ProtobufUtils

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;

import com.google.protobuf.Message;
import com.google.protobuf.Message.Builder;
import com.yundaex.common.exception.WrappedReflectException;

public class ProtobufUtils {
    
    public static <T> byte[] marshal(T graph) {
        if(Message.class.isAssignableFrom(graph.getClass())) {
            Message msg = ((Message)graph);
            return msg.toByteArray();
        } else {
            throw new ProtobufParseException();
        }
    }

    @SuppressWarnings("unchecked")
    public static <T> T unmarshal(InputStream inputStream,Class<T> clazz) {
        Message instance = generateDefaultInstance(clazz);
        Builder builder = null;
        try {
            builder = instance.newBuilderForType().mergeFrom(inputStream);
        } catch (IOException e) {
            throw new ProtobufParseException();
        }
        if (!builder.isInitialized()) {
            // TODO which exception should be thrown here?
            throw new ProtobufParseException();
        }
        return (T) builder.build();
    }
    
    @SuppressWarnings("unchecked")
       public static <T> T unmarshal(byte[] data,Class<T> clazz) {
        Message instance = generateDefaultInstance(clazz);
        Builder builder = null;
           try {
               builder = instance.newBuilderForType().mergeFrom(data);
           } catch (IOException e) {
               throw new ProtobufParseException();
           }
        if (!builder.isInitialized()) {
           // TODO which exception should be thrown here?
           throw new ProtobufParseException();
        }
        return (T) builder.build();
     }
    
    private static <T> Message generateDefaultInstance(Class<T> instanceClass) {
          if (Message.class.isAssignableFrom(instanceClass)) {
              try {
                  Method method = instanceClass.getMethod("getDefaultInstance", new Class[0]);
                  return (Message) method.invoke(null, new Object[0]);
              } catch (Exception ex) {
                  throw new WrappedReflectException();
              }
          } else {
              throw new WrappedReflectException();
          }
      }
}