//  Functions for TwoVector class, polor coord. version
//  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_r = 1;
  m_theta = 0;
}

TwoVector::TwoVector (double x, double y){
  m_r = sqrt(x*x + y*y);
  m_theta = atan2(y,x);
}

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

double TwoVector::x() const { return this->r() * this->cosTheta(); }
double TwoVector::y() const { return this->r() * this->sinTheta(); }

double TwoVector::r() const { return fabs(m_r); }

double TwoVector::cosTheta() const { return cos(m_theta); }
double TwoVector::sinTheta() const { return sin(m_theta); }

double TwoVector::theta() const {

  double theta = m_theta;
  if ( theta < 0 || theta > 2.*M_PI ) {
    double x = this->x();
    double y = this->y();
    theta = atan2 (y, x);
  }
  return theta;

}

// setter-like functions

void TwoVector::set(double x, double y) {
  m_r = sqrt(x*x + y*y);
  m_theta = atan2(y, x);
}

void TwoVector::setX(double x) {
  double y = this->y();
  m_r = sqrt(x*x + y*y);
  m_theta = atan2(y, x);
}

void TwoVector::setY(double y) {
  double x = this->x();
  m_r = sqrt(x*x + y*y);
  m_theta = atan2(y, x);
}

void TwoVector::setR(double r) {
  m_r = r;
}

void TwoVector::setTheta(double t) {
  m_theta = t;
}

void TwoVector::rotate(double alpha) {
  m_theta += alpha;
}

// operators overloaded as member functions

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

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

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

TwoVector&  TwoVector::operator-=(const TwoVector& b) {
  double cx = this->x() - b.x();
  double cy = this->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;
}