Module Module1

    Dim BoardSquare(8, 8) As String, DupeBoard(8, 8) As String
    Dim Flipped(25, 2) As Integer
    Dim PlayerIcon As String = "X", AIIcon As String = "O"
    Dim GameOver As Boolean = False, Hints As Boolean = False

    Sub Main()
        Dim Quit As String
        Dim HintChoice As String

        Do
            Console.Write("Do You Want To Enable Hints (Y/N) : ") : HintChoice = Console.ReadLine.ToLower()
            If HintChoice = "y" Then Hints = True
            Console.Clear()

            Call StartOfGame()

            Console.Write("Do You Wish To Continue (Y/N) : ") : Quit = Console.ReadLine()
        Loop Until Quit.ToLower() = "n"

    End Sub

    Sub StartOfGame()
        Randomize()
        Call AssignArray()
        Dim RndStarter As Integer = CInt(Rnd() * 1)
        Dim NextMove As Integer
        Dim Winner As String

        Console.WriteLine("Player Icon : X     Computer Icon : O ")

        Call ShowBoard()

        If RndStarter = 0 Then
            Call GetAIMove()
            NextMove = 1
        Else
            Call GetPlayerMove()
            NextMove = 2
        End If

        Call ShowBoard()

        Do
            If NextMove = 1 Then
                Call GetPlayerMove()
                NextMove = 2
                Call CheckWin(AIIcon)
                If Hints = True Then Call ShowHints()
                Call ShowBoard()
            ElseIf NextMove = 2 Then
                Call GetAIMove()
                NextMove = 1
                Call CheckWin(PlayerIcon)
                If Hints = True Then Call ShowHints()
                Call ShowBoard()
            End If
        Loop Until GameOver = True

        If NextMove = 2 Then Winner = "You" Else Winner = "Computer"

        Console.WriteLine("{0} Won The Game. Congratulations.", Winner)


    End Sub

    Sub GetPlayerMove()
        Dim XMove, YMove As Integer
        Dim Input As String
        Dim MoveMade As Boolean = False

        Do
            Console.Write("Enter Horizontal Position (A-H) : ") : Input = Console.ReadLine
            XMove = Asc(Input) - 96
            Do
                Console.Write("Enter Vertical Position (1-8) : ") : Input = Console.ReadLine()
                YMove = CInt(Input)
            Loop Until IsNumeric(Input) = True AndAlso CInt(Input) <= 8 AndAlso CInt(Input) >= 1

            If ValidMoveCheck(XMove, YMove, PlayerIcon) <> 0 AndAlso IsOnBoard(XMove, YMove) = True Then
                Call MakeMove(XMove, YMove, PlayerIcon)
                MoveMade = True
            End If

        Loop Until MoveMade = True

    End Sub

    Sub GetAIMove()
        Randomize()
        Dim BestX, BestY, BestScore, ScoreHolder As Integer
        Dim StrChar As String

        'Determines the best scoring move for the computer
        '
        
        Call GetAllValidMoves(AIIcon)

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                If DupeBoard(i, j) = "'" Then
                    ScoreHolder = ValidMoveCheck(i, j, AIIcon)
                    If ScoreHolder > BestScore Then
                        BestScore = ScoreHolder
                        BestX = i
                        BestY = j
                    End If
                    If ScoreHolder = BestScore AndAlso IsCornerSquare(i, j) = True Then
                        BestX = i
                        BestY = j
                    End If
                End If
            Next
        Next

        Call MakeMove(BestX, BestY, AIIcon)

        StrChar = Chr(BestX + 96)
        Console.WriteLine("AI Choose Square  X: {0}  Y: {1}", StrChar, BestY.ToString())

        Console.WriteLine()

    End Sub

    Function ValidMoveCheck(ByVal XCord As Integer, ByVal YCord As Integer, ByVal Icon As String) As Integer
        Dim EnemyIcon As String
        Dim Moves(16) As Integer
        Dim XStart, YStart, YCordTemp, XCordTemp As Integer
        Dim Count As Integer

        For RowCount As Integer = 1 To 25
            For ColCount As Integer = 1 To 2
                Flipped(RowCount, ColCount) = vbNull
            Next
        Next

        If BoardSquare(YCord, XCord) <> " " Or IsOnBoard(YCord, XCord) = False Then
            Return 0
        End If

        XStart = XCord
        YStart = YCord

        BoardSquare(XCord, YCord) = Icon

        If Icon = "X" Then
            EnemyIcon = "O"
        Else
            EnemyIcon = "X"
        End If

        ' Moves(Odd) Increases X    Moves(Even) Increases Y
        Moves(1) = 1 : Moves(2) = 0
        Moves(3) = 1 : Moves(4) = 1
        Moves(5) = 0 : Moves(6) = 1
        Moves(7) = -1 : Moves(8) = 1
        Moves(9) = -1 : Moves(10) = 0
        Moves(11) = -1 : Moves(12) = -1
        Moves(13) = 0 : Moves(14) = -1
        Moves(15) = 1 : Moves(16) = -1
        Count = 1

