/*============================================================================

    WCSLIB 4.3 - an implementation of the FITS WCS standard.
    Copyright (C) 1995-2007, Mark Calabretta

    This file is part of WCSLIB.

    WCSLIB is free software: you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License as published by the
    Free Software Foundation, either version 3 of the License, or (at your
    option) any later version.

    WCSLIB 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 Lesser General Public License for
    more details.

    You should have received a copy of the GNU Lesser General Public License
    along with WCSLIB.  If not, see <http://www.gnu.org/licenses/>.

    Correspondence concerning WCSLIB may be directed to:
       Internet email: mcalabre@atnf.csiro.au
       Postal address: Dr. Mark Calabretta
                       Australia Telescope National Facility, CSIRO
                       PO Box 76
                       Epping NSW 1710
                       AUSTRALIA

    Author: Mark Calabretta, Australia Telescope National Facility
    http://www.atnf.csiro.au/~mcalabre/index.html
    $Id: wcsunits.c,v 4.3 2007/12/27 05:41:36 cal103 Exp $
*===========================================================================*/

#include <math.h>

#include "wcsunits.h"

/* Map status return value to message. */
const char *wcsunits_errmsg[] = {
   "Success",
   "Invalid numeric multiplier",
   "Dangling binary operator",
   "Invalid symbol in INITIAL context",
   "Function in invalid context",
   "Invalid symbol in EXPON context",
   "Unbalanced bracket",
   "Unbalanced parenthesis",
   "Consecutive binary operators",
   "Internal parser error",
   "Non-conformant unit specifications",
   "Non-conformant functions",
   "Potentially unsafe translation"};


/* Unit types. */
const char *wcsunits_types[] = {
   "plane angle",
   "solid angle",
   "charge",
   "mole",
   "temperature",
   "luminous intensity",
   "mass",
   "length",
   "time",
   "beam",
   "bin",
   "bit",
   "count",
   "stellar magnitude",
   "pixel",
   "solar ratio",
   "voxel"};

const char *wcsunits_units[] = {
   "degree",
   "steradian",
   "Coulomb",
   "mole",
   "Kelvin",
   "candela",
   "kilogram",
   "metre",
   "second",
   "", "", "", "", "", "", "", ""};

int wcsunits(
  const char have[],
  const char want[],
  double *scale,
  double *offset,
  double *power)

{
  int    func1, func2, i, status;
  double scale1, scale2, units1[WCSUNITS_NTYPE], units2[WCSUNITS_NTYPE];

  if ((status = wcsulex(have, &func1, &scale1, units1))) {
    return status;
  }

  if ((status = wcsulex(want, &func2, &scale2, units2))) {
    return status;
  }

  /* Check conformance. */
  for (i = 0; i < WCSUNITS_NTYPE; i++) {
    if (units1[i] != units2[i]) {
      return 10;
    }
  }

  *scale  = 0.0;
  *offset = 0.0;
  *power  = 1.0;

  switch (func1) {
  case 0:
    /* No function. */
    if (func2) {
      return 11;
    }

    *scale = scale1 / scale2;
    break;

  case 1:
    /* log(). */
    if (func2 == 1) {
      /* log(). */
      *scale  = 1.0;
      *offset = log10(scale1 / scale2);

    } else if (func2 == 2) {
      /* ln(). */
      *scale  = log(10.0);
      *offset = log(scale1 / scale2);

    } else {
      return 11;
    }

    break;

  case 2:
    /* ln(). */
    if (func2 == 1) {
      /* log(). */
      *scale  = 1.0 / log(10.0);
      *offset = log(scale1 / scale2);

    } else if (func2 == 2) {
      /* ln(). */
      *scale  = 1.0;
      *offset = log(scale1 / scale2);

    } else {
      return 11;
    }

    break;

  case 3:
    /* exp(). */
    if (func2 != 3) {
      return 11;
    }

    *scale = 1.0;
    *power = scale1 / scale2;
    break;

  default:
    /* Internal parser error. */
    return 9;
  }

  return 0;
}