[serde, serde-hjson] Improve HjsonSerde and make it return writer instead of visitor

tweed5/serde-api/src/main/java/de/siphalor/tweed5/dataapi/api/TweedSerde.java

@@ -6,6 +6,11 @@ import java.io.OutputStream;
 
 public interface TweedSerde {
 	TweedDataReader createReader(InputStream inputStream);
-	TweedDataVisitor createWriter(OutputStream outputStream) throws IOException;
+	TweedDataWriter createWriter(OutputStream outputStream) throws IOException;
+
+	/**
+	 * Yields the file extension that should normally be used for this serde.
+	 * @return the file extension, typically with a leading dot.
+	 */
 	String getPreferredFileExtension();
 }

tweed5/serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonSerde.java

@@ -1,24 +1,29 @@
 package de.siphalor.tweed5.data.hjson;
 
 import de.siphalor.tweed5.dataapi.api.TweedDataReader;
-import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
+import de.siphalor.tweed5.dataapi.api.TweedDataWriter;
 import de.siphalor.tweed5.dataapi.api.TweedSerde;
+import lombok.RequiredArgsConstructor;
 
 import java.io.*;
+import java.nio.charset.StandardCharsets;
 
+@RequiredArgsConstructor
 public class HjsonSerde implements TweedSerde {
+	private final HjsonWriter.Options writerOptions;
+
 	@Override
 	public TweedDataReader createReader(InputStream inputStream) {
-		return new HjsonReader(new HjsonLexer(new InputStreamReader(inputStream)));
+		return new HjsonReader(new HjsonLexer(new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8))));
 	}
 
 	@Override
-	public TweedDataVisitor createWriter(OutputStream outputStream) throws IOException {
-		return new HjsonWriter(new OutputStreamWriter(outputStream), new HjsonWriter.Options());
+	public TweedDataWriter createWriter(OutputStream outputStream) {
+		return new HjsonWriter(new BufferedWriter(new OutputStreamWriter(outputStream, StandardCharsets.UTF_8)), writerOptions);
 	}
 
 	@Override
 	public String getPreferredFileExtension() {
-		return "";
+		return ".hjson";
 	}
 }