// 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 sealed class UnsafeKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.UnsafeKeyword)
{
    private static readonly ISet<SyntaxKind> s_validTypeModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.AbstractKeyword,
        SyntaxKind.InternalKeyword,
        SyntaxKind.NewKeyword,
        SyntaxKind.PublicKeyword,
        SyntaxKind.PrivateKeyword,
        SyntaxKind.ProtectedKeyword,
        SyntaxKind.ClosedKeyword,
        SyntaxKind.SealedKeyword,
        SyntaxKind.StaticKeyword,
        SyntaxKind.FileKeyword,
    };

    private static readonly ISet<SyntaxKind> s_validMemberModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.AbstractKeyword,
        SyntaxKind.ExternKeyword,
        SyntaxKind.InternalKeyword,
        SyntaxKind.NewKeyword,
        SyntaxKind.OverrideKeyword,
        SyntaxKind.PublicKeyword,
        SyntaxKind.PrivateKeyword,
        SyntaxKind.ProtectedKeyword,
        SyntaxKind.ReadOnlyKeyword,
        SyntaxKind.SealedKeyword,
        SyntaxKind.StaticKeyword,
        SyntaxKind.VirtualKeyword,
        SyntaxKind.VolatileKeyword,
    };

    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.StaticKeyword,
        SyntaxKind.VolatileKeyword,
    };

    private static readonly ISet<SyntaxKind> s_validLocalFunctionModifiers = new HashSet<SyntaxKind>(SyntaxFacts.EqualityComparer)
    {
        SyntaxKind.ExternKeyword,
        SyntaxKind.StaticKeyword,
        SyntaxKind.AsyncKeyword
    };

    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        var syntaxTree = context.SyntaxTree;
        return
            context.IsStatementContext ||
            context.IsGlobalStatementContext ||
            context.IsTypeDeclarationContext(validModifiers: s_validTypeModifiers, validTypeDeclarations: SyntaxKindSet.NonEnumTypeDeclarations, canBePartial: false, cancellationToken: cancellationToken) ||
            syntaxTree.IsGlobalMemberDeclarationContext(position, s_validGlobalMemberModifiers, cancellationToken) ||
            context.IsMemberDeclarationContext(
                validModifiers: s_validMemberModifiers,
                validTypeDeclarations: SyntaxKindSet.NonEnumTypeDeclarations,
                canBePartial: false,
                cancellationToken: cancellationToken) ||
            syntaxTree.IsLocalFunctionDeclarationContext(position, s_validLocalFunctionModifiers, cancellationToken) ||
            (context.IsInImportsDirective && context.TargetToken.Kind() is SyntaxKind.UsingKeyword or SyntaxKind.StaticKeyword);
    }
}