/*
 * Copyright (c) 2005, Eric Crahen
 *
 * 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.
 *
 */

#ifndef __ZTQUEUE_H__
#define __ZTQUEUE_H__

#include "zthread/Cancelable.h"
#include "zthread/NonCopyable.h"

namespace ZThread {

  /**
   * @class Queue
   * @author Eric Crahen <http://www.code-foo.com>
   * @date <2003-07-16T11:32:42-0400>
   * @version 2.3.0
   *
   * A Queue defines an interface for a value-oriented collection objects (similar to
   * STL collections). 
   */
  template <typename T>
    class Queue : public Cancelable, private NonCopyable {
    public:

    //! Destroy a Queue
    virtual ~Queue() { }

    /**
     * Add an object to this Queue.
     *
     * @param item value to be added to the Queue
     * 
     * @exception Cancellation_Exception thrown if this Queue has been canceled.
     *
     * @pre  The Queue should not have been canceled prior to the invocation of this function.
     * @post If no exception is thrown, a copy of <i>item</i> will have been added to the Queue.
     */
    virtual void add(const T& item) = 0;

    /**
     * Add an object to this Queue.
     *
     * @param item value to be added to the Queue
     * @param timeout maximum amount of time (milliseconds) this method may block
     *        the calling thread.
     *
     * @return 
     *   - <em>true</em> if a copy of <i>item</i> can be added before <i>timeout</i> 
     *     milliseconds elapse.
     *   - <em>false</em> otherwise.
     *
     * @exception Cancellation_Exception thrown if this Queue has been canceled.
     *
     * @pre  The Queue should not have been canceled prior to the invocation of this function.
     * @post If this function returns true a copy of <i>item</i> will have been added to the Queue.
     */
    virtual bool add(const T& item, unsigned long timeout) = 0;

    /**
     * Retrieve and remove a value from this Queue.
     *
     * @return <em>T</em> next available value
     * 
     * @exception Cancellation_Exception thrown if this Queue has been canceled.
     *
     * @pre  The Queue should not have been canceled prior to the invocation of this function.
     * @post The value returned will have been removed from the Queue.
     */
    virtual T next() = 0;

    /**
     * Retrieve and remove a value from this Queue.
     *
     * @param timeout maximum amount of time (milliseconds) this method may block
     *        the calling thread.
     *
     * @return <em>T</em> next available value
     * 
     * @exception Cancellation_Exception thrown if this Queue has been canceled.
     * @exception Timeout_Exception thrown if the timeout expires before a value
     *            can be retrieved.
     *
     * @pre  The Queue should not have been canceled prior to the invocation of this function.
     * @post The value returned will have been removed from the Queue.
     */
    virtual T next(unsigned long timeout) = 0;

    /**
     * Canceling a Queue disables it, disallowing further additions. Values already
     * present in the Queue can still be retrieved and are still available through
     * the next() methods.
     *
     * Canceling a Queue more than once has no effect.
     * 
     * @post The next() methods will continue to return objects until 
     *       the Queue has been emptied. 
     * @post Once emptied, the next() methods will throw a Cancellation_Exception.
     * @post The add() methods will throw a Cancellation_Exceptions from this point on.
     */
    virtual void cancel() = 0;

    /**
     * Count the values present in this Queue. 
     *
     * @return <em>size_t</em> number of elements available in the Queue. 
     */
    virtual size_t size() = 0;

    /**
     * Count the values present in this Queue. 
     *
     * @param timeout maximum amount of time (milliseconds) this method may block
     *        the calling thread.
     *
     * @return <em>size_t</em> number of elements available in the Queue. 
     *
     * @exception Timeout_Exception thrown if <i>timeout</i> milliseconds
     *            expire before a value becomes available
     */
    virtual size_t size(unsigned long timeout) = 0;

    /**
     * Test whether any values are available in this Queue.
     *
     * @return 
     *  - <em>true</em> if there are no values available.
     *  - <em>false</em> if there <i>are</i> values available.
     */
    virtual bool empty() {

      try {

        return size() == 0;

      } catch(Cancellation_Exception&) { }

      return true;

    }

    /**
     * Test whether any values are available in this Queue.
     *
     * @param timeout maximum amount of time (milliseconds) this method may block
     *        the calling thread.
     *
     * @return 
     *  - <em>true</em> if there are no values available.
     *  - <em>false</em> if there <i>are</i> values available.
     *
     * @exception Timeout_Exception thrown if <i>timeout</i> milliseconds
     *            expire before a value becomes available
     */
    virtual bool empty(unsigned long timeout) {

      try {

        return size(timeout) == 0;

      } catch(Cancellation_Exception&) { }

      return true;

    }

  }; /* Queue */

} // namespace ZThread

#endif // __ZTQUEUE_H__