// 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.Collections.Immutable;
using System.Reflection.Metadata;
using System.Runtime.CompilerServices;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis;
 
internal partial struct SymbolKey
{
    private sealed class FunctionPointerTypeSymbolKey : AbstractSymbolKey<IFunctionPointerTypeSymbol>
    {
        public static readonly FunctionPointerTypeSymbolKey Instance = new();
 
        public sealed override void Create(IFunctionPointerTypeSymbol symbol, SymbolKeyWriter visitor)
        {
            var callingConvention = symbol.Signature.CallingConvention;
            visitor.WriteInteger((int)callingConvention);
 
            if (callingConvention == SignatureCallingConvention.Unmanaged)
            {
                visitor.WriteSymbolKeyArray(symbol.Signature.UnmanagedCallingConventionTypes);
            }
 
            visitor.WriteRefKind(symbol.Signature.RefKind);
            visitor.WriteSymbolKey(symbol.Signature.ReturnType);
            visitor.WriteRefKindArray(symbol.Signature.Parameters);
            visitor.WriteParameterTypesArray(symbol.Signature.Parameters);
        }
 
        protected sealed override SymbolKeyResolution Resolve(
            SymbolKeyReader reader, IFunctionPointerTypeSymbol? contextualSymbol, out string? failureReason)
        {
            var callingConvention = (SignatureCallingConvention)reader.ReadInteger();
 
            var callingConventionModifiers = ImmutableArray<INamedTypeSymbol>.Empty;
            if (callingConvention == SignatureCallingConvention.Unmanaged)
            {
                using var modifiersBuilder = reader.ReadSymbolKeyArray<IFunctionPointerTypeSymbol, INamedTypeSymbol>(
                    contextualSymbol,
                    static (contextualSymbol, i) => SafeGet(contextualSymbol.Signature.UnmanagedCallingConventionTypes, i),
                    out var conventionTypesFailureReason);
                if (conventionTypesFailureReason != null)
                {
                    failureReason = $"({nameof(FunctionPointerTypeSymbolKey)} {nameof(callingConventionModifiers)} failed -> {conventionTypesFailureReason})";
                    return default;
                }
 
                callingConventionModifiers = modifiersBuilder.ToImmutable();
            }
 
            var returnRefKind = reader.ReadRefKind();
            var returnType = reader.ReadSymbolKey(contextualSymbol?.Signature.ReturnType, out var returnTypeFailureReason);
            using var paramRefKinds = reader.ReadRefKindArray();
            using var parameterTypes = reader.ReadSymbolKeyArray<IFunctionPointerTypeSymbol, ITypeSymbol>(
                contextualSymbol,
                static (contextualSymbol, i) => SafeGet(contextualSymbol.Signature.Parameters, i)?.Type,
                out var parameterTypesFailureReason);
 
            if (returnTypeFailureReason != null)
            {
                failureReason = $"({nameof(FunctionPointerTypeSymbolKey)} {nameof(returnType)} failed -> {returnTypeFailureReason})";
                return default;
            }
 
            if (parameterTypesFailureReason != null)
            {
                Contract.ThrowIfFalse(parameterTypes.IsDefault);
                failureReason = $"({nameof(FunctionPointerTypeSymbolKey)} {nameof(parameterTypes)} failed -> {parameterTypesFailureReason})";
                return default;
            }
 
            Contract.ThrowIfTrue(parameterTypes.IsDefault);
 
            if (returnType.GetAnySymbol() is not ITypeSymbol returnTypeSymbol)
            {
                failureReason = $"({nameof(FunctionPointerTypeSymbolKey)} no return type)";
                return default;
            }
 
            if (reader.Compilation.Language == LanguageNames.VisualBasic)
            {
                failureReason = $"({nameof(FunctionPointerTypeSymbolKey)} is not supported in {LanguageNames.VisualBasic})";
                return default;
            }
 
            failureReason = null;
            return new SymbolKeyResolution(reader.Compilation.CreateFunctionPointerTypeSymbol(
                returnTypeSymbol, returnRefKind, parameterTypes.ToImmutable(), paramRefKinds.ToImmutable(), callingConvention, callingConventionModifiers));
        }
    }
}