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

// ================= DISPLAY =================
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1

Adafruit_SSD1306 display(
  SCREEN_WIDTH,
  SCREEN_HEIGHT,
  &Wire,
  OLED_RESET
);

// ================= INPUT =================
#define BUTTON_PIN 3
bool lastButtonState = HIGH;

// ================= PLAYER =================
int playerX = 20;
float playerY = 48;
float velocityY = 0;
bool onGround = true;

// ================= PHYSICS =================
const float GRAVITY = 0.6;
const float JUMP_FORCE = -7;

// ================= OBSTACLE =================
int obstacleX = SCREEN_WIDTH;
int obstacleW = 8;

// ================= GAME =================
bool gameOver = false;
unsigned long lastFrame = 0;
unsigned long speedTimer = 0;
int gameSpeed = 3;

// ================= FUNCTIONS =================
void resetGame() {
  playerY = 48;
  velocityY = 0;
  onGround = true;
  obstacleX = SCREEN_WIDTH;
  gameSpeed = 3;
  gameOver = false;
  speedTimer = millis();
}

void updateButton() {
  bool state = digitalRead(BUTTON_PIN);

  if (lastButtonState == HIGH && state == LOW) {
    if (gameOver) {
      resetGame();
    } else if (onGround) {
      velocityY = JUMP_FORCE;
      onGround = false;
    }
  }

  lastButtonState = state;
}

void updatePlayer() {
  velocityY += GRAVITY;
  playerY += velocityY;

  if (playerY >= 48) {
    playerY = 48;
    velocityY = 0;
    onGround = true;
  }
}

void updateObstacle() {
  obstacleX -= gameSpeed;

  if (obstacleX < -obstacleW) {
    obstacleX = SCREEN_WIDTH + random(20, 60);
  }
}

void checkCollision() {
  if (obstacleX < playerX + 6 &&
      obstacleX + obstacleW > playerX &&
      playerY + 6 > 48) {
    gameOver = true;
  }
}

void increaseSpeed() {
  if (millis() - speedTimer > 3000) {
    gameSpeed++;
    speedTimer = millis();
  }
}

void drawGame() {
  display.clearDisplay();

  // chão
  display.drawLine(0, 54, SCREEN_WIDTH, 54, SSD1306_WHITE);

  // jogador
  display.fillRect(playerX, (int)playerY, 6, 6, SSD1306_WHITE);

  // obstáculo
  display.fillRect(obstacleX, 48, obstacleW, 6, SSD1306_WHITE);

  if (gameOver) {
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(32, 20);
    display.print("GAME OVER");
    display.setCursor(18, 36);
    display.print("PRESS BUTTON");
  }

  display.display();
}

// ================= SETUP / LOOP =================
void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    while (true);
  }

  randomSeed(analogRead(0));
  resetGame();
}

void loop() {
  updateButton();

  if (!gameOver && millis() - lastFrame > 33) { // ~30 FPS
    updatePlayer();
    updateObstacle();
    checkCollision();
    increaseSpeed();
    lastFrame = millis();
  }

  drawGame();
}