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/*
 * Copyright 2014 Netflix, Inc.
 *
 * 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 io.reactivex.netty.contexts;

import io.netty.channel.ChannelHandlerContext;
import io.netty.util.AttributeKey;

import java.util.concurrent.ConcurrentHashMap;

/**
 * A utility class to store {@link ContextsContainer} instances as channel attributes.
 *
 * @author Nitesh Kant
 */
public final class ContextAttributeStorageHelper {

    public static final String CONTAINER_ATTRIBUTE_KEY_NAME = "rxnetty_contexts_container";

    /**
     * Why is this a ConcurrentHashMap?
     * This will always be updated from within a Channel handler, which makes sure that this is always updated by a
     * single thread. However, for protocols which have multiple concurrent requests per connection (SPDY, HTTP2, etc)
     * this may not be true if the requests are potentially processed parallely. So, this is just a safety net.
     */
    public static final AttributeKey> CONTAINERS_ATTRIBUTE_KEY =
            AttributeKey.valueOf(CONTAINER_ATTRIBUTE_KEY_NAME);

    private ContextAttributeStorageHelper() {
    }

    public static void setContainer(ChannelHandlerContext ctx, String requestId, ContextsContainer container) {
        if (null == ctx) {
            throw new IllegalArgumentException("Context can not be null.");
        }
        if (null == requestId) {
            throw new IllegalArgumentException("Request id can not be null.");
        }
        if (null == container) {
            throw new IllegalArgumentException("Context container can not be null.");
        }
        ConcurrentHashMap containers = ctx.channel().attr(CONTAINERS_ATTRIBUTE_KEY).get();
        if (null == containers) {
            containers = new ConcurrentHashMap();
            ctx.channel().attr(CONTAINERS_ATTRIBUTE_KEY).set(containers);
        }

        containers.put(requestId, container);
    }

    public static ContextsContainer getContainer(ChannelHandlerContext ctx, String requestId) {
        if (null == ctx) {
            throw new IllegalArgumentException("Context can not be null.");
        }
        if (null == requestId) {
            throw new IllegalArgumentException("Request id can not be null.");
        }
        ConcurrentHashMap containers = ctx.channel().attr(CONTAINERS_ATTRIBUTE_KEY).get();
        if (null != containers) {
            return containers.get(requestId);
        }
        return null;
    }
}