/*
 *  PHEX - The pure-java Gnutella-servent.
 *  Copyright (C) 2001 - 2008 Phex Development Group
 *
 *  This program 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 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 *  --- SVN Information ---
 *  $Id: DoubleToString.java 4365 2009-01-16 11:21:31Z gregork $
 */
package phex.common.format;


public class DoubleToString
{
    //Hardcode some byte arrays to make them quickly available
    private static final char[] INFINITY = {'I','n','f','i','n','i','t','y'};
    private static final char[] NaN = {'N','a','N'};
    private static final char[][] ZEROS = {
        {},
        {'0'},
        {'0','0'},
        {'0','0','0'},
        {'0','0','0','0'},
        {'0','0','0','0','0'},
        {'0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
        {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'},
    };

    private static final char[] charForDigit = {
        '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h',
        'i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'
    };

    //And required double related constants.  
    private static final long  DoubleSignMask = 0x8000000000000000L;
    private static final long  DoubleExpMask  = 0x7ff0000000000000L;
    private static final int  DoubleExpShift = 52;
    private static final int  DoubleExpBias = 1023;

    private static final double[] d_tenthPowers = {
        1e-323D, 1e-322D, 1e-321D, 1e-320D, 1e-319D, 1e-318D, 1e-317D, 1e-316D, 1e-315D, 1e-314D, 
        1e-313D, 1e-312D, 1e-311D, 1e-310D, 1e-309D, 1e-308D, 1e-307D, 1e-306D, 1e-305D, 1e-304D, 
        1e-303D, 1e-302D, 1e-301D, 1e-300D, 1e-299D, 1e-298D, 1e-297D, 1e-296D, 1e-295D, 1e-294D, 
        1e-293D, 1e-292D, 1e-291D, 1e-290D, 1e-289D, 1e-288D, 1e-287D, 1e-286D, 1e-285D, 1e-284D, 
        1e-283D, 1e-282D, 1e-281D, 1e-280D, 1e-279D, 1e-278D, 1e-277D, 1e-276D, 1e-275D, 1e-274D, 
        1e-273D, 1e-272D, 1e-271D, 1e-270D, 1e-269D, 1e-268D, 1e-267D, 1e-266D, 1e-265D, 1e-264D, 
        1e-263D, 1e-262D, 1e-261D, 1e-260D, 1e-259D, 1e-258D, 1e-257D, 1e-256D, 1e-255D, 1e-254D, 
        1e-253D, 1e-252D, 1e-251D, 1e-250D, 1e-249D, 1e-248D, 1e-247D, 1e-246D, 1e-245D, 1e-244D, 
        1e-243D, 1e-242D, 1e-241D, 1e-240D, 1e-239D, 1e-238D, 1e-237D, 1e-236D, 1e-235D, 1e-234D, 
        1e-233D, 1e-232D, 1e-231D, 1e-230D, 1e-229D, 1e-228D, 1e-227D, 1e-226D, 1e-225D, 1e-224D, 
        1e-223D, 1e-222D, 1e-221D, 1e-220D, 1e-219D, 1e-218D, 1e-217D, 1e-216D, 1e-215D, 1e-214D, 
        1e-213D, 1e-212D, 1e-211D, 1e-210D, 1e-209D, 1e-208D, 1e-207D, 1e-206D, 1e-205D, 1e-204D, 
        1e-203D, 1e-202D, 1e-201D, 1e-200D, 1e-199D, 1e-198D, 1e-197D, 1e-196D, 1e-195D, 1e-194D, 
        1e-193D, 1e-192D, 1e-191D, 1e-190D, 1e-189D, 1e-188D, 1e-187D, 1e-186D, 1e-185D, 1e-184D, 
        1e-183D, 1e-182D, 1e-181D, 1e-180D, 1e-179D, 1e-178D, 1e-177D, 1e-176D, 1e-175D, 1e-174D, 
        1e-173D, 1e-172D, 1e-171D, 1e-170D, 1e-169D, 1e-168D, 1e-167D, 1e-166D, 1e-165D, 1e-164D, 
        1e-163D, 1e-162D, 1e-161D, 1e-160D, 1e-159D, 1e-158D, 1e-157D, 1e-156D, 1e-155D, 1e-154D, 
        1e-153D, 1e-152D, 1e-151D, 1e-150D, 1e-149D, 1e-148D, 1e-147D, 1e-146D, 1e-145D, 1e-144D, 
        1e-143D, 1e-142D, 1e-141D, 1e-140D, 1e-139D, 1e-138D, 1e-137D, 1e-136D, 1e-135D, 1e-134D, 
        1e-133D, 1e-132D, 1e-131D, 1e-130D, 1e-129D, 1e-128D, 1e-127D, 1e-126D, 1e-125D, 1e-124D, 
        1e-123D, 1e-122D, 1e-121D, 1e-120D, 1e-119D, 1e-118D, 1e-117D, 1e-116D, 1e-115D, 1e-114D, 
        1e-113D, 1e-112D, 1e-111D, 1e-110D, 1e-109D, 1e-108D, 1e-107D, 1e-106D, 1e-105D, 1e-104D, 
