#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;

namespace HeuristicLab.Analysis.AlgorithmBehavior.Analyzers {
  public static class QhullWrapper {
    [System.Runtime.InteropServices.DllImportAttribute("HeuristicLab.qhull.dll", EntryPoint = "qhull_volume", CallingConvention = CallingConvention.Cdecl)]
    public static extern double qhull_volume(int dim, int numpoints, [In]double[] data);

    [System.Runtime.InteropServices.DllImportAttribute("HeuristicLab.qhull.dll", EntryPoint = "qhull_convex_hull", CallingConvention = CallingConvention.Cdecl)]
    public unsafe static extern IntPtr qhull_convex_hull(int dim, int numpoints, [In]double[] data, [Out] Int32* retCode, [Out] Int32* nrOfFacets);

    [System.Runtime.InteropServices.DllImportAttribute("HeuristicLab.qhull.dll", EntryPoint = "qhull_free", CallingConvention = CallingConvention.Cdecl)]
    public static extern void qhull_free(IntPtr data);

    public static double CalculateVolume(List<double[]> points) {
      double result = 0.0;
      int dimension = points.First().Length;
      int numPoints = points.Count();

      double[] data = new double[dimension * numPoints];

      for (int i = 0; i < numPoints; i++) {
        for (int j = 0; j < dimension; j++) {
          data[i * dimension + j] = points[i][j];
        }
      }
      result = qhull_volume(dimension, numPoints, data);
      return result;
    }

    public unsafe static List<int> CalculateConvexHullIndices(List<double[]> points) {
      int dimension = points.First().Length;
      int numPoints = points.Count();
      List<int> convexHullIndices = new List<int>();

      double[] data = new double[dimension * numPoints];
      for (int i = 0; i < numPoints; i++) {
        for (int j = 0; j < dimension; j++) {
          data[i * dimension + j] = points[i][j];
        }
      }

      IntPtr result = IntPtr.Zero;
      Int32 nrOfFacets = -1;
      Int32 retCode = 0;

      result = qhull_convex_hull(dimension, numPoints, data, &retCode, &nrOfFacets);
      if (result != IntPtr.Zero && retCode == 0) {
        try {
          var faces = new int[nrOfFacets * dimension];
          Marshal.Copy(result, faces, 0, nrOfFacets * dimension);
          convexHullIndices.AddRange(faces.Distinct());
        }
        finally {
          qhull_free(result);
        }
      }
      return convexHullIndices;
    }

    public static List<double[]> Calculate(List<double[]> points) {
      var ret = new List<double[]>();
      List<int> indices = CalculateConvexHullIndices(points);
      foreach (var d in indices) {
        ret.Add(points[d]);
      }
      return ret;
    }
  }
}