SatelliteProvider.Common.Exceptions;
+
+namespace SatelliteProvider.Services.RegionProcessing;
+
+internal enum RegionFailureCategory
+{
+    Timeout,
+    ExternalCancellation,
+    TaskCanceledOther,
+    OperationCanceledOther,
+    RateLimit,
+    Network,
+    Unexpected,
+}
+
+internal sealed record RegionFailureClassification(RegionFailureCategory Category, string ErrorMessage);
+
+internal static class RegionFailureClassifier
+{
+    public const string TimeoutMessage =
+        "Processing timed out after 5 minutes. Unable to download tiles within the time limit.";
+
+    public const string ExternalCancellationMessage =
+        "Processing was cancelled externally (likely application shutdown).";
+
+    public static RegionFailureClassification Classify(
+        Exception ex,
+        CancellationTokenSource timeoutCts,
+        CancellationToken cancellationToken)
+    {
+        ArgumentNullException.ThrowIfNull(ex);
+        ArgumentNullException.ThrowIfNull(timeoutCts);
+
+        return ex switch
+        {
+            TaskCanceledException when timeoutCts.IsCancellationRequested
+                => new RegionFailureClassification(RegionFailureCategory.Timeout, TimeoutMessage),
+
+            TaskCanceledException when cancellationToken.IsCancellationRequested
+                => new RegionFailureClassification(RegionFailureCategory.ExternalCancellation, ExternalCancellationMessage),
+
+            TaskCanceledException
+                => new RegionFailureClassification(
+                    RegionFailureCategory.TaskCanceledOther,
+                    $"Request cancelled or timed out: {ex.Message}. This may indicate HttpClient timeout or network issues."),
+
+            OperationCanceledException when timeoutCts.IsCancellationRequested
+                => new RegionFailureClassification(RegionFailureCategory.Timeout, TimeoutMessage),
+
+            OperationCanceledException
+                => new RegionFailureClassification(
+                    RegionFailureCategory.OperationCanceledOther,
+                    $"Operation cancelled: {ex.Message}"),
+
+            RateLimitException
+                => new RegionFailureClassification(
+                    RegionFailureCategory.RateLimit,
+                    $"Rate limit exceeded: {ex.Message}. Google Maps API rate limit was reached and retries were exhausted."),
+
+            HttpRequestException httpEx
+                => new RegionFailureClassification(
+                    RegionFailureCategory.Network,
+                    $"Network error (HTTP {httpEx.StatusCode}): {httpEx.Message}. Failed to download tiles from Google Maps."),
+
+            _ => new RegionFailureClassification(
+                RegionFailureCategory.Unexpected,
+                $"Unexpected error ({ex.GetType().Name}): {ex.Message}"),
+        };
+    }
+}