#include <Adafruit_GFX.h>
#include <Adafruit_PCD8544.h>

#define PIN_RST  15
#define PIN_CE   14
#define PIN_DC   13
#define PIN_DIN  11
#define PIN_CLK  10

Adafruit_PCD8544 display(PIN_CLK, PIN_DIN, PIN_DC, PIN_CE, PIN_RST);

#define JOY_X A0  // GP26
#define JOY_Y A1  // GP27
#define JOY_BTN 16
#define SWITCH 17

#define WIDTH 84
#define HEIGHT 48
#define SNAKE_SIZE 3

int speedDelay = 200;
int score = 0;
int dirX = SNAKE_SIZE, dirY = 0;
int foodX, foodY;

struct Point { int x, y; };
Point snake[100];
int snakeLength = 5;

void setup() {
    pinMode(JOY_BTN, INPUT_PULLUP);
    pinMode(SWITCH, INPUT_PULLUP);

    display.begin();
    display.setContrast(50);
    display.clearDisplay();
    display.display();

    randomSeed(analogRead(A0));

    for (int i = 0; i < snakeLength; i++) {
        snake[i] = { WIDTH / 2 - i * SNAKE_SIZE, HEIGHT / 2 };
    }
    
    spawnFood();
}

void loop() {
    if (digitalRead(SWITCH) == LOW) {
        showMenu();
        startGame();
    }
}

void showMenu() {
    display.clearDisplay();
    display.setCursor(30, 20);
    display.setTextSize(1);
    display.setTextColor(BLACK);
    display.print("Snake");
    display.display();
    
    while (digitalRead(JOY_BTN) == HIGH);
    delay(300);
}

void startGame() {
    snakeLength = 5;
    score = 0;
    dirX = SNAKE_SIZE;
    dirY = 0;
    speedDelay = 200;
    
    for (int i = 0; i < snakeLength; i++) {
        snake[i] = { WIDTH / 2 - i * SNAKE_SIZE, HEIGHT / 2 };
    }
    
    spawnFood();

    while (true) {
        readJoystick();
        moveSnake();

        if (checkCollision()) {
            gameOver();
            return;
        }

        drawGame();
        delay(speedDelay);
    }
}

void readJoystick() {
    int x = analogRead(JOY_X);
    int y = analogRead(JOY_Y);

    if (x < 300 && dirX == 0) { dirX = -SNAKE_SIZE; dirY = 0; }
    if (x > 700 && dirX == 0) { dirX = SNAKE_SIZE; dirY = 0; }
    if (y < 300 && dirY == 0) { dirX = 0; dirY = -SNAKE_SIZE; }
    if (y > 700 && dirY == 0) { dirX = 0; dirY = SNAKE_SIZE; }
}

void moveSnake() {
    for (int i = snakeLength - 1; i > 0; i--) {
        snake[i] = snake[i - 1];
    }

    snake[0].x += dirX;
    snake[0].y += dirY;

    if (snake[0].x >= WIDTH)  snake[0].x = 0;
    if (snake[0].x < 0)       snake[0].x = WIDTH - SNAKE_SIZE;
    if (snake[0].y >= HEIGHT) snake[0].y = 0;
    if (snake[0].y < 0)       snake[0].y = HEIGHT - SNAKE_SIZE;

    if (snake[0].x == foodX && snake[0].y == foodY) {
        snakeLength++;
        score++;
        if (score % 10 == 0 && speedDelay > 50) speedDelay -= 20;
        spawnFood();
    }
}

void spawnFood() {
    foodX = random(0, WIDTH / SNAKE_SIZE) * SNAKE_SIZE;
    foodY = random(0, HEIGHT / SNAKE_SIZE) * SNAKE_SIZE;
}

bool checkCollision() {
    for (int i = 1; i < snakeLength; i++) {
        if (snake[0].x == snake[i].x && snake[0].y == snake[i].y) {
            return true;
        }
    }
    return false;
}

void gameOver() {
    display.clearDisplay();
    display.setCursor(15, 20);
    display.setTextSize(1);
    display.print("Game Over");
    display.display();
    delay(2000);
}

void drawGame() {
    display.clearDisplay();
    
    for (int i = 0; i < snakeLength; i++) {
        display.fillRect(snake[i].x, snake[i].y, SNAKE_SIZE, SNAKE_SIZE, BLACK);
    }

    display.fillRect(foodX, foodY, SNAKE_SIZE, SNAKE_SIZE, BLACK);
    
    display.display();
}