using System;
using System.Collections;
using System.Threading;

namespace CodeGuru.MultithreadedPart2
{
  /// <remarks>
  /// Example console application demonstrating the use of a
  /// monitor.
  /// </remarks>
  class MonitorExample
  {
    // Constant representing the maximum number of items to enqueue
    const int MAX_QUEUE_SIZE = 10;
    // Queue to hold items
    Queue _queue;

    /// <summary>
    /// Constructor
    /// </summary>
    public MonitorExample()
    {
      this._queue = new Queue();
    }

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main(string[] args)
    {
      // Start two threads to add and remove queue items
      MonitorExample test = new MonitorExample();
      Thread enqueueThread = new Thread(new
                                        ThreadStart(test.Enqueue));
      Thread dequeueThread = new Thread(new
                                        ThreadStart(test.Dequeue));
      enqueueThread.Start();
      dequeueThread.Start();

      // Wait to the end of the two threads then print the number of
      // queue elements
      enqueueThread.Join();
      dequeueThread.Join();
    }

    /// <summary>
    /// Add items to the queue.
    /// </summary>
    public void Enqueue()
    {
      int counter = 0;

      Monitor.Enter(this._queue);
      while( counter < MAX_QUEUE_SIZE )
      {
        // Wait while the queue is busy
        Monitor.Wait(this._queue);

        // Add one item to the queue
        Console.WriteLine("Adding item {0} to queue",
                           counter.ToString());
        this._queue.Enqueue(counter++);

      // Release the queue
      Monitor.Pulse(this._queue);
    }
    Monitor.Exit(this._queue);
  }

    /// <summary>
    /// Remove items from the queue.
    /// </summary>
    public void Dequeue()
    {
      Monitor.Enter(this._queue);

      // Release the queue because we just locked it
      // setting up the region lock
      Monitor.Pulse(this._queue);

      // Wait while the queue is busy
      // and exit on the timeout when the first thread stopped
      while(Monitor.Wait(this._queue, 500))
      {
        // Remove the first item and display it
        int counter = (int)this._queue.Dequeue();
        Console.WriteLine("Removed item {0} from queue",
                           counter.ToString());

        // Release the queue
        Monitor.Pulse(this._queue);
      }
      Monitor.Exit(this._queue);
    }
  }
}