' 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.Threading
Imports Microsoft.CodeAnalysis
Imports Microsoft.CodeAnalysis.Debugging
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 
Namespace Microsoft.CodeAnalysis.VisualBasic.Debugging
    ' TODO: Make this class static when we add that functionality to VB.
    Namespace DataTipInfoGetter
        Friend Module DataTipInfoGetterModule
            Friend Async Function GetInfoAsync(document As Document, position As Integer, cancellationToken As CancellationToken) As Task(Of DebugDataTipInfo)
                Dim root = Await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(False)
                Dim token = root.FindToken(position)
 
                If token.IsKind(SyntaxKind.CommaToken) Then
                    ' The commas in a separated syntax list consider the list's parent
                    ' to be their parent, which leads to false positives below.
                    Return Nothing
                End If
 
                If token.Parent.IsKind(SyntaxKind.ModifiedIdentifier) Then
                    Return New DebugDataTipInfo(token.Span, text:=Nothing)
                End If
 
                Dim expression = TryCast(token.Parent, ExpressionSyntax)
                If expression Is Nothing Then
                    Return If(token.IsKind(SyntaxKind.IdentifierToken),
                        New DebugDataTipInfo(token.Span, text:=Nothing),
                        Nothing)
                End If
 
                If expression.IsAnyLiteralExpression() Then
                    Return Nothing
                End If
 
                Dim conditionalAccess As ExpressionSyntax = Nothing
                If expression.IsRightSideOfDotOrBang() Then
                    expression = DirectCast(expression.Parent, ExpressionSyntax)
                    conditionalAccess = If(expression.GetRootConditionalAccessExpression(), expression)
                End If
 
                If expression.Parent.IsKind(SyntaxKind.InvocationExpression) Then
                    expression = DirectCast(expression.Parent, ExpressionSyntax)
                End If
 
                Dim span = expression.Span
                If conditionalAccess IsNot Nothing Then
                    ' There may not be an ExpressionSyntax corresponding to the range we want.
                    ' For example, for input a?.$$B?.C we want span [|a?.B|].C.
                    span = TextSpan.FromBounds(conditionalAccess.SpanStart, span.End)
                End If
 
                Return New DebugDataTipInfo(span, text:=Nothing)
            End Function
        End Module
    End Namespace
End Namespace