/******************************************************************/
/* 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 "ray_util.h"
#include "random_number.h"
#include "recursiveRaytracing.h"


//////////////////
// Constructors //
//////////////////
recursiveRaytracing::recursiveRaytracing(unsigned int maxDepth, unsigned int samplesPerPixel)
{
  _depth = maxDepth;
  _samples = samplesPerPixel;
}


/////////////
// Methods //
/////////////
image recursiveRaytracing::render(const scene& s) const
{
  image result(s.getCamera().width(), s.getCamera().height());

  // HW5: Implement a recursive ray tracer that shoots '_samples' rays per pixel.
  //      and has a maximum recursion depth of '_depth'. The ray tracer should
  //      only recurse for specular surfaces, and support environment maps and
  //      shadows.
  // Modifes: nothing.
  // Returns: rendered image.

  // for each pixel
  for (image::size_type y = 0; y < result.height(); y++) {

    for (image::size_type x = 0; x < result.width(); x++) {

      // for sample size 1, shoot ray at pixel center
      if (_samples == 1) {
        ray r = s.getCamera()(x + 0.5, y + 0.5);
        result(x, y) = traceRay(s, r, _depth);
      }
      else {
        // for each sample, trace all the rays!
        color pixel = color(0.0f);

        for (unsigned int i = 0; i < _samples; i++) {
          ray r = s.getCamera()(x + random_float(1.0f), y + random_float(1.0f));
          pixel += traceRay(s, r, _depth);
        }

        result(x, y) = pixel / _samples;
      }

    }

  }

  return result;
}


color recursiveRaytracing::traceRay(const scene& s, const ray& r, unsigned int currentDepth) const {
  color result = color(0.0f);

  // base case: bail at max depth
  if (currentDepth == 0) {
    return color();
  }

  // intersect the scene
  intersectionPoint ip = s.intersect(r);

  // if hit, shade pixel
  if (ip.isHit()) {

    // for each light source,
    for (unsigned int l = 0; l < s.numberOfLightsources(); l++) {
      // connect to light source
      lightSample ls = s.getLightsource(l).intensityAt(ip.position());

      // create shadow ray and intersect with light source
      ray shadowRay = createRay(ip, ls.directionToLight());
      intersectionPoint shadow_ip = s.intersect(shadowRay);

      // if object not in shadow, shade it
      if (!(ip.distance(shadow_ip) < ls.distance())) {
        result += ip.shade(ls);
      }

    }

    // if specular, compute indirect lighting and recurse
    if (ip.getShaderProperties().specular) {
      ray reflect_ray = reflectRay(ip);
      intersectionPoint reflect_ip = s.intersect(reflect_ray);

      if (reflect_ip.isHit()) {
        result += (ip.shade(reflect_ray.direction()) * traceRay(s, reflect_ray, --currentDepth));
      }
      else {
        // if scene has environment map, grab texel color from map
        if (s.hasEnvironmentMap()) {
          result += s.evaluateEnvironmentMap(reflect_ray.direction());
        }

      }

    }

  }
  else {

    // if scene has environment map, grab texel color from map
    if (s.hasEnvironmentMap()) {
      result += s.evaluateEnvironmentMap(r.direction());
    }

  }

  return result;
}