#include "Scene.h"
#include <stdlib.h>
#include <string>
#include <vector>
#include <utility>              /* pair */
#include <map>
#include <algorithm>            /* sort() */
#include <functional>           /* binary_function */
#include <typeinfo>             /* typeid operator support */
#include <math.h>
#include "BMP.h"
#include "util/Color.h"
#include "shapes/Shape.h"
#include "Light.h"

using namespace std;

Scene::Scene(const map<string, const char *> & options,
             const char * filename)
{
    m_width = 800;
    m_height = 600;
    m_multisample_level = 1;
    m_output_file_name = "fart.bmp";
    m_vfov = 60.0;
    m_verbose = true;
    m_data = NULL;
    m_ambient_light = Color(0.1, 0.1, 0.1);
    m_max_depth = 10;
    m_transforms.push(Transform());

    load(filename);

    /* after loading the scene file, apply any command-line render options */
    for (map<const string, const char *>::const_iterator it = options.begin();
         it != options.end();
         it++)
    {
        if (it->first == "width")
        {
            m_width = atoi(it->second);
        }
        else if (it->first == "height")
        {
            m_height = atoi(it->second);
        }
        else if (it->first == "multisample")
        {
            m_multisample_level = atoi(it->second);
        }
        else if (it->first == "field-of-view")
        {
            m_vfov = atof(it->second);
        }
        else if (it->first == "output-file")
        {
            m_output_file_name = it->second;
        }
        else if (it->first == "verbose")
        {
            m_verbose = true;
        }
    }

    /* view plane distance is calculated based on the field of view */
    m_view_plane_dist = (m_height / 2.0) / tan(M_PI * m_vfov / 360.0);
    m_sample_span = 1.0 / m_multisample_level;
    m_half_sample_span = m_sample_span / 2.0;
    m_multisample_level_squared = m_multisample_level * m_multisample_level;
}

Scene::~Scene()
{
    if (m_data != NULL)
        delete m_data;
}

void Scene::render()
{
    if (m_verbose)
    {
        cout << " *** Beginning scene render ***" << endl;
        cout << "Parameters:" << endl;
        cout << "----------------------------------------" << endl;
        cout << "    Width: " << m_width << endl;
        cout << "    Height: " << m_height << endl;
        cout << "    Multisample Level: " << m_multisample_level << endl;
        cout << "    Vertical Field of View: " << m_vfov << endl;
        cout << "----------------------------------------" << endl;
    }

    m_data = new unsigned char[m_width * m_height * 3];

    for (int i = 0; i < m_height; i++)
    {
        for (int j = 0; j < m_width; j++)
        {
            renderPixel(j, i, &m_data[3 * (m_width * i + j)]);
        }
    }

    if (m_verbose)
    {
        cout << " *** Ending scene render ***" << endl;
        cout << "Writing output file '" << m_output_file_name << '\'' << endl;
    }
    BMP outputImage(m_output_file_name.c_str(), m_width, m_height, m_data);
}

void Scene::renderPixel(int x, int y, unsigned char * pixel)
{
    /* calculate the ray going from the camera through this pixel */
    Color finalColor;
    for (int i = 0; i < m_multisample_level; i++)
    {
        for (int j = 0; j < m_multisample_level; j++)
        {
            double rx = (x + i * m_sample_span + m_half_sample_span)
                      - (m_width / 2.0);
            double rz = (m_height / 2.0)
                      - (y + j * m_sample_span + m_half_sample_span);

            Ray ray(Vector(0, 0, 0), Vector(rx, m_view_plane_dist, rz));

            finalColor += traceRay(ray);
        }
    }

    /* take the average of all the samples as the final pixel value */
    pixel[BMP_RED] = (unsigned char)
        (0xFF * finalColor.r / m_multisample_level_squared);
    pixel[BMP_GREEN] = (unsigned char)
        (0xFF * finalColor.g / m_multisample_level_squared);
    pixel[BMP_BLUE] = (unsigned char)
        (0xFF * finalColor.b / m_multisample_level_squared);
}

Color Scene::traceRay(const Ray & ray)
{
    return traceRayRecurse(ray, m_max_depth, 1.0);
}

/**
 * factor: the proportion of the final color that this computation is worth
 */
Color Scene::traceRayRecurse(const Ray & ray, int depth, double factor)
{
    Color color;

    ShapeDistance hit = getRayClosestHit(ray);

    if ( ! hit.shape.isNull() )
    {
        /* compute the Phong lighting for each hit */
        refptr<Material> material = hit.shape->getMaterial();

