' 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.Concurrent
Imports System.Collections.Immutable
Imports System.Threading
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax

Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols

    ''' <summary>
    ''' Represents source or metadata assembly.
    ''' </summary>
    ''' <remarks></remarks>
    Friend MustInherit Class MetadataOrSourceAssemblySymbol
        Inherits MetadataOrSourceOrRetargetingAssemblySymbol

        ''' <summary>
        ''' An array of cached Cor types defined in this assembly.
        ''' Lazily filled by GetSpecialType method.
        ''' </summary>
        ''' <remarks></remarks>
        Private _lazySpecialTypes() As NamedTypeSymbol

        ''' <summary>
        ''' How many Cor types have we cached so far.
        ''' </summary>
        Private _cachedSpecialTypes As Integer

        ''' <summary>
        ''' Lookup declaration for predefined CorLib type in this Assembly. Only should be
        ''' called if it is know that this is the Cor Library (mscorlib).
        ''' </summary>
        ''' <param name="type"></param>
        ''' <returns></returns>
        ''' <remarks></remarks>
        Friend Overrides Function GetDeclaredSpecialType(type As ExtendedSpecialType) As NamedTypeSymbol
#If DEBUG Then
            For Each [module] In Me.Modules
                Debug.Assert([module].GetReferencedAssemblies().Length = 0)
            Next
#End If

            If _lazySpecialTypes Is Nothing OrElse _lazySpecialTypes(CInt(type)) Is Nothing Then

                Dim emittedName As MetadataTypeName = MetadataTypeName.FromFullName(SpecialTypes.GetMetadataName(type), useCLSCompliantNameArityEncoding:=True)

                Dim [module] As ModuleSymbol = Me.Modules(0)
                Dim result As NamedTypeSymbol = [module].LookupTopLevelMetadataType(emittedName)
                Debug.Assert(If(Not result?.IsErrorType(), True))

                If result Is Nothing OrElse result.DeclaredAccessibility <> Accessibility.Public Then
                    result = New MissingMetadataTypeSymbol.TopLevel([module], emittedName, type)
                End If
                RegisterDeclaredSpecialType(result)
            End If

            Return _lazySpecialTypes(CInt(type))

        End Function

        ''' <summary>
        ''' Register declaration of predefined CorLib type in this Assembly.
        ''' </summary>
        ''' <param name="corType"></param>
        Friend Overrides Sub RegisterDeclaredSpecialType(corType As NamedTypeSymbol)
            Dim typeId As ExtendedSpecialType = corType.ExtendedSpecialType
            Debug.Assert(typeId <> SpecialType.None)
            Debug.Assert(corType.ContainingAssembly Is Me)
            Debug.Assert(corType.ContainingModule.Ordinal = 0)
            Debug.Assert(Me.CorLibrary Is Me)

            If (_lazySpecialTypes Is Nothing) Then
                Interlocked.CompareExchange(_lazySpecialTypes,
                    New NamedTypeSymbol(InternalSpecialType.NextAvailable - 1) {}, Nothing)
            End If

            If (Interlocked.CompareExchange(_lazySpecialTypes(CInt(typeId)), corType, Nothing) IsNot Nothing) Then
                Debug.Assert(corType Is _lazySpecialTypes(CInt(typeId)) OrElse
                                        (corType.Kind = SymbolKind.ErrorType AndAlso
                                        _lazySpecialTypes(CInt(typeId)).Kind = SymbolKind.ErrorType))
            Else
                Interlocked.Increment(_cachedSpecialTypes)
                Debug.Assert(_cachedSpecialTypes > 0 AndAlso _cachedSpecialTypes < InternalSpecialType.NextAvailable)
            End If
        End Sub

        ''' <summary>
        ''' Continue looking for declaration of predefined CorLib type in this Assembly
        ''' while symbols for new type declarations are constructed.
        ''' </summary>
        Friend Overrides ReadOnly Property KeepLookingForDeclaredSpecialTypes As Boolean
            Get
                Return Me.CorLibrary Is Me AndAlso _cachedSpecialTypes < InternalSpecialType.NextAvailable - 1
            End Get
        End Property

        Private _lazyTypeNames As ICollection(Of String)
        Private _lazyNamespaceNames As ICollection(Of String)

        Public Overrides ReadOnly Property TypeNames As ICollection(Of String)
            Get
                If _lazyTypeNames Is Nothing Then
                    Interlocked.CompareExchange(_lazyTypeNames, UnionCollection(Of String).Create(Me.Modules, Function(m) m.TypeNames), Nothing)
                End If

                Return _lazyTypeNames
            End Get
        End Property

        Public Overrides ReadOnly Property NamespaceNames As ICollection(Of String)
            Get
                If _lazyNamespaceNames Is Nothing Then
                    Interlocked.CompareExchange(_lazyNamespaceNames, UnionCollection(Of String).Create(Me.Modules, Function(m) m.NamespaceNames), Nothing)
                End If
                Return _lazyNamespaceNames
            End Get
        End Property

    End Class
End Namespace