lunarwm/src/Math.cppm

export module LunarWM.Math;

import std;

export namespace LunarWM::Math {

template<typename T = float>
requires std::is_arithmetic_v<T> struct Vec2 {
	template<typename U = T>
	requires std::is_arithmetic_v<U>
	auto operator+(Vec2<U> const &other) -> Vec2<U>
	{
		return { x + other.x, y + other.y };
	}
	template<typename U = T>
	requires std::is_arithmetic_v<U>
	auto operator-(Vec2<U> const &other) -> Vec2<U>
	{
		return { x - other.x, y - other.y };
	}
	template<typename U = T>
	requires std::is_arithmetic_v<U>
	auto operator*(Vec2<U> const &other) -> Vec2<U>
	{
		return { x * other.x, y * other.x };
	}
	template<typename U = T>
	requires std::is_arithmetic_v<U> auto operator*(T scalar) -> Vec2<U>
	{
		return { x * scalar, y * scalar };
	}
	template<typename U = T>
	requires std::is_arithmetic_v<U> auto operator/(T scalar) -> Vec2<U>
	{
		return { x / scalar, y / scalar };
	}
	template<typename U = T>
	requires std::is_arithmetic_v<U> auto operator-() -> Vec2
	{
		return { -x, -y };
	}
	auto length() const -> T { return std::sqrt(x * x + y * y); }
	auto lengthSquared() const -> T { return x * x + y * y; }
	auto normalized() const -> Vec2<T>
	{
		T len = length();
		if (len == T(0)) {
			return { T(0), T(0) };
		}
		return *this / len;
	}

	T x, y;
};

template<typename T>
requires std::is_arithmetic_v<T>
auto operator*(T scalar, Vec2<T> const &v) -> Vec2<T>
{
	return { v.x * scalar, v.y * scalar };
}

template<typename T = float>
requires std::is_arithmetic_v<T> struct Rect {
	Rect(Vec2<T> pos, Vec2<T> size)
	    : pos(pos)
	    , size(size)
	{
	}
	Rect(T x, T y, T w, T h)
	    : pos({ x, y })
	    , size({ w, h })
	{
	}

	auto x() -> T & { return pos.x; }
	auto y() -> T & { return pos.y; }
	auto w() -> T & { return size.x; }
	auto h() -> T & { return size.y; }

	auto x() const -> T { return pos.x; }
	auto y() const -> T { return pos.y; }
	auto w() const -> T { return size.x; }
	auto h() const -> T { return size.y; }

	auto left() const -> T { return x(); }
	auto right() const -> T { return x() + w(); }
	auto top() const -> T { return y(); }
	auto bottom() const -> T { return y() + h(); }

	auto left() -> T & { return x(); }
	auto top() -> T & { return y(); }

	Vec2<T> pos, size;
};

template<typename T = float>
requires std::is_arithmetic_v<T> struct Box {
	template<typename U = int>
	requires std::is_arithmetic_v<U> auto operator[](U const index) -> Vec2<T> &
	{
		if (index < 0 || index > 1) {
			throw std::out_of_range("A box only has two points");
		}
		return m_data[index];
	}
	auto first() -> Vec2<T> & { return m_data[0]; }
	auto second() -> Vec2<T> & { return m_data[1]; }
	auto x0() -> T & { return m_data[0].x; }
	auto y0() -> T & { return m_data[0].y; }
	auto x1() -> T & { return m_data[1].x; }
	auto y1() -> T & { return m_data[1].y; }
	auto left() -> T &
	{
		if (x0() < x1()) {
			return x0();
		}
		return x1();
	}
	auto right() -> T &
	{
		if (x0() > x1()) {
			return x0();
		}
		return x1();
	}
	auto top() -> T &
	{
		if (y0() < y1()) {
			return y0();
		}
		return y1();
	}
	auto bottom() -> T &
	{
		if (y0() > y1()) {
			return y0();
		}
		return y1();
	}

	Box() = default;
	explicit Box(Rect<T> rect)
	{
		this->m_data[0] = rect.pos;
		this->m_data[1] = rect.pos + rect.size;
	}

private:
	std::array<Vec2<T>, 2> m_data = {};
};

template<typename T = int>
requires std::is_arithmetic_v<T>
auto subtract_rect(Math::Rect<T> const &src, Math::Rect<T> const &clip)
    -> std::vector<Math::Rect<T>>
{
	std::vector<Math::Rect<T>> result;

	auto sx = src.x();
	auto sy = src.y();
	auto sw = src.w();
	auto sh = src.h();

	auto cx = clip.x();
	auto cy = clip.y();
	auto cw = clip.w();
	auto ch = clip.h();

	T s_right = sx + sw;
	T s_bottom = sy + sh;

	T c_right = cx + cw;
	T c_bottom = cy + ch;

	// No overlap → keep src
	if (c_right <= sx || cx >= s_right || c_bottom <= sy || cy >= s_bottom) {
		result.push_back(src);
		return result;
	}

	// Top piece
	if (cy > sy) {
		result.emplace_back(sx, sy, sw, cy - sy);
	}

	// Bottom piece
	if (c_bottom < s_bottom) {
		result.emplace_back(sx, c_bottom, sw, s_bottom - c_bottom);
	}

	// Middle pieces left and right of clip
	T middle_top = std::max(sy, cy);
	T middle_bottom = std::min(s_bottom, c_bottom);
	T middle_height = middle_bottom - middle_top;

	if (middle_height > 0) {
		// Left piece
		if (cx > sx) {
			result.emplace_back(sx, middle_top, cx - sx, middle_height);
		}

		// Right piece
		if (c_right < s_right) {
			result.emplace_back(
			    c_right, middle_top, s_right - c_right, middle_height);
		}
	}

	return result;
}

template<typename T = float>
requires std::is_arithmetic_v<T> struct Viewport {
	Rect<T> rect;
	Vec2<T> depth_limits;
};

template<typename T> constexpr auto deg2rad(T degrees) -> T
{
	return degrees * (std::numbers::pi / 180.0);
}

} // namespace LunarWM::Math