refactor(dotnet): normalize learning dataset export inputs

src/dotnet/QuantEngine.Application/Services/LearningDatasetService.cs

@@ -11,7 +11,9 @@ public sealed class LearningDatasetService
 
     public async Task<string> ExportJsonAsync(string outputPath, int limit = 1000)
     {
-        var rows = await _reader.ReadTrainingExamplesAsync(limit);
+        var normalizedOutputPath = RequireValue(outputPath, nameof(outputPath));
+        var normalizedLimit = Math.Clamp(limit, 1, 10000);
+        var rows = await _reader.ReadTrainingExamplesAsync(normalizedLimit);
         var payload = new
         {
             formula_id = "ENGINE_HISTORY_TRAINING_DATASET_V1",
@@ -21,9 +23,19 @@ public sealed class LearningDatasetService
             source = "engine_history.training_example_v1",
             rows
         };
-        var path = Path.GetFullPath(outputPath);
+        var path = Path.GetFullPath(normalizedOutputPath);
         Directory.CreateDirectory(Path.GetDirectoryName(path)!);
         await File.WriteAllTextAsync(path, JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true }));
         return path;
     }
+
+    private static string RequireValue(string value, string parameterName)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new ArgumentException("Value is required.", parameterName);
+        }
+
+        return value.Trim();
+    }
 }

src/dotnet/QuantEngine.Core.Tests/LearningDatasetServiceTests.cs

@@ -0,0 +1,54 @@
+using Moq;
+using QuantEngine.Application.Services;
+using QuantEngine.Core.Interfaces;
+
+namespace QuantEngine.Core.Tests;
+
+public class LearningDatasetServiceTests
+{
+    [Fact]
+    public async Task ExportJsonAsync_TrimsPathAndClampsLimit()
+    {
+        var reader = new Mock<ILearningDatasetReader>(MockBehavior.Strict);
+        reader.Setup(r => r.ReadTrainingExamplesAsync(10000)).ReturnsAsync([]);
+
+        var service = new LearningDatasetService(reader.Object);
+        var root = FindRepoRoot();
+        var outPath = Path.Combine(root, "Temp", "learning_dataset_test.json");
+
+        if (File.Exists(outPath))
+        {
+            File.Delete(outPath);
+        }
+
+        var result = await service.ExportJsonAsync($"  {outPath}  ", 50000);
+
+        Assert.Equal(Path.GetFullPath(outPath), result);
+        Assert.True(File.Exists(result));
+        var text = await File.ReadAllTextAsync(result);
+        Assert.Contains("\"gate\": \"DATA_MISSING\"", text);
+        reader.VerifyAll();
+    }
+
+    [Fact]
+    public async Task ExportJsonAsync_RejectsBlankPath()
+    {
+        var service = new LearningDatasetService(new Mock<ILearningDatasetReader>().Object);
+        await Assert.ThrowsAsync<ArgumentException>(() => service.ExportJsonAsync(" ", 10));
+    }
+
+    private static string FindRepoRoot()
+    {
+        var current = new DirectoryInfo(AppContext.BaseDirectory);
+        while (current != null)
+        {
+            if (Directory.Exists(Path.Combine(current.FullName, ".git")))
+            {
+                return current.FullName;
+            }
+            current = current.Parent;
+        }
+
+        throw new InvalidOperationException("Repository root not found.");
+    }
+}