Guess mime types at run time

app/src/main/java/eu/faircode/email/AdapterAttachment.java

@@ -212,7 +212,7 @@ public class AdapterAttachment extends RecyclerView.Adapter<AdapterAttachment.Vi
                     new Intent(FragmentMessages.ACTION_STORE_ATTACHMENT)
                             .putExtra("id", attachment.id)
                             .putExtra("name", Helper.sanitizeFilename(attachment.name))
-                            .putExtra("type", attachment.type));
+                            .putExtra("type", attachment.getMimeType()));
         }
 
         private void onShare(EntityAttachment attachment) {
@@ -221,13 +221,15 @@ public class AdapterAttachment extends RecyclerView.Adapter<AdapterAttachment.Vi
             Uri uri = FileProvider.getUriForFile(context, BuildConfig.APPLICATION_ID, file);
             Log.i("uri=" + uri);
 
+            String type = attachment.getMimeType();
+
             // Build intent
             Intent intent = new Intent(Intent.ACTION_VIEW);
-            intent.setDataAndType(uri, attachment.type);
+            intent.setDataAndType(uri, type);
             intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
             if (!TextUtils.isEmpty(attachment.name))
                 intent.putExtra(Intent.EXTRA_TITLE, Helper.sanitizeFilename(attachment.name));
-            Log.i("Intent=" + intent + " type=" + attachment.type);
+            Log.i("Intent=" + intent + " type=" + type);
 
             // Get targets
             PackageManager pm = context.getPackageManager();
@@ -241,7 +243,7 @@ public class AdapterAttachment extends RecyclerView.Adapter<AdapterAttachment.Vi
             if (ris.size() == 0)
                 Snackbar.make(
                         (View) itemView.getParent(),
-                        context.getString(R.string.title_no_viewer, attachment.type),
+                        context.getString(R.string.title_no_viewer, type),
                         Snackbar.LENGTH_LONG).show();
             else
                 context.startActivity(intent);

app/src/main/java/eu/faircode/email/EntityAttachment.java

@@ -22,6 +22,7 @@ package eu.faircode.email;
 import android.content.Context;
 import android.os.Build;
 import android.text.TextUtils;
+import android.webkit.MimeTypeMap;
 
 import androidx.annotation.NonNull;
 import androidx.room.Entity;
@@ -34,6 +35,7 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Objects;
 
 import javax.mail.Part;
@@ -146,6 +148,30 @@ public class EntityAttachment {
         }
     }
 
+    String getMimeType() {
+        // Try to guess a better content type
+        // For example, sometimes PDF files are sent as application/octet-stream
+        if (encryption != null)
+            return type;
+
+        String extension = Helper.getExtension(name);
+        if (extension == null)
+            return type;
+
+        if ("application/zip".equals(type) ||
+                "application/octet-stream".equals(type)) {
+            String gtype = MimeTypeMap.getSingleton()
+                    .getMimeTypeFromExtension(extension.toLowerCase(Locale.ROOT));
+            if (gtype == null || gtype.equals(type))
+                return type;
+
+            Log.w("Guessing file=" + name + " type=" + gtype);
+            return gtype;
+        }
+
+        return type;
+    }
+
     @Override
     public boolean equals(Object obj) {
         if (obj instanceof EntityAttachment) {

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -25,7 +25,6 @@ import android.net.MailTo;
 import android.net.Uri;
 import android.text.Html;
 import android.text.TextUtils;
-import android.webkit.MimeTypeMap;
 
 import androidx.preference.PreferenceManager;
 
@@ -1367,27 +1366,10 @@ public class MessageHelper {
                     apart.attachment.cid = (cid == null || cid.length == 0 ? null : MimeUtility.unfold(cid[0]));
                     apart.attachment.encryption = (apart.pgp ? EntityAttachment.PGP_MESSAGE : null);
 
-                    if ("text/calendar".equalsIgnoreCase(apart.attachment.type) && TextUtils.isEmpty(apart.attachment.name))
+                    if ("text/calendar".equalsIgnoreCase(apart.attachment.type) &&
+                            TextUtils.isEmpty(apart.attachment.name))
                         apart.attachment.name = "invite.ics";
 
-                    // Try to guess a better content type
-                    // For example, sometimes PDF files are sent as application/octet-stream
-                    if (!apart.pgp) {
-                        String extension = Helper.getExtension(apart.attachment.name);
-                        if (extension != null) {
-                            if ("application/zip".equals(apart.attachment.type) ||
-                                    "application/octet-stream".equals(apart.attachment.type)) {
-                                String type = MimeTypeMap.getSingleton()
-                                        .getMimeTypeFromExtension(extension.toLowerCase(Locale.ROOT));
-                                if (type != null) {
-                                    if (!type.equals(apart.attachment.type))
-                                        Log.w("Guessing file=" + apart.attachment.name + " type=" + type);
-                                    apart.attachment.type = type;
-                                }
-                            }
-                        }
-                    }
-
                     if (apart.attachment.size <= 0)
                         apart.attachment.size = null;