curses-ox

local curses = require "curses"
local stdscr = curses.initscr ()
local O = {false,false,false,false,false,false,false,false,false}
local X = {false,false,false,false,false,false,false,false,false}
local win = {{1,2,3},
            {4,5,6},
            {7,8,9},
            {1,4,7},
            {2,5,8},
            {3,6,9},
            {1,5,9},
            {3,5,7}}
local rnd = math.random
local max = math.max
local add = table.insert
local unpak = table.unpack
local concat = table.concat
local finished = false

local function all(t1, t2)
  return t1[t2[1]] and t1[t2[2]] and t1[t2[3]]
end

local function any(t1, t2)
  local t = 0
  t = t + (t1[t2[1]] and 1 or 0)
  t = t + (t1[t2[2]] and 1 or 0)
  t = t + (t1[t2[3]] and 1 or 0)
  return t
end

local function randomChoice(args)
    return args[rnd(#args)]
end

local function checkWin(P)
  for _, w in pairs(win) do
    if all(P, w) then
      return true
    end
  end
  return false
end

local function displayOX()
  local map = {}
  for i = 1, 9, 3 do
    map[i] = O[i] and "[O]" or (X[i] and "[X]" or "[_]")
    map[i+1] = O[i+1] and "[O]" or (X[i+1] and "[X]" or "[_]")
    map[i+2] = O[i+2] and "[O]" or (X[i+2] and "[X]" or "[_]")
    stdscr:mvaddstr (((i-1)/3)+5, 30, map[i]..map[i+1]..map[i+2])
  end
  stdscr:mvaddstr (9, 20, "Choose position [1-9]: ")
end

local function reset()
  for i = 1, 9 do
    O[i], X[i] = false, false
  end
  stdscr:mvaddstr(11,32,"     ")
end

local function calSOX(o,x)
  local SO, SX = 0, 0
  local criticalMove = {}
  for _, w in pairs(win) do
    local cO = any(o,w)
    local cX = any(x,w)
    if cX == 0 then
      SO = SO + cO
      if cO == 2 then
        stdscr:mvaddstr(8,27,"critical {".. concat(w,",").."}")
        criticalMove = w
      end
    end
    if cO == 0 then
      SX = SX + cX
    end
  end
  return SO, SX, criticalMove
end

local function evalOX(o,x)
  local SO, SX, criticalMove =calSOX(o,x)
  return (1 + SX - SO), criticalMove
end

local function ai()
  local validMove = {true,true,true,true,true,true,true,true,true}
  for i = 1, 9 do
    validMove[i] = not (O[i] or X[i]) and validMove[i]
  end
  for _, w in pairs(win) do
    local cX = any(X,w)
    for _, v in pairs(w) do
      if cX == 2 and validMove[v] then
        return v
      end
    end
  end
  local V = {-100,-100,-100,-100,-100,-100,-100,-100,-100}
  for i, v in ipairs(validMove) do
    if v then
      local tempX, criticalMove = {unpak(X)}, {}
      tempX[i] = v
      V[i], criticalMove = evalOX(O,tempX)
      if #criticalMove > 0 then
        for _, c in pairs(criticalMove) do
          if validMove[c] then
            return c
          end
        end
      end
    end
  end
  local maxV = max(unpak(V))
  local imaxV = {}
  for i, v in pairs(V) do
    if v == maxV then
      add(imaxV,i)
    end
  end
  return randomChoice(imaxV)
end

local function main ()
  stdscr:clear ()
  stdscr:box (curses.ACS_VLINE, curses.ACS_HLINE)
  while true do
    ::input_here::
    local c = stdscr:getch () --print(c)
    if c > 48 and c < 58 then
      c = tonumber(string.char (c))
      if O[c] or X[c] then
        if not finished then
          stdscr:mvaddstr (9, 20, "Bad move: choose position [1-9]: ")
        end
        goto input_here
      else
        stdscr:mvaddstr (9, 20, "                                 ")
      end
    elseif c == 13 then
      if finished then
        reset()
        finished = false
        displayOX()
      else
        stdscr:mvaddstr (9, 20, "Bad move: choose position [1-9]: ")
      end
      goto input_here
    elseif c == 27 then
      break
    else
      if not finished then
        stdscr:mvaddstr (9, 20, "Bad move: choose position [1-9]: ")
      end
      goto input_here
    end
    stdscr:mvaddstr(8,27,"                 ")
    O[c] = true
    displayOX()
    local msg = "     "
    local d = true
    for i = 1, 9 do
      d = (O[i] or X[i]) and d
    end
    if d then
      msg = "Draw"
      finished = true
    elseif checkWin(O) then
      msg = "O win"
      finished = true
    else
      X[ai()] = true
      displayOX()
      if checkWin(X) then
        msg = "X win"
        finished = true
      end
    end
    stdscr:mvaddstr(11,32,msg)
    stdscr:move(9,43)
  end
  curses.endwin ()
end

local function err (err)
  curses.endwin ()
  print "Caught an error:"
  print (debug.traceback (err, 2))
  os.exit (2)
end

xpcall (main, err)