// 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.Threading;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders;

internal sealed class BaseKeywordRecommender() : AbstractSyntacticSingleKeywordRecommender(SyntaxKind.BaseKeyword)
{
    protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
    {
        // We need to at least be in a type declaration context.  This prevents us from showing
        // calls to 'base' in things like top level repl statements and whatnot.
        if (context.ContainingTypeDeclaration != null)
        {
            return
                IsConstructorInitializerContext(context) ||
                IsInstanceExpressionOrStatement(context);
        }

        return false;
    }

    private static bool IsInstanceExpressionOrStatement(CSharpSyntaxContext context)
    {
        if (context.IsInstanceContext)
        {
            return context.IsNonAttributeExpressionContext || context.IsStatementContext;
        }

        return false;
    }

    private static bool IsConstructorInitializerContext(CSharpSyntaxContext context)
    {
        // cases:
        //   Goo() : |

        var token = context.TargetToken;

        if (token.Kind() == SyntaxKind.ColonToken &&
            token.Parent is ConstructorInitializerSyntax &&
            token.Parent.IsParentKind(SyntaxKind.ConstructorDeclaration) &&
            token.Parent.Parent?.Parent is (kind: SyntaxKind.ClassDeclaration or SyntaxKind.RecordDeclaration))
        {
            var constructor = token.GetRequiredAncestor<ConstructorDeclarationSyntax>();
            if (constructor.Modifiers.Any(SyntaxKind.StaticKeyword))
            {
                return false;
            }

            return true;
        }

        return false;
    }
}