// 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.Generic;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders
{
    internal class StaticKeywordRecommender : AbstractSyntacticSingleKeywordRecommender
    {
        private static readonly ISet<SyntaxKind> s_validTypeModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.ProtectedKeyword,
            SyntaxKind.UnsafeKeyword,
            SyntaxKind.FileKeyword,
        };
 
        private static readonly ISet<SyntaxKind> s_validNonInterfaceMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.AsyncKeyword,
            SyntaxKind.ExternKeyword,
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.ProtectedKeyword,
            SyntaxKind.ReadOnlyKeyword,
            SyntaxKind.UnsafeKeyword,
            SyntaxKind.VolatileKeyword,
        };
 
        private static readonly ISet<SyntaxKind> s_validInterfaceMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.AbstractKeyword,
            SyntaxKind.AsyncKeyword,
            SyntaxKind.ExternKeyword,
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.ProtectedKeyword,
            SyntaxKind.ReadOnlyKeyword,
            SyntaxKind.SealedKeyword,
            SyntaxKind.UnsafeKeyword,
            SyntaxKind.VolatileKeyword,
            SyntaxKind.VirtualKeyword,
        };
 
        private static readonly ISet<SyntaxKind> s_validGlobalMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.ExternKeyword,
            SyntaxKind.InternalKeyword,
            SyntaxKind.NewKeyword,
            SyntaxKind.PublicKeyword,
            SyntaxKind.PrivateKeyword,
            SyntaxKind.ReadOnlyKeyword,
            SyntaxKind.UnsafeKeyword,
            SyntaxKind.VolatileKeyword,
        };
 
        private static readonly ISet<SyntaxKind> s_validLocalFunctionModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
        {
            SyntaxKind.ExternKeyword,
            SyntaxKind.AsyncKeyword,
            SyntaxKind.UnsafeKeyword
        };
 
        public StaticKeywordRecommender()
            : base(SyntaxKind.StaticKeyword)
        {
        }
 
        protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            return
                context.IsGlobalStatementContext ||
                context.TargetToken.IsUsingKeywordInUsingDirective() ||
                IsValidContextForType(context, cancellationToken) ||
                IsValidContextForMember(context, cancellationToken) ||
                context.SyntaxTree.IsLambdaDeclarationContext(position, otherModifier: SyntaxKind.AsyncKeyword, cancellationToken) ||
                context.SyntaxTree.IsLocalFunctionDeclarationContext(position, s_validLocalFunctionModifiers, cancellationToken);
        }
 
        private static bool IsValidContextForMember(CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            return
                context.SyntaxTree.IsGlobalMemberDeclarationContext(context.Position, s_validGlobalMemberModifiers, cancellationToken) ||
                context.IsMemberDeclarationContext(
                    validModifiers: s_validNonInterfaceMemberModifiers,
                    validTypeDeclarations: SyntaxKindSet.ClassStructRecordTypeDeclarations,
                    canBePartial: false,
                    cancellationToken: cancellationToken) ||
                context.IsMemberDeclarationContext(
                    validModifiers: s_validInterfaceMemberModifiers,
                    validTypeDeclarations: SyntaxKindSet.InterfaceOnlyTypeDeclarations,
                    canBePartial: false,
                    cancellationToken: cancellationToken);
        }
 
        private static bool IsValidContextForType(CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            return context.IsTypeDeclarationContext(
                validModifiers: s_validTypeModifiers,
                validTypeDeclarations: SyntaxKindSet.ClassInterfaceStructRecordTypeDeclarations,
                canBePartial: false,
                cancellationToken: cancellationToken);
        }
    }
}