#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const int buttons[9] = {2,3,4,5,6,7,8,9,10};

int board[9];

void drawBoard() {
  display.clearDisplay();
  display.drawLine(42, 0, 42, 64, WHITE);
  display.drawLine(84, 0, 84, 64, WHITE);
  display.drawLine(0, 21, 128, 21, WHITE);
  display.drawLine(0, 43, 128, 43, WHITE);

  for (int i = 0; i < 9; i++) {
    int x = (i % 3) * 42 + 21;
    int y = (i / 3) * 21 + 11;
    if (board[i] == 1) {
      display.drawLine(x-8, y-8, x+8, y+8, WHITE);
      display.drawLine(x-8, y+8, x+8, y-8, WHITE);
    } else if (board[i] == 2) {
      display.drawCircle(x, y, 9, WHITE);
    }
  }
  display.display();
}

bool checkWin(int p) {
  int wins[8][3] = {
    {0,1,2},{3,4,5},{6,7,8},
    {0,3,6},{1,4,7},{2,5,8},
    {0,4,8},{2,4,6}
  };
  for (int i=0;i<8;i++) {
    if (board[wins[i][0]]==p && board[wins[i][1]]==p && board[wins[i][2]]==p) return true;
  }
  return false;
}

bool movesLeft() {
  for (int i=0;i<9;i++) if (board[i]==0) return true;
  return false;
}

// CPU imbatible: estrategia minimax
int minimax(int depth, bool isCPU) {
  if (checkWin(1)) return 10 - depth;
  if (checkWin(2)) return depth - 10;
  if (!movesLeft()) return 0;

  int best = isCPU ? -1000 : 1000;

  for (int i=0;i<9;i++) {
    if (board[i]==0) {
      board[i] = isCPU ? 1 : 2;
      int score = minimax(depth+1, !isCPU);
      board[i] = 0;
      if (isCPU) {
        best = max(best, score);
      } else {
        best = min(best, score);
      }
    }
  }
  return best;
}

int bestMove() {
  int bestVal = -1000;
  int move = -1;
  for (int i=0;i<9;i++) {
    if (board[i]==0) {
      board[i] = 1;
      int moveVal = minimax(0, false);
      board[i] = 0;
      if (moveVal > bestVal) {
        move = i;
        bestVal = moveVal;
      }
    }
  }
  return move;
}

void setup() {
  for (int i=0;i<9;i++) pinMode(buttons[i], INPUT_PULLUP);
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) for(;;);
  display.clearDisplay();
  for (int i=0;i<9;i++) board[i]=0;
  drawBoard();
}

void loop() {
  // Leer botones
  for (int i=0;i<9;i++) {
    if (digitalRead(buttons[i]) == LOW && board[i]==0) {
      board[i] = 2; // Jugador marca O
      drawBoard();
      if (checkWin(2)) { delay(2000); resetGame(); return; }
      if (!movesLeft()) { delay(2000); resetGame(); return; }
      
      int cpu = bestMove();
      if (cpu != -1) board[cpu] = 1; // CPU marca X
      drawBoard();
      if (checkWin(1)) { delay(2000); resetGame(); return; }
      if (!movesLeft()) { delay(2000); resetGame(); return; }
    }
  }
}

void resetGame() {
  for (int i=0;i<9;i++) board[i]=0;
  drawBoard();
}