support for bysetpos with freq=weekly

Author: nehresma

lib/ice_cube.rb

@@ -49,6 +49,7 @@ module Validations
     autoload :YearlyInterval, "ice_cube/validations/yearly_interval"
     autoload :HourlyInterval, "ice_cube/validations/hourly_interval"
 
+    autoload :WeeklyBySetPos, 'ice_cube/validations/weekly_by_set_pos'
     autoload :MonthlyBySetPos, 'ice_cube/validations/monthly_by_set_pos'
     autoload :YearlyBySetPos, 'ice_cube/validations/yearly_by_set_pos'
 

lib/ice_cube/rules/weekly_rule.rb

@@ -10,6 +10,7 @@ class WeeklyRule < ValidatedRule
     # include Validations::DayOfYear    # n/a
 
     include Validations::WeeklyInterval
+    include Validations::WeeklyBySetPos
 
     attr_reader :week_start
 

lib/ice_cube/validations/weekly_by_set_pos.rb

@@ -0,0 +1,91 @@
+module IceCube
+  module Validations::WeeklyBySetPos
+    def by_set_pos(*by_set_pos)
+      by_set_pos.flatten!
+      by_set_pos.each do |set_pos|
+        unless (-366..366).include?(set_pos) && set_pos != 0
+          raise ArgumentError, "Expecting number in [-366, -1] or [1, 366], got #{set_pos} (#{by_set_pos})"
+        end
+      end
+
+      @by_set_pos = by_set_pos
+      replace_validations_for(:by_set_pos, [Validation.new(by_set_pos, self)])
+      self
+    end
+
+    class Validation
+
+      attr_reader :rule, :by_set_pos
+
+      def initialize(by_set_pos, rule)
+        @by_set_pos = by_set_pos
+        @rule = rule
+      end
+
+      def type
+        :day
+      end
+
+      def dst_adjust?
+        true
+      end
+
+      def validate(step_time, start_time)
+        # Use vanilla Ruby Date objects so we can add and subtract dates across DST changes
+        step_time_date = step_time.to_date
+        start_day_of_week = TimeUtil.sym_to_wday(rule.week_start)
+        step_time_day_of_week = step_time_date.wday
+        days_delta = step_time_day_of_week - start_day_of_week
+        days_to_start = days_delta >= 0 ? days_delta : 7 + days_delta
+        start_of_week_date = step_time_date - days_to_start
+        end_of_week_date = start_of_week_date + 6
+        start_of_week = IceCube::TimeUtil.build_in_zone(
+          [start_of_week_date.year, start_of_week_date.month, start_of_week_date.day, 0, 0, 0], step_time
+        )
+        end_of_week = IceCube::TimeUtil.build_in_zone(
+          [end_of_week_date.year, end_of_week_date.month, end_of_week_date.day, 23, 59, 59], step_time
+        )
+
+        # Needs to start on the first day of the week at the step_time's hour, min, sec
+        start_of_week_adjusted = IceCube::TimeUtil.build_in_zone(
+          [
+            start_of_week_date.year, start_of_week_date.month, start_of_week_date.day,
+            step_time.hour, step_time.min, step_time.sec
+          ], step_time
+        )
+        new_schedule = IceCube::Schedule.new(start_of_week_adjusted) do |s|
+          s.add_recurrence_rule(IceCube::Rule.from_hash(rule.to_hash.except(:by_set_pos, :count, :until)))
+        end
+
+        occurrences = new_schedule.occurrences_between(start_of_week, end_of_week)
+        index = occurrences.index(step_time)
+        if index.nil?
+          1
+        else
+          positive_set_pos = index + 1
+          negative_set_pos = index - occurrences.length
+
+          if @by_set_pos.include?(positive_set_pos) || @by_set_pos.include?(negative_set_pos)
+            0
+          else
+            1
+          end
+        end
+      end
+
+      def build_s(builder)
+        builder.piece(:by_set_pos) << by_set_pos
+      end
+
+      def build_hash(builder)
+        builder[:by_set_pos] = by_set_pos
+      end
+
+      def build_ical(builder)
+        builder['BYSETPOS'] << by_set_pos
+      end
+
+      nil
+    end
+  end
+end

spec/examples/by_set_pos_spec.rb

@@ -1,6 +1,34 @@
 require File.dirname(__FILE__) + '/../spec_helper'
 
 module IceCube
+  describe WeeklyRule, 'BYSETPOS' do
+    it 'should behave correctly' do
+      # Weekly on Monday, Wednesday, and Friday with the week starting on Wednesday, the last day of the set
+      schedule = IceCube::Schedule.from_ical("RRULE:FREQ=WEEKLY;COUNT=4;WKST=WE;BYDAY=MO,WE,FR;BYSETPOS=-1")
+      schedule.start_time = Time.new(2022, 12, 27, 12, 0, 0)
+      expect(schedule.occurrences_between(Time.new(2022, 01, 01), Time.new(2024, 01, 01))).
+        to eq([
+          Time.new(2023,1,2,12,0,0),
+          Time.new(2023,1,9,12,0,0),
+          Time.new(2023,1,16,12,0,0),
+          Time.new(2023,1,23,12,0,0)
+        ])
+    end
+
+    it 'should work with intervals' do
+      # Every 2 weeks on Monday, Wednesday, and Friday with the week starting on Wednesday, the last day of the set
+      schedule = IceCube::Schedule.from_ical("RRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;WKST=WE;BYDAY=MO,WE,FR;BYSETPOS=-1")
+      schedule.start_time = Time.new(2022, 12, 27, 12, 0, 0)
+      expect(schedule.occurrences_between(Time.new(2022, 01, 01), Time.new(2024, 01, 01))).
+        to eq([
+          Time.new(2023,1,9,12,0,0),
+          Time.new(2023,1,23,12,0,0),
+          Time.new(2023,2,6,12,0,0),
+          Time.new(2023,2,20,12,0,0)
+        ])
+    end
+  end
+
   describe MonthlyRule, 'BYSETPOS' do
     it 'should behave correctly' do
       schedule = IceCube::Schedule.from_ical "RRULE:FREQ=MONTHLY;COUNT=4;BYDAY=WE;BYSETPOS=4"