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package com.sun.grizzly.async;

import com.sun.grizzly.util.DataStructures;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Class implements {@link Map}-like collection, maps keys to values, where
 * single key could have queue of correspondent values.
 *
 * @author Alexey Stashok
 */
public class AsyncQueue {
    private final ConcurrentMap queueMap =
            new ConcurrentHashMap();
    
    /**
     * Add data to the {@link AsyncQueue}, corresponding to the given
     * E key
     * 
     * @param key E
     * @param queueRecord data unit
     */
    public void offer(K key, E queueRecord) {
        AsyncQueueEntry entry = obtainAsyncQueueEntry(key);
        entry.queue.offer(queueRecord);
    }
    
    /**
     * Get head element of E key related queue.
     * Element will not be removed from queue.
     * 
     * @param key K
     *
     * @return E data unit
     */
    public E peek(K key) {
        AsyncQueueEntry entry = queueMap.get(key);
        if (entry != null) {
            return entry.queue.peek();
        }
        
        return null;
    }

    /**
     * Get head element of K key related queue.
     * Element will be removed from queue.
     * 
     * @param key K
     *
     * @return E data unit
     */
    public E poll(K key) {
        AsyncQueueEntry entry = queueMap.get(key);
        if (entry != null) {
            return entry.queue.poll();
        }
        
        return null;
    }

    /**
     * Remove head element of K key related queue.
     * 
     * @param key K
     * @return removed entry
     */
    public AsyncQueueEntry removeEntry(K key) {
        return queueMap.remove(key);
    }

    /**
     * Get the size of K key related queue.
     * 
     * @param key K
     * @return size of K key related queue.
     */
    public int size(K key) {
        AsyncQueueEntry entry = queueMap.get(key);
        return entry == null ? 0 : entry.queue.size();
    }
    
    /**
     * Checks if K key related queue is empty.
     * 
     * @param key K
     * @return true, if K key related queue is empty, false otherwise
     */
    public boolean isEmpty(K key) {
        AsyncQueueEntry entry = queueMap.get(key);
        return entry == null || entry.queue.isEmpty();
    }

    public void clear() {
        queueMap.clear();
    }

    protected AsyncQueueEntry obtainAsyncQueueEntry(K key) {
        AsyncQueueEntry entry = queueMap.get(key);
        if (entry == null) {
            synchronized(key) {
                entry = queueMap.get(key);
                if (entry == null) {
                    entry = new AsyncQueueEntry();
                    queueMap.put(key, entry);
                }
            }
        }
        return entry;
    }

    protected AsyncQueueEntry getAsyncQueueEntry(K key) {
        return queueMap.get(key);
    }
    /**
     * {@link AsyncQueue} data unit
     */
    public class AsyncQueueEntry {
        public final Queue queue;
        public final AtomicReference currentElement;
        public final ReentrantLock queuedActionLock;
        // Amound of data, processed by the key
        public final AtomicInteger processedDataSize;
        // Number of queue elements processed
        public final AtomicInteger processedElementsCount;
        // Total number of elements were requested to be processed
        public final AtomicInteger totalElementsCount;
        // Number of elements passed throw the async queue (not processed directly)
        public final AtomicInteger queuedElementsCount;
        
        protected OperationResult tmpResult;

        public AsyncQueueEntry() {
            queue = (Queue) DataStructures.getCLQinstance();
            currentElement = new AtomicReference();
            queuedActionLock = new ReentrantLock();
            processedDataSize = new AtomicInteger();
            processedElementsCount = new AtomicInteger();
            totalElementsCount = new AtomicInteger();
            queuedElementsCount = new AtomicInteger();
            tmpResult = new OperationResult();
        }
    }    
}