#pragma once
#include <cstring>
#include <array>
#include <ostream>

namespace Eule
{
	template <class T>
	class Vector3;
	typedef Vector3<double> Vector3d;

	/** A matrix 4x4 class representing a 3d transformation.
	* This matrix consists of a 3x3 matrix containing scaling and rotation information, and a vector (d,h,l)
	* representing the translation.
	*
	* ```
	* myMatrix[y][x] = 3
	*
	*  X ==============>
	* Y
	* |  # # # # # # # # # # #
	* |  #   a   b   c   d   #
	* |  #                   #
	* |  #   e   f   g   h   #
	* |  #                   #
	* V  #   i   j   k   l   #
	*    #                   #
	*    #   m   n   o   p   #
	*    # # # # # # # # # # #
	*
	* ```
	*
	* Note: This class can also be used to compute regular 4x4 multiplications. Use Multiply4x4() for that.
	*/

	class Matrix4x4
	{
	public:
		Matrix4x4();
		Matrix4x4(const Matrix4x4& other);
		Matrix4x4(Matrix4x4&& other) noexcept;

		//! Array holding the matrices values
		std::array<std::array<double, 4>, 4> v;

		Matrix4x4 operator*(const Matrix4x4& other) const;
		void operator*=(const Matrix4x4& other);

		Matrix4x4 operator/(const Matrix4x4& other) const;
		void operator/=(const Matrix4x4& other);

		//! Cellwise scaling
		Matrix4x4 operator*(const double scalar) const;
		//! Cellwise scaling
		void operator*=(const double scalar);

		//! Cellwise division
		Matrix4x4 operator/(const double denominator) const;
		//! Cellwise division
		void operator/=(const double denominator);

		//! Cellwise addition
		Matrix4x4 operator+(const Matrix4x4& other) const;
		//! Cellwise addition
		void operator+=(const Matrix4x4& other);

		//! Cellwise subtraction
		Matrix4x4 operator-(const Matrix4x4& other) const;
		//! Cellwise subtraction
		void operator-=(const Matrix4x4& other);


		std::array<double, 4>& operator[](std::size_t y);
		const std::array<double, 4>& operator[](std::size_t y) const;

		void operator=(const Matrix4x4& other);
		void operator=(Matrix4x4&& other) noexcept;

		bool operator==(const Matrix4x4& other);
		bool operator!=(const Matrix4x4& other);

		//! Will return d,h,l as a Vector3d(x,y,z)
		const Vector3d GetTranslationComponent() const;
		//! Will set d,h,l from a Vector3d(x,y,z)
		void SetTranslationComponent(const Vector3d& trans);

		//! Will return this Matrix4x4 with d,h,l being set to 0
		Matrix4x4 DropTranslationComponents() const;

		//! Will return the 3x3 transpose of this matrix
		Matrix4x4 Transpose3x3() const;

		//! Will return the 4x4 transpose of this matrix
		Matrix4x4 Transpose4x4() const;

		//! Will return the Matrix4x4 of an actual 4x4 multiplication. operator* only does a 3x3
		Matrix4x4 Multiply4x4(const Matrix4x4& o) const;

		//! Will return the cofactors of this matrix, by dimension n
		Matrix4x4 GetCofactors(std::size_t p, std::size_t q, std::size_t n) const;

		//! Will return the determinant, by dimension n
		double Determinant(std::size_t n) const;

		//! Will return the adjoint of this matrix, by dimension n
		Matrix4x4 Adjoint(std::size_t n) const;

		//! Will return the 3x3-inverse of this matrix.  
		//! Meaning, the 3x3 component will be inverted, and the translation component will be negated
		Matrix4x4 Inverse3x3() const;

		//! Will return the full 4x4-inverse of this matrix
		Matrix4x4 Inverse4x4() const;

		//! Will check if the 3x3-component is inversible
		bool IsInversible3x3() const;

		//! Will check if the entire matrix is inversible
		bool IsInversible4x4() const;

		//! Will compare if two matrices are similar to a certain epsilon value
		bool Similar(const Matrix4x4& other, double epsilon = 0.00001) const;

		friend std::ostream& operator<<(std::ostream& os, const Matrix4x4& m);
		friend std::wostream& operator<<(std::wostream& os, const Matrix4x4& m);

		// Shorthands
		double& a = v[0][0];
		double& b = v[0][1];
		double& c = v[0][2];
		double& d = v[0][3];
		double& e = v[1][0];
		double& f = v[1][1];
		double& g = v[1][2];
		double& h = v[1][3];
		double& i = v[2][0];
		double& j = v[2][1];
		double& k = v[2][2];
		double& l = v[2][3];
		double& m = v[3][0];
		double& n = v[3][1];
		double& o = v[3][2];
		double& p = v[3][3];
	};
}
