/******************************************************************/
/* 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 <cassert>
#include <algorithm>

#include "boundedCompound.h"
#include "intersector_factory_base.h"

/////////////////
// Constructor //
/////////////////
boundedCompound::boundedCompound(void)
  : boundedPrimitive()
{
  _transform = transformation3d();
  _intersector = nullptr;
}


boundedCompound::boundedCompound(const transformation3d& transform, const std::shared_ptr<const shader_base>& shader)
				 
  : boundedPrimitive(boundingBox(), shader)
{
  _transform = transform;
  _intersector = nullptr;
}


/////////////
// Methods //
/////////////
intersectionPoint boundedCompound::intersect(const ray& r) const
{
  // sanity check
  assert(_intersector);

  // inverse transform ray
  ray transformedRay = inverseTransform(r, _transform);

  // pass intersection computation to _intersector
  intersectionPoint ip = _intersector->intersect( transformedRay );

  // if no shader, insert current shader
  if(!ip.hasShader()) ip.setShader(_shader);

  // transform the intersection point
  ip.transform(_transform);

  // Done.
  return ip;
}


float boundedCompound::area(void) const
{
  float total_area = 0.0f;
  for_each(compounds().begin(), compounds().end(), [&](const std::shared_ptr<const boundedPrimitive>& prim)
  {
    total_area += prim->area();
  });

  // Done.
  return total_area;
}


surfaceSample boundedCompound::sample(float r1, float r2) const
{
  float total_area = area();
  auto primItr = compounds().begin();

  // sample compounds (proportional to area)
  float prim_area = (*primItr)->area();
  float residual = r1*total_area;
  while(residual > prim_area && std::next(primItr) != compounds().end())
  {
    residual -= prim_area;
    primItr++;
    prim_area = (*primItr)->area();
  }

  // rescale the random variable
  r1 = std::min(residual / prim_area, 1.0f);

  // sample point in triangle (and adjust pdf to include the above selection)
  surfaceSample sample = (*primItr)->sample(r1, r2) * (prim_area / total_area);

  // apply transformation
  sample.transform(_transform);

  // Done.
  return sample;
}


void boundedCompound::initialize(const intersector_factory_base& ifb)
{
  // create the _intersector
  _intersector = ifb(*this);
}
 

void boundedCompound::initializeBoundingBox(void)
{
  // compute the bounding box in world coordinates
  _bb = boundingBox();
  for_each(compounds().begin(), compounds().end(), [&](const std::shared_ptr<const boundedPrimitive>& prim)
  {
    _bb += transform(prim->boundingbox(), _transform);
  });
}


bool boundedCompound::hasShader(void) const
{
  // check if this has a shader
  if(boundedPrimitive::hasShader()) return true;

  // check if each child has a shader
  for(auto itr = compounds().begin(); itr != compounds().end(); itr++)
  {
    if(!(*itr)->hasShader()) return false;
  }

  // Done.
  return true;
}


void boundedCompound::_print(std::ostream& s) const
{
  s << "boundedCompound (" << _bb << ", " << compounds().size() << " compounds)";
}