## Copyright (C) 2000, 2001, 2002, 2003, 2005, 2006, 2007 Paul Kienzle
##
## This file is part of Octave.
##
## Octave 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.
##
## Octave 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 Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {@var{str} =} datestr (@var{date}, [@var{f}, [@var{p}]])
## Format the given date/time according to the format @code{f} and return
## the result in @var{str}. @var{date} is a serial date number (see
## @code{datenum}) or a date vector (see @code{datevec}).  The value of
## @var{date} may also be a string or cell array of strings.
##
## @var{f} can be an integer which corresponds to one of the codes in
## the table below, or a date format string.
##
## @var{p} is the year at the start of the century in which two-digit years
## are to be interpreted in. If not specified, it defaults to the current
## year minus 50.
##
## For example, the date 730736.65149 (2000-09-07 15:38:09.0934) would be
## formatted as follows:
##
## @multitable @columnfractions 0.1 0.45 0.35
## @headitem Code @tab Format @tab Example
## @item  0 @tab dd-mmm-yyyy HH:MM:SS   @tab 07-Sep-2000 15:38:09
## @item  1 @tab dd-mmm-yyyy            @tab 07-Sep-2000
## @item  2 @tab mm/dd/yy               @tab 09/07/00
## @item  3 @tab mmm                    @tab Sep
## @item  4 @tab m                      @tab S
## @item  5 @tab mm                     @tab 09
## @item  6 @tab mm/dd                  @tab 09/07
## @item  7 @tab dd                     @tab 07
## @item  8 @tab ddd                    @tab Thu
## @item  9 @tab d                      @tab T
## @item 10 @tab yyyy                   @tab 2000
## @item 11 @tab yy                     @tab 00
## @item 12 @tab mmmyy                  @tab Sep00
## @item 13 @tab HH:MM:SS               @tab 15:38:09
## @item 14 @tab HH:MM:SS PM            @tab 03:38:09 PM
## @item 15 @tab HH:MM                  @tab 15:38
## @item 16 @tab HH:MM PM               @tab 03:38 PM
## @item 17 @tab QQ-YY                  @tab Q3-00
## @item 18 @tab QQ                     @tab Q3
## @item 19 @tab dd/mm                  @tab 13/03
## @item 20 @tab dd/mm/yy               @tab 13/03/95
## @item 21 @tab mmm.dd.yyyy HH:MM:SS   @tab Mar.03.1962 13:53:06
## @item 22 @tab mmm.dd.yyyy            @tab Mar.03.1962
## @item 23 @tab mm/dd/yyyy             @tab 03/13/1962
## @item 24 @tab dd/mm/yyyy             @tab 12/03/1962
## @item 25 @tab yy/mm/dd               @tab 95/03/13
## @item 26 @tab yyyy/mm/dd             @tab 1995/03/13
## @item 27 @tab QQ-YYYY                @tab Q4-2132
## @item 28 @tab mmmyyyy                @tab Mar2047
## @item 29 @tab yyyymmdd               @tab 20470313
## @item 30 @tab yyyymmddTHHMMSS        @tab 20470313T132603
## @item 31 @tab yyyy-mm-dd HH:MM:SS    @tab 1047-03-13 13:26:03
## @end multitable
##
## If @var{f} is a format string, the following symbols are recognised:
##
## @multitable @columnfractions 0.1 0.7 0.2
## @headitem Symbol @tab Meaning @tab Example
## @item yyyy @tab Full year                                    @tab 2005
## @item yy   @tab Two-digit year                               @tab 2005
## @item mmmm @tab Full month name                              @tab December
## @item mmm  @tab Abbreviated month name                       @tab Dec
## @item mm   @tab Numeric month number (padded with zeros)     @tab 01, 08, 12
## @item m    @tab First letter of month name (capitalized)     @tab D
## @item dddd @tab Full weekday name                            @tab Sunday
## @item ddd  @tab Abbreviated weekday name                     @tab Sun
## @item dd   @tab Numeric day of month (padded with zeros)     @tab 11
## @item d    @tab First letter of weekday name (capitalized)   @tab S
## @item HH   @tab Hour of day, padded with zeros if PM is set  @tab 09:00
## @item      @tab and not padded with zeros otherwise          @tab 9:00 AM
## @item MM   @tab Minute of hour (padded with zeros)           @tab 10:05
## @item SS   @tab Second of minute (padded with zeros)         @tab 10:05:03
## @item PM   @tab Use 12-hour time format                      @tab 11:30 PM
## @end multitable
##
## If @var{f} is not specified or is @code{-1}, then use 0, 1 or 16,
## depending on whether the date portion or the time portion of
## @var{date} is empty.
##
## If @var{p} is nor specified, it defaults to the current year minus 50.
##
## If a matrix or cell array of dates is given, a vector of date strings is
## returned.
##
## @seealso{datenum, datevec, date, clock, now, datetick}
## @end deftypefn

## TODO: parse arbitrary code strings.
## TODO: e.g., for  Wednesday 2001-03-05 09:04:06 AM, use
## TODO:     yy    01
## TODO:     yyyy  2001
## TODO:     m     M
## TODO:     mm    03
## TODO:     mmm   Mar
## TODO:     d     W
## TODO:     dd    05
## TODO:     ddd   Wed
## TODO:     HH    09
## TODO:     MM    04
## TODO:     SS    06
## TODO:     PM    AM
## TODO: Vectorize.  It is particularly easy since all the codes are
## TODO:    fixed width.  Just generate the parts in separate arrays and
## TODO:    concatenate.

