#include <FastLED.h>

#define LED_PIN 6
#define WIDTH 16
#define HEIGHT 16
#define NUM_LEDS (WIDTH * HEIGHT)
CRGB leds[NUM_LEDS];

int index(int x, int y) {
  if (y % 2 == 0)
    return y * WIDTH + WIDTH - x - 1;
  else
    return y * WIDTH + x;
}

class keyboard_t {
private:
  int row_pins[4];
  int col_pins[4];

public:
  keyboard_t(int rows[4], int cols[4]) {
    for (int i = 0; i < 4; i++) {
      int row_pin = rows[i];
      row_pins[i] = row_pin;
      pinMode(row_pin, INPUT_PULLUP);
    }

    for (int i = 0; i < 4; i++) {
      int col_pin = cols[i];
      col_pins[i] = col_pin;
      pinMode(col_pin, INPUT);
    }
  }

  bool isPressed(int x, int y) {
    int col_pin_no = this->col_pins[x];
    pinMode(col_pin_no, OUTPUT);
    digitalWrite(col_pin_no, LOW);

    int row_pin_no = this->row_pins[y];
    int return_value = digitalRead(row_pin_no);

    pinMode(col_pin_no, INPUT);
    if (return_value != 0)
      return 0;
    else
      return 1;
  }
};

int row_pins[] = { 2, 3, 4, 5 };
int col_pins[] = { A0, A1, A2, A3 };
keyboard_t kbd(row_pins, col_pins);

#define SNAKE_CAPACITY 20
int snake_size = 2;
int food_x;
int food_y;
CRGB food_color;

int pixel_x[SNAKE_CAPACITY] = { 0 };
int pixel_y[SNAKE_CAPACITY] = { 0 };
int pixel_vx = 0;
int pixel_vy = 1;
int tick = 0;
int deadline = 0;

void spawnfood() {
  while (1) {
    food_x = random(0, WIDTH);
    food_y = random(0, HEIGHT);
    food_color.setRGB(random(50, 256), random(50, 256), random(50, 256));

    bool in_snake = false;
    for (int i = 0; i < snake_size; i++) {
      if (pixel_x[i] == food_x && pixel_y[i] == food_y)
        in_snake = true;
    }

    if (in_snake)
      continue;
    else
      break;
  }
}

void setup() {
  Serial.begin(115200);
  FastLED.addLeds<NEOPIXEL, LED_PIN>(leds, NUM_LEDS);
  FastLED.setBrightness(50);
  srand(analogRead(A5));
  spawnfood();
}

int snakecheck() {
  for (int i = 0; i < snake_size; i++) {
    for (int j = 0; j < snake_size; j++) {
      if (i == j)
        continue;
      if (pixel_x[i] == pixel_x[j] && pixel_y[i] == pixel_y[j])
        return 1;
    }
  }
  return 0;
}

// https://pastebin.com/Q7z3eXXG
void loop() {
  if (kbd.isPressed(1, 0) && pixel_vy >= 0) {  //вверх
    pixel_vx = 0;
    pixel_vy = 1;
  } else if (kbd.isPressed(0, 1) && pixel_vx <= 0) {
    pixel_vx = -1;
    pixel_vy = 0;
  } else if (kbd.isPressed(2, 1) && pixel_vx >= 0) {
    pixel_vx = +1;
    pixel_vy = 0;
  } else if (kbd.isPressed(1, 2) && pixel_vy <= 0) {
    pixel_vx = 0;
    pixel_vy = -1;
  }

  int now = millis();
  if (now >= deadline) {
    for (int i = 0; i < NUM_LEDS; i++)
      leds[i].setRGB(0, 0, 0);

    for (int i = snake_size - 1; i > 0; i--) {
      pixel_x[i] = pixel_x[i - 1];
      pixel_y[i] = pixel_y[i - 1];
    }
    pixel_x[0] = pixel_x[1] + pixel_vx;
    pixel_y[0] = pixel_y[1] + pixel_vy;
    if (pixel_x[0] < 0)
      pixel_x[0] = WIDTH - 1;
    if (pixel_x[0] >= WIDTH)
      pixel_x[0] = 0;
    if (pixel_y[0] < 0)
      pixel_y[0] = HEIGHT - 1;
    if (pixel_y[0] >= HEIGHT)
      pixel_y[0] = 0;

    if (snakecheck() && tick >= snake_size) {
      for (int i = 0; i < NUM_LEDS; i++)
        leds[i].setRGB(50, 0, 0);

      FastLED.show();
      unsigned int x;
      while (true) {
        x = 0;
      }
    }

    for (int i = 0; i < snake_size; i++) {
      if (i == 0) {
        leds[index(pixel_x[i], pixel_y[i])].setRGB(255, 0, 0);
      } else if (i == snake_size - 1) {
        leds[index(pixel_x[i], pixel_y[i])].setRGB(255, 255, 0);
      } else {
        leds[index(pixel_x[i], pixel_y[i])].setRGB(0, 255, 0);
      }
    }
    leds[index(food_x, food_y)] = food_color;

    if (food_x == pixel_x[0] && food_y == pixel_y[0]) {
      snake_size += 1;
      spawnfood();
    }

    FastLED.show();

    deadline = now + 250;
    tick++;
  }
}