Introduced main game loop, a player character, fruits and walls

Game resets on player colliding with themselves or a wall.

Fruit increases size of player, and player's body follows the head.

There is text on the top left corner which shows time elapsed and
current score.

src/main.cpp

@@ -9,19 +9,272 @@
  * Description: Entrypoint
  */
 
+#include <algorithm>
+#include <chrono>
+#include <cstring>
+#include <iostream>
 #include <raylib.h>
+#include <sstream>
+#include <string>
+#include <vector>
 
 #define WIDTH  800
 #define HEIGHT 600
 
+long mod(long a, long b)
+{
+  return (a % b + b) % b;
+}
+
+enum class Type
+{
+  EMPTY,
+  WALL,
+  FRUIT,
+};
+
+enum class Direction
+{
+  UP    = 1,
+  LEFT  = 2,
+  RIGHT = -2,
+  DOWN  = -1
+};
+
+struct Point
+{
+  int x, y;
+
+  bool operator==(const struct Point &p) const
+  {
+    return x == p.x && y == p.y;
+  }
+
+  Point() : x{0}, y{0}
+  {}
+
+  Point(int x, int y) : x{x}, y{y}
+  {}
+
+  Point(Direction dir)
+  {
+    switch (dir)
+    {
+    case Direction::UP:
+      *this = Point{0, -1};
+      break;
+    case Direction::DOWN:
+      *this = Point{0, 1};
+      break;
+    case Direction::LEFT:
+      *this = Point{-1, 0};
+      break;
+    case Direction::RIGHT:
+      *this = Point{1, 0};
+      break;
+    }
+  }
+};
+
+template <size_t a, size_t b>
+struct State
+{
+  static constexpr double mx          = WIDTH / a;
+  static constexpr double my          = HEIGHT / b;
+  static constexpr double square_size = mx < my ? mx : my;
+
+  struct Player
+  {
+    std::vector<Point> points;
+  } player;
+
+  Type grid[a][b];
+
+  bool is_player(size_t x, size_t y) const
+  {
+    return std::find(player.points.begin(), player.points.end(),
+                     Point{(int)x, (int)y}) != player.points.end();
+  }
+
+  double rescale(size_t grid, bool smaller, double translation) const
+  {
+    double x = grid * square_size;
+    if (smaller)
+      x += translation;
+    return x;
+  }
+
+  void draw_grid() const
+  {
+    for (size_t x = 0; x < a; ++x)
+    {
+      double x_ = rescale(x, HEIGHT < WIDTH, (WIDTH - HEIGHT) / 2);
+      for (size_t y = 0; y < b; ++y)
+      {
+        double y_ = rescale(y, WIDTH < HEIGHT, (HEIGHT - WIDTH) / 2);
+
+        if (grid[x][y] == Type::EMPTY)
+          DrawRectangleLines(x_, y_, square_size, square_size, WHITE);
+        else if (grid[x][y] == Type::WALL)
+          DrawRectangle(x_, y_, square_size, square_size, WHITE);
+        else if (grid[x][y] == Type::FRUIT)
+          DrawRectangle(x_, y_, square_size, square_size, RED);
+      }
+    }
+
+    for (const auto p : player.points)
+    {
+      double x_ = rescale(p.x, HEIGHT < WIDTH, (WIDTH - HEIGHT) / 2);
+      double y_ = rescale(p.y, WIDTH < HEIGHT, (HEIGHT - WIDTH) / 2);
+      DrawRectangle(x_, y_, square_size, square_size, GREEN);
+    }
+  }
+
+  std::vector<Point>::iterator player_head(void)
+  {
+    return player.points.begin();
+  }
+
+  bool update_player_head(Point dir)
+  {
+    auto head          = player_head();
+    Point old_position = *head;
+    Point new_position = old_position;
+    new_position.y += dir.y;
+    new_position.x += dir.x;
+    new_position.x = mod(new_position.x, a);
+    new_position.y = mod(new_position.y, b);
+
