/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cassandra.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.db.*;
import org.apache.cassandra.db.partitions.*;
import org.apache.cassandra.net.MessageIn;
import org.apache.cassandra.utils.concurrent.Accumulator;

public abstract class ResponseResolver
{
    protected static final Logger logger = LoggerFactory.getLogger(ResponseResolver.class);

    protected final Keyspace keyspace;
    protected final ReadCommand command;
    protected final ConsistencyLevel consistency;

    // Accumulator gives us non-blocking thread-safety with optimal algorithmic constraints
    protected final Accumulator<MessageIn<ReadResponse>> responses;

    public ResponseResolver(Keyspace keyspace, ReadCommand command, ConsistencyLevel consistency, int maxResponseCount)
    {
        this.keyspace = keyspace;
        this.command = command;
        this.consistency = consistency;
        this.responses = new Accumulator<>(maxResponseCount);
    }

    public abstract PartitionIterator getData();
    public abstract PartitionIterator resolve() throws DigestMismatchException;

    
Compares received responses, potentially triggering a digest mismatch (for a digest resolver) and read-repairs
(for a data resolver).
 This is functionally equivalent to calling resolve() and consuming the result, but can be slightly more efficient in some case due to the fact that we don't care about the result itself. This is used when doing asynchronous read-repairs. 
Throws:
DigestMismatchException – if it's a digest resolver and the responses don't match./**
     * Compares received responses, potentially triggering a digest mismatch (for a digest resolver) and read-repairs
     * (for a data resolver).
     * <p>
     * This is functionally equivalent to calling {@link #resolve()} and consuming the result, but can be slightly more
     * efficient in some case due to the fact that we don't care about the result itself. This is used when doing
     * asynchronous read-repairs.
     *
     * @throws DigestMismatchException if it's a digest resolver and the responses don't match.
     */
    public abstract void compareResponses() throws DigestMismatchException;

    public abstract boolean isDataPresent();

    public void preprocess(MessageIn<ReadResponse> message)
    {
        responses.add(message);
    }

    public Iterable<MessageIn<ReadResponse>> getMessages()
    {
        return responses;
    }
}