## Author: pkienzle <pkienzle@users.sf.net>
## Created: 10 October 2001 (CVS)
## Adapted-By: William Poetra Yoga Hadisoeseno <williampoetra@gmail.com>

function retval = datestr (date, f, p)

  persistent dateform names_mmmm names_mmm names_m names_dddd names_ddd names_d;

  if (isempty (dateform))

    dateform = cell (32, 1);
    dateform{1} = "dd-mmm-yyyy HH:MM:SS";
    dateform{2} = "dd-mmm-yyyy";
    dateform{3} = "mm/dd/yy";
    dateform{4} = "mmm";
    dateform{5} = "m";
    dateform{6} = "mm";
    dateform{7} = "mm/dd";
    dateform{8} = "dd";
    dateform{9} = "ddd";
    dateform{10} = "d";
    dateform{11} = "yyyy";
    dateform{12} = "yy";
    dateform{13} = "mmmyy";
    dateform{14} = "HH:MM:SS";
    dateform{15} = "HH:MM:SS PM";
    dateform{16} = "HH:MM";
    dateform{17} = "HH:MM PM";
    dateform{18} = "QQ-YY";
    dateform{19} = "QQ";
    dateform{20} = "dd/mm";
    dateform{21} = "dd/mm/yy";
    dateform{22} = "mmm.dd.yyyy HH:MM:SS";
    dateform{23} = "mmm.dd.yyyy";
    dateform{24} = "mm/dd/yyyy";
    dateform{25} = "dd/mm/yyyy";
    dateform{26} = "yy/mm/dd";
    dateform{27} = "yyyy/mm/dd";
    dateform{28} = "QQ-YYYY";
    dateform{29} = "mmmyyyy";
    dateform{30} = "yyyymmdd";
    dateform{31} = "yyyymmddTHHMMSS";
    dateform{32} = "yyyy-mm-dd HH:MM:SS";

    names_mmmm = {"January"; "February"; "March"; "April";
                  "May"; "June"; "July"; "August";
                  "September"; "October"; "November"; "December"};

    names_mmm = {"Jan"; "Feb"; "Mar"; "Apr"; "May"; "Jun";
                 "Jul"; "Aug"; "Sep"; "Oct"; "Nov"; "Dec"};

    names_m = {"J"; "F"; "M"; "A"; "M"; "J"; "J"; "A"; "S"; "O"; "N"; "D"};

    names_dddd = {"Sunday"; "Monday"; "Tuesday"; "Wednesday";
                  "Thursday"; "Friday"; "Saturday"};

    names_ddd = {"Sun"; "Mon"; "Tue"; "Wed"; "Thu"; "Fri"; "Sat"};

    names_d = {"S"; "M"; "T"; "W"; "T"; "F"; "S"};

  endif

  if (nargin < 1 || nargin > 3)
    print_usage ();
  endif

  if (nargin < 2)
    f = [];
  endif
  if (nargin < 3)
    p = [];
  endif

  if (ischar (date))
    t = date;
    date = cell (1);
    date{1} = t;
  endif

  # guess, so we might be wrong
  if (iscell (date) || columns (date) != 6)
    v = datevec (date, p);
  else
    v = date;
  endif

  for i = 1:(rows (v))

    if (isempty (f) || f == -1)
      if (v(i,4:6) == 0)
        f = 1;
      #elseif (v(i,1:3) == [0, 1, 1])
      elseif (v(i,1:3) == [-1, 12, 31])
        f = 16;
      else
        f = 0;
      endif
    endif

