' 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.Threading

Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
    Friend NotInheritable Class SourceLambdaSymbol
        Inherits LambdaSymbol

        Private ReadOnly _unboundLambda As UnboundLambda

        ' The anonymous type symbol associated with this lambda
        Private _lazyAnonymousDelegateSymbol As NamedTypeSymbol = ErrorTypeSymbol.UnknownResultType

        Public Sub New(
            syntaxNode As SyntaxNode,
            unboundLambda As UnboundLambda,
            parameters As ImmutableArray(Of BoundLambdaParameterSymbol),
            returnType As TypeSymbol,
            binder As Binder)

            MyBase.New(syntaxNode, parameters, returnType, binder)

            Debug.Assert(returnType IsNot ReturnTypePendingDelegate)
            Debug.Assert(unboundLambda IsNot Nothing)

            _unboundLambda = unboundLambda
        End Sub

        Public ReadOnly Property UnboundLambda As UnboundLambda
            Get
                Return _unboundLambda
            End Get
        End Property

        Public Overrides ReadOnly Property SynthesizedKind As SynthesizedLambdaKind
            Get
                Return SynthesizedLambdaKind.UserDefined
            End Get
        End Property

        Public Overrides ReadOnly Property IsAsync As Boolean
            Get
                Return (_unboundLambda.Flags And SourceMemberFlags.Async) <> 0
            End Get
        End Property

        Public Overrides ReadOnly Property IsIterator As Boolean
            Get
                Return (_unboundLambda.Flags And SourceMemberFlags.Iterator) <> 0
            End Get
        End Property

        Public Overrides ReadOnly Property AssociatedAnonymousDelegate As NamedTypeSymbol
            Get
                If Me._lazyAnonymousDelegateSymbol Is ErrorTypeSymbol.UnknownResultType Then
                    Dim newValue As NamedTypeSymbol = MakeAssociatedAnonymousDelegate()
                    Dim oldValue As NamedTypeSymbol = Interlocked.CompareExchange(Me._lazyAnonymousDelegateSymbol, newValue, ErrorTypeSymbol.UnknownResultType)
                    Debug.Assert(oldValue Is ErrorTypeSymbol.UnknownResultType OrElse oldValue Is newValue)
                End If
                Return Me._lazyAnonymousDelegateSymbol
            End Get
        End Property

        Friend Function MakeAssociatedAnonymousDelegate() As NamedTypeSymbol
            Dim anonymousDelegateSymbol As NamedTypeSymbol = Me._unboundLambda.InferredAnonymousDelegate.Key
            Dim targetSignature As New UnboundLambda.TargetSignature(anonymousDelegateSymbol.DelegateInvokeMethod)
            Dim boundLambda As BoundLambda = Me._unboundLambda.Bind(targetSignature)

            ' NOTE: If the lambda does not have an associated anonymous delegate, but 
            ' NOTE: the target signature of the lambda is the same as its anonymous delegate 
            ' NOTE: would have had if it were created, we still return this delegate. 
            ' NOTE: This is caused by performance trade-offs made in lambda binding

            If boundLambda.LambdaSymbol IsNot Me Then
                Return Nothing
            End If

            Return anonymousDelegateSymbol
        End Function
    End Class
End Namespace