// 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.
 
#nullable disable
 
using System.Runtime.InteropServices;
using Microsoft.CodeAnalysis;
using Microsoft.VisualStudio.LanguageServices.Implementation.Interop;
using Microsoft.VisualStudio.LanguageServices.Implementation.Utilities;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.ExternalElements;
 
[ComVisible(true)]
[ComDefaultInterface(typeof(EnvDTE.CodeVariable))]
public sealed class ExternalCodeVariable : AbstractExternalCodeMember, EnvDTE.CodeVariable, EnvDTE80.CodeVariable2
{
    internal static EnvDTE.CodeVariable Create(CodeModelState state, ProjectId projectId, ISymbol symbol)
    {
        var element = new ExternalCodeVariable(state, projectId, symbol);
        return (EnvDTE.CodeVariable)ComAggregate.CreateAggregatedObject(element);
    }
 
    private ExternalCodeVariable(CodeModelState state, ProjectId projectId, ISymbol symbol)
        : base(state, projectId, symbol)
    {
    }
 
    private ITypeSymbol GetSymbolType()
    {
        var symbol = LookupSymbol();
        if (symbol != null)
        {
            switch (symbol.Kind)
            {
                case SymbolKind.Field:
                    return ((IFieldSymbol)symbol).Type;
                case SymbolKind.Property:
                    // Note: VB WithEvents fields are represented as properties
                    return ((IPropertySymbol)symbol).Type;
            }
        }
 
        return null;
    }
 
    public override EnvDTE.vsCMElement Kind
    {
        get { return EnvDTE.vsCMElement.vsCMElementVariable; }
    }
 
    public object InitExpression
    {
        get
        {
            throw Exceptions.ThrowEFail();
        }
 
        set
        {
            throw Exceptions.ThrowEFail();
        }
    }
 
    public bool IsConstant
    {
        get
        {
            if (LookupSymbol() is not IFieldSymbol fieldSymbol)
            {
                return false;
            }
 
            return fieldSymbol.IsConst
                || fieldSymbol.IsReadOnly;
        }
 
        set
        {
            throw Exceptions.ThrowEFail();
        }
    }
 
    public EnvDTE.CodeTypeRef Type
    {
        get
        {
            var type = GetSymbolType();
            if (type == null)
            {
                throw Exceptions.ThrowEFail();
            }
 
            return CodeTypeRef.Create(this.State, this, this.ProjectId, type);
        }
 
        set
        {
            throw Exceptions.ThrowEFail();
        }
    }
 
    public EnvDTE80.vsCMConstKind ConstKind
    {
        get
        {
            if (LookupSymbol() is not IFieldSymbol fieldSymbol)
            {
                return EnvDTE80.vsCMConstKind.vsCMConstKindNone;
            }
 
            if (fieldSymbol.IsConst)
            {
                return EnvDTE80.vsCMConstKind.vsCMConstKindConst;
            }
            else if (fieldSymbol.IsReadOnly)
            {
                return EnvDTE80.vsCMConstKind.vsCMConstKindReadOnly;
            }
            else
            {
                return EnvDTE80.vsCMConstKind.vsCMConstKindNone;
            }
        }
 
        set
        {
            throw Exceptions.ThrowEFail();
        }
    }
 
    public bool IsGeneric
    {
        get
        {
            // TODO: C# checks whether the field Type is generic. What does VB do?
            return GetSymbolType() is INamedTypeSymbol namedType
                ? namedType.IsGenericType
                : false;
        }
    }
}