// 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.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.KeywordRecommenders
{
    internal class EqualsKeywordRecommender : AbstractSyntacticSingleKeywordRecommender
    {
        public EqualsKeywordRecommender()
            : base(SyntaxKind.EqualsKeyword)
        {
        }
 
        protected override bool IsValidContext(int position, CSharpSyntaxContext context, CancellationToken cancellationToken)
        {
            // cases:
            //   join a in expr o1 |
            //   join a in expr o1 e|
 
            var token = context.TargetToken;
 
            var join = token.GetAncestor<JoinClauseSyntax>();
            if (join == null)
            {
                return false;
            }
 
            var lastToken = join.LeftExpression.GetLastToken(includeSkipped: true);
 
            // join a in expr |
            if (join.LeftExpression.Width() > 0 &&
                token == lastToken)
            {
                return true;
            }
 
            return false;
        }
    }
}