/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   www.cs.sandia.gov/~sjplimp/lammps.html
   Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under 
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
#include "region_triangle.h"
#include "stdlib.h"
#include "string.h"
#include "error.h"

using namespace LAMMPS_NS;

#define MIN(A,B) ((A) < (B) ? (A) : (B))
#define MAX(A,B) ((A) > (B) ? (A) : (B))

/* ---------------------------------------------------------------------- */

RegTriangle::RegTriangle(LAMMPS *lmp, int narg, char **arg) :
  Region(lmp, narg, arg)
{
  options(narg-8,&arg[8]);

  x1 = xscale*atof(arg[2]);
  y1 = yscale*atof(arg[3]);
  x2 = xscale*atof(arg[4]);
  y2 = yscale*atof(arg[5]);
  x3 = xscale*atof(arg[6]);
  y3 = yscale*atof(arg[7]);

  // extent of 2d triangle

  extent_xlo = MIN(x1,x2);
  extent_xlo = MIN(extent_xlo,x3);
  extent_xhi = MAX(x1,x2);
  extent_xhi = MAX(extent_xhi,x3);

  extent_ylo = MIN(y1,y2);
  extent_ylo = MIN(extent_ylo,y3);
  extent_yhi = MAX(y1,y2);
  extent_yhi = MAX(extent_yhi,y3);

  extent_zlo = -0.5;
  extent_zhi = 0.5;
}

/* ---------------------------------------------------------------------- */

int RegTriangle::match(double x, double y, double z)
{
  double side1 = (x-x1)*(y2-y1) - (y-y1)*(x2-x1);
  double side2 = (x-x2)*(y3-y2) - (y-y2)*(x3-x2);
  double side3 = (x-x3)*(y1-y3) - (y-y3)*(x1-x3);

  int inside;
  if (side1 > 0.0 && side2 > 0.0 && side3 > 0.0) inside = 1;
  else inside = 0;

  return !(inside ^ interior);         // 1 if same, 0 if different
}