// Copyright (C) 2009-present, Panagiotis Christopoulos Charitos and contributors.
// All rights reserved.
// Code licensed under the BSD License.
// http://www.anki3d.org/LICENSE

#pragma once

#include <AnKi/Math/Common.h>

namespace anki {

// Euler angles. Used for rotations. It cannot describe a rotation accurately though
template<typename T>
class TEuler
{
public:
	// Data //

	// Skip some warnings cause we really nead anonymous structs inside unions
#if ANKI_COMPILER_MSVC
#	pragma warning(push)
#	pragma warning(disable : 4201)
#elif ANKI_COMPILER_GCC_COMPATIBLE
#	pragma GCC diagnostic push
#	pragma GCC diagnostic ignored "-Wgnu-anonymous-struct"
#	pragma GCC diagnostic ignored "-Wnested-anon-types"
#endif
	union
	{
		struct
		{
			T x; // Rotation around the x axiz
			T y; // Rotation around the y axiz
			T z; // Rotation around the z axiz
		};

		Array<T, 3> m_arr;
	};
#if ANKI_COMPILER_MSVC
#	pragma warning(pop)
#elif ANKI_COMPILER_GCC_COMPATIBLE
#	pragma GCC diagnostic pop
#endif

	// Constructors //

	constexpr TEuler()
		: x(0)
		, y(0)
		, z(0)
	{
	}

	constexpr TEuler(const T x_, const T y_, const T z_)
		: x(x_)
		, y(y_)
		, z(z_)
	{
	}

	constexpr TEuler(const TEuler& b)
		: x(b.x)
		, y(b.y)
		, z(b.z)
	{
	}

	explicit TEuler(const TQuat<T>& q)
	{
		const T test = q.x * q.y + q.z * q.w;
		if(test > T(0.499))
		{
			y = T(2) * atan2<T>(q.x, q.w);
			z = kPi / T(2);
			x = T(0);
		}
		else if(test < T(-0.499))
		{
			y = -T(2) * atan2<T>(q.x, q.w);
			z = -kPi / T(2);
			x = T(0);
		}
		else
		{
			const T sqx = q.x * q.x;
			const T sqy = q.y * q.y;
			const T sqz = q.z * q.z;
			y = atan2<T>(T(2) * q.y * q.w - T(2) * q.x * q.z, T(1) - T(2) * sqy - T(2) * sqz);
			z = asin<T>(T(2) * test);
			x = atan2<T>(T(2) * q.x * q.w - T(2) * q.y * q.z, T(1) - T(2) * sqx - T(2) * sqz);
		}
	}

	explicit TEuler(const TMat<T, 3, 3>& m3)
	{
		if(m3(1, 0) > T(0.998))
		{
			// Singularity at north pole
			y = atan2(m3(0, 2), m3(2, 2));
			z = kPi / T(2);
			x = T(0);
		}
		else if(m3(1, 0) < T(-0.998))
		{
			// Singularity at south pole
			y = atan2(m3(0, 2), m3(2, 2));
			z = -kPi / T(2);
			x = T(0);
		}
		else
		{
			y = atan2(-m3(2, 0), m3(0, 0));
			z = asin(m3(1, 0));
			x = atan2(-m3(1, 2), m3(1, 1));
		}
	}

	// Accessors //

	T& operator[](const U i)
	{
		return m_arr[i];
	}

	T operator[](const U i) const
	{
		return m_arr[i];
	}

	// Operators with same type //

	TEuler& operator=(const TEuler& b)
	{
		x = b.x;
		y = b.y;
		z = b.z;
		return *this;
	}

	// Other //

	// Return lerp(this, v1, t)
	[[nodiscard]] TEuler lerp(const TEuler& v1, T t) const
	{
		TEuler out;
		for(U i = 0; i < 3; ++i)
		{
			out[i] = m_arr[i] * (T(1) - t) + v1.m_arr[i] * t;
		}
		return out;
	}

	String toString() const requires(std::is_floating_point<T>::value)
	{
		return String().sprintf("%f %f %f", x, y, z);
	}

	String toStringDegrees() const requires(std::is_floating_point<T>::value)
	{
		return String().sprintf("%f %f %f", toDegrees(x), toDegrees(y), toDegrees(z));
	}
};

using Euler = TEuler<F32>;
using DEuler = TEuler<F64>;

} // end namespace anki