        Vector surfacePoint = ray[hit.dist];
        Vector surfaceNormal = hit.shape->getNormalAt(surfacePoint);

        color = computePhong(material,
                             ray,
                             surfacePoint,
                             surfaceNormal);

        if (depth > 0 && factor > SCENE_FACTOR_THRESHOLD)
        {
            double reflectance = material->getReflectance();
            if (factor * reflectance > SCENE_FACTOR_THRESHOLD)
            {
                color *= (1.0 - reflectance);
                Vector reflected_direction =
                    (-ray.getDirection()).reflect(surfaceNormal);
                Ray newRay(surfacePoint, reflected_direction);
                Vector jitter_surface_point = newRay[0.0001];
                Ray jitterNewRay(jitter_surface_point, reflected_direction);
                Color c = traceRayRecurse(jitterNewRay,
                                          depth - 1,
                                          factor * reflectance);
                color += c * reflectance;
            }

            double transparency = material->getTransparency();
            if (factor * transparency > SCENE_FACTOR_THRESHOLD)
            {
                color *= (1.0 - transparency);
                Vector jitter_surface_point = ray[hit.dist + 0.0001];
                Ray newRay(jitter_surface_point, ray.getDirection());
                Color c = traceRayRecurse(newRay,
                                          depth - 1,
                                          factor * transparency);
                color += c * transparency;
            }
        }
    }

    return color;
}

Scene::ShapeDistance Scene::getRayClosestHit(const Ray & ray)
{
    ShapeDistance hit;
    bool foundOne = false;

    /* loop through all shapes in the scene */
    for (vector< refptr<Shape> >::iterator it = m_shapes.begin();
         it != m_shapes.end();
         it++)
    {
        Shape::IntersectionList intersections = (*it)->intersect(*it, ray);

        for (int i = 0, num_results = intersections.size();
             i < num_results;
             i++)
        {
            refptr<Shape> shape = intersections[i].shape;
            const Vector & isect_point = intersections[i].vector;
            Vector normal = shape->getNormalAt(isect_point);
            double intersect_dist = (isect_point - ray.getOrigin()).mag();
            if (foundOne == false || intersect_dist < hit.dist)
            {
                hit.shape = shape;
                hit.dist = intersect_dist;
                foundOne = true;
            }
        }
    }

    return hit;
}

Color Scene::computePhong(const refptr<Material> material,
                          const Ray & viewRay,
                          const Vector & surfacePoint,
                          const Vector & surfaceNormal)
{
    Color result = m_ambient_light * material->getAmbientColor();

    Vector viewDirection = -viewRay.getDirection();
    double shininess = material->getShininess();
    const Color & diffuseColor = material->getDiffuseColor();
    const Color & specularColor = material->getSpecularColor();

    for (std::vector< refptr<Light> >::const_iterator it = m_lights.begin();
         it != m_lights.end();
         it++)
    {
        Vector directionToLight = (*it)->getPosition() - surfacePoint;
        directionToLight.normalize();
        Vector reflectedLightDirection =
            directionToLight.reflect(surfaceNormal);

        Ray surfaceToLight(surfacePoint, directionToLight);
        double light_contribution =
            calculateLightContribution(surfaceToLight.shift(0.0001), *it);

        if (light_contribution > 0.0)
        {
            /* calculate the diffuse term */
            double diffuse_coef = directionToLight % surfaceNormal;
            if (diffuse_coef > 0.0)
            {
                result += diffuseColor
                        * (*it)->getDiffuseColor()
                        * diffuse_coef
                        * light_contribution;
            }

            /* calculate the specular term */
            double specular_coef = reflectedLightDirection % viewDirection;
            if (specular_coef > 0.0)
            {
                result += specularColor
                        * (*it)->getSpecularColor()
                        * pow(specular_coef, shininess)
                        * light_contribution;
            }
        }
    }

    /* TODO: figure out better scaling */
    if (result.r > 1.0)
        result.r = 1.0;
    if (result.g > 1.0)
        result.g = 1.0;
    if (result.b > 1.0)
        result.b = 1.0;

    return result;
}

double Scene::calculateLightContribution(const Ray & toLight,
                                         refptr<Light> light)
{
    double contrib = 1.0;
    double dist_to_light = toLight.getOrigin().dist_to(light->getPosition());
    double dist_so_far = 0.0;

    Ray currentRay = toLight;

    for (;;)
    {
        ShapeDistance hit = getRayClosestHit(currentRay);

        if ( hit.shape.isNull() )
            break;

        if ( dist_so_far + hit.dist > dist_to_light )
            break;

        contrib *= hit.shape->getMaterial()->getTransparency();

        if ( contrib < SCENE_FACTOR_THRESHOLD )
            break;

        dist_so_far += hit.dist + 0.0001;
    }

    return contrib;
}

bool operator<(const Scene::ShapeDistance & sd1,
               const Scene::ShapeDistance & sd2)
{
    return sd1.dist < sd2.dist;
}