#include "Subtract.h"
#include <iostream>
using namespace std;

Subtract::Subtract(const vector< refptr<Shape> > & shapes)
{
    int num_shapes = shapes.size();
    if (num_shapes > 2)
    {
        m_shape2 = shapes[num_shapes - 1];
        vector< refptr<Shape> > rest = shapes;
        rest.pop_back();
        m_shape1 = new Subtract(rest);
    }
    else if (num_shapes == 2)
    {
        m_shape1 = shapes[0];
        m_shape2 = shapes[1];
    }
    else
    {
        cerr << __FILE__ << ": " << __LINE__
             << ": error: Subtract::Subtract() called with only "
             << num_shapes
             << " sub-shapes!"
             << endl;
        exit(4);
    }
}

Shape::IntersectionList Subtract::intersect(refptr<Shape> _this, const Ray & ray)
{
    IntersectionList res1 = m_shape1->intersect(m_shape1, ray);
    IntersectionList res2 = m_shape2->intersect(m_shape2, ray);
    BoolIntersectionList merged(res1, res2, ray.getOrigin());

    IntersectionList res;
    bool in1 = false, in2 = false;

    /* initially go through the merged intersections to see whether
     * the ray started inside one of the sub-objects */
    for (int i = 0, sz = merged.size(), saw1 = 0, saw2 = 0;
         i < sz && (!saw1 || !saw2);
         i++)
    {
        Vector normal = merged[i].intersection.normal;
        double dot = - (ray.getDirection() % normal);
        bool back = dot < 0.0;
        bool left = merged[i].left;
        if (back)
        {
            if (left && !saw1)
                in1 = true;
            else if (!left && !saw2)
                in2 = true;
        }
        if (left)
            saw1 = 1;
        else
            saw2 = 1;
    }

    bool in_bool = in1 && !in2;
    for (int i = 0, sz = merged.size(); i < sz; i++)
    {
        Vector normal = merged[i].intersection.normal;
        double dot = - (ray.getDirection() % normal);
        bool front = dot > 0.0;
        bool left = merged[i].left;
        if (left)
            in1 = front;
        else
            in2 = front;
        if (!in_bool && in1 && !in2)
        {
            /* we found an intersection point
             * to get into the boolean object */
            in_bool = true;
            BoolIntersection bi = merged[i];
            Intersection i = bi.intersection;
            if ( ! left )   /* if this point came from object B (A - B) */
                i.normal = - i.normal;
            res.add(i);
        }
        else if (in_bool && !(in1 && !in2))
        {
            /* we found an intersection point
             * to get out of the boolean object */
            BoolIntersection bi = merged[i];
            Intersection i = bi.intersection;
            if ( ! left )   /* if this point came from object B (A - B) */
                i.normal = - i.normal;
            res.add(i);
            in_bool = false;
        }
    }

    return res;
}