/*
 * AverageShortValueOverTime.cs
 *
 * Copyright © 2009
 * Diversified Technical Systems, Inc.
 * All Rights Reserved
 */

using DTS.Common.Utilities.Logging;
using System.Collections.Generic;
using System.Linq;

namespace DTS.Common.Utilities
{
    /// <summary>
    /// A class to represent the average value of a set of shorts over time.
    /// </summary>
    public class AverageShortValueOverTime
        : AverageValueOverTime<short>
    {
        /// <summary>
        /// Initialize an instance of the AverageShortValueOverTime class, assuming that no
        /// averaging has been done yet.
        /// </summary>
        /// <param name="initialTime">
        /// The <see cref="double"/> begin time of the average (using the time units specified
        /// by the "TimeUnitSymbol" property.
        /// </param>
        /// 
        /// <param name="sampleRate">
        /// The <see cref="double"/> sample rate of the items being averaged (using the time units
        /// specifed by the "TimeUnitSymbol" property.
        /// </param>
        /// 
        /// <param name="timeUnitSymbol">
        /// The <see cref="string"/> time unit description for begin/end times and the sample rate.
        /// </param>
        /// 
        public AverageShortValueOverTime(double initialTime,
                                          double sampleRate,
                                          string timeUnitSymbol)
            : base(initialTime,
                    sampleRate,
                    0,
                    timeUnitSymbol)
        {
        }

        /// <summary>
        /// Initialize an instance of the AverageShortValueOverTime class.
        /// </summary>
        /// 
        /// <param name="beginTime">
        /// The <see cref="double"/> begin time of the average (using the time units specified
        /// by the "TimeUnitSymbol" property.
        /// </param>
        /// 
        /// <param name="endTime">
        /// The <see cref="double"/> end time of the average (using the time units specified
        /// by the "TimeUnitSymbol" property.
        /// </param>
        /// 
        /// <param name="sampleRate">
        /// The <see cref="double"/> sample rate of the items being averaged (using the time units
        /// specifed by the "TimeUnitSymbol" property.
        /// </param>
        /// 
        /// <param name="initialAverage">
        /// The <see cref="short"/> pre-existing average to be appended to.
        /// </param>
        /// 
        /// <param name="timeUnitSymbol">
        /// The <see cref="string"/> time unit description for begin/end times and the sample rate.
        /// </param>
        /// 
        public AverageShortValueOverTime(double beginTime,
                                          double endTime,
                                          double sampleRate,
                                          short initialAverage,
                                          string timeUnitSymbol)
            : base(beginTime,
                    endTime,
                    sampleRate,
                    initialAverage,
                    timeUnitSymbol)
        {
        }

        /// <summary>
        /// Append the specified <see cref="T:List"/> of values to the running average.
        /// </summary>
        /// 
        /// <param name="values">
        /// The <see cref="T:List"/> of <see cref="short"/>s to be appended to the running average.
        /// </param>
        /// 
        public override void AppendValues(List<short> values)
        {
            AppendValues(values.ToArray());
        }

        /// <summary>
        /// Append the specified array of values to the running average.
        /// </summary>
        /// 
        /// <param name="values">
        /// The array of <see cref="short"/>s to be appended to the running average.
        /// </param>
        /// 
        public override void AppendValues(short[] values)
        {
            if (0 == values.Length)
            {
                APILogger.Log($"AverageShortValueOverTime.AppendValues - no values to append");
                return;
            }
            //
            // Get the average of the appended values by themselves.
            //
            var numAppendixSamples = values.Length;
            var appendixSamples = new double[numAppendixSamples];
            for (var i = 0; i < numAppendixSamples; i++)
                appendixSamples[i] = values[i];
            var appendixAverage = appendixSamples.Average();

            //
            // Get the previous average and number of samples.
            //
            var numPreviousSamples = (ulong)((EndTime - BeginTime) * SampleRate);
            double previousAverage = CurrentAverage;

            //
            // Now combine them with the previous average values (with the
            // appropriate weighting) to get a new combined average.
            //
            var numTotalSamples = numPreviousSamples + (ulong)numAppendixSamples;
            var combinedAverage = ((previousAverage * numPreviousSamples) + (appendixAverage * numAppendixSamples)) / numTotalSamples;

            // Save our new average.
            CurrentAverage = (short)combinedAverage;

            // Update the end time to take into account the appended data.
            EndTime += (numAppendixSamples / SampleRate);
        }
    }
}