+    if (is_player(new_position.x, new_position.y) ||
+        grid[new_position.x][new_position.y] == Type::WALL)
+      return true;
+
+    *head = new_position;
+
+    for (size_t i = 1; i < player.points.size(); ++i)
+    {
+      Point cpy        = player.points[i];
+      player.points[i] = old_position;
+      old_position     = cpy;
+    }
+    return false;
+  }
+
+  void player_fruit_collision(void)
+  {
+    const auto point = player_head();
+    if (grid[point->x][point->y] == Type::FRUIT)
+    {
+      grid[point->x][point->y]          = Type::EMPTY;
+      std::vector<Point>::iterator last = player.points.end() - 1;
+      player.points.push_back({last->x + 1, last->y});
+    }
+  }
+
+  void reset(void)
+  {
+    player.points.clear();
+    player.points.push_back({a / 2, b / 2});
+    memset(grid, 0, sizeof(Type) * a * b);
+  }
+};
+
+namespace chrono = std::chrono;
+
+struct Time
+{
+  size_t hours, minutes, seconds;
+
+  Time(size_t s)
+  {
+    hours = s / 3600;
+    s -= (hours * 3600);
+    minutes = s / 60;
+    s -= (minutes * 60);
+    seconds = s;
+  }
+
+  std::string to_str(void)
+  {
+    std::stringstream s;
+    if (hours < 10)
+      s << "0";
+    s << std::to_string(hours) + ":";
+    if (minutes < 10)
+      s << "0";
+    s << std::to_string(minutes) + ":";
+    if (seconds < 10)
+      s << "0";
+    s << std::to_string(seconds);
+    return s.str();
+  }
+};
+
+using Clock = chrono::steady_clock;
 int main(void)
 {
+  constexpr size_t X = 50, Y = 50;
+  State<X, Y> state;
+  state.player.points.push_back({15, 15});
+  for (size_t i = 0; i < X; ++i)
+    for (size_t j = 0; j < Y; ++j)
+      state.grid[i][j] = Type::FRUIT;
+
+  Direction dir = Direction::LEFT;
   InitWindow(WIDTH, HEIGHT, "snek");
+  int fps = 10;
+  SetTargetFPS(fps);
+
+  chrono::time_point<Clock> beg{Clock::now()};
   while (!WindowShouldClose())
   {
+    state.player_fruit_collision();
+
+    if (IsKeyDown(KEY_J) && (Direction)(-((int)dir)) != Direction::DOWN)
+      dir = Direction::DOWN;
+    else if (IsKeyDown(KEY_K) && (Direction)(-((int)dir)) != Direction::UP)
+      dir = Direction::UP;
+    else if (IsKeyDown(KEY_H) && (Direction)(-((int)dir)) != Direction::LEFT)
+      dir = Direction::LEFT;
+    else if (IsKeyDown(KEY_L) && (Direction)(-((int)dir)) != Direction::RIGHT)
+      dir = Direction::RIGHT;
+    else if (IsKeyDown(KEY_EQUAL))
+    {
+      ++fps;
+      if (fps > 60)
+        fps = 60;
+      SetTargetFPS(fps);
+    }
+    else if (IsKeyDown(KEY_MINUS))
+    {
+      --fps;
+      if (fps < 0)
+        fps = 1;
+      SetTargetFPS(fps);
+    }
+
+    bool collide = state.update_player_head(dir);
+    if (collide)
+    {
+      state.reset();
+      beg = Clock::now();
+    }
+
     BeginDrawing();
     ClearBackground(BLACK);
-    DrawTriangle({400, 0}, {100, 300}, {700, 300}, RED);
+    state.draw_grid();
+    DrawText("TIME", 0, 0, 25, YELLOW);
+    DrawText(
+        Time(chrono::duration_cast<chrono::seconds>(Clock::now() - beg).count())
+            .to_str()
+            .c_str(),
+        0, 25, 25, YELLOW);
+
+    std::stringstream ss;
+    ss << "Score: ";
+    ss << state.player.points.size() - 1;
+    DrawText(ss.str().c_str(), 0, 50, 20, YELLOW);
+
     EndDrawing();
   }
   CloseWindow();