#include <Arduino.h>
#include <Wire.h>
#include <SSD1306Ascii.h>
#include <SSD1306AsciiWire.h>

SSD1306AsciiWire o;

#define X  A0
#define Y  A1
#define SW D2
#define BZ D3
#define L1 D4
#define L2 D5

#define W 16
#define H 5
#define N 25

uint8_t sx[N];
uint8_t sy[N];

uint8_t len;

uint8_t fx;
uint8_t fy;

int8_t dx = 1;
int8_t dy = 0;

uint8_t score = 0;

bool game = false;

unsigned long tm = 0;

uint16_t speed = 300;


// =====================================================
// FOOD
// =====================================================

bool snakeHere(uint8_t x, uint8_t y)
{
  for (uint8_t i = 0; i < len; i++)
  {
    if (sx[i] == x && sy[i] == y)
      return true;
  }

  return false;
}


void placeFood()
{
  uint8_t start = (score * 7 + 3) % (W * H);

  for (uint8_t k = 0; k < W * H; k++)
  {
    uint8_t p = (start + k) % (W * H);

    uint8_t x = p % W;
    uint8_t y = p / W;

    if (!snakeHere(x, y))
    {
      fx = x;
      fy = y;
      return;
    }
  }
}


// =====================================================
// GAME SCREEN
// =====================================================

void screen()
{
  o.clear();

  // -----------------------------
  // SCORE
  // -----------------------------

  o.print("SCORE:");

  if (score < 10)
    o.print("0");

  o.println(score);

  // -----------------------------
  // TOP BORDER
  // -----------------------------

  o.println("----------------");

  // -----------------------------
  // FOOD
  // -----------------------------

  o.setCursor(fx, fy + 2);
  o.print("*");

  // -----------------------------
  // SNAKE
  // -----------------------------

  for (int i = len - 1; i >= 0; i--)
  {
    o.setCursor(sx[i], sy[i] + 2);

    if (i == 0)
      o.print("@");
    else
      o.print("o");
  }

  // -----------------------------
  // BOTTOM BORDER
  // -----------------------------

  o.setCursor(0, 7);
  o.print("----------------");
}


// =====================================================
// START GAME
// =====================================================

void start()
{
  sx[0] = 7;
  sy[0] = 2;

  sx[1] = 6;
  sy[1] = 2;

  sx[2] = 5;
  sy[2] = 2;

  len = 3;

  score = 0;

  dx = 1;
  dy = 0;

  speed = 300;

  placeFood();

  game = true;

  digitalWrite(L1, HIGH);
  digitalWrite(L2, LOW);

  tone(BZ, 1000, 60);

  screen();
}


// =====================================================
// JOYSTICK
// =====================================================

void joy()
{
  int x = analogRead(X);
  int y = analogRead(Y);

  // LEFT
  if (x > 700 && dx == 0)
  {
    dx = -1;
    dy = 0;
  }

  // RIGHT
  if (x < 300 && dx == 0)
  {
    dx = 1;
    dy = 0;
  }

  // UP
  if (y > 700 && dy == 0)
  {
    dx = 0;
    dy = -1;
  }

  // DOWN
  if (y < 300 && dy == 0)
  {
    dx = 0;
    dy = 1;
  }
}


// =====================================================
// MOVE
// =====================================================

void moveSnake()
{
  int nx = sx[0] + dx;
  int ny = sy[0] + dy;

  // Wall collision
  if (nx < 0 || nx >= W ||
      ny < 0 || ny >= H)
  {
    game = false;
    return;
  }

  // Self collision
  for (uint8_t i = 0; i < len; i++)
  {
    if (sx[i] == nx && sy[i] == ny)
    {
      game = false;
      return;
    }
  }

  // Food
  bool eat = (nx == fx && ny == fy);

  if (eat)
  {
    if (len < N)
      len++;

    score++;

    if (speed > 120)
      speed -= 15;

    tone(BZ, 1500, 50);
  }

  // Move body
  for (int i = len - 1; i > 0; i--)
  {
    sx[i] = sx[i - 1];
    sy[i] = sy[i - 1];
  }

  sx[0] = nx;
  sy[0] = ny;

  if (eat)
    placeFood();
}


// =====================================================
// GAME OVER
// =====================================================

void gameOver()
{
  digitalWrite(L1, LOW);
  digitalWrite(L2, HIGH);

  tone(BZ, 300, 300);

  o.clear();

  o.println();
  o.println("   GAME OVER");
  o.println();
  o.print("   SCORE:");

  if (score < 10)
    o.print("0");

  o.println(score);

  o.println();
  o.println(" PRESS BUTTON");
  o.println("   TO RETRY");
}


// =====================================================
// SETUP
// =====================================================

void setup()
{
  Wire.setSDA(PB7);
  Wire.setSCL(PB6);
  Wire.begin();

  Wire.setClock(400000);

  pinMode(X, INPUT);
  pinMode(Y, INPUT);
  pinMode(SW, INPUT_PULLUP);

  pinMode(BZ, OUTPUT);
  pinMode(L1, OUTPUT);
  pinMode(L2, OUTPUT);

  o.begin(&Adafruit128x64, 0x3C);

  o.setFont(System5x7);

  o.clear();

  // -----------------------------
  // NOKIA START SCREEN
  // -----------------------------

  o.println("     NOKIA");
  o.println();
  o.println("   SNAKE GAME");
  o.println();
  o.println("    @oo  *");
  o.println();
  o.println(" PRESS BUTTON");
  o.println("   TO START");

  digitalWrite(L1, LOW);
  digitalWrite(L2, LOW);
}


// =====================================================
// LOOP
// =====================================================

void loop()
{
  // -----------------------------
  // WAIT / RESTART
  // -----------------------------

  if (!game)
  {
    if (digitalRead(SW) == LOW)
    {
      delay(200);

      start();

      tm = millis();
    }

    return;
  }

  // -----------------------------
  // JOYSTICK
  // -----------------------------

  joy();

  // -----------------------------
  // GAME TICK
  // -----------------------------

  if (millis() - tm >= speed)
  {
    tm = millis();

    moveSnake();

    if (game)
    {
      screen();
    }
    else
    {
      gameOver();
    }
  }
}