' 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.

Namespace Microsoft.CodeAnalysis.VisualBasic
    ''' <summary>
    ''' Represents a <see cref="VisualBasicSyntaxVisitor"/> that descends an entire <see cref="SyntaxNode"/> tree
    ''' visiting each SyntaxNode and its child <see cref="SyntaxNode"/>s and <see cref="SyntaxToken"/>s in depth-first order.
    ''' </summary>
    Public MustInherit Class VisualBasicSyntaxWalker
        Inherits VisualBasicSyntaxVisitor

        Protected ReadOnly Property Depth As SyntaxWalkerDepth

        Protected Sub New(Optional depth As SyntaxWalkerDepth = SyntaxWalkerDepth.Node)
            Me.Depth = depth
        End Sub

        Private _recursionDepth As Integer

        Public Overrides Sub Visit(node As SyntaxNode)
            If node IsNot Nothing Then
                _recursionDepth += 1

                StackGuard.EnsureSufficientExecutionStack(_recursionDepth)
                DirectCast(node, VisualBasicSyntaxNode).Accept(Me)

                _recursionDepth -= 1
            End If
        End Sub

        Public Overrides Sub DefaultVisit(node As SyntaxNode)
            Dim list = node.ChildNodesAndTokens()
            Dim childCnt = list.Count

            Dim i As Integer = 0
            Do
                Dim child = list(i)
                i = i + 1

                Dim asNode = child.AsNode()
                If asNode IsNot Nothing Then
                    If Depth >= SyntaxWalkerDepth.Node Then
                        Me.Visit(asNode)
                    End If
                Else
                    If Depth >= SyntaxWalkerDepth.Token Then
                        Me.VisitToken(child.AsToken())
                    End If
                End If
            Loop While i < childCnt

        End Sub

        Public Overridable Sub VisitToken(token As SyntaxToken)
            If Depth >= SyntaxWalkerDepth.Trivia Then
                Me.VisitLeadingTrivia(token)
                Me.VisitTrailingTrivia(token)
            End If
        End Sub

        Public Overridable Sub VisitLeadingTrivia(token As SyntaxToken)
            If token.HasLeadingTrivia Then
                For Each tr In token.LeadingTrivia
                    VisitTrivia(tr)
                Next
            End If
        End Sub

        Public Overridable Sub VisitTrailingTrivia(token As SyntaxToken)
            If token.HasTrailingTrivia Then
                For Each tr In token.TrailingTrivia
                    VisitTrivia(tr)
                Next
            End If
        End Sub

        Public Overridable Sub VisitTrivia(trivia As SyntaxTrivia)
            If Depth >= SyntaxWalkerDepth.StructuredTrivia AndAlso trivia.HasStructure Then
                Visit(DirectCast(trivia.GetStructure(), VisualBasicSyntaxNode))
            End If
        End Sub
    End Class
End Namespace