package voldemort.serialization.protobuf;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import voldemort.serialization.SerializationUtils;
import voldemort.serialization.Serializer;

import com.google.protobuf.Message;

/**
 * A serializer that relies on Protocol Buffers for serialization and
 * deserialization. Only Java clients are supported currently, but there are
 * plans to support clients in other languages.
 * 
 * An example configuration of a value-serializer follows.
 * 
 * <pre>
 * <value-serializer>
 *   <type>protobuf</type>
 *   <schema-info>java=com.linkedin.foobar.FooMessage</schema-info>
 * </value-serializer>
 * </pre>
 * 
 * Once support for clients in other languages is available, a comma-separated
 * list will be accepted for the schema-info element (one for each language).
 */
public class ProtoBufSerializer<T extends Message> implements Serializer<T> {

    private final Method parseFromMethod;
    private final Class<T> messageClass;

    @SuppressWarnings("unchecked")
    public ProtoBufSerializer(String currentSchemaInfo) {
        try {
            this.messageClass = (Class<T>) Class.forName(SerializationUtils.getJavaClassFromSchemaInfo(currentSchemaInfo),
                                                         false,
                                                         Thread.currentThread()
                                                               .getContextClassLoader());

            if(!Message.class.isAssignableFrom(messageClass))
                throw new IllegalArgumentException("Class provided should be a subtype of Message");

            parseFromMethod = messageClass.getMethod("parseFrom", byte[].class);
        } catch(NoSuchMethodException e) {
            throw new IllegalArgumentException("No parseFrom static method found, the provided class is not a Message.",
                                               e);
        } catch(ClassNotFoundException e) {
            throw new IllegalArgumentException(e);
        }
    }

    public byte[] toBytes(T object) {
        return object.toByteArray();
    }

    public T toObject(byte[] bytes) {
        try {
            return messageClass.cast(parseFromMethod.invoke(null, bytes));
        } catch(InvocationTargetException e) {
            throw new IllegalArgumentException(e);
        } catch(IllegalAccessException e) {
            throw new IllegalArgumentException(e);
        }
    }
}