// 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;
 
namespace Microsoft.CodeAnalysis.Shared.Extensions
{
    internal partial class ITypeSymbolExtensions
    {
        private class MinimalAccessibilityVisitor : SymbolVisitor<Accessibility>
        {
            public static readonly SymbolVisitor<Accessibility> Instance = new MinimalAccessibilityVisitor();
 
            public override Accessibility DefaultVisit(ISymbol node)
                => throw new NotImplementedException();
 
            public override Accessibility VisitAlias(IAliasSymbol symbol)
                => symbol.Target.Accept(this);
 
            public override Accessibility VisitArrayType(IArrayTypeSymbol symbol)
                => symbol.ElementType.Accept(this);
 
            public override Accessibility VisitDynamicType(IDynamicTypeSymbol symbol)
                => Accessibility.Public;
 
            public override Accessibility VisitFunctionPointerType(IFunctionPointerTypeSymbol symbol)
            {
                var accessibility = symbol.DeclaredAccessibility;
 
                accessibility = AccessibilityUtilities.Minimum(accessibility, symbol.Signature.ReturnType.Accept(this));
 
                foreach (var parameter in symbol.Signature.Parameters)
                {
                    accessibility = AccessibilityUtilities.Minimum(accessibility, parameter.Type.Accept(this));
                }
 
                // CallingConvention types are currently specced to always be public, but if that spec ever changes
                // or the runtime creates special private types for it's own use, we'll be ready.
                foreach (var callingConventionType in symbol.Signature.UnmanagedCallingConventionTypes)
                {
                    accessibility = AccessibilityUtilities.Minimum(accessibility, callingConventionType.Accept(this));
                }
 
                return accessibility;
            }
 
            public override Accessibility VisitNamedType(INamedTypeSymbol symbol)
            {
                var accessibility = symbol.DeclaredAccessibility;
 
                foreach (var arg in symbol.TypeArguments)
                {
                    accessibility = AccessibilityUtilities.Minimum(accessibility, arg.Accept(this));
                }
 
                if (symbol.ContainingType != null)
                {
                    accessibility = AccessibilityUtilities.Minimum(accessibility, symbol.ContainingType.Accept(this));
                }
 
                return accessibility;
            }
 
            public override Accessibility VisitPointerType(IPointerTypeSymbol symbol)
                => symbol.PointedAtType.Accept(this);
 
            public override Accessibility VisitTypeParameter(ITypeParameterSymbol symbol)
            {
                // TODO(cyrusn): Do we have to consider the constraints?
                return Accessibility.Public;
            }
        }
    }
}