File: calculations.rb

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mhc 1.2.1-2
 `123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153` ``````module RiCal module CoreExtensions #:nodoc: module Time #:nodoc: #- ©2009 Rick DeNatale #- All rights reserved. Refer to the file README.txt for the license # # Provide calculation methods for use by the RiCal gem # This module is included by Time, Date, and DateTime module Calculations # A predicate method used to determine if the receiver is within a leap year def leap_year? year % 4 == 0 && (year % 400 == 0 || year % 100 != 0) end # Return the number of days in the month which includes the receiver def days_in_month raw = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][self.month] self.month == 2 && leap_year? ? raw + 1 : raw end # Return the date on which the first iso week with a given starting week day occurs # for a given iso year # # # From RFC 2445 page 43: # A week is defined as a seven day period, starting on the day of the week defined to be the # week start (see WKST). Week number one of the calendar year is the first week which contains # at least four (4) days in that calendar # year. # # == parameters # year:: the iso year # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def self.iso_week_one(year, wkst) # # Note that wkst uses the ruby definition, with Sunday = 0 # # A good article about calculating ISO week number is at # http://www.boyet.com/Articles/PublishedArticles/CalculatingtheISOweeknumb.html # # RFC 2445 generalizes the notion of ISO week by allowing the start of the week to vary. # In order to adopt the algorithm in the referenced article, we must determine, for each # wkst value, the day in January which must be contained in week 1 of the year. # # For a given wkst week 1 for a year is the first week which # 1) Starts with a day with a wday of wkst # 2) Contains a majority (4 or more) of days in that year # # If end of prior Dec, start of Jan Week 1 starts on For WKST = # MO TU WE TH FR SA SU MO TU WE TH FR SA SU MO TU WE TH FR SA SU # 01 02 03 04 05 06 07 08 09 10 11 12 13 14 01-07 02-08 03-09 04-10 05-11 06-12 07-13 # 31 01 02 03 04 05 06 07 08 09 10 11 12 13 31-06 01-07 02-08 03-09 04-10 05-11 06-12 # 30 31 01 02 03 04 05 06 07 08 09 10 11 12 30-05 31-06 01-07 02-08 03-09 04-10 05-11 # 29 30 31 01 02 03 04 05 06 07 08 09 10 11 29-04 30-05 31-06 01-07 02-08 03-09 04-10 # 28 29 30 31 01 02 03 04 05 06 07 08 09 10 04-10 29-04 30-05 31-06 01-07 02-08 03-09 # 27 28 29 30 31 01 02 03 04 05 06 07 08 09 03-09 04-10 29-04 30-05 31-06 01-07 02-08 # 26 27 28 29 30 31 01 02 03 04 05 06 07 08 02-08 03-09 04-10 29-04 30-05 31-06 01-07 # 25 26 27 28 29 30 31 01 02 03 04 05 06 07 01-07 02-08 03-09 04-10 29-04 30-05 31-06 # Week 1 must contain 4 4 4 4 ? ? ? # # So for a wkst of FR, SA, or SU, there is no date which MUST be contained in the 1st week # We'll have to brute force that if (1..4).include?(wkst) # return the date of the wkst day which is less than or equal to jan4th jan4th = ::Date.new(year, 1, 4) result = jan4th - (convert_wday(jan4th.wday) - convert_wday(wkst)) else # return the date of the wkst day which is greater than or equal to Dec 31 of the prior year dec29th = ::Date.new(year-1, 12, 29) result = dec29th + convert_wday(wkst) - convert_wday(dec29th.wday) end result end # Convert the receivers wday to RFC 2445 format. Whereas the Ruby time/date classes use # 0 to represent Sunday, RFC 2445 uses 7. def self.convert_wday(wday) wday == 0 ? 7 : wday end # Return an array containing the iso year and iso week number for the receiver. # Note that the iso year may be the year before or after the calendar year containing the receiver. # == parameter # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def iso_year_and_week_one_start(wkst) iso_year = self.year date = ::Date.new(self.year, self.month, self.mday) if (date >= ::Date.new(iso_year, 12, 29)) week_one_start = Calculations.iso_week_one(iso_year + 1, wkst) if date < week_one_start week_one_start = Calculations.iso_week_one(iso_year, wkst) else iso_year += 1 end else week_one_start = Calculations.iso_week_one(iso_year, wkst) if (date < week_one_start) iso_year -= 1 week_one_start = Calculations.iso_week_one(iso_year, wkst) end end [iso_year, week_one_start] end def iso_year_and_week_num(wkst) #:nodoc: iso_year, week_one_start = *iso_year_and_week_one_start(wkst) [iso_year, (::Date.new(self.year, self.month, self.mday) - week_one_start).to_i / 7 + 1] end # return the number of weeks in the the iso year containing the receiver # == parameter # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def iso_weeks_in_year(wkst) iso_year, week_one_start = *iso_year_and_week_one_start(wkst) probe_date = week_one_start + (7*52) if probe_date.iso_year(wkst) == iso_year 53 else 52 end end # return the iso week number of the receiver # == parameter # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def iso_week_num(wkst) iso_year_and_week_num(wkst)[1] end # return the iso year of the receiver # == parameter # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def iso_year(wkst) iso_year_and_week_num(wkst)[0] end # return the first day of the iso year of the receiver # == parameter # wkst:: an integer representing the day of the week on which weeks are deemed to start. This uses # the ruby convention where 0 represents Sunday. def iso_year_start(wkst) iso_year_and_week_one_start(wkst)[1] end end end end end``````