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/*
 * MIT License
 *
 * Copyright (c) 2002-2023 Mikko Tommila
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.apfloat.internal;

import java.util.Map;
import java.util.HashMap;

import org.apfloat.ApfloatRuntimeException;

/**
 * Message passing helper class for parallel codes.
 * The message passer can hold one message for each receiver.
 * This class is safe for concurrent use from multiple threads.
 *
 * @param  The receiver type for this message passer.
 * @param  The message type for this message passer.
 *
 * @since 1.6
 * @version 1.9.0
 * @author Mikko Tommila
 */

public class MessagePasser
{
    private Map messages;

    /**
     * Default constructor.
     */

    public MessagePasser()
    {
        this.messages = new HashMap<>();
    }

    /**
     * Send a message.
     *
     * @param receiver The receiver.
     * @param message The message. Must not be null.
     */

    public synchronized void sendMessage(K receiver, V message)
    {
        assert (message != null);
        assert (!this.messages.containsKey(receiver));

        this.messages.put(receiver, message);

        notifyAll();
    }

    /**
     * Get a message if one is available. This method will not block.
     *
     * @param receiver The receiver.
     *
     * @return The message, or null if none is available.
     */

    public synchronized V getMessage(K receiver)
    {
        V message = this.messages.remove(receiver);

        return message;
    }

    /**
     * Receive a message. This method will block until a message is available.
     *
     * @param receiver The receiver.
     *
     * @return The message.
     */

    public synchronized V receiveMessage(K receiver)
        throws ApfloatRuntimeException
    {
        V message;
        while ((message = this.messages.remove(receiver)) == null)
        {
            try
            {
                wait();
            }
            catch (InterruptedException ie)
            {
                throw new ApfloatInternalException("Wait for received message interrupted", ie);
            }
        }

        return message;
    }
}