// 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;
using System.Runtime.Serialization;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis;
 
/// <summary>
/// Provides information about the way a particular symbol is being used at a symbol reference node.
/// For namespaces and types, this corresponds to values from <see cref="TypeOrNamespaceUsageInfo"/>.
/// For methods, fields, properties, events, locals and parameters, this corresponds to values from <see cref="ValueUsageInfo"/>.
/// </summary>
[DataContract]
internal readonly struct SymbolUsageInfo : IEquatable<SymbolUsageInfo>
{
    public static readonly SymbolUsageInfo None = Create(ValueUsageInfo.None);
 
    [DataMember(Order = 0)]
    public ValueUsageInfo? ValueUsageInfoOpt { get; }
 
    [DataMember(Order = 1)]
    public TypeOrNamespaceUsageInfo? TypeOrNamespaceUsageInfoOpt { get; }
 
    // Must be public since it's used for deserialization.
    public SymbolUsageInfo(ValueUsageInfo? valueUsageInfoOpt, TypeOrNamespaceUsageInfo? typeOrNamespaceUsageInfoOpt)
    {
        Debug.Assert(valueUsageInfoOpt.HasValue ^ typeOrNamespaceUsageInfoOpt.HasValue);
 
        ValueUsageInfoOpt = valueUsageInfoOpt;
        TypeOrNamespaceUsageInfoOpt = typeOrNamespaceUsageInfoOpt;
    }
 
    public static SymbolUsageInfo Create(ValueUsageInfo valueUsageInfo)
        => new(valueUsageInfo, typeOrNamespaceUsageInfoOpt: null);
 
    public static SymbolUsageInfo Create(TypeOrNamespaceUsageInfo typeOrNamespaceUsageInfo)
        => new(valueUsageInfoOpt: null, typeOrNamespaceUsageInfo);
 
    public bool IsReadFrom()
        => ValueUsageInfoOpt.HasValue && ValueUsageInfoOpt.Value.IsReadFrom();
 
    public bool IsWrittenTo()
        => ValueUsageInfoOpt.HasValue && ValueUsageInfoOpt.Value.IsWrittenTo();
 
    public bool IsNameOnly()
        => ValueUsageInfoOpt.HasValue && ValueUsageInfoOpt.Value.IsNameOnly();
 
    public override bool Equals(object? obj)
        => obj is SymbolUsageInfo && Equals((SymbolUsageInfo)obj);
 
    public bool Equals(SymbolUsageInfo other)
    {
        if (ValueUsageInfoOpt.HasValue)
        {
            return other.ValueUsageInfoOpt.HasValue &&
                ValueUsageInfoOpt.Value == other.ValueUsageInfoOpt.Value;
        }
        else
        {
            RoslynDebug.Assert(TypeOrNamespaceUsageInfoOpt.HasValue);
            return other.TypeOrNamespaceUsageInfoOpt.HasValue &&
                TypeOrNamespaceUsageInfoOpt.Value == other.TypeOrNamespaceUsageInfoOpt.Value;
        }
    }
 
    public override int GetHashCode()
        => Hash.Combine(((int?)ValueUsageInfoOpt)?.GetHashCode() ?? 0, ((int?)TypeOrNamespaceUsageInfoOpt)?.GetHashCode() ?? 0);
}