' 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
Imports Microsoft.CodeAnalysis
Imports Microsoft.CodeAnalysis.ExtractMethod
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax

Namespace Microsoft.CodeAnalysis.VisualBasic.ExtractMethod
    Partial Friend NotInheritable Class VisualBasicExtractMethodService
        Partial Friend Class VisualBasicMethodExtractor
            Partial Private Class VisualBasicCodeGenerator
                Private Class ExpressionCodeGenerator
                    Inherits VisualBasicCodeGenerator

                    Public Sub New(
                            selectionResult As SelectionResult,
                            analyzerResult As AnalyzerResult,
                            options As ExtractMethodGenerationOptions)
                        MyBase.New(selectionResult, analyzerResult, options)
                    End Sub

                    Protected Overrides Function CreateMethodName() As SyntaxToken
                        Dim methodName = "NewMethod"
                        Dim containingScope = Me.SelectionResult.GetContainingScope()

                        methodName = GetMethodNameBasedOnExpression(methodName, containingScope)

                        Dim semanticModel = SemanticDocument.SemanticModel
                        Dim nameGenerator = New UniqueNameGenerator(semanticModel)
                        Return SyntaxFactory.Identifier(
                            nameGenerator.CreateUniqueMethodName(containingScope, methodName))
                    End Function

                    Private Shared Function GetMethodNameBasedOnExpression(methodName As String, expression As SyntaxNode) As String
                        If expression.IsParentKind(SyntaxKind.EqualsValue) AndAlso
                           expression.Parent.IsParentKind(SyntaxKind.VariableDeclarator) Then

                            Dim varDecl = DirectCast(expression.Parent.Parent, VariableDeclaratorSyntax)
                            If varDecl.Names.Count <> 1 Then
                                Return methodName
                            End If

                            Dim identifierNode = varDecl.Names(0)
                            If identifierNode Is Nothing Then
                                Return methodName
                            End If

                            Dim name = identifierNode.Identifier.ValueText
                            Return If(name IsNot Nothing AndAlso name.Length > 0, MakeMethodName("Get", name, camelCase:=False), methodName)
                        End If

                        If TypeOf expression Is MemberAccessExpressionSyntax Then
                            expression = CType(expression, MemberAccessExpressionSyntax).Name
                        End If

                        If TypeOf expression Is NameSyntax Then
                            Dim lastDottedName = CType(expression, NameSyntax).GetLastDottedName()
                            Dim plainName = CType(lastDottedName, SimpleNameSyntax).Identifier.ValueText
                            Return If(plainName IsNot Nothing AndAlso plainName.Length > 0, MakeMethodName("Get", plainName, camelCase:=False), methodName)
                        End If

                        Return methodName
                    End Function

                    Protected Overrides Function GetInitialStatementsForMethodDefinitions() As ImmutableArray(Of StatementSyntax)
                        Contract.ThrowIfFalse(Me.SelectionResult.IsExtractMethodOnExpression)

                        Dim expression = DirectCast(Me.SelectionResult.GetContainingScope(), ExpressionSyntax)

                        If Me.AnalyzerResult.CoreReturnType.SpecialType <> SpecialType.System_Void Then
                            Return ImmutableArray.Create(Of StatementSyntax)(SyntaxFactory.ReturnStatement(expression))
                        Else
                            ' we have expression for void method (Sub). make the expression as call
                            ' statement if possible we can create call statement only from invocation
                            ' and member access expression. otherwise, it is not a valid expression.
                            ' return error code
                            If expression.Kind <> SyntaxKind.InvocationExpression AndAlso
                               expression.Kind <> SyntaxKind.SimpleMemberAccessExpression Then
                                Return ImmutableArray(Of StatementSyntax).Empty
                            End If

                            Return ImmutableArray.Create(Of StatementSyntax)(SyntaxFactory.ExpressionStatement(expression))
                        End If
                    End Function

                    Protected Overrides Function GetFirstStatementOrInitializerSelectedAtCallSite() As StatementSyntax
                        Return Me.SelectionResult.GetContainingScopeOf(Of StatementSyntax)()
                    End Function

                    Protected Overrides Function GetLastStatementOrInitializerSelectedAtCallSite() As StatementSyntax
                        Return GetFirstStatementOrInitializerSelectedAtCallSite()
                    End Function

                    Protected Overrides Async Function GetStatementOrInitializerContainingInvocationToExtractedMethodAsync(cancellationToken As CancellationToken) As Task(Of StatementSyntax)
                        Dim enclosingStatement = GetFirstStatementOrInitializerSelectedAtCallSite()
                        Dim callSignature = CreateCallSignature().WithAdditionalAnnotations(CallSiteAnnotation)

                        Dim sourceNode = Me.SelectionResult.GetContainingScope()
                        Contract.ThrowIfTrue(
                            sourceNode.IsParentKind(SyntaxKind.SimpleMemberAccessExpression) AndAlso
                            DirectCast(sourceNode.Parent, MemberAccessExpressionSyntax).Name Is sourceNode,
                            "invalid scope. scope is not an expression")

                        ' To lower the chances that replacing sourceNode with callSignature will break the user's
                        ' code, we make the enclosing statement semantically explicit. This ends up being a little
                        ' bit more work because we need to annotate the sourceNode so that we can get back to it
                        ' after rewriting the enclosing statement.
                        Dim sourceNodeAnnotation = New SyntaxAnnotation()
                        Dim enclosingStatementAnnotation = New SyntaxAnnotation()
                        Dim newEnclosingStatement = enclosingStatement.
                            ReplaceNode(sourceNode, sourceNode.WithAdditionalAnnotations(sourceNodeAnnotation)).
                            WithAdditionalAnnotations(enclosingStatementAnnotation)

                        Dim updatedDocument = Await Me.SemanticDocument.Document.ReplaceNodeAsync(enclosingStatement, newEnclosingStatement, cancellationToken).ConfigureAwait(False)
                        Dim updatedRoot = Await updatedDocument.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(False)

                        newEnclosingStatement = DirectCast(updatedRoot.GetAnnotatedNodesAndTokens(enclosingStatementAnnotation).Single().AsNode(), StatementSyntax)

                        ' because of the complexification we cannot guarantee that there is only one annotation.
                        ' however complexification of names is prepended, so the last annotation should be the original one.
                        sourceNode = updatedRoot.GetAnnotatedNodesAndTokens(sourceNodeAnnotation).Last().AsNode()

                        Return newEnclosingStatement.ReplaceNode(sourceNode, callSignature)
                    End Function
                End Class
            End Class
        End Class
    End Class
End Namespace