Public Class frmSki
    Dim ItemNames(3), ItemCosts(3) As String ' Declaring Arrays
    Dim Total, TotalIndex As Integer ' Necessary global variables
    Dim Discount As Decimal

    Private Sub frmSki_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim Count As Integer
        Dim ColsFormat As String = "{0, -12}{1, -15}{2, -15}{3, -15}" ' Spacings for list box
        LoadItems(True) ' Runs LoadItems, Creating/writing to file if not found.
        For Count = 0 To 3 ' Loop, adding read items to the combo box
            cboItems.Items.Add(ItemNames(Count))
        Next
        cboItems.SelectedIndex = 0 ' Select the first index (prevents blank combo box at startup)
        lstItems.Items.Add(String.Format(ColsFormat, "Quantity", "Item Name", "Cost per unit", "Total Cost")) ' Adds headers to list box
        TotalIndex = 0 ' Sets global variable TotalIndex.
        nudWeeks.Value = 1
        nudWeeks.Minimum = 1 ' already set on form, just to prove there's no need for negative validation.
    End Sub

    Private Sub LoadItems(ByVal Create As Boolean) ' Create as in Create/Write file.
        Dim Count As Integer

        Dim FilePathN As String = Application.StartupPath + "\ItemNames.ben" ' file path (app.path + filename)
        Dim FilePathC As String = Application.StartupPath + "\ItemCosts.ben"

        If System.IO.File.Exists(FilePathN) And System.IO.File.Exists(FilePathC) Then ' Validation, if both files exist.
            Dim ItemCostR As New System.IO.StreamReader(FilePathC, True) ' Loading StreamReaders
            Dim ItemListR As New System.IO.StreamReader(FilePathN, True)
            For Count = 0 To 3 ' loops to fill array
                ItemNames(Count) = ItemListR.ReadLine ' Reads appropriate line of text file, filling array.
                ItemCosts(Count) = ItemCostR.ReadLine
            Next Count
            ItemCostR.Close() ' Closes StreamReaders, allowing files to be used by other programs.
            ItemListR.Close()
        ElseIf Create = True Then ' If files aren't found
            ItemNames(0) = "Jacket" 'Fills arrays
            ItemNames(1) = "Helmet"
            ItemNames(2) = "Salopettes"
            ItemNames(3) = "Goggles"

            ItemCosts(0) = "14.0"
            ItemCosts(1) = "14.0"
            ItemCosts(2) = "12.0"
            ItemCosts(3) = "8.0"

            System.IO.File.WriteAllLines(FilePathN, ItemNames) ' Creates both files, writing arrays to them.
            System.IO.File.WriteAllLines(FilePathC, ItemCosts)
        End If
    End Sub

    Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        Dim ColsFormat As String = "{0, -15}{1, -20}{2, -17}{3, -15}" ' Listbox spacing
        Dim ItemName As String ' Necessary local variables
        Dim UnitPrice, Quantity, TotalItemPrice, Count As Integer
        ItemName = cboItems.Text ' Setting variables to appropriate data
        Quantity = nudItemNo.Value
        If Quantity > 0 Then ' Validation, preventing "0" or negative values (despite the nud minimum being 0.)
            For Count = 0 To 3 ' Loops a case, checking the array and setting the unit price.
                Select Case ItemName
                    Case ItemNames(Count)
                        UnitPrice = ItemCosts(Count) ' Unit price for a length of time.
                End Select
            Next
            TotalItemPrice = UnitPrice * Quantity ' Sets the price for current addition
            Total = Total + TotalItemPrice ' Updates Total
            lstItems.Items.Add(String.Format(ColsFormat, Quantity, ItemName, FormatCurrency(UnitPrice), FormatCurrency(TotalItemPrice))) ' Adds data to listbox
            UpdateTotal() ' Runs UpdateTotal.
            TotalIndex = TotalIndex + 1 ' Updates TotalIndex global variable.
        Else
            Console.Beep()
            MsgBox("Please enter a quantity.")
        End If
    End Sub

    Private Sub UpdateTotal()
        Dim Weeks As Integer
        Dim TotalW As Decimal
        Weeks = nudWeeks.Value
        Discount = 1 ' Sets base discount value.
        lblDiscount.Visible = True ' Sets both labels visible on first run (invisible prior for aesthetics).
        lblTotal.Visible = True
        If chkTrip.Checked Then ' Sets discount if necessary.
            Discount = 0.9
        End If
        TotalW = Total * Weeks
        lblTotal.Text = FormatCurrency(TotalW * Discount) ' Works out the total cost (inc. Discount)
        lblDiscount.Text = FormatCurrency(TotalW - (TotalW * Discount)) ' Works Out Discount.
    End Sub

    Private Sub chkTrip_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chkTrip.CheckedChanged
        UpdateTotal() ' If the discount checkbox is changed, runs UpdateTotal.
    End Sub

    Private Sub btnOutput_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOutput.Click
        Dim Count As Integer
        Dim List(TotalIndex), DiscountT, TotalT, File As String ' Declares string variables (inc. array)
        Dim FilePathO As String = Application.StartupPath + "\Output.ben" ' Sets the file path.
        If Not lblDiscount.Text = "" Then
            File = "Notepad " + FilePathO ' Sets a string for use in Shell()
            TotalT = lblTotal.Text ' Sets necessary variables.
            DiscountT = lblDiscount.Text
            For Count = 0 To TotalIndex ' Fills out the array with the necessary number of items.
                List(Count) = lstItems.Items(Count) ' Uses the listboxes data.
            Next
            System.IO.File.WriteAllLines(FilePathO, List) ' Writes to text file, overwriting previous data
            Dim TotalsO As New System.IO.StreamWriter(FilePathO, True) ' Opens StreamWriter
            TotalsO.WriteLine("Discount " + DiscountT, True) ' Writes Discount to file
            TotalsO.WriteLine("Total " + TotalT, True) ' Writes Total to file
            TotalsO.Close() ' Closes StreamWriter so file can be opened by other programs.
            Shell(File) ' Runs File in shell, opening Notepad, along with Output.ben
        Else
            MsgBox("Please add some items before output.")
        End If
    End Sub
End Class