' 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 Microsoft.CodeAnalysis
Imports Microsoft.CodeAnalysis.Simplification
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax

Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions

    Friend Class ExpressionSyntaxGeneratorVisitor
        Inherits SymbolVisitor(Of ExpressionSyntax)

        ' Public Shared ReadOnly Instance As ExpressionSyntaxGeneratorVisitor = New ExpressionSyntaxGeneratorVisitor()

        Private ReadOnly _addGlobal As Boolean

        Public Sub New(addGlobal As Boolean)
            Me._addGlobal = addGlobal
        End Sub

        Public Overrides Function DefaultVisit(symbol As ISymbol) As ExpressionSyntax
            Return symbol.Accept(TypeSyntaxGeneratorVisitor.Create(_addGlobal))
        End Function

        Private Shared Function AddInformationTo(Of TExpressionSyntax As ExpressionSyntax)(expression As TExpressionSyntax, symbol As ISymbol) As TExpressionSyntax
            expression = expression.WithPrependedLeadingTrivia(SyntaxFactory.ElasticMarker).WithAppendedTrailingTrivia(SyntaxFactory.ElasticMarker)
            expression = expression.WithAdditionalAnnotations(SymbolAnnotation.Create(symbol))
            Return expression
        End Function

        Public Overrides Function VisitNamedType(symbol As INamedTypeSymbol) As ExpressionSyntax
            Dim typeSyntax = TypeSyntaxGeneratorVisitor.Create(_addGlobal).CreateSimpleTypeSyntax(symbol)
            If Not (TypeOf typeSyntax Is SimpleNameSyntax) Then
                Return typeSyntax
            End If

            Dim simpleNameSyntax = DirectCast(typeSyntax, SimpleNameSyntax)
            If symbol.ContainingType IsNot Nothing Then
                If symbol.ContainingType.TypeKind = TypeKind.Submission Then
                    Return simpleNameSyntax
                Else
                    Dim container = symbol.ContainingType.Accept(Me)
                    Return CreateMemberAccessExpression(symbol, container, simpleNameSyntax)
                End If
            ElseIf symbol.ContainingNamespace IsNot Nothing Then
                If symbol.ContainingNamespace.IsGlobalNamespace Then
                    If symbol.TypeKind <> TypeKind.[Error] Then
                        Return CreateMemberAccessExpression(symbol, SyntaxFactory.GlobalName(), simpleNameSyntax)
                    End If
                Else
                    Dim container = symbol.ContainingNamespace.Accept(Me)
                    Return CreateMemberAccessExpression(symbol, container, simpleNameSyntax)
                End If
            End If

            Return simpleNameSyntax
        End Function

        Public Overrides Function VisitNamespace(symbol As INamespaceSymbol) As ExpressionSyntax
            Dim result = AddInformationTo(symbol.Name.ToIdentifierName, symbol)
            If symbol.ContainingNamespace Is Nothing Then
                Return result
            End If

            If symbol.ContainingNamespace.IsGlobalNamespace Then
                Return CreateMemberAccessExpression(symbol, SyntaxFactory.GlobalName(), result)
            Else
                Dim container = symbol.ContainingNamespace.Accept(Me)
                Return CreateMemberAccessExpression(symbol, container, result)
            End If
        End Function

        Private Shared Function CreateMemberAccessExpression(symbol As ISymbol, container As ExpressionSyntax, simpleName As SimpleNameSyntax) As ExpressionSyntax
            Return AddInformationTo(SyntaxFactory.SimpleMemberAccessExpression(container, SyntaxFactory.Token(SyntaxKind.DotToken), simpleName), symbol)
        End Function
    End Class
End Namespace