#include <Arduino.h>
#include <Wire.h>
#include <U8g2lib.h>

// OLED
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(
  U8G2_R0,
  U8X8_PIN_NONE
);

// Touch pins
#define PIN_LEFT   D1
#define PIN_RIGHT  D7
#define PIN_DOWN   D8
#define PIN_UP     D0
#define PIN_FIRE   D9

#define N_TOUCH    5
#define THRESHOLD  6

enum TouchIndex {
  T_LEFT = 0,
  T_RIGHT,
  T_DOWN,
  T_UP,
  T_FIRE
};

const uint8_t touchPins[N_TOUCH] = {
  PIN_LEFT,
  PIN_RIGHT,
  PIN_DOWN,
  PIN_UP,
  PIN_FIRE
};

bool touchedNow[N_TOUCH] = {
  false,
  false,
  false,
  false,
  false
};

bool touchedBefore[N_TOUCH] = {
  false,
  false,
  false,
  false,
  false
};

// Screen
const int SCREEN_W = 128;
const int SCREEN_H = 64;

// Player
const int PLAYER_W = 14;
const int PLAYER_H = 9;

int playerX = 15;
int playerY = 28;

// Player pixel art
const char playerShip[PLAYER_H][PLAYER_W + 1] = {
  "..##..........",
  ".####.........",
  "######........",
  "##.#####......",
  "###########...",
  "##.#####......",
  "######........",
  ".####.........",
  "..##.........."
};

// Bullets
struct Bullet {
  int x;
  int y;
  bool active;
};

const int MAX_BULLETS = 8;

Bullet bullets[MAX_BULLETS];

unsigned long lastBulletUpdate = 0;
const unsigned long BULLET_INTERVAL = 25;

// Update touch
void updateTouch() {
  const int maxCount = 200;

  for (int i = 0; i < N_TOUCH; i++) {
    touchedBefore[i] = touchedNow[i];

    pinMode(touchPins[i], OUTPUT);
    digitalWrite(touchPins[i], LOW);

    delayMicroseconds(25);

    pinMode(touchPins[i], INPUT_PULLUP);

    int count = 0;

    while (
      digitalRead(touchPins[i]) == LOW &&
      count < maxCount
    ) {
      count++;
    }

    touchedNow[i] = count > THRESHOLD;
  }
}

// Touch held
bool touchHeld(int index) {
  return touchedNow[index];
}

// Touch pressed
bool touchPressed(int index) {
  return touchedNow[index] && !touchedBefore[index];
}

// Update player
void updatePlayer() {
  if (touchHeld(T_LEFT)) {
    playerX -= 2;
  }

  if (touchHeld(T_RIGHT)) {
    playerX += 2;
  }

  if (touchHeld(T_UP)) {
    playerY -= 2;
  }

  if (touchHeld(T_DOWN)) {
    playerY += 2;
  }

  playerX = constrain(
    playerX,
    1,
    SCREEN_W - PLAYER_W - 1
  );

  playerY = constrain(
    playerY,
    1,
    SCREEN_H - PLAYER_H - 1
  );
}

// Fire bullet
void fireBullet() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) {
      bullets[i].active = true;

      bullets[i].x =
        playerX + PLAYER_W;

      bullets[i].y =
        playerY + PLAYER_H / 2;

      return;
    }
  }
}

// Update bullets
void updateBullets() {
  if (
    millis() - lastBulletUpdate <
    BULLET_INTERVAL
  ) {
    return;
  }

  lastBulletUpdate = millis();

  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) {
      continue;
    }

    bullets[i].x += 4;

    if (bullets[i].x > 127) {
      bullets[i].active = false;
    }
  }
}

// Draw player
void drawPlayerShip(
  int xPos,
  int yPos
) {
  for (int y = 0; y < PLAYER_H; y++) {
    for (int x = 0; x < PLAYER_W; x++) {
      if (playerShip[y][x] == '#') {
        u8g2.drawPixel(
          xPos + x,
          yPos + y
        );
      }
    }
  }

  // Engine flame
  if ((millis() / 80) % 2 == 0) {
    u8g2.drawPixel(
      xPos - 1,
      yPos + 4
    );

    u8g2.drawPixel(
      xPos - 2,
      yPos + 4
    );
  }
}

// Draw bullets
void drawBullets() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) {
      continue;
    }

    u8g2.drawLine(
      bullets[i].x,
      bullets[i].y,
      bullets[i].x + 4,
      bullets[i].y
    );

    u8g2.drawPixel(
      bullets[i].x + 2,
      bullets[i].y - 1
    );
  }
}

// Draw game
void drawGame() {
  u8g2.clearBuffer();

  // Stars
  u8g2.drawPixel(20, 12);
  u8g2.drawPixel(40, 48);
  u8g2.drawPixel(61, 22);
  u8g2.drawPixel(78, 52);
  u8g2.drawPixel(91, 16);
  u8g2.drawPixel(110, 39);

  drawPlayerShip(
    playerX,
    playerY
  );

  drawBullets();

  u8g2.sendBuffer();
}

// Setup
void setup() {
  Serial.begin(115200);

  Wire.begin();

  u8g2.begin();

  for (int i = 0; i < MAX_BULLETS; i++) {
    bullets[i].active = false;
  }
}

// Loop
void loop() {
  updateTouch();

  updatePlayer();

  // Fire once per tap
  if (touchPressed(T_FIRE)) {
    fireBullet();
  }

  updateBullets();

  drawGame();

  delay(25);
}