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#pragma once

#include <cmath>
#include "matrix.h"

namespace RadeonProRender
{
    class quaternion
    {
    public:
        quaternion (float xx = 0.f, float yy = 0.f, float zz = 0.f, float ww = 1.f) : x(xx), y(yy), z(zz), w(ww) {}

        //explicit			   quaternion( const vector<T,4>& v );
        /// create quaternion from a orthogonal(!) matrix
        /// make sure the matrix is ORTHOGONAL
        explicit			   quaternion( const matrix& m );

        /// convert quaternion to matrix
        //void				   to_matrix( matrix<T,4,4>& pM ) const;
        void to_matrix(matrix& m) const;

        quaternion      operator -() const { return quaternion(-x, -y, -z, -w); }
        quaternion&     operator +=( quaternion const& o ) { x+=o.x; y+=o.y; z+=o.z; w+=o.w; return *this; }
        quaternion&     operator -=( quaternion const& o ) { x-=o.x; y-=o.y; z-=o.z; w-=o.w; return *this; }
        quaternion&     operator *=( quaternion const& o ) { x*=o.x; y*=o.y; z*=o.z; w*=o.w; return *this; }
        quaternion&     operator *=( float a ) { x*=a; y*=a; z*=a; w*=a; return *this; }
        quaternion&     operator /=( float a ) { float inva = 1.f/a; x*=inva; y*=inva; z*=inva; w*=inva; return *this; }

        quaternion      conjugate() const { return quaternion(-x, -y, -z, w); }
        quaternion      inverse()   const; 

        float  sqnorm() const { return x * x + y * y + z * z + w * w; }
        float  norm()   const { return std::sqrt(sqnorm()); }

        float x, y, z, w;
    };

    inline quaternion::quaternion (const matrix& m)
    {
        float tr = m.m00 + m.m11 + m.m22;

        if (tr > 0) 
        { 
            float S = sqrt(tr+1.f) * 2;
            w = 0.25f * S;
            x = (m.m21 - m.m12) / S;
            y = (m.m02 - m.m20) / S; 
            z = (m.m10 - m.m01) / S; 
        } 
        else if ((m.m00 > m.m11)&(m.m00 > m.m22)) 
        { 
            float S = sqrt(1.f + m.m00 - m.m11 - m.m22) * 2;
            w = (m.m21 - m.m12) / S;
            x = 0.25f * S;
            y = (m.m01 + m.m10) / S; 
            z = (m.m02 + m.m20) / S; 
        } 
        else if (m.m11 > m.m22) 
        { 
            float S = sqrt(1.f + m.m11 - m.m00 - m.m22) * 2; // S=4*qy
            w = (m.m02 - m.m20) / S;
            x = (m.m01 + m.m10) / S; 
            y = 0.25f * S;
            z = (m.m12 + m.m21) / S; 
        } 
        else 
        { 
            float S = sqrt(1.f + m.m22 - m.m00 - m.m11) * 2; // S=4*qz
            w = (m.m10 - m.m01) / S;
            x = (m.m02 + m.m20) / S;
            y = (m.m12 + m.m21) / S;
            z = 0.25f * S;
        }
    }
    
    inline quaternion      quaternion::inverse()   const
    {
        if (sqnorm() == 0)
        {
            return quaternion();
        }
        else
        {
            quaternion q = conjugate();
            q /= sqnorm();
            return q;
        }
    }

    inline quaternion operator * (quaternion const& q1,  quaternion const& q2)
    {
        quaternion res;
        res.x = q1.y*q2.z - q1.z*q2.y + q2.w*q1.x + q1.w*q2.x;
        res.y = q1.z*q2.x - q1.x*q2.z + q2.w*q1.y + q1.w*q2.y;
        res.z = q1.x*q2.y - q2.x*q1.y + q2.w*q1.z + q1.w*q2.z;
        res.w = q1.w*q2.w - q1.x*q2.x - q1.y*q2.y - q1.z*q2.z;
        return res;
    }

    inline quaternion operator / ( const quaternion& q,  float a )
    {
        quaternion res = q;
        return res /= a;
    }

    inline quaternion operator + ( const quaternion& q1,  const quaternion& q2 )
    {
        quaternion res = q1;
        return res += q2;
    }

    inline quaternion operator - ( const quaternion& q1,  const quaternion& q2 )
    {
        quaternion res = q1;
        return res -= q2;
    }

    inline quaternion operator * ( const quaternion& q,  float a )
    {
        quaternion res = q;
        return res *= a;
    }

    inline quaternion operator * ( float a, quaternion const& q )
    {
        quaternion res = q;
        return res *= a;
    }

    inline quaternion normalize( quaternion const& q )
    {
        float norm = q.norm();
        return q / norm;
    }
    
	inline float dot(quaternion const& v1, quaternion const& v2)
    {
        return v1.x * v2.x + v1.y * v2.y + v1.z * v2.z + v1.w * v2.w;
    }

    inline void quaternion::to_matrix( matrix& m ) const
    {
        float s = 2.f/norm();
        m.m00 = 1 - s*(y*y + z*z); m.m01 = s * (x*y - w*z);	    m.m02 = s * (x*z + w*y);     m.m03 = 0;
        m.m10 = s * (x*y + w*z);   m.m11 = 1 - s * (x*x + z*z); m.m12 = s * (y*z - w*x);     m.m13 = 0;
        m.m20 = s * (x*z - w*y);   m.m21 = s * (y*z + w*x);	    m.m22 = 1 - s * (x*x + y*y); m.m23 = 0;
        m.m30 =                    m.m31 =                      m.m32;                       m.m33 = 1;
    }

	//linear interpolation of 2 quaternions
	inline quaternion slerp(quaternion const& v0_, quaternion const& v1_, float t) 
	{
		quaternion v0 = normalize(v0_);
		quaternion v1 = normalize(v1_);

		float dotr = dot(v0, v1);

		if (dotr < 0.0f) 
		{
			v1 = -v1;
			dotr = -dotr;
		}  

		const float DOT_THRESHOLD = 0.9995f;
		if (dotr > DOT_THRESHOLD) 
		{
			quaternion result = v0 + t*(v1 - v0);
			result = normalize(result);
			return result;
		}

		float theta_0 = acosf(dotr);
		float theta = theta_0*t;
		float sin_theta = sinf(theta);
		float sin_theta_0 = sinf(theta_0);

		float s0 = cosf(theta) - dotr * sin_theta / sin_theta_0;
		float s1 = sin_theta / sin_theta_0;

		return (s0 * v0) + (s1 * v1);
	}
}