' 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.

Imports System.Collections.Immutable
Imports System.Threading
Imports Microsoft.CodeAnalysis.Completion.Providers
Imports Microsoft.CodeAnalysis.VisualBasic.Extensions.ContextQuery
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax

Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.KeywordRecommenders.Expressions
    ''' <summary>
    ''' Recommends the "Key" keyword.
    ''' </summary>
    Friend Class KeyKeywordRecommender
        Inherits AbstractKeywordRecommender

        Private Shared ReadOnly s_keywords As ImmutableArray(Of RecommendedKeyword) =
            ImmutableArray.Create(New RecommendedKeyword("Key", VBFeaturesResources.Identifies_a_key_field_in_an_anonymous_type_definition))

        Protected Overrides Function RecommendKeywords(context As VisualBasicSyntaxContext, cancellationToken As CancellationToken) As ImmutableArray(Of RecommendedKeyword)
            If context.FollowsEndOfStatement Then
                Return ImmutableArray(Of RecommendedKeyword).Empty
            End If

            Dim targetToken = context.TargetToken

            ' Key can only come after a { or a , in a initializer
            If targetToken.IsKind(SyntaxKind.OpenBraceToken, SyntaxKind.CommaToken) AndAlso
               targetToken.Parent.IsKind(SyntaxKind.ObjectMemberInitializer) Then
                ' We might be in an expression...
                If targetToken.Parent.GetParentOrNull().IsKind(SyntaxKind.AnonymousObjectCreationExpression) Then
                    Return s_keywords
                End If

                ' Or we might be in an AsNew. In this case, we need to check to make sure the type is correct
                If targetToken.Parent.GetParentOrNull().GetParentOrNull().IsKind(SyntaxKind.AsNewClause) Then
                    Dim asNewClause = DirectCast(targetToken.Parent.Parent.Parent, AsNewClauseSyntax)
                    If asNewClause.Type.IsMissing Then
                        Return s_keywords
                    End If
                End If
            End If

            Return ImmutableArray(Of RecommendedKeyword).Empty
        End Function
    End Class
End Namespace