    if (isnumeric (f))
      df = dateform{f + 1};
    else
      df = f;
    endif

    ## dates to lowercase (note: we cannot convert MM to mm)
    df = strrep (df, "YYYY", "yyyy");
    df = strrep (df, "YY", "yy");
    df = strrep (df, "QQ", "qq");
    df = strrep (df, "MMMM", "mmmm");
    df = strrep (df, "MMM", "mmm");
    #### BEGIN NOT-SO-UGLY HACK ####
    idx_MM = strfind (df, "MM");
    idx_AM = strfind (df, "AM");
    idx_PM = strfind (df, "PM");
    df = strrep (df, "M", "m");
    df([idx_MM, idx_MM + 1, idx_AM + 1, idx_PM + 1]) = "M";
    df(idx_AM) = "A";
    df(idx_PM) = "P";
    ####  END NOT-SO-UGLY HACK  ####
    df = strrep (df, "DDDD", "dddd");
    df = strrep (df, "DDD", "ddd");
    df = strrep (df, "DD", "dd");
    df = strrep (df, "D", "d");
    ## times to uppercase (also cannot convert mm to MM)
    df = strrep (df, "hh", "HH");
    df = strrep (df, "ss", "SS");
    df = strrep (df, "am", "AM");
    df = strrep (df, "pm", "PM");

    str = df;
    ## replace date symbols with actual values
    str = strrep (str, "yyyy", sprintf ("%04d", v(i,1)));
    str = strrep (str, "yy", sprintf ("%02d", rem (v(i,1), 100)));
    str = strrep (str, "qq", sprintf ("Q%d", fix ((v(i,2) + 2) / 3)));
    str = strrep (str, "mmmm", names_mmmm{v(i,2)});
    str = strrep (str, "mmm", names_mmm{v(i,2)});
    str = strrep (str, "mm", sprintf ("%02d", v(i,2)));
    str = strrep (str, "m", names_m{v(i,2)});
    str = strrep (str, "dddd", names_dddd{weekday (datenum (v(i,1), v(i,2), v(i,3)))});
    str = strrep (str, "ddd", names_ddd{weekday (datenum (v(i,1), v(i,2), v(i,3)))});
    str = strrep (str, "dd", sprintf ("%02d", v(i,3)));
    str = strrep (str, "d", names_d{weekday (datenum (v(i,1), v(i,2), v(i,3)))});
    ## replace time symbols with actual values
    if ((any (strfind (str, "AM")) || any (strfind (str, "PM"))))
      if (v(i,4) > 12)
        str = strrep (str, "HH", sprintf ("%d", v(i,4) - 12));
      else
        str = strrep (str, "HH", sprintf ("%d", v(i,4)));
      endif
      if (v(i,4) < 12)
        str = strrep (str, "AM", "AM");
        str = strrep (str, "PM", "AM");
      else
        str = strrep (str, "AM", "PM");
        str = strrep (str, "PM", "PM");
      endif
    else
      str = strrep (str, "HH", sprintf ("%02d", v(i,4)));
    endif
    str = strrep (str, "MM", sprintf ("%02d", v(i,5)));
    str = strrep (str, "SS", sprintf ("%02d", v(i,6)));

    if (i == 1)
      retval = str;
    else
      retval = [retval; str];
    endif

  endfor

endfunction

# simple tests
%!shared testtime
%! testtime = [2005.0000, 12.0000, 18.0000, 2.0000, 33.0000, 17.3822];
%!assert(datestr(testtime,0),"18-Dec-2005 02:33:17");
%!assert(datestr(testtime,1),"18-Dec-2005");
%!assert(datestr(testtime,2),"12/18/05");
%!assert(datestr(testtime,3),"Dec");
%!assert(datestr(testtime,4),"D");
%!assert(datestr(testtime,5),"12");
%!assert(datestr(testtime,6),"12/18");
%!assert(datestr(testtime,7),"18");
%!assert(datestr(testtime,8),"Sun");
%!assert(datestr(testtime,9),"S");
%!assert(datestr(testtime,10),"2005");
%!assert(datestr(testtime,11),"05");
%!assert(datestr(testtime,12),"Dec05");
%!assert(datestr(testtime,13),"02:33:17");
%!assert(datestr(testtime,14),"2:33:17 AM");
%!assert(datestr(testtime,15),"02:33");
%!assert(datestr(testtime,16),"2:33 AM");
%!assert(datestr(testtime,17),"Q4-05");
%!assert(datestr(testtime,18),"Q4");
%!assert(datestr(testtime,19),"18/12");
%!assert(datestr(testtime,20),"18/12/05");
%!assert(datestr(testtime,21),"Dec.18.2005 02:33:17");
%!assert(datestr(testtime,22),"Dec.18.2005");
%!assert(datestr(testtime,23),"12/18/2005");
%!assert(datestr(testtime,24),"18/12/2005");
%!assert(datestr(testtime,25),"05/12/18");
%!assert(datestr(testtime,26),"2005/12/18");
%!assert(datestr(testtime,27),"Q4-2005");
%!assert(datestr(testtime,28),"Dec2005");
%!assert(datestr(testtime,29),"20051218");
%!assert(datestr(testtime,30),"20051218T023317");
%!assert(datestr(testtime,31),"2005-12-18 02:33:17");
# demos
%!demo
%! datestr (now ())
%!demo
%! datestr (rem (now (), 1))
%!demo
%! datestr (floor (now ()))