namespace ImageSharp.Tests.TestUtilities
{
    using System;
    using System.Collections.Generic;

    /// <summary>
    /// Allows the comparison of single-precision floating point values by precision.
    /// </summary>
    public struct FloatRoundingComparer : IEqualityComparer<float>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="FloatRoundingComparer"/> struct.
        /// </summary>
        /// <param name="precision">The number of decimal places (valid values: 0-7)</param>
        public FloatRoundingComparer(int precision)
        {
            this.Precision = precision;
        }

        /// <summary>
        /// Gets the number of decimal places (valid values: 0-7)
        /// </summary>
        public int Precision { get; }

        /// <inheritdoc />
        public bool Equals(float x, float y)
        {
            float xp = (float)Math.Round(x, this.Precision, MidpointRounding.AwayFromZero);
            float yp = (float)Math.Round(y, this.Precision, MidpointRounding.AwayFromZero);

            return Comparer<float>.Default.Compare(xp, yp) == 0;
        }

        /// <inheritdoc />
        public int GetHashCode(float obj)
        {
            unchecked
            {
                int hashCode = obj.GetHashCode();
                hashCode = (hashCode * 397) ^ this.Precision.GetHashCode();
                return hashCode;
            }
        }
    }
}