Fixed subject folding

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

@@ -24,12 +24,16 @@ import android.content.SharedPreferences;
 import android.net.MailTo;
 import android.net.Uri;
 import android.text.TextUtils;
+import android.util.Base64;
 
 import androidx.documentfile.provider.DocumentFile;
 import androidx.preference.PreferenceManager;
 
+import com.sun.mail.util.ASCIIUtility;
+import com.sun.mail.util.BASE64DecoderStream;
 import com.sun.mail.util.FolderClosedIOException;
 import com.sun.mail.util.MessageRemovedIOException;
+import com.sun.mail.util.QDecoderStream;
 
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Element;
@@ -37,6 +41,7 @@ import org.jsoup.nodes.Element;
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
@@ -1186,11 +1191,11 @@ public class MessageHelper {
         if (text == null)
             return null;
 
+        // https://tools.ietf.org/html/rfc2045
         // https://tools.ietf.org/html/rfc2047
         // encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
 
         int i = 0;
-        boolean first = true;
         List<MimeTextPart> parts = new ArrayList<>();
 
         while (i < text.length()) {
@@ -1211,8 +1216,6 @@ public class MessageHelper {
                 break;
 
             String plain = text.substring(i, s);
-            if (!first)
-                plain = plain.replaceAll("[ \t\n\r]$", "");
             if (!TextUtils.isEmpty(plain))
                 parts.add(new MimeTextPart(plain));
 
@@ -1222,7 +1225,6 @@ public class MessageHelper {
                     text.substring(q2 + 1, e)));
 
             i = e + 2;
-            first = false;
         }
 
         if (i < text.length())
@@ -1235,6 +1237,20 @@ public class MessageHelper {
             MimeTextPart p2 = parts.get(p + 1);
             if (p1.charset != null && p1.charset.equalsIgnoreCase(p2.charset) &&
                     p1.encoding != null && p1.encoding.equalsIgnoreCase(p2.encoding)) {
+                try {
+                    byte[] b1 = decodeWord(p1.text, p1.encoding);
+                    byte[] b2 = decodeWord(p2.text, p2.encoding);
+                    byte[] b = new byte[b1.length + b2.length];
+                    System.arraycopy(b1, 0, b, 0, b1.length);
+                    System.arraycopy(b2, 0, b, b1.length, b2.length);
+                    p1.text = new String(b, p1.charset);
+                    p1.charset = null;
+                    p2.encoding = null;
+                    parts.remove(p + 1);
+                    continue;
+                } catch (Throwable ex) {
+                    Log.w(ex);
+                }
                 p1.text += p2.text;
                 parts.remove(p + 1);
             } else
@@ -1247,6 +1263,24 @@ public class MessageHelper {
         return sb.toString();
     }
 
+    static byte[] decodeWord(String word, String encoding) throws IOException {
+        ByteArrayInputStream bis = new ByteArrayInputStream(ASCIIUtility.getBytes(word));
+
+        InputStream is;
+        if (encoding.equalsIgnoreCase("B"))
+            is = new BASE64DecoderStream(bis);
+        else if (encoding.equalsIgnoreCase("Q"))
+            is = new QDecoderStream(bis);
+        else
+            throw new UnsupportedEncodingException("Encoding=" + encoding);
+
+        int count = bis.available();
+        byte[] bytes = new byte[count];
+        count = is.read(bytes, 0, count);
+
+        return Arrays.copyOf(bytes, count);
+    }
+
     private static class MimeTextPart {
         String charset;
         String encoding;
@@ -1267,10 +1301,10 @@ public class MessageHelper {
             if (charset == null)
                 return text;
 
-            String word = "=?" + charset + "?" + encoding + "?" + text + "?=";
             try {
-                return decodeMime(MimeUtility.decodeWord(word));
+                return decodeMime(new String(decodeWord(text, encoding), charset));
             } catch (Throwable ex) {
+                String word = "=?" + charset + "?" + encoding + "?" + text + "?=";
                 Log.w(new IllegalArgumentException(word, ex));
                 return word;
             }