// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Diagnostics.CodeAnalysis;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Options
{
    /// <inheritdoc cref="OptionKey2"/>
    [NonDefaultable]
    public readonly struct OptionKey : IEquatable<OptionKey>
    {
        /// <inheritdoc cref="OptionKey2.Option"/>
        public IOption Option { get; }
 
        /// <inheritdoc cref="OptionKey2.Language"/>
        public string? Language { get; }
 
        public OptionKey(IOption option, string? language = null)
        {
            if (option is null)
            {
                throw new ArgumentNullException(nameof(option));
            }
 
            if (language != null && !option.IsPerLanguage)
            {
                throw new ArgumentException(WorkspacesResources.A_language_name_cannot_be_specified_for_this_option);
            }
 
            if (language == null && option.IsPerLanguage)
            {
                throw new ArgumentNullException(WorkspacesResources.A_language_name_must_be_specified_for_this_option);
            }
 
            Option = option;
            Language = language;
        }
 
        public override bool Equals(object? obj)
        {
            return obj is OptionKey key &&
                   Equals(key);
        }
 
        public bool Equals(OptionKey other)
        {
            return OptionEqual(Option, other.Option) && Language == other.Language;
 
            static bool OptionEqual(IOption thisOption, IOption otherOption)
            {
                if (thisOption is not IOption2 thisOption2 ||
                    otherOption is not IOption2 otherOption2)
                {
                    // Third party definition of 'IOption'.
                    return thisOption.Equals(otherOption);
                }
 
                return thisOption2.Equals(otherOption2);
            }
        }
 
        public override int GetHashCode()
        {
            var hash = Option?.GetHashCode() ?? 0;
 
            if (Language != null)
            {
                hash = unchecked((hash * (int)0xA5555529) + Language.GetHashCode());
            }
 
            return hash;
        }
 
        public override string ToString()
        {
            if (Option is null)
            {
                return "";
            }
 
            var languageDisplay = Option.IsPerLanguage
                ? $"({Language}) "
                : string.Empty;
 
            return languageDisplay + Option.ToString();
        }
 
        public static bool operator ==(OptionKey left, OptionKey right)
            => left.Equals(right);
 
        public static bool operator !=(OptionKey left, OptionKey right)
            => !left.Equals(right);
    }
}