//  Functions for TwoVector class
//  Glen Cowan, RHUL Physics Dept., October 2004

#include <iostream>
#include <cmath>
#include "TwoVector.h"

using namespace std;

// constructors

TwoVector::TwoVector(){   // default is unit vector along x
  m_x = 1;
  m_y = 0;
}

TwoVector::TwoVector (double x, double y){
  m_x = x;
  m_y = y;
}

// getter-like functions (const, since object's state unchanged)

double TwoVector::x() const { return m_x; }
double TwoVector::y() const { return m_y; }

double TwoVector::r() const {
  double rVal = sqrt(m_x*m_x + m_y*m_y);
  return rVal;
}

double TwoVector::cosTheta() const {
  double rVal = this->r();
  double cosThetaVal;
  if ( rVal > 0 ) {
    cosThetaVal = m_x / rVal;
  }
  else {
    cosThetaVal = 1.0;
  }
  return cosThetaVal;
}

double TwoVector::sinTheta() const {
  double rVal = this->r();
  double sinThetaVal;
  if ( rVal > 0 ) {
    sinThetaVal = m_y / rVal;
  }
  else {
    sinThetaVal = 0.0;
  }
  return sinThetaVal;
}

double TwoVector::theta() const {
  double thetaVal = atan2 (m_y, m_x);
  return thetaVal;
}

// setter-like functions

void TwoVector::set(double x, double y) {
  m_x = x;
  m_y = y;
}

void TwoVector::setX(double x) {
  m_x = x;
}

void TwoVector::setY(double y) {
  m_y = y;
}

void TwoVector::setR(double r) {
  double c = this->cosTheta();
  double s = this->sinTheta();
  m_x = r * c;
  m_y = r * s;
}

void TwoVector::setTheta(double t) {
  double r = this->r();
  m_x = r * cos(t);
  m_y = r * sin(t);
}

void TwoVector::rotate(double alpha) {
  double newTheta = this->theta() + alpha;
  double r = this->r();
  m_x = r * cos(newTheta);
  m_y = r * sin(newTheta);
}

// operators overloaded as member functions

TwoVector TwoVector::operator+(const TwoVector& b) {
  double cx = this->m_x + b.x();
  double cy = this->m_y + b.y();
  TwoVector c(cx, cy);
  return c;
}

TwoVector TwoVector::operator-(const TwoVector& b) {
  double cx = this->m_x - b.x();
  double cy = this->m_y - b.y();
  TwoVector c(cx, cy);
  return c;
}

TwoVector& TwoVector::operator+=(const TwoVector& b) {
  double cx = this->m_x + b.x();
  double cy = this->m_y + b.y();
  this->setX(cx);
  this->setY(cy);
  return *this;
}

TwoVector&  TwoVector::operator-=(const TwoVector& b) {
  double cx = this->m_x - b.x();
  double cy = this->m_y - b.y();
  this->setX(cx);
  this->setY(cy);
  return *this;
}

// non-member operators and functions

TwoVector operator*(const TwoVector& a, double b) {
  double cx = a.x()*b;
  double cy = a.y()*b;
  TwoVector c(cx, cy);
  return c;
}

TwoVector operator*(double b, const TwoVector& a) {
  double cx = a.x()*b;
  double cy = a.y()*b;
  TwoVector c(cx, cy);
  return c;
}

double dot(const TwoVector & a, const TwoVector & b) {
  double dotVal = a.x()*b.x() + a.y()*b.y();
  return dotVal;
}

TwoVector rotate(const TwoVector& a, double alpha) {
  double newTheta = a.theta() + alpha;
  double r = a.r();
  TwoVector b (r, 0);     // create with right length
  b.setTheta(newTheta);
  return b;
}