EML: show detected charset

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

@@ -64,6 +64,8 @@ import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.text.DateFormat;
 import java.util.ArrayList;
 import java.util.Enumeration;
@@ -77,6 +79,7 @@ import javax.mail.Message;
 import javax.mail.Multipart;
 import javax.mail.Part;
 import javax.mail.Session;
+import javax.mail.internet.ContentType;
 import javax.mail.internet.MimeMessage;
 
 public class ActivityEML extends ActivityBase {
@@ -422,6 +425,35 @@ public class ActivityEML extends ActivityBase {
                             .append(size > 0 ? Helper.humanReadableByteCount(size) : "?")
                             .append('\n');
 
+                    if (!part.isMimeType("multipart/*")) {
+                        Object content = part.getContent();
+                        if (content instanceof String) {
+                            String text = (String) content;
+                            Charset detected = CharsetHelper.detect(text);
+
+                            String charset;
+                            try {
+                                ContentType ct = new ContentType(part.getContentType());
+                                charset = ct.getParameter("charset");
+                            } catch (Throwable ignored) {
+                                charset = null;
+                            }
+                            if (charset == null)
+                                charset = StandardCharsets.ISO_8859_1.name();
+
+                            Charset cs = Charset.forName(charset);
+                            boolean isUtf8 = CharsetHelper.isUTF8(text.getBytes(cs));
+
+                            for (int i = 0; i < level; i++)
+                                ssb.append("  ");
+
+                            ssb.append("Detected: ")
+                                    .append(detected == null ? "?" : detected.toString())
+                                    .append(" isUTF8=").append(Boolean.toString(isUtf8))
+                                    .append('\n');
+                        }
+                    }
+
                     ssb.append('\n');
 
                     if (part.isMimeType("multipart/*")) {

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

@@ -48,11 +48,13 @@ public class CharsetHelper {
     static boolean isUTF8(String text) {
         // Get extended ASCII characters
         byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
+        return isUTF8(octets);
+    }
 
+    static boolean isUTF8(byte[] octets) {
         CharsetDecoder utf8Decoder = StandardCharsets.UTF_8.newDecoder()
                 .onMalformedInput(CodingErrorAction.REPORT)
                 .onUnmappableCharacter(CodingErrorAction.REPORT);
-
         try {
             utf8Decoder.decode(ByteBuffer.wrap(octets));
             return true;