using System;
using System.Collections;
using System.Collections.Generic;

namespace Core.Common.TestUtil
{
    /// <summary>
    /// This class can be used to compare doubles with a given tolerance, which can be useful to overcome double precision
    /// errors.
    /// </summary>
    public class DoubleWithToleranceComparer : IComparer, IComparer<double>
    {
        private readonly double tolerance;

        public DoubleWithToleranceComparer(double tolerance)
        {
            this.tolerance = tolerance;
        }

        public int Compare(double firstDouble, double secondDouble)
        {
            var diff = firstDouble - secondDouble;

            var tolerable = Math.Abs(diff) <= tolerance;

            var nonTolerableDiff = !tolerable && diff < 0 ? -1 : 1;

            return tolerable ? 0 : nonTolerableDiff;
        }

        public int Compare(object x, object y)
        {
            if (!(x is double) || !(y is double))
            {
                throw new ArgumentException(string.Format("Cannot compare objects other than {0} with this comparer.", typeof(Double)));
            }
            return Compare((double)x, (double)y);
        }
    }
}