76 lines
2.5 KiB
Ruby
76 lines
2.5 KiB
Ruby
# frozen_string_literal: true
|
|
|
|
module Jekyll
|
|
module Utils
|
|
module WinTZ
|
|
extend self
|
|
|
|
# Public: Calculate the Timezone for Windows when the config file has a defined
|
|
# 'timezone' key.
|
|
#
|
|
# timezone - the IANA Time Zone specified in "_config.yml"
|
|
#
|
|
# Returns a string that ultimately re-defines ENV["TZ"] in Windows
|
|
def calculate(timezone)
|
|
External.require_with_graceful_fail("tzinfo") unless defined?(TZInfo)
|
|
tz = TZInfo::Timezone.get(timezone)
|
|
difference = Time.now.to_i - tz.now.to_i
|
|
#
|
|
# POSIX style definition reverses the offset sign.
|
|
# e.g. Eastern Standard Time (EST) that is 5Hrs. to the 'west' of Prime Meridian
|
|
# is denoted as:
|
|
# EST+5 (or) EST+05:00
|
|
# Reference: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
|
|
sign = difference.negative? ? "-" : "+"
|
|
offset = sign == "-" ? "+" : "-" unless difference.zero?
|
|
#
|
|
# convert the difference (in seconds) to hours, as a rational number, and perform
|
|
# a modulo operation on it.
|
|
modulo = modulo_of(rational_hour(difference))
|
|
#
|
|
# Format the hour as a two-digit number.
|
|
# Establish the minutes based on modulo expression.
|
|
hh = format("%02d", absolute_hour(difference).ceil)
|
|
mm = modulo.zero? ? "00" : "30"
|
|
|
|
Jekyll.logger.debug "Timezone:", "#{timezone} #{offset}#{hh}:#{mm}"
|
|
#
|
|
# Note: The 3-letter-word below doesn't have a particular significance.
|
|
"WTZ#{sign}#{hh}:#{mm}"
|
|
end
|
|
|
|
private
|
|
|
|
# Private: Convert given seconds to an hour as a rational number.
|
|
#
|
|
# seconds - supplied as an integer, it is converted to a rational number.
|
|
# 3600 - no. of seconds in an hour.
|
|
#
|
|
# Returns a rational number.
|
|
def rational_hour(seconds)
|
|
seconds.to_r / 3600
|
|
end
|
|
|
|
# Private: Convert given seconds to an hour as an absolute number.
|
|
#
|
|
# seconds - supplied as an integer, it is converted to its absolute.
|
|
# 3600 - no. of seconds in an hour.
|
|
#
|
|
# Returns an integer.
|
|
def absolute_hour(seconds)
|
|
seconds.abs / 3600
|
|
end
|
|
|
|
# Private: Perform a modulo operation on a given fraction.
|
|
#
|
|
# fraction - supplied as a rational number, its numerator is divided
|
|
# by its denominator and the remainder returned.
|
|
#
|
|
# Returns an integer.
|
|
def modulo_of(fraction)
|
|
fraction.numerator % fraction.denominator
|
|
end
|
|
end
|
|
end
|
|
end
|