Vending machine (Console)

Option Explicit Off
Module Module1

    '' DEBUG-MODE 1 (True), 0 (False)
#Const DEBUG = 1

    Dim credit As Integer = -1 '' Credit with dummy value
    Dim S_product As String() = {"Cheese 'n onion walkers", "Rockstar Energy drink", "Twix", "Snickers", "Ready salted"}
    Dim N_product As Integer() = {50, 99, 69, 67, 50}
    Dim list(5) As String   '' List of products (5 values maximum)
    Dim itemsBought As Integer = 0

    '' Adds a product to the list of bought items.
    '' n (int) - The position of the list
    '' name (string) - Product name
    Sub addProduct(n As Integer, name As String)
        list(n) = name
        Debug.Print("Added product: " & name & " to list at position {0}", n)
    End Sub

    '' Checks if you have enough to buy an item by comparing
    '' an integer with the amount of credit the user has.
    ''Params: n (int) the integer to compare with credit
    Function isEnough(ByVal n As Integer) As Boolean
        If credit >= n Then
            Return True
        End If

#If Debug = 1 Then
        Debug.Print("Credit is {0} however not enough.", credit)
#End If

        Return False
    End Function

    '' Buy product with the given product position.
    '' Returns True if product is bought without problem otherwise
    '' false which could be due to having not enough credit or
    '' an incorrect given position.

    Function buyProduct(ByVal productPosition As Integer) As Boolean
        If productPosition >= 1 And productPosition <= 5 Then
            '' Check if user has enough money
            Dim productPrice As Integer = N_product(productPosition - 1)
            Debug.Assert(IsNumeric(productPrice))   '' is the position correct and will it return a numeric value?

            If isEnough(productPrice) Then
                credit = credit - productPrice

                Dim prodName As String = S_product(productPosition - 1)
                Console.WriteLine("Bought item: {0} current credit: {1}p", prodName, credit)

#If Debug = 1 Then
                Debug.Print("Bought item: {0}", prodName)
                Debug.Print("Credit reduced to {0}.", credit)
#End If


                '' Increment counter
                itemsBought = itemsBought + 1
                '' Same case with list array.
                list(itemsBought - 1) = prodName
                Return True
            Else
                Console.WriteLine("Not enough credit")
                Return False
            End If
        Else

#If Debug = 1 Then
            Debug.Print("Incorrect product position")   '' Kill the user.
#End If
            Return False
        End If
    End Function

    '' Loop until a valid amount of credit is input.
    Sub getCoins()
        Dim counter = 0
        If itemsBought >= 1 Then
            Console.WriteLine("Type 'exit' otherwise continue!")
            Dim tmp As String = Console.ReadLine()
            If tmp = "exit" Then
                getItemsBought()
                Stop
            End If
        End If

        Do
            Console.WriteLine("Please enter the amount of credit you wish to input in pennies (£1 (100p), £2 (200p), 50p): ")
            Dim tmp As String
            tmp = Console.ReadLine()
            If IsNumeric(tmp) Then
                credit = tmp
            Else
                counter = counter + 1
            End If

            '' Exit loop....
            If counter = 5 Then
                Stop
            End If
        Loop Until (credit > -1)

    End Sub

    Sub getItemsBought()
        For i = 0 To list.Length - 1
            If Not IsNothing(list(i)) Then
                Console.WriteLine("#{0} Item bought: {1}", i + 1, list(i))
            End If
        Next
    End Sub

    Sub getItemsForSale()
        For i = 0 To S_product.Length - 1
            Console.WriteLine("Number: {0} || Product name: {1}", i + 1, S_product(i))
        Next
    End Sub

    '' Use simple recursion to get the input of user.
    Function handleItemList(Optional ByVal n As Integer = 0) As Integer
        Dim counter = n
        If counter >= 5 Then
            Return -1
        End If

        getItemsForSale()
        Console.WriteLine("Type the number of the product you would like to buy otherwise type 'exit': ")
        Dim S_tmp As String = Console.ReadLine()
        Dim N_tmp As Integer = -1
        If IsNumeric(S_tmp) Then
            N_tmp = S_tmp

            If N_tmp >= 1 Or N_tmp <= 5 Then
                Return N_tmp
            Else
                counter = counter + 1
                Return handleItemList(counter)
            End If


        ElseIf S_tmp = "exit" Then
            Return -1
        Else
            Return handleItemList()
        End If

    End Function

    Sub Main()
        Dim stopProgram As Boolean = False
        While stopProgram <> True
            '' Ask for more coins.
            If credit <= 20 Then
                getCoins()
            End If

            Dim item As Integer = handleItemList()
            If item <> -1 Then
                buyProduct(item)
            Else
                getItemsBought()
                Exit While
            End If

        End While
        Console.ReadLine()
    End Sub

End Module