// Copyright (C) Stichting Deltares 2024. All rights reserved.
// 
// This file is part of the application DAM - UI.
// 
// DAM - UI is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// 
// All names, logos, and references to "Deltares" are registered trademarks of
// Stichting Deltares and remain full property of Stichting Deltares at all times.
// All rights reserved.

using System;
using System.Collections.Generic;

namespace Deltares.Dam.StixFileReader.Tests.TestUtils;

/// <summary>
/// Class which contains methods for comparing <see cref="double"/>.
/// </summary>
public class DoubleEqualityComparer : IEqualityComparer<double>
{
    private readonly double tolerance;

    /// <summary>
    /// Create a new instance of <see cref="DoubleEqualityComparer"/>.
    /// </summary>
    /// <param name="tolerance">The tolerance to use when comparing.</param>
    public DoubleEqualityComparer(double tolerance)
    {
        this.tolerance = tolerance;
    }

    /// <summary>
    /// Creates a new instance of <see cref="DoubleEqualityComparer"/>.
    /// </summary>
    public DoubleEqualityComparer() : this(0) {}

    /// <inheritdoc />
    public bool Equals(double x, double y)
    {
        return AreEqual(x, y);
    }

    /// <inheritdoc />
    public int GetHashCode(double obj)
    {
        unchecked
        {
            return 51 * (int) obj;
        }
    }

    private bool AreEqual(double x, double y)
    {
        return IsBothNaN(x, y) || IsValueEqual(x, y);
    }

    private bool IsValueEqual(double x, double y)
    {
        return x == y || Math.Abs(x - y) <= tolerance;
    }

    private static bool IsBothNaN(double x, double y)
    {
        return double.IsNaN(x) && double.IsNaN(y);
    }
}