#!/usr/bin/env ruby
# fdate [DATE] - print French Revolutionary Calendar date and time
# DATE is anything GNU date -d understands.
# fdate uses local time, define a TZ with offset +0009.21 for Paris local time.
#
# To the extent possible under law, Leah Neukirchen has waived
# all copyright and related or neighboring rights to this work.
# http://creativecommons.org/publicdomain/zero/1.0/

require 'date'

def roman_numeral(n)
  symbols = { 1000 => "M", 900 => "CM", 500 => "D", 400 => "CD",
               100 => "C",  90 => "XC",  50 => "L",  40 => "XL",
                10 => "X",   9 => "IX",   5 => "V",   4 => "IV",
                 1 => "I" }
  r = ""
  symbols.each { |num, sym|
    r << (sym * (n/num))
    n %= num
  }
  r
end

if ARGV.empty?
  time = Time.now
else
  s = IO.popen(["date", "+%s.%N", "-d", ARGV.join(' ')]) { |p| p.read }
  if $?.success?
    time = Time.at(s.to_f)
  else
    exit $?.exitstatus
  end
end

total_days = time.to_date.jd - Date.new(1792,9,22).jd

revday = 0
revmthnum = 1
revyr = 1

1.upto(total_days) {
  revday += 1
  if revday == 31
    revmthnum += 1
    revday = 1
  end
  if revmthnum == 13
    if revyr == 3 || revyr == 7 || revyr == 11 || revyr == 15 ||  # Romme
       (revyr > 20 &&
        ((revyr % 4 == 0) && ((revyr % 100 != 0) || (revyr % 400 == 0))))
      # leap year
      sclen = 6
    else
      sclen = 5
    end
    if revday > sclen
      revday = 1
      revmthnum = 1
      revyr += 1
    end
  end
}

WEEKDAYS = %w{Primidi Duodi Tridi Quartidi Quintidi Sextidi Septidi Octidi Nonidi Décadi}

MONTHS = %w{Vendémiaire Brumaire Frimaire Nivôse Pluviôse Ventôse Germinal Floréal Prairial Messidor Thermidor Fructidor}

FETES = [
  "fête de la vertu",
  "fête du génie",
  "fête du travail",
  "fête de l'opinion",
  "fête des récompenses",
  "fête de la Révolution",
]

if revmthnum == 13
  print "Primidi, "
  print FETES[revday-1]
else
  print WEEKDAYS[(revday - 1) % 10], ", "
  print revday, " "
  print MONTHS[revmthnum-1]
end
print " #{roman_numeral revyr} (#{revyr}) "

# Jean-Charles de Borda, 13 Vendémiaire II:
# 10 hours a 100 min a 100 sec
secs = time - Time.new(time.year, time.month, time.day)
dtime = "%05d" % ((secs / 8640.0)*10000).round   # round to decimal seconds
print dtime[0],":",dtime[1..2],":",dtime[3..4],"\n"