# Date using the international format defined by ISO 8601.
#
# Usage:
#
#     # By default ISODate at today.
#     var date = new ISODate
#     var tm = new Tm.localtime
#     assert date.year == tm.year + 1900
#     assert date.month == tm.mon + 1
#     assert date.day == tm.mday
#
#     # ISODate can be initialized from a String.
#     date = new ISODate.from_string("1970-01-01T00:00:00Z")
#     assert date.year == 1970
#     assert date.month == 1
#     assert date.day == 1
#
#     # ISODate can be printed as String following the ISO format.
#     assert date.to_s == "1970-01-01T00:00:00Z"
#
# Note that only the `YYYY-MM-DDTHH:MM:SSZ` is supported for now.
#
# See <http://www.w3.org/QA/Tips/iso-date>
class ISODate
	super Comparable

	# UTC years as Int.
	var year: Int is noinit

	# UTC months as Int (`1` for January).
	var month: Int is noinit

	# UTC days as Int (starting at `1`).
	var day: Int is noinit

	# UTC hours as Int.
	var hours: Int is noinit

	# UTC minutes as Int.
	var minutes: Int is noinit

	# UTC seconds as Int.
	var seconds: Int is noinit

	# UTC timezone marker.
	#
	# Note that I don't know what will happen if you change this value...
	var timezone = "Z"

	init do
		var t = new Tm.localtime
		year = 1900 + t.year
		month = t.mon + 1
		day = t.mday
		hours = t.hour
		minutes = t.min
		seconds = t.sec
	end

	# Init `self` from a ISODate formatted string.
	init from_string(str: String) do
		year = str.substring(0, 4).to_i
		month = str.substring(5, 2).to_i
		day = str.substring(8, 2).to_i
		hours = str.substring(11, 2).to_i
		minutes = str.substring(14, 2).to_i
		seconds = str.substring(17, 2).to_i
		timezone = str.substring(19, str.length)
	end

	redef fun to_s do
		var buff = new FlatBuffer
		buff.append year.to_s
		buff.add '-'
		if month < 10 then buff.add '0'
		buff.append month.to_s
		buff.add '-'
		if day < 10 then buff.add '0'
		buff.append day.to_s
		buff.add 'T'
		if hours < 10 then buff.add '0'
		buff.append hours.to_s
		buff.add ':'
		if minutes < 10 then buff.add '0'
		buff.append minutes.to_s
		buff.add ':'
		if seconds < 10 then buff.add '0'
		buff.append seconds.to_s
		buff.append timezone
		return buff.write_to_string
	end

	redef type OTHER: ISODate

	# TODO handle timezones
	redef fun <(o) do return to_s < o.to_s
end