1 files changed, 23 insertions, 0 deletions
diff --git a/src/main/java/eu/siacs/conversations/utils/FileUtils.java b/src/main/java/eu/siacs/conversations/utils/FileUtils.java
index 1f2a71ca..18014894 100644
--- a/src/main/java/eu/siacs/conversations/utils/FileUtils.java
+++ b/src/main/java/eu/siacs/conversations/utils/FileUtils.java
@@ -17,6 +17,8 @@ import java.util.List;
 
 import de.thedevstack.conversationsplus.ConversationsPlusApplication;
 
+import eu.siacs.conversations.entities.Transferable;
+
 public final class FileUtils {
 
 	/**
@@ -160,6 +162,27 @@ public final class FileUtils {
 		return "com.android.providers.media.documents".equals(uri.getAuthority());
 	}
 
+    public static String getRelevantExtension(String path) {
+        if (path == null || path.isEmpty()) {
+            return null;
+        }
+
+        String filename = path.substring(path.lastIndexOf('/') + 1).toLowerCase();
+
+        final String lastPart = FileUtils.getLastExtension(filename);
+
+        if (!lastPart.isEmpty()) {
+            // we want the real file extension, not the crypto one
+            final String secondToLastPart = FileUtils.getSecondToLastExtension(filename);
+            if (!secondToLastPart.isEmpty() && Transferable.VALID_CRYPTO_EXTENSIONS.contains(lastPart)) {
+                return secondToLastPart;
+            } else {
+                return lastPart;
+            }
+        }
+        return null;
+    }
+
 	/**
 	 * @param filename The filename to extract extension from
 	 * @return last extension or empty string