Imports System

Imports System.Collections.ObjectModel

Imports System.Collections.Specialized

Imports System.Text.RegularExpressions

Imports Xceed.Wpf.DataGrid.Stats

Namespace Xceed.Wpf.Documentation

  ' This statistical function derives from CumulativeStatFunction because it can

  ' accumulate "partial" results. For instance, results of sub-group. This allows

  ' for better performance.

  Public Class CountIfFunction

    Inherits CumulativeStatFunction

    ' A parameterless constructor is necessary to use the class in XAML.

    Public Sub New()

      MyBase.New()

      m_conditions = New ObservableCollection(Of String)()

      AddHandler m_conditions.CollectionChanged, AddressOf m_conditions_CollectionChanged

    End Sub

    ' Initialize a new instance of the CountIfFunction specifying the ResultPropertyName

    ' and the SourcePropertyName.

    Public Sub New(ByVal resultPropertyName As String, ByVal sourcePropertyNames As String)

      MyBase.New(resultPropertyName, sourcePropertyNames)

      m_conditions = New ObservableCollection(Of String)()

      AddHandler m_conditions.CollectionChanged, AddressOf m_conditions_CollectionChanged

    End Sub

    ' Each condition applies to the values of the corresponding source property name

    ' (e.g., the first condition applies to the values of the first source property name).

    ' Gets the conditions that will be applied to the various values.

    Public ReadOnly Property Conditions() As ObservableCollection(Of String)

      Get

        Return m_conditions

      End Get

    End Property

    ' When the grid needs to create temporary CountIfFunction instances for its

    ' calculation, this method will be called. Be sure to initialize everything

    ' having an impact on the result here.

    Protected Overrides Sub InitializeFromInstance(ByVal source As StatFunction)

      MyBase.InitializeFromInstance(source)

      For Each condition As String In (CType(source, CountIfFunction)).Conditions

        Me.Conditions.Add(condition)

      Next condition

    End Sub

    ' Validate the CountIf statistical function to make sure that it is capable

    ' to calculate its result. In our case, we need to make sure that a ResultPropertyName

    ' has been specified and that we have the same number of source property names

    ' as conditions.

    Protected Overrides Sub Validate()

      If (Me.ResultPropertyName Is Nothing) OrElse

         (Me.ResultPropertyName = String.Empty) OrElse

         (m_conditions.Count <> Me.SourcePropertyName.Split(","c).Length) Then

        Throw New InvalidOperationException()

      End If

    End Sub

    ' This method will be called when a new calculation is about to begin.

    Protected Overrides Sub Reset()

      m_count = 0

    End Sub

    ' This method will be called for each data item that is part of the set (a group or

    ' the grid).

    Protected Overrides Sub Accumulate(ByVal values As Object())

      Dim i As Integer = 0

      Do While i < m_conditions.Count

        ' As soon as one condition does not match is associated value, we simply

        ' return without having done the accumulation (the count increment).

        If (Not Regex.IsMatch(values(i).ToString(), m_conditions(i))) Then

          Return

        End If

        i += 1

      Loop

      ' The compilation configuration will cause this line to throw

      ' if an OverflowException occurs.

      m_count += 1

    End Sub

    ' This method will be called when calculating the result of a group having

    ' sub-groups. Obviously, it will be called once for each sub-group.

    Protected Overrides Sub AccumulateChildResult(ByVal childResult As StatResult)

      m_count += Convert.ToInt64(childResult.Value)

    End Sub

    ' This method should return the result calculated so far.

    Protected Overrides Function GetResult() As StatResult

      Return New StatResult(m_count)

    End Function

    ' The addition of the Conditions property, which influences the result of the

    ' statistical function, the CountIf function requires us to override IsEquivalent

    ' and GetEquivalenceKey to return a new key when 2 instances are compared.

    Protected Overrides Function IsEquivalent(ByVal statFunction As StatFunction) As Boolean

      Dim countIfFunction As CountIfFunction = TryCast(statFunction, CountIfFunction)

      If countIfFunction Is Nothing Then

        Return False

      End If

      If m_conditions.Count <> countIfFunction.Conditions.Count Then

        Return False

      End If

      Dim i As Integer = 0

      Do While i < m_conditions.Count

        If m_conditions(i) <> countIfFunction.Conditions(i) Then

          Return False

        End If

        i += 1

      Loop

      Return MyBase.IsEquivalent(statFunction)

    End Function

    Protected Overrides Function GetEquivalenceKey() As Integer

      Dim hashCode As Integer = MyBase.GetEquivalenceKey()

      Dim i As Integer = 0

      Do While i < m_conditions.Count

        hashCode = hashCode Xor m_conditions(i).GetHashCode()

        i += 1

      Loop

      Return hashCode

    End Function

    ' Do not allow the Conditions property to be changed if the statistical function has

    ' been sealed (i.e, assigned to the DataGridCollectionView.StatFunctions property).

    Private Sub m_conditions_CollectionChanged(ByVal sender As Object, ByVal e As NotifyCollectionChangedEventArgs)

      Me.CheckSealed()

    End Sub

    Private m_conditions As ObservableCollection(Of String)

    Private m_count As Long

  End Class

End Namespace