// 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.Linq;
using System.Runtime.InteropServices;
using Microsoft.CodeAnalysis;
using Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Collections;
using Microsoft.VisualStudio.LanguageServices.Implementation.Interop;
using Microsoft.VisualStudio.LanguageServices.Implementation.Utilities;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.ExternalElements
{
    [ComVisible(true)]
    [ComDefaultInterface(typeof(EnvDTE.CodeFunction))]
    public sealed class ExternalCodeFunction : AbstractExternalCodeMember, ICodeElementContainer<ExternalCodeParameter>, EnvDTE.CodeFunction, EnvDTE80.CodeFunction2
    {
        internal static EnvDTE.CodeFunction Create(CodeModelState state, ProjectId projectId, IMethodSymbol symbol)
        {
            var element = new ExternalCodeFunction(state, projectId, symbol);
            return (EnvDTE.CodeFunction)ComAggregate.CreateAggregatedObject(element);
        }
 
        private ExternalCodeFunction(CodeModelState state, ProjectId projectId, IMethodSymbol symbol)
            : base(state, projectId, symbol)
        {
        }
 
        private IMethodSymbol MethodSymbol
        {
            get { return (IMethodSymbol)LookupSymbol(); }
        }
 
        EnvDTE.CodeElements ICodeElementContainer<ExternalCodeParameter>.GetCollection()
            => this.Parameters;
 
        public override EnvDTE.vsCMElement Kind
        {
            get { return EnvDTE.vsCMElement.vsCMElementFunction; }
        }
 
        public EnvDTE.vsCMFunction FunctionKind
        {
            get
            {
                // TODO: Verify VB implementation
                switch (MethodSymbol.MethodKind)
                {
                    case MethodKind.Constructor:
                        return EnvDTE.vsCMFunction.vsCMFunctionConstructor;
                    case MethodKind.Destructor:
                        return EnvDTE.vsCMFunction.vsCMFunctionDestructor;
                    case MethodKind.UserDefinedOperator:
                    case MethodKind.Conversion:
                        return EnvDTE.vsCMFunction.vsCMFunctionOperator;
                    case MethodKind.Ordinary:
                        return EnvDTE.vsCMFunction.vsCMFunctionFunction;
                    default:
                        throw Exceptions.ThrowEFail();
                }
            }
        }
 
        public bool IsOverloaded
        {
            get
            {
                var symbol = (IMethodSymbol)LookupSymbol();
 
                // Only methods and constructors can be overloaded
                if (symbol.MethodKind is not MethodKind.Ordinary and
                    not MethodKind.Constructor)
                {
                    return false;
                }
 
                var methodsOfName = symbol.ContainingType.GetMembers(symbol.Name)
                                                         .Where(m => m.Kind == SymbolKind.Method);
 
                return methodsOfName.Count() > 1;
            }
        }
 
        public EnvDTE.CodeElements Overloads
        {
            get
            {
                return ExternalOverloadsCollection.Create(this.State, this, this.ProjectId);
            }
        }
 
        public EnvDTE.CodeTypeRef Type
        {
            get
            {
                // TODO: What if ReturnType is null?
                return CodeTypeRef.Create(this.State, this, this.ProjectId, MethodSymbol.ReturnType);
            }
 
            set
            {
                throw Exceptions.ThrowEFail();
            }
        }
 
        public bool IsGeneric
        {
            get { return MethodSymbol.IsGenericMethod; }
        }
 
        public EnvDTE80.vsCMOverrideKind OverrideKind
        {
            get
            {
                // TODO: Verify VB implementation
 
                var symbol = MethodSymbol;
                var result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindNone;
 
                if (symbol.IsAbstract)
                {
                    result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindAbstract;
                }
 
                if (symbol.IsVirtual)
                {
                    result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindVirtual;
                }
 
                if (symbol.IsOverride)
                {
                    result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindOverride;
                }
 
                if (symbol.HidesBaseMethodsByName)
                {
                    result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindNew;
                }
 
                if (symbol.IsSealed)
                {
                    result = EnvDTE80.vsCMOverrideKind.vsCMOverrideKindSealed;
                }
 
                return result;
            }
 
            set
            {
                throw Exceptions.ThrowEFail();
            }
        }
    }
}