#include "geometry.h"


static void edgeVertex(Vertex *v, int edge, const Rectangle *rect) {
  if(edge == EDGE_NONE)
    edge = rect->edges(*v);
  
  if(edge & EDGE_LEFT) v->setX(rect->getVertex1().getX());
  else if(edge & EDGE_RIGHT) v->setX(rect->getVertex2().getX());
  
  if(edge & EDGE_TOP) v->setY(rect->getVertex1().getY());
  else if(edge & EDGE_BOTTOM) v->setY(rect->getVertex2().getY());
}

static int simplifyVertex(Vertex *v, const Vertex *to, const Rectangle *rect) {
  Line l(*v, *to);
  int edge, edge2;
  
  
  edge = rect->edges(*v);
  if(edge == EDGE_NONE) return EDGE_NONE;
  
  edge2 = rect->intersects(l, v, edge);
  if(edge2 != EDGE_NONE) return edge2;
  
  edgeVertex(v, edge, rect);
  return edge;
}

static void addSimplifiedLine(const Vertex *v1, const Vertex *v2, const Rectangle *rect, int last, Polygon *out) {
  const Line d1(rect->getVertex1(), rect->getVertex2());
  const Line d2(rect->getVertex1().getX(), rect->getVertex2().getY(), rect->getVertex2().getX(), rect->getVertex1().getY());
  
  Line l(*v1, *v2);
  Vertex v, vi;
  int edge1, edge2;
  
  
  v = *v1;
  if((edge1 = simplifyVertex(&v, v2, rect)) != EDGE_NONE)
    out->push_back(v);
  
  v = *v2;
  edge2 = simplifyVertex(&v, v1, rect);
  
  if(edge1 != EDGE_NONE && edge2 != EDGE_NONE && !(edge1 & edge2)) {
    if(l.intersects(d1, &vi) == INTERSECTION_SEGMENT_LINE) {
      edgeVertex(&vi, 0, rect);
      out->push_back(vi);
    }
    else if(l.intersects(d1, &vi) == INTERSECTION_SEGMENT_LINE) {
      edgeVertex(&vi, 0, rect);
      out->push_back(vi);
    }
  }
  
  if(!last)
    out->push_back(v);
}

void simplifyPolygon(const Polygon *in, const Rectangle *rect, Polygon *out) {
  Vertex v;
  
  if(in->empty()) return;
  else if(in->size() == 1) {
    out->push_back(in->front());
    return;
  }
  
  v = in->front();
  simplifyVertex(&v, &in->back(), rect);
  out->push_back(v);
  
  for(Polygon::const_iterator v2 = in->begin(); v2 != in->end(); v2++) {
    Polygon::const_iterator v3 = v2+1;
    if(v3 == in->end()) v3 = in->begin();
    
    addSimplifiedLine(&*v2, &*v3, rect, (v3 == in->begin()), out);
  }
}