        For i As Integer = 1 To 8

            XCordTemp = XCord + Moves((i * 2) - 1)
            YCordTemp = YCord + Moves(i * 2)

            While IsOnBoard(XCordTemp, YCordTemp) = True AndAlso BoardSquare(XCordTemp, YCordTemp) = EnemyIcon

                XCordTemp = XCordTemp + Moves(((i * 2) - 1))
                YCordTemp = YCordTemp + Moves((i * 2))

                If IsOnBoard(XCordTemp, YCordTemp) = False Then
                    Exit While
                End If

                If BoardSquare(XCordTemp, YCordTemp) = Icon Then

                    While True
                        XCordTemp -= Moves((i * 2) - 1)
                        YCordTemp -= Moves(i * 2)

                        If XCordTemp = XStart AndAlso YCordTemp = YStart Then
                            Exit While
                        End If

                        Flipped(Count, 1) = XCordTemp 'Assigns values for all flipped pieces
                        Flipped(Count, 2) = YCordTemp
                        Count += 1
                    End While
                End If
            End While
        Next

        BoardSquare(XCord, YCord) = " "

        If Count <> 1 Then
            Return Count
        Else
            Return 0
        End If


    End Function

    Function IsOnBoard(ByVal XCord As Integer, ByVal YCord As Integer) As Boolean

        If YCord > 8 Or YCord < 1 Or XCord > 8 Or XCord < 1 Then
            Return False
        Else
            Return True
        End If

    End Function

    Function IsCornerSquare(ByVal XCord As Integer, ByVal YCord As Integer) As Boolean

        If (XCord = 8 AndAlso YCord = 8) Or (XCord = 1 AndAlso YCord = 8) Or (XCord = 1 AndAlso YCord = 1) Or _
        (XCord = 8 AndAlso YCord = 1) Then
            Return True
        Else
            Return False
        End If

    End Function

    Sub MakeMove(ByVal XCord As Integer, ByVal YCord As Integer, ByVal Icon As String)
        Dim Count As Integer = 1

        If ValidMoveCheck(XCord, YCord, Icon) <> 0 Then
            BoardSquare(XCord, YCord) = Icon

            While Flipped(Count, 1) <> vbNull
                BoardSquare(Flipped(Count, 1), Flipped(Count, 2)) = Icon
                Count += 1
            End While

        End If
    End Sub

    Sub AssignArray()

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                BoardSquare(i, j) = (" ")
            Next
        Next

        BoardSquare(5, 5) = "X"
        BoardSquare(4, 4) = "X"
        BoardSquare(4, 5) = "O"
        BoardSquare(5, 4) = "O"

    End Sub

    Sub ShowBoard()
        Dim HLine As String = "  +--+--+--+--+--+--+--+--+ "
        Dim XScore As Integer = 0
        Dim OScore As Integer = 0

        Console.WriteLine()
        Console.WriteLine("   A  B  C  D  E  F  G  H")

        For i As Integer = 1 To 8
            Console.WriteLine(HLine)
            For j As Integer = 1 To 1
                Console.Write(i.ToString() + " ")
                Console.Write("|" + BoardSquare(1, i) + " |" + BoardSquare(2, i) + " |" + BoardSquare(3, i) + " |" + _
                              BoardSquare(4, i) + " |" + BoardSquare(5, i) + " |" + BoardSquare(6, i) + " |" + _
                              BoardSquare(7, i) + " |" + BoardSquare(8, i) + " |")
            Next
            Console.WriteLine()
        Next

        Console.WriteLine(HLine)

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                If BoardSquare(i, j) = "X" Then XScore += 1
                If BoardSquare(i, j) = "O" Then OScore += 1
            Next
        Next

        Console.WriteLine()
        Console.WriteLine("   Computer : {0}    Player : {1}  ", OScore, XScore)
        Console.WriteLine()

    End Sub

    Sub GetAllValidMoves(ByVal Icon As String)

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                DupeBoard(i, j) = " "
            Next
        Next

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                If ValidMoveCheck(i, j, Icon) <> 0 Then
                    DupeBoard(i, j) = "'"
                End If
            Next
        Next

    End Sub

    Sub ShowHints()

        Call GetAllValidMoves(PlayerIcon)

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                If DupeBoard(i, j) = "'" AndAlso BoardSquare(i, j) = " " Then BoardSquare(i, j) = DupeBoard(i, j)
            Next
        Next

    End Sub

    Sub CheckWin(ByVal Icon As String)

        Call GetAllValidMoves(Icon)

        For i As Integer = 1 To 8
            For j As Integer = 1 To 8
                If DupeBoard(i, j) = "'" Then
                    GameOver = False
                    Exit Sub
                End If
            Next
        Next

        GameOver = True

    End Sub

End Module