74 lines
2.5 KiB
Ruby
74 lines
2.5 KiB
Ruby
module Jekyll
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module Utils
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module WinTZ
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extend self
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# Public: Calculate the Timezone for Windows when the config file has a defined
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# 'timezone' key.
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#
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# timezone - the IANA Time Zone specified in "_config.yml"
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#
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# Returns a string that ultimately re-defines ENV["TZ"] in Windows
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def calculate(timezone)
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External.require_with_graceful_fail("tzinfo")
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tz = TZInfo::Timezone.get(timezone)
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difference = Time.now.to_i - tz.now.to_i
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#
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# POSIX style definition reverses the offset sign.
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# e.g. Eastern Standard Time (EST) that is 5Hrs. to the 'west' of Prime Meridian
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# is denoted as:
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# EST+5 (or) EST+05:00
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# Reference: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
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sign = difference < 0 ? "-" : "+"
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offset = sign == "-" ? "+" : "-" unless difference.zero?
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#
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# convert the difference (in seconds) to hours, as a rational number, and perform
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# a modulo operation on it.
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modulo = modulo_of(rational_hour(difference))
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#
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# Format the hour as a two-digit number.
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# Establish the minutes based on modulo expression.
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hh = format("%02d", absolute_hour(difference).ceil)
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mm = modulo.zero? ? "00" : "30"
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Jekyll.logger.debug "Timezone:", "#{timezone} #{offset}#{hh}:#{mm}"
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#
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# Note: The 3-letter-word below doesn't have a particular significance.
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"WTZ#{sign}#{hh}:#{mm}"
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end
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private
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# Private: Convert given seconds to an hour as a rational number.
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#
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# seconds - supplied as an integer, it is converted to a rational number.
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# 3600 - no. of seconds in an hour.
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#
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# Returns a rational number.
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def rational_hour(seconds)
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seconds.to_r/3600
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end
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# Private: Convert given seconds to an hour as an absolute number.
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#
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# seconds - supplied as an integer, it is converted to its absolute.
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# 3600 - no. of seconds in an hour.
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#
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# Returns an integer.
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def absolute_hour(seconds)
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seconds.abs/3600
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end
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# Private: Perform a modulo operation on a given fraction.
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#
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# fraction - supplied as a rational number, its numerator is divided
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# by its denominator and the remainder returned.
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#
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# Returns an integer.
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def modulo_of(fraction)
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fraction.numerator % fraction.denominator
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end
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end
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end
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end
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