// $Id$
//
//  Copyright (C) 2004-2006 Rational Discovery LLC
//
//  @@ All Rights Reserved @@
//
#include "DiscreteDistMat.h"
#include "DiscreteValueVect.h"
#include <iostream>
#include "DatastructsException.h"

void _fillDistMat(unsigned int dmat[], unsigned int nBits) {
  unsigned int i,j, a, b, ta, tb, dist;
  int temp;
  unsigned int mask = ((1<<nBits) -1);
  for (i = 0; i < 256; ++i) {
    for (j = 0; j < 256; ++j) {
      dist = 0;
      a = i;
      b = j;
      while (a || b) {
        ta = a&mask;
        tb = b&mask;
        temp = ta-tb;
        if (temp > 0) {
          dist += temp;
        } else {
          dist -= temp;
        }
        a >>= nBits;
        b >>= nBits;
      }
      dmat[i*256 + j] = dist;
    }
  }
}

DiscreteDistMat::DiscreteDistMat() {
  // fill in the distance matrix table

  // one bit per value table
  _fillDistMat(d_oneBitTab, 1);

  // two bits per value table
  _fillDistMat(d_twoBitTab, 2);

  // four bits per value table
  _fillDistMat(d_fourBitTab, 4);
}

unsigned int DiscreteDistMat::getDist(unsigned char v1, 
                                     unsigned char v2, 
                                     DiscreteValueVect::DiscreteValueType type) {
  unsigned int res=0;
  int temp;
  unsigned int id = static_cast<unsigned int>(v1)*256 + static_cast<unsigned int>(v2);
  switch(type) {
  case DiscreteValueVect::ONEBITVALUE :
    res = d_oneBitTab[id];
    break;
  case DiscreteValueVect::TWOBITVALUE :
    res = d_twoBitTab[id];
    break;
  case DiscreteValueVect::FOURBITVALUE :
    res = d_fourBitTab[id];
    break;
  case DiscreteValueVect::EIGHTBITVALUE :
    temp = static_cast<unsigned int>(v1) - static_cast<unsigned int>(v2);
    if (temp < 0) {
      res -= temp;
    } else {
      res += temp;
    }
    break;
  default:
    // ummm.. we shouldn't have come here
    throw DatastructsException("We shouldn't be here");
  }
  return res;
}

static DiscreteDistMat discreteDMat;
DiscreteDistMat *getDiscreteDistMat() {
  return &discreteDMat;
}