package org.infinispan.server.resp.commands.list;

import java.util.List;
import java.util.concurrent.CompletionStage;

import org.infinispan.multimap.impl.EmbeddedMultimapListCache;
import org.infinispan.server.resp.Resp3Handler;
import org.infinispan.server.resp.RespCommand;
import org.infinispan.server.resp.RespRequestHandler;
import org.infinispan.server.resp.commands.Resp3Command;
import org.infinispan.server.resp.serialization.Resp3Response;

import io.netty.channel.ChannelHandlerContext;

/**
 * @link https://redis.io/commands/llen/
 *
 * Returns the length of the list stored at key. If key does not exist,
 * it is interpreted as an empty list and 0 is returned.
 * When the value at key is not a list, an error is returned.
 *
 * @since 15.0
 */
public class LLEN extends RespCommand implements Resp3Command {
   public LLEN() {
      super(2, 1, 1, 1);
   }

   @Override
   public CompletionStage<RespRequestHandler> perform(Resp3Handler handler,
                                                      ChannelHandlerContext ctx,
                                                      List<byte[]> arguments) {

      byte[] key = arguments.get(0);
      EmbeddedMultimapListCache<byte[], byte[]> listMultimap = handler.getListMultimap();
      return handler.stageToReturn(listMultimap.size(key), ctx, Resp3Response.INTEGER);
   }

}
