' 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 Microsoft.CodeAnalysis.VisualBasic.Syntax

Namespace Microsoft.CodeAnalysis.VisualBasic.Utilities
    Friend Class ImportsStatementComparer
        Implements IComparer(Of ImportsStatementSyntax)

        Public Shared ReadOnly SystemFirstInstance As IComparer(Of ImportsStatementSyntax) = New ImportsStatementComparer(TokenComparer.SystemFirstInstance)
        Public Shared ReadOnly NormalInstance As IComparer(Of ImportsStatementSyntax) = New ImportsStatementComparer(TokenComparer.NormalInstance)

        Private ReadOnly _importsClauseComparer As IComparer(Of ImportsClauseSyntax)

        Public Sub New(tokenComparer As IComparer(Of SyntaxToken))
            Debug.Assert(tokenComparer IsNot Nothing)
            Me._importsClauseComparer = New ImportsClauseComparer(tokenComparer)
        End Sub

        Public Function Compare(directive1 As ImportsStatementSyntax, directive2 As ImportsStatementSyntax) As Integer Implements IComparer(Of ImportsStatementSyntax).Compare
            If directive1 Is directive2 Then
                Return 0
            End If

            ' the clauses will already be sorted by now.
            If directive1.ImportsClauses.Count = 0 And directive2.ImportsClauses.Count = 0 Then
                Return 0
            ElseIf directive1.ImportsClauses.Count = 0 Then
                Return -1
            ElseIf directive2.ImportsClauses.Count = 0 Then
                Return 1
            Else
                Return _importsClauseComparer.Compare(directive1.ImportsClauses(0), directive2.ImportsClauses(0))
            End If
        End Function
    End Class
End Namespace