example.clla

import rl "opt/raylib"
import "fmt"

TICK_RATE ::= 0.13;
WINDOW_SIZE ::= 1000;
GRID_LENGTH ::= 20;
CELL_SIZE ::= 16;
MAX_SNAKE_LENGTH ::= GRID_LENGTH * GRID_LENGTH;
CANVAS_SIZE :: GRID_LENGTH * CELL_SIZE;

alias Vec2i: [2]int;

snake: [MAX_SNAKE_LENGTH]Vec2i;
snake_len: uint;
move_dir: Vec2i = [0, 1];
tick_timer: float = TICK_RATE;
game_over: bool = false;
food_pos: Vec2i;

func place_food() {
  occupied: [GRID_LENGTH][GRID_LENGTH]bool;
  for (i in 0..<snake_len) {
    occupied[snake[i][0]][snake[i][1]] = true;
  }

  free_cells: [^]Vec2i = make [^]Vec2i;
  defer destroy free_cells;

  for (x in 0..<GRID_LENGTH) {
    for (y in 0..<GRID_LENGTH) {
      if (not occupied[x][y])
        append(&free_cells, Vec2i { x, y });
    }
  }

  if (free_cells.len > 0) {
    random_cell_idx := rl::get_random_value(0, int32(len(free_cells) - 1));
    food_pos = free_cells[random_cell_idx];
  }
}

func restart() {
  start_head_pos := Vec2i { GRID_LENGTH / 2, GRID_LENGTH / 2 };
  snake[0] = tstart_head_pos;
  snake[1] = start_head_pos - [0, 1];
  snake[2] = start_head_pos - [0, 2];
  snake_len = 3;
  move_dir = [0, 1];
  game_over = false;
  place_food();
}

func main() : int {
  rl::SetConfigFlags(rl::Flag.VSYNC_HINT);
  rl::InitWindow(WINDOW_SIZE, WINDOW_SIZE, "Snake");

  restart();

  while (not rl::window_should_close()) {
    if (rl::is_key_down(rl::Key.UP)) {
      move_dir = [0, -1];
    } else if (rl::is_key_down(rl::Key.DOWN)) {
      move_dir = [0, 1];
    } else if (rl::is_key_down(rl::Key.LEFT)) {
      move_dir = [-1, 0];
    } else if (rl::is_key_down(rl::Key.RIGHT)) {
      move_dir = [1, 0];
    }

    if (game_over) {
      if (rl::is_key_down(rl::Key.ENTER))
        restart();
    } else {
      tick_timer -= rl::GetFrameTime();
    }

    if (tick_timer <= 0) {
      next_part_pos := snake[0];
      snake[0] = snake[0] - move_dir;
      head_pos := snake[0];

      if (head_pos[0] < 0 or head_pos[1] < 0 or head_pos[0] >= GRID_LENGTH or head_pos[1] >= GRID_LENGTH) {
        game_over = true;
      }

      for (i in 1..<snake_len) {
        curr_pos := snake[i];
        if (curr_pos == head_pos) game_over = true;

        snake[i] = next_part_pos;
        next_part_pos = curr_pos;
      }

      if (head_pos == food_pos) {
        snake_len += 1;
        snake[snake_len - 1] = next_part_pos;
        place_food();
      }

      tick_timer += TICK_RATE
    }

    camera := rl::Camera2D {
      zoom = float(WINDOW_SIZE) / CANVAS_SIZE,
    };

    rl::BeginDrawing();
    rl::ClearBackground(rl::Color { 76, 53, 83, 255 });

    rl::BeginMode2D(camera);

    food_rect := rl::Rectangle {
      float(food_pos[0]) * CELL_SIZE,
      float(food_pos[1]) * CELL_SIZE,
      CELL_SIZE,
      CELL_SIZE,
    };

    rl::DrawRectangleRec(food_rect, rl::RED);

    for (i in 0..<snake_len) {
      snake_rect := rl::Rectangle {
        float(snake[i][0] * CELL_SIZE),
        float(snake[i][1] * CELL_SIZE),
        CELL_SIZE,
        CELL_SIZE,
      };

      rl::DrawRectangleRec(snake_rect, rl::WHITE);
    }

    if (game_over) {
      rl::DrawText("Game over", 4, 4, 25, rl::RED);
      rl::DrawText("Press ENTER to play again", 4, 30, 15, rl::BLACK);
    }

    score := snake_len - 3;
    score_msg: ^string = fmt::alloc_sprintf("Score %v", score)!;
    defer free score_msg;
    rl::DrawText(score_msg.char_ptr, 4, CANVAS_SIZE - 14, 10, rl::GRAY);

    rl::EndMode2D();
    rl::EndDrawing();
  }

  return 0;
}