Option Explicit On
Option Strict On
Option Infer Off
Public Class frmMain
    'declare array at class level ?
    Dim inAvailableDvds As IO.StreamReader
    Dim strDVDs As String
    Dim dblPrices() As Double

    Public Sub frmMain_Load(sender As Object, e As EventArgs) Handles Me.Load
        'display availableDVDs.txt on load
        'assign to array and display first column
        'if file exists, open file
        If IO.File.Exists("availableDVDs.txt") Then
            inAvailableDvds = IO.File.OpenText("availableDVDs.txt")

            'add items to listbox from file
            Do Until inAvailableDvds.Peek = -1
                'read file
                strDVDs = inAvailableDvds.ReadLine
                'display titles - find and stop at comma
                lstDvds.Items.Add(strDVDs.Substring(0, strDVDs.IndexOf(",")))
                'find comma, pull remaining string
                Dim strTemp As String = strDVDs.Substring(strDVDs.IndexOf(",") + 1)
                'convert string to double

                'assign to array
            Loop
            'bring selected index to first option and close file
            lstDvds.SelectedIndex = 0
            inAvailableDvds.Close()
        End If

    End Sub
    Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
        'if no selection made, prompt user to select an item and set index to 0
        'else add item to cart and remove from dvd list
        If lstDvds.SelectedIndex = -1 Then
            MessageBox.Show("Please select an item to add.")
            lstDvds.SelectedIndex = 0
        Else
            'add item to cart
            lstCart.Items.Add(lstDvds.SelectedItem)
            'remove from dvds
            lstDvds.Items.Remove(lstDvds.SelectedItem)

            'insert calculation method below
            'CalculateTotals()
        End If

    End Sub

    Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click
        'if no selection is made (or no items in cart) prompt user to select an item
        'else remove item from the cart and add it back to the dvd list
        If lstCart.Items.Count = 0 Then
            MessageBox.Show("Your cart is currently empty. Please add an item.")
        ElseIf lstCart.SelectedIndex = -1 Then
            MessageBox.Show("Please select an item to remove.")
            lstCart.SelectedIndex = 0
        Else
            'add item back to dvds
            lstDvds.Items.Add(lstCart.SelectedItem)
            'remove item from cart
            lstCart.Items.Remove(lstCart.SelectedItem)

            'insert calculation method below
        End If

    End Sub

    Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        Dim strCustNumber As String = txtCustNum.Text

        If strCustNumber Like "####" Then
            'store customer number and write to file




        ElseIf strCustNumber = String.Empty Then 'check if empty
            MessageBox.Show("Please enter a customer number to save this order before creating a new order.")
        ElseIf strCustNumber <> "####" Then 'check for length
            MessageBox.Show("The customer number must contain 4 digits.")
        End If

    End Sub
    Private Sub CalculateTotals()
        Const dblTaxRate As Double = 0.04
        Const intShippingCharge As Integer = 1
        Dim dblSubtotal As Double


        'temporary display placeholders


        txtSubtotal.Text = dblSubtotal.ToString("C2")
        'calculate tax amt * subtotal = tax
        txtTax.Text = dblTaxRate.ToString("C2")
        'calculate shipping - not > $5
        txtShipping.Text = intShippingCharge.ToString("C2")

    End Sub
    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        'exits application
        Me.Close()
    End Sub
End Class