#include <iostream>
#include <limits>
#include <cstdlib>
#include <cmath>

#include <omp.h>

#include "tracer.hpp"

using namespace std;

using std::numeric_limits;
using glm::normalize;
using glm::radians;
using glm::dot;

static const vec3 BCKG_COLOR = vec3(0.16f, 0.66f, 0.72f);

static inline float max(float a, float b) {
  return a >= b ? a : b;
}

static inline float random01() {
  return static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
}

Tracer::Tracer(): m_h(640), m_w(480), m_fov(90.0f), m_a_ratio(640.0f / 480.0f) {}

Tracer::Tracer(int h, int w, float fov): m_h(h), m_w(w), m_fov(fov) {
  m_a_ratio = static_cast<float>(w) / h;
}

vec2 Tracer::sample_pixel(int i, int j) const {
  float pxNDC;
  float pyNDC;
  float pxS;
  float pyS;
  pyNDC = (static_cast<float>(i) + random01()) / m_h;
  pyS = (1.0f - (2.0f * pyNDC)) * tan(radians(m_fov) / 2);
  pxNDC = (static_cast<float>(j) + random01()) / m_w;
  pxS = (2.0f * pxNDC) - 1.0f;
  pxS *= m_a_ratio * tan(radians(m_fov) / 2);

  return vec2(pxS, pyS);
}

vec3 Tracer::trace_ray(Ray & r, vector<Figure *> & vf, vector<Light *> & vl, unsigned int rec_level) const {
  float t, _t, n_dot_l;
  Figure * _f;
  vec3 n, color, i_pos;
  vec3 light_dir;

  t = numeric_limits<float>::max();
  _f = NULL;
  
  for (size_t f = 0; f < vf.size(); f++) {
    if (vf[f]->intersect(r, _t) && _t < t) {
      t = _t;
      _f = vf[f];
    }
  }
  
  i_pos = r.m_origin + (t * r.m_direction);

  if (_f != NULL) {
    for (size_t l = 0; l < vl.size(); l++) {
      n = _f->normal_at_int(r, t);
      light_dir = vl[l]->m_position;
      n_dot_l = max(dot(n, light_dir), 0.0);
      color += (_f->color / 3.1416f) * vl[l]->m_diffuse * n_dot_l;
    }

    return color;
  } else
    return vec3(BCKG_COLOR);
}