// 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;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Emit;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Symbols;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.CSharp.Symbols.Retargeting
{
    /// <summary>
    /// Represents a method in a RetargetingModuleSymbol. Essentially this is a wrapper around 
    /// another MethodSymbol that is responsible for retargeting symbols from one assembly to another. 
    /// It can retarget symbols for multiple assemblies at the same time.
    /// </summary>
    internal sealed class RetargetingMethodSymbol : WrappedMethodSymbol
    {
        /// <summary>
        /// Owning RetargetingModuleSymbol.
        /// </summary>
        private readonly RetargetingModuleSymbol _retargetingModule;

        /// <summary>
        /// The underlying MethodSymbol.
        /// </summary>
        private readonly MethodSymbol _underlyingMethod;

        private ImmutableArray<TypeParameterSymbol> _lazyTypeParameters;

        private ImmutableArray<ParameterSymbol> _lazyParameters;

        private ImmutableArray<CustomModifier> _lazyRefCustomModifiers;

        /// <summary>
        /// Retargeted custom attributes
        /// </summary>
        private ImmutableArray<CSharpAttributeData> _lazyCustomAttributes;

        /// <summary>
        /// Retargeted return type custom attributes
        /// </summary>
        private ImmutableArray<CSharpAttributeData> _lazyReturnTypeCustomAttributes;

        private ImmutableArray<MethodSymbol> _lazyExplicitInterfaceImplementations;
        private CachedUseSiteInfo<AssemblySymbol> _lazyCachedUseSiteInfo = CachedUseSiteInfo<AssemblySymbol>.Uninitialized;

        private TypeWithAnnotations.Boxed _lazyReturnType;

        private UnmanagedCallersOnlyAttributeData _lazyUnmanagedAttributeData = UnmanagedCallersOnlyAttributeData.Uninitialized;

        public RetargetingMethodSymbol(RetargetingModuleSymbol retargetingModule, MethodSymbol underlyingMethod)
        {
            Debug.Assert((object)retargetingModule != null);
            Debug.Assert((object)underlyingMethod != null);
            Debug.Assert(!(underlyingMethod is RetargetingMethodSymbol));

            _retargetingModule = retargetingModule;
            _underlyingMethod = underlyingMethod;
        }

        private RetargetingModuleSymbol.RetargetingSymbolTranslator RetargetingTranslator
        {
            get
            {
                return _retargetingModule.RetargetingTranslator;
            }
        }

        public RetargetingModuleSymbol RetargetingModule
        {
            get
            {
                return _retargetingModule;
            }
        }

        public override MethodSymbol UnderlyingMethod
        {
            get
            {
                return _underlyingMethod;
            }
        }

        public override ImmutableArray<TypeParameterSymbol> TypeParameters
        {
            get
            {
                if (_lazyTypeParameters.IsDefault)
                {
                    if (!IsGenericMethod)
                    {
                        _lazyTypeParameters = ImmutableArray<TypeParameterSymbol>.Empty;
                    }
                    else
                    {
                        ImmutableInterlocked.InterlockedCompareExchange(ref _lazyTypeParameters,
                            this.RetargetingTranslator.Retarget(_underlyingMethod.TypeParameters), default(ImmutableArray<TypeParameterSymbol>));
                    }
                }

                return _lazyTypeParameters;
            }
        }

        public override ImmutableArray<TypeWithAnnotations> TypeArgumentsWithAnnotations
        {
            get
            {
                if (IsGenericMethod)
                {
                    return GetTypeParametersAsTypeArguments();
                }
                else
                {
                    return ImmutableArray<TypeWithAnnotations>.Empty;
                }
            }
        }

        public override bool IsAsync => _underlyingMethod.IsAsync;

        internal sealed override ThreeState RuntimeAsyncMethodGenerationAttributeSetting => throw ExceptionUtilities.Unreachable();

        public override TypeWithAnnotations ReturnTypeWithAnnotations
        {
            get
            {
                if (_lazyReturnType is null)
                {
                    Interlocked.CompareExchange(ref _lazyReturnType,
                                                new TypeWithAnnotations.Boxed(this.RetargetingTranslator.Retarget(_underlyingMethod.ReturnTypeWithAnnotations, RetargetOptions.RetargetPrimitiveTypesByTypeCode, this.ContainingType)),
                                                null);
                }
                return _lazyReturnType.Value;
            }
        }