        1e-103D, 1e-102D, 1e-101D, 1e-100D, 1e-99D, 1e-98D, 1e-97D, 1e-96D, 1e-95D, 1e-94D, 
        1e-93D, 1e-92D, 1e-91D, 1e-90D, 1e-89D, 1e-88D, 1e-87D, 1e-86D, 1e-85D, 1e-84D, 
        1e-83D, 1e-82D, 1e-81D, 1e-80D, 1e-79D, 1e-78D, 1e-77D, 1e-76D, 1e-75D, 1e-74D, 
        1e-73D, 1e-72D, 1e-71D, 1e-70D, 1e-69D, 1e-68D, 1e-67D, 1e-66D, 1e-65D, 1e-64D, 
        1e-63D, 1e-62D, 1e-61D, 1e-60D, 1e-59D, 1e-58D, 1e-57D, 1e-56D, 1e-55D, 1e-54D, 
        1e-53D, 1e-52D, 1e-51D, 1e-50D, 1e-49D, 1e-48D, 1e-47D, 1e-46D, 1e-45D, 1e-44D, 
        1e-43D, 1e-42D, 1e-41D, 1e-40D, 1e-39D, 1e-38D, 1e-37D, 1e-36D, 1e-35D, 1e-34D, 
        1e-33D, 1e-32D, 1e-31D, 1e-30D, 1e-29D, 1e-28D, 1e-27D, 1e-26D, 1e-25D, 1e-24D, 
        1e-23D, 1e-22D, 1e-21D, 1e-20D, 1e-19D, 1e-18D, 1e-17D, 1e-16D, 1e-15D, 1e-14D, 
        1e-13D, 1e-12D, 1e-11D, 1e-10D, 1e-9D, 1e-8D, 1e-7D, 1e-6D, 1e-5D, 1e-4D, 
        1e-3D, 1e-2D, 1e-1D, 1e0D, 1e1D, 1e2D, 1e3D, 1e4D, 
        1e5D, 1e6D, 1e7D, 1e8D, 1e9D, 1e10D, 1e11D, 1e12D, 1e13D, 1e14D, 
        1e15D, 1e16D, 1e17D, 1e18D, 1e19D, 1e20D, 1e21D, 1e22D, 1e23D, 1e24D, 
        1e25D, 1e26D, 1e27D, 1e28D, 1e29D, 1e30D, 1e31D, 1e32D, 1e33D, 1e34D, 
        1e35D, 1e36D, 1e37D, 1e38D, 1e39D, 1e40D, 1e41D, 1e42D, 1e43D, 1e44D, 
        1e45D, 1e46D, 1e47D, 1e48D, 1e49D, 1e50D, 1e51D, 1e52D, 1e53D, 1e54D, 
        1e55D, 1e56D, 1e57D, 1e58D, 1e59D, 1e60D, 1e61D, 1e62D, 1e63D, 1e64D, 
        1e65D, 1e66D, 1e67D, 1e68D, 1e69D, 1e70D, 1e71D, 1e72D, 1e73D, 1e74D, 
        1e75D, 1e76D, 1e77D, 1e78D, 1e79D, 1e80D, 1e81D, 1e82D, 1e83D, 1e84D, 
        1e85D, 1e86D, 1e87D, 1e88D, 1e89D, 1e90D, 1e91D, 1e92D, 1e93D, 1e94D, 
        1e95D, 1e96D, 1e97D, 1e98D, 1e99D, 1e100D, 1e101D, 1e102D, 1e103D, 1e104D, 
        1e105D, 1e106D, 1e107D, 1e108D, 1e109D, 1e110D, 1e111D, 1e112D, 1e113D, 1e114D, 
        1e115D, 1e116D, 1e117D, 1e118D, 1e119D, 1e120D, 1e121D, 1e122D, 1e123D, 1e124D, 
        1e125D, 1e126D, 1e127D, 1e128D, 1e129D, 1e130D, 1e131D, 1e132D, 1e133D, 1e134D, 
        1e135D, 1e136D, 1e137D, 1e138D, 1e139D, 1e140D, 1e141D, 1e142D, 1e143D, 1e144D, 
        1e145D, 1e146D, 1e147D, 1e148D, 1e149D, 1e150D, 1e151D, 1e152D, 1e153D, 1e154D, 
        1e155D, 1e156D, 1e157D, 1e158D, 1e159D, 1e160D, 1e161D, 1e162D, 1e163D, 1e164D, 
        1e165D, 1e166D, 1e167D, 1e168D, 1e169D, 1e170D, 1e171D, 1e172D, 1e173D, 1e174D, 
        1e175D, 1e176D, 1e177D, 1e178D, 1e179D, 1e180D, 1e181D, 1e182D, 1e183D, 1e184D, 
        1e185D, 1e186D, 1e187D, 1e188D, 1e189D, 1e190D, 1e191D, 1e192D, 1e193D, 1e194D, 
        1e195D, 1e196D, 1e197D, 1e198D, 1e199D, 1e200D, 1e201D, 1e202D, 1e203D, 1e204D, 
        1e205D, 1e206D, 1e207D, 1e208D, 1e209D, 1e210D, 1e211D, 1e212D, 1e213D, 1e214D, 
        1e215D, 1e216D, 1e217D, 1e218D, 1e219D, 1e220D, 1e221D, 1e222D, 1e223D, 1e224D, 
        1e225D, 1e226D, 1e227D, 1e228D, 1e229D, 1e230D, 1e231D, 1e232D, 1e233D, 1e234D, 
        1e235D, 1e236D, 1e237D, 1e238D, 1e239D, 1e240D, 1e241D, 1e242D, 1e243D, 1e244D, 
        1e245D, 1e246D, 1e247D, 1e248D, 1e249D, 1e250D, 1e251D, 1e252D, 1e253D, 1e254D, 
        1e255D, 1e256D, 1e257D, 1e258D, 1e259D, 1e260D, 1e261D, 1e262D, 1e263D, 1e264D, 
        1e265D, 1e266D, 1e267D, 1e268D, 1e269D, 1e270D, 1e271D, 1e272D, 1e273D, 1e274D, 
        1e275D, 1e276D, 1e277D, 1e278D, 1e279D, 1e280D, 1e281D, 1e282D, 1e283D, 1e284D, 
        1e285D, 1e286D, 1e287D, 1e288D, 1e289D, 1e290D, 1e291D, 1e292D, 1e293D, 1e294D, 
        1e295D, 1e296D, 1e297D, 1e298D, 1e299D, 1e300D, 1e301D, 1e302D, 1e303D, 1e304D, 
        1e305D, 1e306D, 1e307D, 1e308D
    };


