' 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.Runtime.InteropServices
Imports System.Threading
Imports Microsoft.CodeAnalysis.Host.Mef
Imports Microsoft.CodeAnalysis.LanguageService
Imports Microsoft.CodeAnalysis.SignatureHelp
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 
Namespace Microsoft.CodeAnalysis.VisualBasic.SignatureHelp
    <ExportSignatureHelpProvider(NameOf(CollectionInitializerSignatureHelpProvider), LanguageNames.VisualBasic), [Shared]>
    Partial Friend Class CollectionInitializerSignatureHelpProvider
        Inherits AbstractOrdinaryMethodSignatureHelpProvider
 
        <ImportingConstructor>
        <Obsolete(MefConstruction.ImportingConstructorMessage, True)>
        Public Sub New()
        End Sub
 
        Public Overrides Function IsTriggerCharacter(ch As Char) As Boolean
            Return ch = "{"c OrElse ch = ","c
        End Function
 
        Public Overrides Function IsRetriggerCharacter(ch As Char) As Boolean
            Return ch = "}"c
        End Function
 
        Private Function TryGetInitializerExpression(root As SyntaxNode, position As Integer, syntaxFacts As ISyntaxFactsService, triggerReason As SignatureHelpTriggerReason, cancellationToken As CancellationToken, <Out> ByRef expression As CollectionInitializerSyntax) As Boolean
            Return CommonSignatureHelpUtilities.TryGetSyntax(root, position, syntaxFacts, triggerReason, AddressOf IsTriggerToken, AddressOf IsInitializerExpressionToken, cancellationToken, expression) AndAlso
                   expression IsNot Nothing
        End Function
 
        Private Function IsTriggerToken(token As SyntaxToken) As Boolean
            Return Not token.IsKind(SyntaxKind.None) AndAlso
               token.ValueText.Length = 1 AndAlso
               IsTriggerCharacter(token.ValueText(0)) AndAlso
               TypeOf token.Parent Is CollectionInitializerSyntax
        End Function
 
        Private Shared Function IsInitializerExpressionToken(expression As CollectionInitializerSyntax, token As SyntaxToken) As Boolean
            Return expression.Span.Contains(token.SpanStart) AndAlso token <> expression.CloseBraceToken
        End Function
 
        Protected Overrides Async Function GetItemsWorkerAsync(document As Document, position As Integer, triggerInfo As SignatureHelpTriggerInfo, options As MemberDisplayOptions, cancellationToken As CancellationToken) As Task(Of SignatureHelpItems)
            Dim root = Await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(False)
            Dim collectionInitializer As CollectionInitializerSyntax = Nothing
            If Not TryGetInitializerExpression(root, position, document.GetLanguageService(Of ISyntaxFactsService)(), triggerInfo.TriggerReason, cancellationToken, collectionInitializer) Then
                Return Nothing
            End If
 
            Dim addMethods = Await CommonSignatureHelpUtilities.GetCollectionInitializerAddMethodsAsync(
                document, collectionInitializer.Parent, options, cancellationToken).ConfigureAwait(False)
            If addMethods.IsDefaultOrEmpty Then
                Return Nothing
            End If
 
            Dim textSpan = GetSignatureHelpSpan(collectionInitializer)
            Dim syntaxFacts = document.GetLanguageService(Of ISyntaxFactsService)()
 
            Dim semanticModel = Await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(False)
            Return CreateCollectionInitializerSignatureHelpItems(
                addMethods.Select(Function(s) ConvertMemberGroupMember(document, s, collectionInitializer.OpenBraceToken.SpanStart, semanticModel)).ToList(),
                textSpan, GetCurrentArgumentState(root, position, syntaxFacts, textSpan, cancellationToken))
        End Function
 
        Private Function GetCurrentArgumentState(root As SyntaxNode, position As Integer, syntaxFacts As ISyntaxFactsService, currentSpan As TextSpan, cancellationToken As CancellationToken) As SignatureHelpState?
            Dim expression As CollectionInitializerSyntax = Nothing
            If TryGetInitializerExpression(
                        root,
                        position,
                        syntaxFacts,
                        SignatureHelpTriggerReason.InvokeSignatureHelpCommand,
                        cancellationToken,
                        expression) AndAlso
                    currentSpan.Start = GetSignatureHelpSpan(expression).Start Then
                Return GetSignatureHelpState(expression, position)
            End If
 
            Return Nothing
        End Function
    End Class
 
End Namespace