        public override ImmutableArray<CustomModifier> RefCustomModifiers
        {
            get
            {
                return RetargetingTranslator.RetargetModifiers(_underlyingMethod.RefCustomModifiers, ref _lazyRefCustomModifiers);
            }
        }

        public override ImmutableArray<ParameterSymbol> Parameters
        {
            get
            {
                if (_lazyParameters.IsDefault)
                {
                    ImmutableInterlocked.InterlockedInitialize(ref _lazyParameters, this.RetargetParameters());
                }

                return _lazyParameters;
            }
        }

        private ImmutableArray<ParameterSymbol> RetargetParameters()
        {
            var list = _underlyingMethod.Parameters;
            int count = list.Length;

            if (count == 0)
            {
                return ImmutableArray<ParameterSymbol>.Empty;
            }
            else
            {
                var parameters = ArrayBuilder<ParameterSymbol>.GetInstance(count);

                for (int i = 0; i < count; i++)
                {
                    parameters.Add(new RetargetingMethodParameterSymbol(this, list[i]));
                }

                return parameters.ToImmutableAndFree();
            }
        }

        public override Symbol AssociatedSymbol
        {
            get
            {
                var associatedPropertyOrEvent = _underlyingMethod.AssociatedSymbol;
                return (object)associatedPropertyOrEvent == null ? null : this.RetargetingTranslator.Retarget(associatedPropertyOrEvent);
            }
        }

        public override Symbol ContainingSymbol
        {
            get
            {
                return this.RetargetingTranslator.Retarget(_underlyingMethod.ContainingSymbol);
            }
        }

        internal override MarshalPseudoCustomAttributeData ReturnValueMarshallingInformation
        {
            get
            {
                return _retargetingModule.RetargetingTranslator.Retarget(_underlyingMethod.ReturnValueMarshallingInformation);
            }
        }

        public override ImmutableArray<CSharpAttributeData> GetAttributes()
        {
            return this.RetargetingTranslator.GetRetargetedAttributes(_underlyingMethod.GetAttributes(), ref _lazyCustomAttributes);
        }

        internal override IEnumerable<CSharpAttributeData> GetCustomAttributesToEmit(PEModuleBuilder moduleBuilder)
        {
            return this.RetargetingTranslator.RetargetAttributes(_underlyingMethod.GetCustomAttributesToEmit(moduleBuilder));
        }

        // Get return type attributes
        public override ImmutableArray<CSharpAttributeData> GetReturnTypeAttributes()
        {
            return this.RetargetingTranslator.GetRetargetedAttributes(_underlyingMethod.GetReturnTypeAttributes(), ref _lazyReturnTypeCustomAttributes);
        }

#nullable enable
        internal override UnmanagedCallersOnlyAttributeData? GetUnmanagedCallersOnlyAttributeData(bool forceComplete)
        {
            if (ReferenceEquals(_lazyUnmanagedAttributeData, UnmanagedCallersOnlyAttributeData.Uninitialized))
            {
                var data = _underlyingMethod.GetUnmanagedCallersOnlyAttributeData(forceComplete);
                if (ReferenceEquals(data, UnmanagedCallersOnlyAttributeData.Uninitialized)
                    || ReferenceEquals(data, UnmanagedCallersOnlyAttributeData.AttributePresentDataNotBound))
                {
                    // Underlying hasn't been found yet either, just return it. We'll check again the next
                    // time this is called
                    return data;
                }

                if (data?.CallingConventionTypes.IsEmpty == false)
                {
                    var builder = PooledHashSet<INamedTypeSymbolInternal>.GetInstance();
                    foreach (var identifier in data.CallingConventionTypes)
                    {
                        builder.Add((INamedTypeSymbolInternal)RetargetingTranslator.Retarget((NamedTypeSymbol)identifier));
                    }

                    data = UnmanagedCallersOnlyAttributeData.Create(builder.ToImmutableHashSet());
                    builder.Free();
                }

