' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.

Imports System.Collections.Immutable
Imports System.Composition
Imports System.Globalization
Imports System.Threading
Imports Microsoft.CodeAnalysis.Completion
Imports Microsoft.CodeAnalysis.Completion.Providers
Imports Microsoft.CodeAnalysis.Host.Mef
Imports Microsoft.CodeAnalysis.Options
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
Imports Microsoft.CodeAnalysis.VisualBasic.Completion.SuggestionMode
Imports Microsoft.CodeAnalysis.Host

Namespace Microsoft.CodeAnalysis.VisualBasic.Completion
    <ExportLanguageServiceFactory(GetType(CompletionService), LanguageNames.VisualBasic), [Shared]>
    Friend Class VisualBasicCompletionServiceFactory
        Implements ILanguageServiceFactory

        Public Function CreateLanguageService(languageServices As HostLanguageServices) As ILanguageService Implements ILanguageServiceFactory.CreateLanguageService
            Return New VisualBasicCompletionService(languageServices.WorkspaceServices.Workspace)
        End Function
    End Class

    Partial Friend Class VisualBasicCompletionService
        Inherits CommonCompletionService

        Private ReadOnly _completionProviders As ImmutableArray(Of CompletionProvider) = ImmutableArray.Create(Of CompletionProvider)(
            New KeywordCompletionProvider(),
            New SymbolCompletionProvider(),
            New ObjectInitializerCompletionProvider(),
            New ObjectCreationCompletionProvider(),
            New EnumCompletionProvider(),
            New NamedParameterCompletionProvider(),
            New VisualBasicSuggestionModeCompletionProvider(),
            New ImplementsClauseCompletionProvider(),
            New HandlesClauseCompletionProvider(),
            New PartialTypeCompletionProvider(),
            New CrefCompletionProvider(),
            New CompletionListTagCompletionProvider(),
            New OverrideCompletionProvider(),
            New XmlDocCommentCompletionProvider()
        )

        Private ReadOnly _workspace As Workspace

        Public Sub New(workspace As Workspace,
                       Optional exclusiveProviders As ImmutableArray(Of CompletionProvider) ? = Nothing)
            MyBase.New(workspace, exclusiveProviders)
            _workspace = workspace
        End Sub

        Public Overrides ReadOnly Property Language As String
            Get
                Return LanguageNames.VisualBasic
            End Get
        End Property

        Private Shared s_defaultCompletionRules As CompletionRules =
            CompletionRules.Create(
                dismissIfEmpty:=True,
                dismissIfLastCharacterDeleted:=True,
                defaultCommitCharacters:=CompletionRules.Default.DefaultCommitCharacters,
                defaultEnterKeyRule:=EnterKeyRule.Always)

        Public Overrides Function GetRules() As CompletionRules
            Return s_defaultCompletionRules
        End Function

        Protected Overrides Function GetBuiltInProviders() As ImmutableArray(Of CompletionProvider)
            Return _completionProviders
        End Function

        Protected Overrides Function GetProviders(roles As ImmutableHashSet(Of String), trigger As CompletionTrigger) As ImmutableArray(Of CompletionProvider)
            Dim _providers = MyBase.GetProviders(roles)

            If trigger.Kind = CompletionTriggerKind.Snippets Then
                _providers = _providers.Where(Function(p) p.IsSnippetProvider).ToImmutableArray()
            Else
                _providers = _providers.Where(Function(p) Not p.IsSnippetProvider).ToImmutableArray()
            End If

            Return _providers
        End Function

        Protected Overrides Function GetBetterItem(item As CompletionItem, existingItem As CompletionItem) As CompletionItem
            ' If one Is a keyword, And the other Is some other item that inserts the same text as the keyword,
            ' keep the keyword (VB only), unless the other item is preselected
            If IsKeywordItem(existingItem) AndAlso existingItem.Rules.MatchPriority >= item.Rules.MatchPriority Then
                Return existingItem
            End If

            Return MyBase.GetBetterItem(item, existingItem)
        End Function

        Protected Overrides Function ItemsMatch(item As CompletionItem, existingItem As CompletionItem) As Boolean
            If Not MyBase.ItemsMatch(item, existingItem) Then
                Return False
            End If

            ' DevDiv 957450 Normally, we want to show items with the same display text And
            ' different glyphs. That way, the we won't hide user - defined symbols that happen
            ' to match a keyword (Like Select). However, we want to avoid showing the keyword
            ' for an intrinsic right next to the item for the corresponding symbol. 
            ' Therefore, if a keyword claims to represent an "intrinsic" item, we'll ignore
            ' the glyph when matching.

            Dim keywordCompletionItem = If(IsKeywordItem(existingItem), existingItem, If(IsKeywordItem(item), item, Nothing))
            If keywordCompletionItem IsNot Nothing AndAlso keywordCompletionItem.Tags.Contains(CompletionTags.Intrinsic) Then
                Dim otherItem = If(keywordCompletionItem Is item, existingItem, item)
                Dim changeText = GetChangeText(otherItem)
                If changeText = keywordCompletionItem.DisplayText Then
                    Return True
                Else
                    Return False
                End If
            End If

            Return item.Tags = existingItem.Tags OrElse Enumerable.SequenceEqual(item.Tags, existingItem.Tags)
        End Function

        Private Function GetChangeText(item As CompletionItem) As String
            Dim provider = TryCast(GetProvider(item), CommonCompletionProvider)
            If provider IsNot Nothing Then
                ' TODO: Document Is Not available in this code path.. what about providers that need to reconstruct information before producing text?
                Dim result = provider.GetTextChangeAsync(Nothing, item, Nothing, CancellationToken.None).Result
                If result IsNot Nothing Then
                    Return result.Value.NewText
                End If
            End If

            Return item.DisplayText
        End Function

        Public Overrides Function GetDefaultItemSpan(text As SourceText, caretPosition As Integer) As TextSpan
            Return CompletionUtilities.GetCompletionItemSpan(text, caretPosition)
        End Function

        Public Overrides Function ShouldTriggerCompletion(text As SourceText, position As Integer, trigger As CompletionTrigger, Optional roles As ImmutableHashSet(Of String) = Nothing, Optional options As OptionSet = Nothing) As Boolean
            options = If(options, _workspace.Options)

            If Not options.GetOption(CompletionOptions.TriggerOnTyping, Me.Language) Then
                Return False
            End If

            If trigger.Kind = CompletionTriggerKind.Deletion AndAlso (Char.IsLetterOrDigit(trigger.Character) OrElse trigger.Character = "."c) Then
                Return True
            Else
                Return MyBase.ShouldTriggerCompletion(text, position, trigger, roles, options)
            End If
        End Function
    End Class
End Namespace