Lua MiniMax AI tictactoe(Easy Mode AI)

_G.m = math
local AI = nil
local Player = nil
local Board = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
}
local PrevPlayed = nil
local Turn = nil

-- Basic Function TicTacToe
function DrawBoard()
    print(string.rep("-", 13))
    for i = 1, 3 do
        print("| "..tostring(Board[i][1]).." | "..tostring(Board[i][2]).." | "..tostring(Board[i][3]).." |")
    end
    print(string.rep("-", 13))
end

function ChooseTeam()
    ::again::
    io.write("Choose You Team (O or X) : ")
    local PlayerInput = string.upper(io.read())
    if PlayerInput == "O" then
        Player = PlayerInput
        AI = "X"
    elseif PlayerInput == "X" then
        Player = PlayerInput
        AI = "O"
    else
        print("Invaild Team, Choose Again")
        goto again
    end
end

function StartTurn()
    local n = m.random(1, 2)
    if n == 1 then Turn = Player else Turn = AI end
end

function IsAbleToFill(row, col)
    return type(Board[row][col])=="number"
end

function IsTie()
    for i = 1,3 do
        for j= 1, 3 do
            if IsAbleToFill(i, j) then
                return false
            end
        end
    end
    return true
end

function IsGameOver()
    for i = 1, 3 do
        -- Check Left or Right
        if Board[i][1] == Board[i][2] and Board[i][2] == Board[i][3] then
            return true
        -- Check Up and Down
        elseif Board[1][i] == Board[2][i] and Board[2][i] == Board[3][i] then
            return true
        end
    end
    -- More
    if Board[1][1] == Board[2][2] and Board[2][2] == Board[3][3] then
        return true
    elseif Board[1][3] == Board[2][2] and Board[2][2] == Board[3][1] then
        return true
    end
    return false
end

function PlayerFillBoard(row, col)
    if IsAbleToFill(row, col) then
        Board[row][col] = Player
    else
        return
    end
end

function AutoPlayRound()
    -- Function
    local function PlayerPlay()
        print("Player Turn!:")
        ::again::
        io.write("Choose to Fill Board from 1-9: ")
        local row, col
        local PlayerInput = tonumber(io.read())
        if PlayerInput > 9 then print("Invaild Team Try Again") goto again end
        -- Player Handle Choosing
        if PlayerInput <= 3 then
            row, col = 1, PlayerInput
            if not IsAbleToFill(row, col) then print("Board Already Filled Choose Another") goto again end
            PlayerFillBoard(row, col)
        elseif PlayerInput <= 6 then
            row, col = 2, PlayerInput-3
            if not IsAbleToFill(row, col) then print("Board Already Filled Choose Another") goto again end
            PlayerFillBoard(row, col)
        elseif PlayerInput <= 9 then
            print("AI Turn!:")
            row, col = 3, PlayerInput-6
            if not IsAbleToFill(row, col) then print("Board Already Filled Choose Another") goto again end
            PlayerFillBoard(row, col)
        end
        -- Change Turn
        PrevPlayed = Player
        Turn = AI
    end

    local function AIPlay()
        print("AI is Thinking and Choosing...")
        AIFill()
        PrevPlayed = AI
        Turn = Player
    end
    -- Turn AutoPlay
    if Turn == Player then PlayerPlay() else AIPlay() end
end
-- Minimax AI code

function MiniMaxCheckGameOver()
    for i = 1, 3 do
        -- Check Left or Right
        if Board[i][1] == Board[i][2] and Board[i][2] == Board[i][3] then
            return Board[i][1]
        -- Check Up and Down
        elseif Board[1][i] == Board[2][i] and Board[2][i] == Board[3][i] then
            return Board[1][i]
        end
    end
    -- More
    if Board[1][1] == Board[2][2] and Board[2][2] == Board[3][3] then
        return Board[1][1]
    elseif Board[1][3] == Board[2][2] and Board[2][2] == Board[3][1] then
        return Board[1][3]
    end
    return nil
end

function MiniMax(ismaxing)
    if MiniMaxCheckGameOver() == AI then return 1 end
    if MiniMaxCheckGameOver() == Player then return -1 end
    if IsTie() then return 0 end
    if ismaxing then
        -- MaxScore
        local maxscore = -m.huge
        for i = 1,3 do
            for j = 1, 3 do
                if IsAbleToFill(i, j) then
                    local temp = Board[i][j]
                    Board[i][j] = AI
                    local score = MiniMax(false)
                    maxscore = m.max(score, maxscore)
                    Board[i][j] = temp
                end
            end
        end
        return maxscore
    else
        -- MinScore
        local minscore = m.huge
        for i = 1,3 do
            for j = 1, 3 do
                if IsAbleToFill(i, j) then
                    local temp = Board[i][j]
                    Board[i][j] = AI
                    local score = MiniMax(true)
                    minscore = m.max(score, minscore)
                    Board[i][j] = temp
                end
            end
        end
        return minscore
    end
end

function AIFill()
    local bestscore = -m.huge
    local bestfill = nil
    for i = 1, 3 do
        for j = 1,3 do
            if IsAbleToFill(i, j) then
                local score = MiniMax(false)
                if score > bestscore then
                    bestscore = score
                    bestfill = {i, j}
                end
            end
        end
    end
    Board[bestfill[1]][bestfill[2]] = AI
end
-- Main Game Code
ChooseTeam()
StartTurn()
while true do
    DrawBoard()
    if IsGameOver() then print("Game Over Winner : "..PrevPlayed) break end
    if IsTie() then print("Game Tie!") break end
    AutoPlayRound()
end