/******************************************************************/
/* This file is part of the homework assignments for CSCI-427/527 */
/* at The College of William & Mary and authored by Pieter Peers. */
/* No part of this file, whether altered or in original form, can */
/* be distributed or used outside the context of CSCI-427/527     */
/* without consent of either the College of William & Mary or     */
/* Pieter Peers.                                                  */
/******************************************************************/
#include <cmath>
#include "constants.h"
#include "phongBrdf.h"

//////////////////
// Constructors //
//////////////////
phongBrdf::phongBrdf(const color& albedo, float sharpness)
{
  _albedo = albedo;
  _sharpness = sharpness;
}


phongBrdf::phongBrdf(const phongBrdf& src)
{
  _albedo = src._albedo;
  _sharpness = src._sharpness;
}


///////////////
// Operators //
///////////////
phongBrdf& phongBrdf::operator=(const phongBrdf& src)
{
  _assign(src);
  return *this;
}


/////////////
// Methods //
/////////////
color phongBrdf::shade(const vec3d& in, const vec3d& out) const
{
  // HW3: Implement this.
  //      Returns the phong shaded color from a specular surface for an
  //      incident lighting direction of 'in', and view direction of 'out'.
  //      The surface normal = (0,0,1).
  // Returns: shaded color
  // Modifies: nothing.
  if (out.z < EPSILON) { return color(0.0f); }

  vec3d normal, r;
  float r_dot_out;

  normal = vec3d(0, 0, 1);
  r = (2 * normal.dot(in) * normal) - in;
  r_dot_out = r.dot(out);
  if (r_dot_out < EPSILON) { return color(0.0f); }
  else if (r_dot_out > EPSILON + 1) { r_dot_out = 1; }
  return color(_albedo * pow(r_dot_out, _sharpness));
}


bool phongBrdf::isSpecular(void) const
{
  // Consider low roughness to be diffuse.
  // Use 5.0f as an arbitrary threshold.
  return (_sharpness > 5.0f);
}


bool phongBrdf::isDiffuse(void) const
{
  return !isSpecular();
}


/////////////////////
// Private Methods //
/////////////////////
void phongBrdf::_assign(const phongBrdf& src)
{
  _albedo = src._albedo;
  _sharpness = src._sharpness;
}


void phongBrdf::_swap(phongBrdf& src)
{
  swap(_albedo, src._albedo);
  std::swap(_sharpness, src._sharpness);
}


void phongBrdf::_print(std::ostream& s) const
{
  s << "Phong BRDF: albedo=" << _albedo << ", sharpness=" << _sharpness;
}