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/*******************************************************************************
 * Copyright 2011 Netflix
 *
 * Licensed 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 com.netflix.dyno.connectionpool.impl;

import com.netflix.dyno.connectionpool.BaseOperation;
import com.netflix.dyno.connectionpool.Connection;
import com.netflix.dyno.connectionpool.Host;
import com.netflix.dyno.connectionpool.HostConnectionPool;
import com.netflix.dyno.connectionpool.exception.NoAvailableHostsException;
import com.netflix.dyno.connectionpool.impl.lb.HostToken;

import java.util.Collection;
import java.util.List;
import java.util.Map;

/**
 * Interface that encapsulates a strategy for selecting a {@link Connection} to a {@link Host} for the given {@link BaseOperation}
 *
 * @param 
 * @author poberai
 */
public interface HostSelectionStrategy {

    /**
     * @param op
     * @param hashtag
     * @return
     * @throws NoAvailableHostsException
     */
    HostConnectionPool getPoolForOperation(BaseOperation op, String hashtag)
            throws NoAvailableHostsException;

    /**
     * @param ops
     * @return
     * @throws NoAvailableHostsException
     */
    Map, BaseOperation> getPoolsForOperationBatch(Collection> ops) throws NoAvailableHostsException;

    /**
     * @return
     */
    List> getOrderedHostPools();

    /**
     * @param token
     * @return
     */
    HostConnectionPool getPoolForToken(Long token);

    /**
     * @param start
     * @param end
     * @return
     */
    List> getPoolsForTokens(Long start, Long end);

    /**
     * Finds the server Host that owns the specified key.
     *
     * @param key
     * @return {@link HostToken}
     * @throws UnsupportedOperationException for non-token aware load balancing strategies
     */
    HostToken getTokenForKey(String key) throws UnsupportedOperationException;


    /**
     * Finds the server Host that owns the specified binary key.
     *
     * @param key
     * @return {@link HostToken}
     * @throws UnsupportedOperationException for non-token aware load balancing strategies
     */
    HostToken getTokenForKey(byte[] key) throws UnsupportedOperationException;


    /**
     * Init the connection pool with the set of hosts provided
     *
     * @param hostPools
     */
    void initWithHosts(Map> hostPools);

    /**
     * Add a host to the selection strategy. This is useful when the underlying dynomite topology changes.
     *
     * @param {@link   com.netflix.dyno.connectionpool.impl.lb.HostToken}
     * @param hostPool
     * @return true/false indicating whether the pool was indeed added
     */
    boolean addHostPool(HostToken host, HostConnectionPool hostPool);

    /**
     * Remove a host from the selection strategy. This is useful when the underlying dynomite topology changes.
     *
     * @param {@link com.netflix.dyno.connectionpool.impl.lb.HostToken}
     * @return true/false indicating whether the pool was indeed removed
     */
    boolean removeHostPool(HostToken host);

    boolean isTokenAware();

    boolean isEmpty();

    interface HostSelectionStrategyFactory {

        /**
         * Create/Return a HostSelectionStrategy
         *
         * @return HostSelectionStrategy
         */
        public HostSelectionStrategy vendPoolSelectionStrategy();
    }


}