using System;

namespace Umbraco.Core.Collections
{
    /// <summary>
    /// Represents a composite key of (int, string) for fast dictionaries.
    /// </summary>
    /// <remarks>
    /// <para>The integer part of the key must be greater than, or equal to, zero.</para>
    /// <para>The string part of the key is case-insensitive.</para>
    /// <para>Null is a valid value for both parts.</para>
    /// </remarks>
    public struct CompositeIntStringKey : IEquatable<CompositeIntStringKey>
    {
        private readonly int _key1;
        private readonly string _key2;

        /// <summary>
        /// Initializes a new instance of the <see cref="CompositeIntStringKey"/> struct.
        /// </summary>
        public CompositeIntStringKey(int? key1, string key2)
        {
            if (key1 < 0) throw new ArgumentOutOfRangeException(nameof(key1));
            _key1 = key1 ?? -1;
            _key2 = key2?.ToLowerInvariant() ?? "NULL";
        }

        public bool Equals(CompositeIntStringKey other)
            => _key2 == other._key2 && _key1 == other._key1;

        public override bool Equals(object obj)
            => obj is CompositeIntStringKey other && _key2 == other._key2 && _key1 == other._key1;

        public override int GetHashCode()
            => _key2.GetHashCode() * 31 + _key1;

        public static bool operator ==(CompositeIntStringKey key1, CompositeIntStringKey key2)
            => key1._key2 == key2._key2 && key1._key1 == key2._key1;

        public static bool operator !=(CompositeIntStringKey key1, CompositeIntStringKey key2)
            => key1._key2 != key2._key2 || key1._key1 != key2._key1;
    }
}