// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is furnished to do
// so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

namespace YamlDotNet.Core
{
    /// <summary>
    /// Supports implementations of <see cref="object.GetHashCode"/> by providing methods to combine two hash codes.
    /// </summary>
    internal static class HashCode
    {
        /// <summary>
        /// Combines two hash codes.
        /// </summary>
        /// <param name="h1">The first hash code.</param>
        /// <param name="h2">The second hash code.</param>
        /// <returns></returns>
        public static int CombineHashCodes(int h1, int h2)
        {
            return ((h1 << 5) + h1) ^ h2;
        }

        public static int CombineHashCodes(int h1, object? o2)
        {
            return CombineHashCodes(h1, GetHashCode(o2));
        }

        public static int CombineHashCodes(object? first, params object?[] others)
        {
            var hashCode = GetHashCode(first);
            foreach (var other in others)
            {
                hashCode = CombineHashCodes(hashCode, other);
            }
            return hashCode;
        }

        private static int GetHashCode(object? obj)
        {
            return obj != null ? obj.GetHashCode() : 0;
        }
    }
}
