' 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.Collections.Immutable
Imports System.Composition
Imports System.Threading
Imports Microsoft.CodeAnalysis.Collections
Imports Microsoft.CodeAnalysis.DocumentationComments
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("InvocationExpressionSignatureHelpProvider", LanguageNames.VisualBasic), [Shared]>
    Partial Friend Class InvocationExpressionSignatureHelpProvider
        Inherits AbstractOrdinaryMethodSignatureHelpProvider

        <ImportingConstructor>
        <Obsolete(MefConstruction.ImportingConstructorMessage, True)>
        Public Sub New()
        End Sub

        Public Overrides ReadOnly Property TriggerCharacters As ImmutableArray(Of Char) = ImmutableArray.Create("("c, ","c)

        Public Overrides ReadOnly Property RetriggerCharacters As ImmutableArray(Of Char) = ImmutableArray.Create(")"c)

        Private Shared Function GetCurrentArgumentState(root As SyntaxNode, position As Integer, syntaxFacts As ISyntaxFactsService, currentSpan As TextSpan, cancellationToken As CancellationToken) As SignatureHelpState?
            Dim expression As InvocationExpressionSyntax = Nothing
            If TryGetInvocationExpression(root, position, syntaxFacts, SignatureHelpTriggerReason.InvokeSignatureHelpCommand, cancellationToken, expression) AndAlso
                currentSpan.Start = GetSignatureHelpSpan(expression.ArgumentList).Start Then

                Return GetSignatureHelpState(expression.ArgumentList, position)
            End If

            Return Nothing
        End Function

        Private Shared Function TryGetInvocationExpression(root As SyntaxNode, position As Integer, syntaxFacts As ISyntaxFactsService, triggerReason As SignatureHelpTriggerReason, cancellationToken As CancellationToken, ByRef expression As InvocationExpressionSyntax) As Boolean
            If Not CommonSignatureHelpUtilities.TryGetSyntax(root, position, syntaxFacts, triggerReason, AddressOf IsTriggerToken, AddressOf IsArgumentListToken, cancellationToken, expression) Then
                Return False
            End If

            Return expression.ArgumentList IsNot Nothing
        End Function

        Private Shared Function IsTriggerToken(token As SyntaxToken) As Boolean
            Return (token.Kind = SyntaxKind.OpenParenToken OrElse token.Kind = SyntaxKind.CommaToken) AndAlso
                    TypeOf token.Parent Is ArgumentListSyntax AndAlso
                    TypeOf token.Parent.Parent Is InvocationExpressionSyntax
        End Function

        Private Shared Function IsArgumentListToken(node As InvocationExpressionSyntax, token As SyntaxToken) As Boolean
            Return node.ArgumentList IsNot Nothing AndAlso
                node.ArgumentList.Span.Contains(token.SpanStart) AndAlso
                token <> node.ArgumentList.CloseParenToken
        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 invocationExpression As InvocationExpressionSyntax = Nothing
            If Not TryGetInvocationExpression(root, position, document.GetLanguageService(Of ISyntaxFactsService), triggerInfo.TriggerReason, cancellationToken, invocationExpression) Then
                Return Nothing
            End If

            Dim semanticModel = Await document.ReuseExistingSpeculativeModelAsync(invocationExpression, cancellationToken).ConfigureAwait(False)
            Dim within = semanticModel.GetEnclosingNamedTypeOrAssembly(position, cancellationToken)
            If within Is Nothing Then
                Return Nothing
            End If

            Dim targetExpression = If(invocationExpression.Expression Is Nothing AndAlso invocationExpression.Parent.IsKind(SyntaxKind.ConditionalAccessExpression),
                DirectCast(invocationExpression.Parent, ConditionalAccessExpressionSyntax).Expression,
                invocationExpression.Expression)

            ' get the regular signature help items
            Dim memberGroup = semanticModel.GetMemberGroup(targetExpression, cancellationToken).
                                            FilterToVisibleAndBrowsableSymbolsAndNotUnsafeSymbols(options.HideAdvancedMembers, semanticModel.Compilation)

            ' try to bind to the actual method
            Dim symbolInfo = semanticModel.GetSymbolInfo(invocationExpression, cancellationToken)
            Dim matchedMethodSymbol = TryCast(symbolInfo.Symbol, IMethodSymbol)

            ' if the symbol could be bound, replace that item in the symbol list
            If matchedMethodSymbol IsNot Nothing AndAlso matchedMethodSymbol.IsGenericMethod Then
                memberGroup = memberGroup.SelectAsArray(Function(m) If(Equals(matchedMethodSymbol.OriginalDefinition, m), matchedMethodSymbol, m))
            End If

            Dim enclosingSymbol = semanticModel.GetEnclosingSymbol(position, cancellationToken)
            If enclosingSymbol.IsConstructor() Then
                memberGroup = memberGroup.WhereAsArray(Function(m) Not m.Equals(enclosingSymbol))
            End If

            memberGroup = memberGroup.Sort(semanticModel, invocationExpression.SpanStart)

            Dim typeInfo = semanticModel.GetTypeInfo(targetExpression, cancellationToken)
            Dim expressionType = If(typeInfo.Type, typeInfo.ConvertedType)
            Dim defaultProperties =
                If(expressionType Is Nothing,
                   SpecializedCollections.EmptyList(Of IPropertySymbol),
                   semanticModel.LookupSymbols(position, expressionType, includeReducedExtensionMethods:=True).
                                 OfType(Of IPropertySymbol).
                                 ToImmutableArrayOrEmpty().
                                 WhereAsArray(Function(p) p.IsIndexer).
                                 FilterToVisibleAndBrowsableSymbolsAndNotUnsafeSymbols(options.HideAdvancedMembers, semanticModel.Compilation).
                                 Sort(semanticModel, invocationExpression.SpanStart))

            Dim structuralTypeDisplayService = document.GetLanguageService(Of IStructuralTypeDisplayService)()
            Dim documentationCommentFormattingService = document.GetLanguageService(Of IDocumentationCommentFormattingService)()

            Dim items = New List(Of SignatureHelpItem)
            Dim accessibleMembers = ImmutableArray(Of ISymbol).Empty
            If memberGroup.Length > 0 Then
                accessibleMembers = GetAccessibleMembers(invocationExpression, semanticModel, within, memberGroup, cancellationToken)
                items.AddRange(GetMemberGroupItems(accessibleMembers, document, invocationExpression, semanticModel))
            End If

            If expressionType.IsDelegateType() Then
                items.AddRange(GetDelegateInvokeItems(invocationExpression, semanticModel, structuralTypeDisplayService, documentationCommentFormattingService, DirectCast(expressionType, INamedTypeSymbol), cancellationToken))
            End If

            If defaultProperties.Count > 0 Then
                items.AddRange(GetElementAccessItems(targetExpression, semanticModel, structuralTypeDisplayService, documentationCommentFormattingService, within, defaultProperties, cancellationToken))
            End If

            Dim textSpan = GetSignatureHelpSpan(invocationExpression.ArgumentList)
            Dim syntaxFacts = document.GetLanguageService(Of ISyntaxFactsService)

            Dim selectedItem = TryGetSelectedIndex(accessibleMembers, symbolInfo.Symbol)
            Return CreateSignatureHelpItems(
                items, textSpan, GetCurrentArgumentState(root, position, syntaxFacts, textSpan, cancellationToken),
                selectedItem, parameterIndexOverride:=-1)
        End Function
    End Class
End Namespace