' 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.Linq.Expressions
Imports System.ComponentModel
 
Namespace Microsoft.VisualStudio.LanguageServices.UnitTests
    Public Class PropertyChangedTestMonitor
 
        Private ReadOnly _propertyChangedObject As INotifyPropertyChanged
        Private ReadOnly _expectationCountMap As Dictionary(Of String, Integer)
        Private ReadOnly _failures As List(Of String)
 
        Public Sub New(propertyChangedObject As INotifyPropertyChanged, Optional strict As Boolean = False)
            AddHandler propertyChangedObject.PropertyChanged, AddressOf PropertyChangedHandler
            Me._propertyChangedObject = propertyChangedObject
            Me.strict = strict
 
            _failures = New List(Of String)
            _expectationCountMap = New Dictionary(Of String, Integer)
        End Sub
 
        Private Property strict As Boolean
 
        Public Sub AddExpectation(Of TResult)(expectation As Expression(Of Func(Of TResult)), Optional count As Integer = 1)
            Dim propertyName = DirectCast(expectation.Body, MemberExpression).Member.Name
 
            If _expectationCountMap.ContainsKey(propertyName) Then
                _expectationCountMap(propertyName) += count
            Else
                _expectationCountMap(propertyName) = count
            End If
        End Sub
 
        Private Sub PropertyChangedHandler(sender As Object, e As PropertyChangedEventArgs)
            If _expectationCountMap.ContainsKey(e.PropertyName) Then
                _expectationCountMap(e.PropertyName) -= 1
                If _expectationCountMap(e.PropertyName) < 0 AndAlso strict Then
                    _failures.Add(String.Format("Property '{0}' was updated more times than expected.", e.PropertyName))
                End If
            ElseIf strict Then
                _failures.Add(String.Format("Property '{0}' was unexpectedly updated.", e.PropertyName))
            End If
        End Sub
 
        Public Sub VerifyExpectations()
            For Each failureCase In _expectationCountMap.Where(Function(e) e.Value > 0)
                _failures.Add(String.Format("Property '{0}' was expected to be updated {1} more time(s) than it was", failureCase.Key, failureCase.Value))
            Next
 
            If _failures.Any() Then
                Assert.False(True, String.Format("The following INotifyPropertyChanged expectations were not met: {0}", Environment.NewLine + String.Join(Environment.NewLine, _failures)))
            End If
        End Sub
 
        Public Sub Detach()
            RemoveHandler _propertyChangedObject.PropertyChanged, AddressOf PropertyChangedHandler
        End Sub
    End Class
End Namespace