OUT-798: Normalize file names of attachments

PEPAttachment.cs

@@ -1049,6 +1049,56 @@ namespace pEp
             return isAttachedMail;
         }
 
+        /// <summary>
+        /// Normalizes the file name of a given attachment.
+        /// </summary>
+        /// <param name="attachmentFileNames">The list of file names in this message before processing.</param>
+        /// <param name="normalizedAttachments">The list of normalized file names.</param>
+        public void NormalizeFileName(List<string> attachmentFileNames, List<PEPAttachment> normalizedAttachments)
+        {
+            if (string.IsNullOrEmpty(this.FileName))
+            {
+                return;
+            }
+
+            // Remove file path
+            if (this.FileName.Contains('\\'))
+            {
+                this.FileName = this.FileName.Split('\\')?.Last();
+            }
+
+            /* Add numbering to file name if necessary. If 'file.ext' exists multiple times, 
+             * rename to 'file.ext', 'file (1).ext', 'file (2).ext' etc.
+             */
+            bool error = false;
+            int counter = 1;
+            string normalizedFileName = this.FileName;
+
+            // If there is already a file with this file name, add number
+            while (normalizedAttachments.Any(a => a.FileName?.Equals(normalizedFileName) == true) &&
+                   (error == false))
+            {
+                do
+                {
+                    try
+                    {
+                        var fileParts = this.FileName.Split('.');
+                        normalizedFileName = string.Join("", new ArraySegment<string>(fileParts, 0, fileParts.Length - 1));
+                        normalizedFileName += " (" + counter++ + ")." + fileParts.Last();
+                    }
+                    catch (Exception ex)
+                    {
+                        error = true;
+                        Log.Error("NormalizeFileNames: Error occured. " + ex.ToString());
+                    }
+
+                // Doublecheck to make sure the modified file name doesn't exist yet
+                } while ((attachmentFileNames.Contains(normalizedFileName)) &&
+                         (error == false));
+            }
+
+            this.FileName = normalizedFileName;
+        }
 
         /**************************************************************
          * 

PEPMessage.cs

@@ -3294,6 +3294,15 @@ namespace pEp
                     // Attachments
                     newMessage.Attachments.Clear();
                     attachments = omi.Attachments;
+
+                    // Create a preliminary list for later normalizing of file names
+                    List<string> attachmentFileNames = new List<string>();
+                    for (int i = 1; i <= attachments.Count; i++)
+                    {
+                        attachmentFileNames.Add(attachments[i].FileName.Split('\\').Last());
+                    }
+
+                    // Add attachments to new message
                     for (int i = 1; i <= attachments.Count; i++)
                     {
                         attachment = attachments[i];
@@ -3303,6 +3312,9 @@ namespace pEp
                             var newAttachment = new PEPAttachment(attachment, newMessage.LongMsgFormattedHtml ?? newMessage.LongMsgFormattedRtf ?? newMessage.LongMsg);
                             if (newAttachment?.Data != null)
                             {
+                                // Normalize the file name if necessary
+                                newAttachment.NormalizeFileName(attachmentFileNames, newMessage.Attachments);
+
                                 newMessage.Attachments.Add(newAttachment);
                             }
                         }