                Interlocked.CompareExchange(ref _lazyUnmanagedAttributeData, data, UnmanagedCallersOnlyAttributeData.Uninitialized);
            }

            return _lazyUnmanagedAttributeData;
        }

        internal sealed override bool HasSpecialNameAttribute => throw ExceptionUtilities.Unreachable();

        internal override bool TryGetThisParameter(out ParameterSymbol? thisParameter)
        {
            if (!_underlyingMethod.TryGetThisParameter(out var underlyingParameter))
            {
                thisParameter = null;
                return false;
            }

            thisParameter = underlyingParameter is { }
                ? new ThisParameterSymbol(this)
                : null;
            return true;
        }

        internal override int TryGetOverloadResolutionPriority()
            => _underlyingMethod.TryGetOverloadResolutionPriority();
#nullable disable

        public override AssemblySymbol ContainingAssembly
        {
            get
            {
                return _retargetingModule.ContainingAssembly;
            }
        }

        internal override ModuleSymbol ContainingModule
        {
            get
            {
                return _retargetingModule;
            }
        }

        internal override bool IsExplicitInterfaceImplementation
        {
            get { return _underlyingMethod.IsExplicitInterfaceImplementation; }
        }

        public override ImmutableArray<MethodSymbol> ExplicitInterfaceImplementations
        {
            get
            {
                if (_lazyExplicitInterfaceImplementations.IsDefault)
                {
                    ImmutableInterlocked.InterlockedCompareExchange(
                        ref _lazyExplicitInterfaceImplementations,
                        this.RetargetExplicitInterfaceImplementations(),
                        default(ImmutableArray<MethodSymbol>));
                }
                return _lazyExplicitInterfaceImplementations;
            }
        }

        private ImmutableArray<MethodSymbol> RetargetExplicitInterfaceImplementations()
        {
            var impls = _underlyingMethod.ExplicitInterfaceImplementations;

            if (impls.IsEmpty)
            {
                return impls;
            }

            // CONSIDER: we could skip the builder until the first time we see a different method after retargeting

            var builder = ArrayBuilder<MethodSymbol>.GetInstance();

            for (int i = 0; i < impls.Length; i++)
            {
                var retargeted = this.RetargetingTranslator.Retarget(impls[i], MemberSignatureComparer.RetargetedExplicitImplementationComparer);
                if ((object)retargeted != null)
                {
                    builder.Add(retargeted);
                }
            }

            return builder.ToImmutableAndFree();
        }

        /// <summary>
        /// The explicitly overridden method (e.g. as would be declared in the PE method in covariant return scenarios).
        /// </summary>
        internal MethodSymbol ExplicitlyOverriddenClassMethod
        {
            get
            {
                return
                    _underlyingMethod.RequiresExplicitOverride(out _)
                        ? this.RetargetingTranslator.Retarget(_underlyingMethod.OverriddenMethod, MemberSignatureComparer.RetargetedExplicitImplementationComparer)
                        : null;
            }
        }

        internal override UseSiteInfo<AssemblySymbol> GetUseSiteInfo()
        {
            if (!_lazyCachedUseSiteInfo.IsInitialized)
            {
                AssemblySymbol primaryDependency = PrimaryDependency;
                var result = new UseSiteInfo<AssemblySymbol>(primaryDependency);
                CalculateUseSiteDiagnostic(ref result);
                _lazyCachedUseSiteInfo.Initialize(primaryDependency, result);
            }

            return _lazyCachedUseSiteInfo.ToUseSiteInfo(PrimaryDependency);
        }

        internal sealed override CSharpCompilation DeclaringCompilation // perf, not correctness
        {
            get { return null; }
        }

        internal override bool GenerateDebugInfo
        {
            get { return false; }
        }

        internal override int CalculateLocalSyntaxOffset(int localPosition, SyntaxTree localTree)
        {
            // retargeting symbols refer to a symbol from another compilation, they don't define locals in the current compilation
            throw ExceptionUtilities.Unreachable();
        }

        internal override bool IsNullableAnalysisEnabled() => throw ExceptionUtilities.Unreachable();

        internal sealed override bool HasAsyncMethodBuilderAttribute(out TypeSymbol builderArgument)
        {
            if (_underlyingMethod.HasAsyncMethodBuilderAttribute(out builderArgument))
            {
                builderArgument = this.RetargetingTranslator.Retarget(builderArgument, RetargetOptions.RetargetPrimitiveTypesByTypeCode);
                return true;
            }

            builderArgument = null;
            return false;
        }

        internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, ref ArrayBuilder<CSharpAttributeData> attributes)
            => throw ExceptionUtilities.Unreachable();

        internal override CallerUnsafeMode GetCallerUnsafeMode(ConsList<FieldSymbol> fieldsBeingBound) => UnderlyingMethod.GetCallerUnsafeMode(fieldsBeingBound);
    }
}