using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace DTS.Common.Utilities
{
    /// <summary>
    /// handles averaging over a queue of values (like in realtime mode)
    /// </summary>
    /// <remarks>thread safe</remarks>
    public class AverageQueue
    {
        private Queue<double> Queue { get; set; }
        private readonly object _queueLock;
        private int QueueLength { get; set; }
        private double _queueSum;
        /// <summary>
        /// constructs a queue that will maintain track of the average of the contents
        /// </summary>
        /// <param name="length">the length of the queue, when contents exceed size,
        /// the first item is dequeued
        /// </param>
        public AverageQueue(int length)
        {
            Queue = new Queue<double>(length);
            QueueLength = length;
            _queueLock = new object();
        }
        /// <summary>
        /// pushes a new value into the queue
        /// </summary>
        /// <param name="newValue">value to be pushed onto queue</param>
        /// <returns>current average</returns>
        public double Push(double newValue)
        {
            lock (_queueLock)
            {
                // enqueue the new value
                Queue.Enqueue(newValue);
                // add it to the sum
                _queueSum += newValue;
                if (Queue.Count > QueueLength)
                {
                    // we have a full queue, remove the oldest
                    var discard = Queue.Dequeue();
                    // subtract it from sum
                    _queueSum -= discard;
                }
                // return the average of the queue
                return _queueSum / Queue.Count;
            }
        }

        /// <summary>
        /// returns current average
        /// </summary>
        /// <returns>current average</returns>
        public double GetAverage()
        {
            lock (_queueLock)
            {
                return _queueSum / Queue.Count;
            }
        }
        /// <summary>
        /// removes all entries in the queue.
        /// </summary>
        public void Reset()
        {
            lock (_queueLock)
            {
                Queue.Clear();
                _queueSum = 0;
            }
        }
        public double GetMin()
        {
            lock (_queueLock) { return Queue.Min(); }
        }
        public double GetMax()
        {
            lock (_queueLock) { return Queue.Max(); }
        }
    }
}