    public void appendFormatted(StringBuffer s, double d, int numFractDigits,
        char decimalPoint, char thousandsSeparator, int numDigitsSeparated, 
        char negativePrefix, char negativeSuffix)
    {
        //First check for the special cases, +/-infinity, Not-a-number and -0.0
        if (d == Double.NEGATIVE_INFINITY)
        {
          //d == -Infinity
          if (negativePrefix != '\uFFFF')
            s.append(negativePrefix);
          s.append(INFINITY);
          if (negativeSuffix != '\uFFFF')
            s.append(negativeSuffix);
        }
        else if (d == Double.POSITIVE_INFINITY)
          //d == Infinity
          s.append(INFINITY);
        else if (d != d)
          //d == NaN
          s.append(NaN);
        else if (d == 0.0)
        {
          if ( (Double.doubleToLongBits(d) & DoubleSignMask) != 0)
          {
            //d == -0.0
            if (negativePrefix != '\uFFFF')
              s.append(negativePrefix);
            s.append('0');
            if ( numFractDigits > 0 )
            {
                s.append(decimalPoint).append(ZEROS[numFractDigits]);
            }
            if (negativeSuffix != '\uFFFF')
              s.append(negativeSuffix);
          }
          else
            //d == 0.0
            s.append('0');
            if ( numFractDigits > 0 )
            {
                s.append(decimalPoint).append(ZEROS[numFractDigits]);
            }
        }
        else
        {
          //convert to a positive format, and record whether we have a negative
          //number so that we know later whether to add the negativeSuffix
          boolean negative = false;
          if (d < 0)
          {
            //Even if the number is negative, we only need to set the
            //negative flag if there is a printable negativeSuffix
            if (negativeSuffix != '\uFFFF')
              negative = true;
            if (negativePrefix != '\uFFFF')
              s.append(negativePrefix);
            d = -d;
          }

