struct LinePoint {
	Vector2 position;
	float distance;
}
class HandDrawLine {
public:
	void StartDraw(Vector2 start_pos)
	void AddPoint(Vector2 new_pos); // 鼠标每移动 5.0f 距离添加一个新点 (意思是连续的线由一个个线段拼起来)
	void EndDraw();
	
	void RenderLine(); // 根据 points_ 画出一个个线段，连起来看就是一条直线了
	
  float GetTotalLength() const { return total_length_; }
  bool IsDrawing() const { return is_drawing_; }
  bool IsCurrentlyDrawing() const { return is_drawing_; }
  bool IsEmpty() const { return points.size() < 2; }

private:
	std::vector<LinePoint> points_;
	float total_length_;
	bool is_drawing_;
}

HandDrawLine::HandDrawLine() {}

HandDrawLine::~HandDrawLine() {}

void HandDrawLine::StartDraw(Vector2 start_pos) {
  points.clear();
  points.emplace_back(start_pos, 0.0f);
  total_length_ = 0.0f;
  is_drawing_ = true;
}

void HandDrawLine::AddPoint(Vector2 new_pos) {
  if (!is_drawing_ || points.empty()) return;

  Vector2 last_pos = points.back().position;
  float segment_length = sqrt((pow(new_pos.x - last_pos.x, 2) + pow(new_pos.y - last_pos.y, 2)));
  if (segment_length > 5.0f) {
    total_length_ += segment_length;
    points.emplace_back(new_pos, total_length_);
  }
}

void HandDrawLine::EndDraw() { is_drawing_ = false; }

void HandDrawLine::RenderLine() {
  if (points.size() < 2) return;

  for (size_t i = 1; i < points.size(); i++) {
    DrawLineEx(points[i].position, points[i + 1].position, 3.0f, BLUE);
  }
}

Vector2 HandDrawLine::GetPositionAtDistance(float target_distance) const {
  if (points.size() < 2) return {0, 0};
  if (target_distance <= 0) return points.front().position;
  if (target_distance >= total_length_) return points.back().position;

  for (size_t i = 1; i < points.size(); i++) {
    if (points[i].distance >= target_distance) {
      Vector2 p1 = points[i - 1].position;
      Vector2 p2 = points[i].position;
      float segment_length = points[i].distance - points[i - 1].distance;
      float t = (target_distance - points[i - 1].distance) / segment_length;
      return {p1.x + t * (p2.x - p1.x), p1.y + t * (p2.y - p1.y)};
    }
  }
  return points.back().position;
}