#include "NiQuaternion.h"

// C++
#include <cmath>

// Static Variables
const NiQuaternion NiQuaternion::IDENTITY(1, 0, 0, 0);

//! The initializer
NiQuaternion::NiQuaternion(void) {
	this->w = 1;
	this->x = 0;
	this->y = 0;
	this->z = 0;
}

//! The initializer
NiQuaternion::NiQuaternion(float w, float x, float y, float z) {
	this->w = w;
	this->x = x;
	this->y = y;
	this->z = z;
}

//! Destructor
NiQuaternion::~NiQuaternion(void) {}


// MARK: Setters / Getters

//! Gets the W coordinate
float NiQuaternion::GetW(void) const {
	return this->w;
}

//! Sets the W coordinate
void NiQuaternion::SetW(float w) {
	this->w = w;
}

//! Gets the X coordinate
float NiQuaternion::GetX(void) const {
	return this->x;
}

//! Sets the X coordinate
void NiQuaternion::SetX(float x) {
	this->x = x;
}

//! Gets the Y coordinate
float NiQuaternion::GetY(void) const {
	return this->y;
}

//! Sets the Y coordinate
void NiQuaternion::SetY(float y) {
	this->y = y;
}

//! Gets the Z coordinate
float NiQuaternion::GetZ(void) const {
	return this->z;
}

//! Sets the Z coordinate
void NiQuaternion::SetZ(float z) {
	this->z = z;
}


// MARK: Member Functions

//! Returns the forward vector from the quaternion
Vector3 NiQuaternion::GetForwardVector(void) const {
	return Vector3(2 * (x * z + w * y), 2 * (y * z - w * x), 1 - 2 * (x * x + y * y));
}

//! Returns the up vector from the quaternion
Vector3 NiQuaternion::GetUpVector(void) const {
	return Vector3(2 * (x * y - w * z), 1 - 2 * (x * x + z * z), 2 * (y * z + w * x));
}

//! Returns the right vector from the quaternion
Vector3 NiQuaternion::GetRightVector(void) const {
	return Vector3(1 - 2 * (y * y + z * z), 2 * (x * y + w * z), 2 * (x * z - w * y));
}

Vector3 NiQuaternion::GetEulerAngles() const {
	Vector3 angles;

	// roll (x-axis rotation)
	const float sinr_cosp = 2 * (w * x + y * z);
	const float cosr_cosp = 1 - 2 * (x * x + y * y);
	angles.x = std::atan2(sinr_cosp, cosr_cosp);

	// pitch (y-axis rotation)
	const float sinp = 2 * (w * y - z * x);

	if (std::abs(sinp) >= 1) {
		angles.y = std::copysign(3.14 / 2, sinp); // use 90 degrees if out of range
	} else {
		angles.y = std::asin(sinp);
	}

	// yaw (z-axis rotation)
	const float siny_cosp = 2 * (w * z + x * y);
	const float cosy_cosp = 1 - 2 * (y * y + z * z);
	angles.z = std::atan2(siny_cosp, cosy_cosp);

	return angles;
}

// MARK: Operators

//! Operator to check for equality
bool NiQuaternion::operator==(const NiQuaternion& rot) const {
	return rot.x == this->x && rot.y == this->y && rot.z == this->z && rot.w == this->w;
}

//! Operator to check for inequality
bool NiQuaternion::operator!=(const NiQuaternion& rot) const {
	return !(*this == rot);
}


// MARK: Helper Functions

//! Look from a specific point in space to another point in space
NiQuaternion NiQuaternion::LookAt(const NiPoint3& sourcePoint, const NiPoint3& destPoint) {
	//To make sure we don't orient around the X/Z axis:
	NiPoint3 source = sourcePoint;
	NiPoint3 dest = destPoint;
	source.y = 0.0f;
	dest.y = 0.0f;

	NiPoint3 forwardVector = NiPoint3(dest - source).Unitize();

	NiPoint3 posZ = NiPoint3::UNIT_Z;
	NiPoint3 vecA = posZ.CrossProduct(forwardVector).Unitize();

	float dot = posZ.DotProduct(forwardVector);
	float rotAngle = static_cast<float>(acos(dot));

	NiPoint3 vecB = vecA.CrossProduct(posZ);

	if (vecB.DotProduct(forwardVector) < 0) rotAngle = -rotAngle;
	return NiQuaternion::CreateFromAxisAngle(vecA, rotAngle);
}

NiQuaternion NiQuaternion::LookAtUnlocked(const NiPoint3& sourcePoint, const NiPoint3& destPoint) {
	NiPoint3 forwardVector = NiPoint3(destPoint - sourcePoint).Unitize();

	NiPoint3 posZ = NiPoint3::UNIT_Z;
	NiPoint3 vecA = posZ.CrossProduct(forwardVector).Unitize();

	float dot = posZ.DotProduct(forwardVector);
	float rotAngle = static_cast<float>(acos(dot));

	NiPoint3 vecB = vecA.CrossProduct(posZ);

	if (vecB.DotProduct(forwardVector) < 0) rotAngle = -rotAngle;
	return NiQuaternion::CreateFromAxisAngle(vecA, rotAngle);
}

//! Creates a Quaternion from a specific axis and angle relative to that axis
NiQuaternion NiQuaternion::CreateFromAxisAngle(const Vector3& axis, float angle) {
	float halfAngle = angle * 0.5f;
	float s = static_cast<float>(sin(halfAngle));

	NiQuaternion q;
	q.x = axis.GetX() * s;
	q.y = axis.GetY() * s;
	q.z = axis.GetZ() * s;
	q.w = static_cast<float>(cos(halfAngle));

	return q;
}

NiQuaternion NiQuaternion::FromEulerAngles(const NiPoint3& eulerAngles) {
	// Abbreviations for the various angular functions
	float cy = cos(eulerAngles.z * 0.5);
	float sy = sin(eulerAngles.z * 0.5);
	float cp = cos(eulerAngles.y * 0.5);
	float sp = sin(eulerAngles.y * 0.5);
	float cr = cos(eulerAngles.x * 0.5);
	float sr = sin(eulerAngles.x * 0.5);

	NiQuaternion q;
	q.w = cr * cp * cy + sr * sp * sy;
	q.x = sr * cp * cy - cr * sp * sy;
	q.y = cr * sp * cy + sr * cp * sy;
	q.z = cr * cp * sy - sr * sp * cy;

	return q;
}