' 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.Composition
Imports System.Diagnostics.CodeAnalysis
Imports Microsoft.CodeAnalysis.Formatting
Imports Microsoft.CodeAnalysis.Formatting.Rules
Imports Microsoft.CodeAnalysis.Host.Mef
Imports Microsoft.CodeAnalysis.Indentation
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 
Namespace Microsoft.CodeAnalysis.VisualBasic.Indentation
    <ExportLanguageService(GetType(IIndentationService), LanguageNames.VisualBasic), [Shared]>
    Partial Friend NotInheritable Class VisualBasicIndentationService
        Inherits AbstractIndentationService(Of CompilationUnitSyntax)
 
        Public Shared ReadOnly WithoutParameterAlignmentInstance As New VisualBasicIndentationService(NoOpFormattingRule.Instance)
 
        Private ReadOnly _specializedIndentationRule As AbstractFormattingRule
 
        <ImportingConstructor>
        <Obsolete(MefConstruction.ImportingConstructorMessage, True)>
        Public Sub New()
            Me.New(Nothing)
        End Sub
 
        <SuppressMessage("RoslynDiagnosticsReliability", "RS0034:Exported parts should have [ImportingConstructor]", Justification:="Intentionally used for creating multiple instances")>
        Private Sub New(specializedIndentationRule As AbstractFormattingRule)
            _specializedIndentationRule = specializedIndentationRule
        End Sub
 
        Protected Overrides Function GetSpecializedIndentationFormattingRule(indentStyle As FormattingOptions2.IndentStyle) As AbstractFormattingRule
            Return If(_specializedIndentationRule, New SpecialFormattingRule(indentStyle))
        End Function
 
        Public Overloads Shared Function ShouldUseSmartTokenFormatterInsteadOfIndenter(
                formattingRules As IEnumerable(Of AbstractFormattingRule),
                root As CompilationUnitSyntax,
                line As TextLine,
                options As SyntaxFormattingOptions,
                ByRef token As SyntaxToken,
                Optional neverUseWhenHavingMissingToken As Boolean = True) As Boolean
 
            ' find first text on line
            Dim firstNonWhitespacePosition = line.GetFirstNonWhitespacePosition()
            If Not firstNonWhitespacePosition.HasValue Then
                Return False
            End If
 
            ' enter on token only works when first token on line is first text on line
            token = root.FindToken(firstNonWhitespacePosition.Value)
            If IsInvalidToken(token) Then
                Return False
            End If
 
            If token.Kind = SyntaxKind.None OrElse token.SpanStart <> firstNonWhitespacePosition Then
                Return False
            End If
 
            ' now try to gather various token information to see whether we are at an applicable position.
            ' all these are heuristic based
            ' 
            ' we need at least current and previous tokens to ask about existing line break formatting rules 
            Dim previousToken = token.GetPreviousToken(includeZeroWidth:=True)
 
            ' only use smart token formatter when we have at least two visible tokens.
            If previousToken.Kind = SyntaxKind.None Then
                Return False
            End If
 
            ' check special case 
            ' if previous token (or one before previous token if the previous token is statement terminator token) is missing, make sure
            ' we are a first token of a statement
            If previousToken.IsMissing AndAlso neverUseWhenHavingMissingToken Then
                Return False
            ElseIf previousToken.IsMissing Then
                Dim statement = token.GetAncestor(Of StatementSyntax)()
                If statement Is Nothing Then
                    Return False
                End If
 
                ' check whether current token is first token of a statement
                Return statement.GetFirstToken() = token
            End If
 
            ' now, regular case. ask formatting rule to see whether we should use token formatter or not
            Dim lineOperation = FormattingOperations.GetAdjustNewLinesOperation(formattingRules, previousToken, token, options)
            If lineOperation IsNot Nothing AndAlso lineOperation.Option <> AdjustNewLinesOption.ForceLinesIfOnSingleLine Then
                Return True
            End If
 
            ' check whether there is an alignment operation
            Dim startNode = token.Parent
 
            Dim currentNode = startNode
            Dim localToken = token
            Do While currentNode IsNot Nothing
                Dim operations = FormattingOperations.GetAlignTokensOperations(
                    formattingRules, currentNode, options)
 
                If Not operations.Any() Then
                    currentNode = currentNode.Parent
                    Continue Do
                End If
 
                ' make sure we have the given token as one of tokens to be aligned to the base token
                Dim match = operations.FirstOrDefault(Function(o) o.Tokens.Contains(localToken))
                If match IsNot Nothing Then
                    Return True
                End If
 
                currentNode = currentNode.Parent
            Loop
 
            ' no indentation operation, nothing to do for smart token formatter
            Return False
        End Function
 
        Private Shared Function IsInvalidToken(token As SyntaxToken) As Boolean
            ' invalid token to be formatted
            Return token.Kind = SyntaxKind.None OrElse
                   token.Kind = SyntaxKind.EndOfFileToken
        End Function
    End Class
End Namespace