          //Find the magnitude. This is basically the exponent in normal form.
          int magnitude = magnitude(d);
    
          //First off, if the number is too small for the given format, we
          //only print 0.0..., which makes this real quick
          if ( (magnitude + numFractDigits) < 0)
          {
            appendNearlyZeroNumber(s, d, magnitude, numFractDigits, decimalPoint);
            if (negative)
              s.append(negativeSuffix);
            return;
          }
    
          long l;
          //Now scale the double to the biggest long value we need
          //We need to handle the smallest magnitudes differently because of rounding errors
    
          //This test is unlikely to ever be true. It would require numFractDigits
          //to be 305 or more, which is pretty unlikely.
          if (magnitude < -305)
            l = (long) ((d*1E18) / d_tenthPowers[magnitude + 324]);
          else
            l = (long) (d / d_tenthPowers[magnitude + 323 - 17]);
    
          //And round up if necessary. Add one to the numFractDigits digit if the
          //numFractDigits+1 digit is 5 or greater. It is useful to know that
          //given a long, l, the nth digit is obtained using the formula
          //  nthDigit = (l/(tenthPower(l)/l_tenthPowers[n-1]))%10;
    
          long l_tenthPower = tenthPower(l);
          //The numFractDigits+1 digit of the double is the 
          //numFractDigits+1+magnitude digit of the long.
          //We only need worry about digits within the long. Very large numbers are
          //not rounded because all the digits after the decimal points are 0 anyway
          if (numFractDigits+magnitude+1 < l_tenthPowers.length)
          {
            long digit = (l/(l_tenthPower/l_tenthPowers[numFractDigits+magnitude+1]))%10;
            if (digit >= 5)
            {
              l += l_tenthPower/l_tenthPowers[numFractDigits+magnitude];
            }
          }      
    
          //And now we just print out our long, with the decimal point character
          //inserted in the right place, using as many places as we wanted.
          appendAsDouble(s, l, l_tenthPower, magnitude, numFractDigits, decimalPoint, thousandsSeparator,
                         numDigitsSeparated, negativePrefix, negativeSuffix);
    
          //Finally, append the negativeSuffix if necessary
          if (negative)
            s.append(negativeSuffix);
        }
      }

    public void appendAsDouble(StringBuffer s, long l, long l_mag, int d_magnitude,
        int numFractDigits, char decimalPoint, char thousandsSeparator,
        int numDigitsSeparated, char negativePrefix, char negativeSuffix)
    {
        //If the magnitude is negative, we have a 0.xxx number
        if (d_magnitude < 0)
        {
          s.append('0').append(decimalPoint).append(ZEROS[-d_magnitude-1]);
          //And just print successive digits until we have reached numFractDigits
          //First decrement numFractDigits by the number of digits already printed
          numFractDigits += d_magnitude;
    
          //get the magnitude of l
          long c;
          while(numFractDigits-- >= 0)
          {
            //Get the leading character (e.g. '62345/10000 = 6' using integer-divide)
            c = l/l_mag;
            //Append the digit character for this digit (e.g. number is 6, so character is '6')
            s.append(charForDigit[(int) c]);
            //Multiply by the leading digit by the magnitude so that we can eliminate the leading digit
            //(e.g. 6 * 10000 = 60000)
            c *= l_mag;
            //and eliminate the leading digit (e.g. 62345-60000 = 2345)
            if ( c <= l)
              l -= c;
            //Decrease the magnitude by 10, and repeat the loop.
            l_mag = l_mag/10;
          }
        }
        else
        {
          //Just keep printing until magnitude is 0
          long c;
          while(d_magnitude-- >= 0)
          {
            if (l_mag == 0) {s.append('0');continue;}
            //Get the leading character (e.g. '62345/10000 = 6' using integer-divide)
            c = l/l_mag;
            //Append the digit character for this digit (e.g. number is 6, so character is '6')
            s.append(charForDigit[(int) c]);
    
            //Don't forget about the thousands separator
            if (d_magnitude % numDigitsSeparated == (numDigitsSeparated-1))
              s.append(thousandsSeparator);
    
