/**************************************************************
 *  SNAKE SDL + OpenGL Test Game to be ported to UWP
 *  ----------------------------------------------------------
 *  How to build (mingw mysys):
 *  g++ snake.cpp -o snake -lmingw32 -lSDL2main -lSDL2 -lopengl32 -mwindows
 *
 *  Controls:
 *  Arrow Keys to move the snake.
 *  ESC or close window to quit.
 **************************************************************/

#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>
#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>

static const int GRID_WIDTH = 20;
static const int GRID_HEIGHT = 15;
static const int WINDOW_SCALE = 32;

struct Segment {
    int x, y;
};

enum Direction {
    UP,
    DOWN,
    LEFT,
    RIGHT
};

int main(int argc, char* argv[]) {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        std::cerr << "Failed to initialize SDL: " << SDL_GetError() << std::endl;
        return 1;
    }
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY);
    int windowWidth = GRID_WIDTH * WINDOW_SCALE;
    int windowHeight = GRID_HEIGHT * WINDOW_SCALE;
    SDL_Window* window = SDL_CreateWindow(
        "Snake (SDL2 + OpenGL)",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        windowWidth,
        windowHeight,
        SDL_WINDOW_OPENGL
    );
    if (!window) {
        std::cerr << "Failed to create window: " << SDL_GetError() << std::endl;
        SDL_Quit();
        return 1;
    }
    SDL_GLContext glContext = SDL_GL_CreateContext(window);
    if (!glContext) {
        std::cerr << "Failed to create GL context: " << SDL_GetError() << std::endl;
        SDL_DestroyWindow(window);
        SDL_Quit();
        return 1;
    }
    SDL_GL_SetSwapInterval(1);
    glViewport(0, 0, windowWidth, windowHeight);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, (GLdouble)windowWidth, (GLdouble)windowHeight, 0.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClearColor(0.f, 0.f, 0.f, 1.f);
    std::srand((unsigned int)std::time(nullptr));
    std::vector<Segment> snake;
    snake.push_back({GRID_WIDTH / 2, GRID_HEIGHT / 2});
    Direction dir = RIGHT;
    int foodX = rand() % GRID_WIDTH;
    int foodY = rand() % GRID_HEIGHT;
    const float MOVE_INTERVAL = 0.15f;
    float timer = 0.0f;
    bool running = true;
    Uint32 lastTicks = SDL_GetTicks();
    int score = 0;
    while (running) {
        SDL_Event e;
        while (SDL_PollEvent(&e)) {
            if (e.type == SDL_QUIT) {
                running = false;
            } else if (e.type == SDL_KEYDOWN) {
                switch (e.key.keysym.sym) {
                    case SDLK_ESCAPE:
                        running = false;
                        break;
                    case SDLK_UP:
                        if (dir != DOWN) dir = UP;
                        break;
                    case SDLK_DOWN:
                        if (dir != UP) dir = DOWN;
                        break;
                    case SDLK_LEFT:
                        if (dir != RIGHT) dir = LEFT;
                        break;
                    case SDLK_RIGHT:
                        if (dir != LEFT) dir = RIGHT;
                        break;
                    default:
                        break;
                }
            }
        }
        Uint32 currentTicks = SDL_GetTicks();
        float deltaTime = (currentTicks - lastTicks) / 1000.0f;
        lastTicks = currentTicks;
        timer += deltaTime;
        if (timer >= MOVE_INTERVAL) {
            timer -= MOVE_INTERVAL;
            Segment head = snake.front();
            switch (dir) {
                case UP: head.y -= 1; break;
                case DOWN: head.y += 1; break;
                case LEFT: head.x -= 1; break;
                case RIGHT: head.x += 1; break;
            }
            if (head.x < 0) head.x = GRID_WIDTH - 1;
            else if (head.x >= GRID_WIDTH) head.x = 0;
            if (head.y < 0) head.y = GRID_HEIGHT - 1;
            else if (head.y >= GRID_HEIGHT) head.y = 0;
            for (size_t i = 0; i < snake.size(); i++) {
                if (snake[i].x == head.x && snake[i].y == head.y) {
                    std::cout << "Game Over! You ate yourself. Final score: " << score << std::endl;
                    running = false;
                    break;
                }
            }
            if (running) {
                snake.insert(snake.begin(), head);
                if (head.x == foodX && head.y == foodY) {
                    score++;
                    foodX = rand() % GRID_WIDTH;
                    foodY = rand() % GRID_HEIGHT;
                } else {
                    snake.pop_back();
                }
            }
        }
        glClear(GL_COLOR_BUFFER_BIT);
        glLoadIdentity();
        glColor3f(1.0f, 0.0f, 0.0f);
        glBegin(GL_QUADS);
        float fx = (float)foodX * WINDOW_SCALE;
        float fy = (float)foodY * WINDOW_SCALE;
        glVertex2f(fx, fy);
        glVertex2f(fx + WINDOW_SCALE, fy);
        glVertex2f(fx + WINDOW_SCALE, fy + WINDOW_SCALE);
        glVertex2f(fx, fy + WINDOW_SCALE);
        glEnd();
        glColor3f(0.0f, 1.0f, 0.0f);
        glBegin(GL_QUADS);
        for (auto &seg : snake) {
            float sx = (float)seg.x * WINDOW_SCALE;
            float sy = (float)seg.y * WINDOW_SCALE;
            glVertex2f(sx, sy);
            glVertex2f(sx + WINDOW_SCALE, sy);
            glVertex2f(sx + WINDOW_SCALE, sy + WINDOW_SCALE);
            glVertex2f(sx, sy + WINDOW_SCALE);
        }
        glEnd();
        SDL_GL_SwapWindow(window);
    }
    SDL_GL_DeleteContext(glContext);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 0;
}