#! /usr/bin/env python
#
def doomsday_gregorian ( y, m, d ):

#*****************************************************************************80
#
## DOOMSDAY_GREGORIAN: weekday given any date in Gregorian calendar.
#
#  Discussion:
#
#    This procedure does not include any procedure to switch to the Julian
#    calendar for dates early enough that that calendar was used instead.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    20 August 2015
#
#  Author:
#
#    John Burkardt
#
#  Reference:
#
#    John Conway,
#    Tomorrow is the Day After Doomsday,
#    Eureka,
#    Volume 36, October 1973, pages 28-31.
#
#  Parameters:
#
#    Input, integer ( kind = 4 ) Y, M, D, the year, month and day of the date.
#    Note that the year must be positive.
#
#    Output, integer ( kind = 4  ) W, the weekday of the date.
#
  import numpy as np
  from i4_wrap import i4_wrap
  from year_is_leap_gregorian import year_is_leap_gregorian

  anchor = np.array ( [ 1, 6, 4, 3 ] )
  mdoom = np.array ( [ 3, 28, 0, 4, 9, 6, 11, 8, 5, 10, 7, 12 ] )
#
#  Refuse to handle Y <= 0.
#
  if ( y <= 0 ):
    print ( '' )
    print ( 'DOOMSDAY_GREGORIAN - Fatal error!' )
    print ( '  Y <= 0.' )
    exit ( 'DOOMSDAY_GREGORIAN - Fatal error!' )
#
#  Force Y to be an integer value.
#
  y = int ( y )
#
#  Determine the century C.
#
  c = y // 100
#
#  Determine the last two digits of the year, YY
#
  yy = ( y % 100 )
#
#  Divide the last two digits of the year by 12.
#
  yy = ( y % 100 )
  yy12d = ( yy // 12 )
  yy12r = ( yy % 12 ) 
  yy12r4d = ( yy12r // 4 )
  drd = yy12d + yy12r + yy12r4d
  drdr = ( drd % 7 )
  t = ( ( c - 1 ) % 4 )
  ydoom = anchor[t] + drdr
  ydoom = i4_wrap ( ydoom, 1, 7 )
#
#  If M = 1 or 2, and leap year, add 1.
#
  if ( ( m == 1 or m == 2 ) and year_is_leap_gregorian ( y ) ):
    l = 1
  else:
    l = 0

  w = ydoom + ( d -  mdoom[m-1] - l )
  w = i4_wrap ( w, 1, 7 )

  return w

def doomsday_gregorian_test01 ( ):

#*****************************************************************************80
#
## DOOMSDAY_GREGORIAN_TEST01 tests DOOMSDAY_GREGORIAN against a couple of test dates.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    20 August 2015
#
#  Author:
#
#    John Burkardt
#
  import platform
  from weekday_to_name_common import weekday_to_name_common

  print ( ' ' )
  print ( 'DOOMSDAY_GREGORIAN_TEST01' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  Try a couple selected dates.' )
  print ( ' ' )
  print ( '  YYYY  MM  DD  Weekday    Weekday' )
  print ( '                Tabulated  Computed' )
  print ( ' ' )

  y = 1989
  m = 7
  d = 13
  w = doomsday_gregorian ( y, m, d )
  s1 = weekday_to_name_common ( w )
  s2 = 'Thursday'
  print ( '  %4d  %2d  %2d  %10s  %10s' % ( y, m, d, s1, s2 ) )

  y = 2012
  m = 5
  d = 26
  w = doomsday_gregorian ( y, m, d )
  s1 = weekday_to_name_common ( w )
  s2 = 'Saturday'
  print ( '  %4d  %2d  %2d  %10s  %10s' % ( y, m, d, s1, s2 ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'DOOMSDAY_GREGORIAN_TEST01' )
  print ( '  Normal end of execution.' )

  return

def doomsday_gregorian_test02 ( ):

#*****************************************************************************80
#
## DOOMSDAY_GREGORIAN_TEST02 tests DOOMSDAY_GREGORIAN against a number of known values.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    28 May 2012
#
#  Author:
#
#    John Burkardt
#
  import platform
  from weekday_to_name_common import weekday_to_name_common
  from weekday_values import weekday_values

  print ( ' ' )
  print ( 'DOOMSDAY_GREGORIAN_TEST02' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  WEEKDAY_VALUES supplies a list of dates and weekdays.' )
  print ( ' ' )
  print ( '  YYYY  MM  DD  Weekday    Weekday' )
  print ( '                Tabulated  Computed' )
  print ( ' ' )

  n_data = 0

  while ( True ):

    n_data, y, m, d, w1 = weekday_values ( n_data )

    if ( n_data <= 0 ):
      break
#
#  The transition from Julian to Gregorian calendars occurred in 1582
#  (for some people).  The data in "WEEKDAY_VALUES" before the transition
#  is stored in Julian format, which DOOMSDAY_GREGORIAN can't handle.
#  So let's just refuse to handle 1582 or earlier#
#
    if ( y <= 1582 ):
      continue

    w2 = doomsday_gregorian ( y, m, d )

    s1 = weekday_to_name_common ( w1 )
    s2 = weekday_to_name_common ( w2 )

    print ( '  %4d  %2d  %2d  %10s  %10s' % ( y, m, d, s1, s2 ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'DOOMSDAY_GREGORIAN_TEST02' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  doomsday_gregorian_test01 ( )
  doomsday_gregorian_test02 ( )
  timestamp ( )