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Services/FilePickerService.cs

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+using Microsoft.Win32;
+
+namespace CRAWLER.Services;
+
+internal interface IFilePickerService
+{
+    IReadOnlyList<string> PickPdfFiles(bool multiselect);
+}
+
+internal sealed class FilePickerService : IFilePickerService
+{
+    public IReadOnlyList<string> PickPdfFiles(bool multiselect)
+    {
+        var dialog = new OpenFileDialog
+        {
+            Filter = "PDF (*.pdf)|*.pdf",
+            Multiselect = multiselect,
+            CheckFileExists = true,
+            CheckPathExists = true
+        };
+
+        return dialog.ShowDialog() == true
+            ? dialog.FileNames
+            : Array.Empty<string>();
+    }
+}