I #7: Handle exception when encryption not supported by PdfSharp

There is no version of PDF Sharp which will support the encryption
algorithm used in a certain file. A human-readable message is
at least preferable to a crash.

Author: Graham Downs

SplitPdf.Engine/EncryptedPdfException.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace SplitPdf.Engine
+{
+  public class EncryptedPdfException : Exception
+  {
+    public string FileName { get; set; }
+
+    public EncryptedPdfException(string fileName)
+      : base($"The PDF document, \"{fileName}\", was encrypted using an algorithm not yet " +
+              "supported by this program.\r\n" +
+              "\r\n" +
+              "Open the file and \"PDF Print\" it. Then try this operation again.")
+    {
+      FileName = fileName;
+    }
+  }
+}

SplitPdf.Engine/Runner.cs

@@ -32,7 +32,7 @@ public void Run(List<string> inputFiles, string mergeOutputFile)
 
     private void DoSplit(string file)
     {
-      var inputDocument = PdfReader.Open(file, PdfDocumentOpenMode.Import);
+      var inputDocument = OpenPdfFile(file);
       var destFolder = Path.GetDirectoryName(inputDocument.FullPath);
       var destFileName = Path.GetFileNameWithoutExtension(file);
       var destFileExtension = Path.GetExtension(file);
@@ -49,6 +49,22 @@ private void DoSplit(string file)
       }
     }
 
+    private PdfDocument OpenPdfFile(string file)
+    {
+      try
+      {
+        return PdfReader.Open(file, PdfDocumentOpenMode.Import);
+      }
+      catch (PdfReaderException exception)
+      {
+        if (exception.Message != "The PDF document is protected with an encryption not " + 
+                                 "supported by PDFsharp.")
+          throw;
+
+        throw new EncryptedPdfException(file);
+      }
+    }
+
     private void DoMerge(List<string> inputFiles, string mergeOutputFile)
     {
       var outputDocument = new PdfDocument();

SplitPdf.Engine/SplitPdf.Engine.csproj

@@ -47,6 +47,7 @@
     <Compile Include="ArgumentsInterpreter.cs" />
     <Compile Include="ArgumentsValidator.cs" />
     <Compile Include="ArgumentValidationException.cs" />
+    <Compile Include="EncryptedPdfException.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Runner.cs" />
     <Compile Include="RunnerProgressEventArgs.cs" />

SplitPdf/Program.cs

@@ -25,8 +25,7 @@ private static void Main(string[] args)
           // If it's time for a check, but it wasn't specifically 
           // requested by the user, we should still run (and validate
           // args) first.
-          runner.Progress += (sender, e) => Console.WriteLine(e.ProgressMessage);
-          runner.Run(argumentsInterpreter.InputFiles, argumentsInterpreter.MergeOutputFile);
+          Run(runner, argumentsInterpreter);
 
           if (Settings.Default.DaysBetweenUpgradeCheck == -1)
             return;
@@ -45,6 +44,19 @@ private static void Main(string[] args)
       }
     }
 
+    private static void Run(Runner runner, ArgumentsInterpreter argumentsInterpreter)
+    {
+      try
+      {
+        runner.Progress += (sender, e) => Console.WriteLine(e.ProgressMessage);
+        runner.Run(argumentsInterpreter.InputFiles, argumentsInterpreter.MergeOutputFile);
+      }
+      catch (EncryptedPdfException exception)
+      {
+        Console.WriteLine(exception.Message);
+      }
+    }
+
     private static void CheckForUpgrades(
       UpgradeRequiredChecker upgradeChecker)
     {