            //Multiply by the leading digit by the magnitude so that we can eliminate the leading digit
            //(e.g. 6 * 10000 = 60000)
            c *= l_mag;
            //and eliminate the leading digit (e.g. 62345-60000 = 2345)
            if ( c <= l)
              l -= c;
            //Decrease the magnitude by 10, and repeat the loop.
            l_mag = l_mag/10;
          }
          if ( numFractDigits > 0 )
          {
              s.append(decimalPoint);
          }
          if (l_mag == 0)
            s.append(ZEROS[numFractDigits]);
          else
          {
            while(numFractDigits-- > 0)
            {
              if (l_mag == 0) {s.append('0');continue;}
              //Get the leading character (e.g. '62345/10000 = 6' using integer-divide)
              c = l/l_mag;
              //Append the digit character for this digit (e.g. number is 6, so character is '6')
              s.append(charForDigit[(int) c]);
              //Multiply by the leading digit by the magnitude so that we can eliminate the leading digit
              //(e.g. 6 * 10000 = 60000)
              c *= l_mag;
              //and eliminate the leading digit (e.g. 62345-60000 = 2345)
              if ( c <= l)
                l -= c;
              //Decrease the magnitude by 10, and repeat the loop.
              l_mag = l_mag/10;
            }
          }
        }
    }


  private void appendNearlyZeroNumber(StringBuffer s, double d, int d_magnitude, 
                               int numFractDigits, char decimalPoint)
  {
    if (d_magnitude + numFractDigits == -1)
    {
      //Possibly too small, depends on whether the top digit is 5 or greater
      //So we have to scale to get the leading digit
      int i;
      if (d_magnitude < -305)
        //Probably not necessary. Who is going to print 305 places?
        i = (int) ((d*1E19) / d_tenthPowers[d_magnitude + 324 + 18]);
      else
        i = (int) (d / d_tenthPowers[d_magnitude + 323]);

      if (i >= 5)
      {
        //Not too small, we get to round up
        s.append('0').append(decimalPoint).append(ZEROS[numFractDigits-1]);
        s.append('1');
      }
      else
      {
        //Definitely too small. Just print zeros
        s.append('0').append(decimalPoint).append(ZEROS[numFractDigits]);
      }
    }
    else
    {
      //Definitely too small
      s.append('0').append(decimalPoint).append(ZEROS[numFractDigits]);
    }
  }

  /**
   * Assumes i is positive. Returns the magnitude of i in base 10.
   */
  private static long tenthPower(long i)
  {
    if (i < 10L) return 1;
    else if (i < 100L) return 10L;
    else if (i < 1000L) return 100L;
    else if (i < 10000L) return 1000L;
    else if (i < 100000L) return 10000L;
    else if (i < 1000000L) return 100000L;
    else if (i < 10000000L) return 1000000L;
    else if (i < 100000000L) return 10000000L;
    else if (i < 1000000000L) return 100000000L;
    else if (i < 10000000000L) return 1000000000L;
    else if (i < 100000000000L) return 10000000000L;
    else if (i < 1000000000000L) return 100000000000L;
    else if (i < 10000000000000L) return 1000000000000L;
    else if (i < 100000000000000L) return 10000000000000L;
    else if (i < 1000000000000000L) return 100000000000000L;
    else if (i < 10000000000000000L) return 1000000000000000L;
    else if (i < 100000000000000000L) return 10000000000000000L;
    else if (i < 1000000000000000000L) return 100000000000000000L;
    else return  1000000000000000000L;
  }


  private static int magnitude(double d)
  {
    //It works. What else can I say.
    long doubleToLongBits = Double.doubleToLongBits(d);
    int magnitude = 
      (int) ((((doubleToLongBits & DoubleExpMask) >> DoubleExpShift) - DoubleExpBias) * 0.301029995663981);

    if (magnitude < -323)
      magnitude = -323;
    else if (magnitude > 308)
      magnitude = 308;

    if (d >= d_tenthPowers[magnitude+323])
    {
      while(magnitude < 309 && d >= d_tenthPowers[magnitude+323])
        magnitude++;
      magnitude--;
      return magnitude;
    }
    else
    {
      while(magnitude > -324 && d < d_tenthPowers[magnitude+323])
        magnitude--;
      return magnitude;
    }
  }

  static long[] l_tenthPowers = {
    1,
    10L,
    100L,
    1000L,
    10000L,
    100000L,
    1000000L,
    10000000L,
    100000000L,
    1000000000L,
    10000000000L,
    100000000000L,
    1000000000000L,
    10000000000000L,
    100000000000000L,
    1000000000000000L,
    10000000000000000L,
    100000000000000000L,
    1000000000000000000L,
  };

  public static long getNthDigit(long l, int n)
  {
    return (l/(tenthPower(l)/l_tenthPowers[n-1]))%10;
  }
}