review fixes and added comments

lib/ice_cube/rules/weekly_rule.rb

@@ -35,7 +35,14 @@ def realign(step_time, start_time)
       time = TimeUtil::TimeWrapper.new(start_time)
       offset = wday_offset(step_time, start_time)
       time.add(:day, offset)
-      super step_time, time.to_timezoneless_time
+      realigned_time = time.to_time
+      # when the realigned time is in a different hour, we need to adjust the
+      # time to the correct hour with a fixed timezone offset, otherwise
+      # the time will be off by an hour
+      # WARNING: if the next DST change is within the interval, the occurrences
+      # after the next DST change will be off by an hour because the timezone is fixed
+      realigned_time = time.to_timezoneless_time if realigned_time.hour != start_time.hour
+      super step_time, realigned_time
     end
 
     # Calculate how many days to the first wday validation in the correct

spec/examples/fixed_value_spec.rb

@@ -14,4 +14,4 @@
       expect(validation.validate(time_in_zone, start_time)).to eq 1
     end
   end
-end
+end

spec/examples/schedule_spec.rb

@@ -391,31 +391,39 @@
         Time.utc(2014, 1, 2, 0o1, 34, 56)]
     end
 
-    context "Cairo timezone" do
+    context "Cairo timezone", system_time_zone: 'Africa/Cairo' do
+      require "active_support/time"
+
       let(:schedule) do
         IceCube::Schedule.from_yaml("---\n:start_time:\n  :time: 2022-05-05 22:20:00.000000000 Z\n  :zone: Africa/Cairo\n:end_time:\n  :time: 2022-05-06 21:40:00.000000000 Z\n  :zone: Africa/Cairo\n:rrules:\n- :validations:\n    :day:\n    - 5\n  :rule_type: IceCube::WeeklyRule\n  :interval: 1\n  :week_start: 1\n:rtimes: []\n:extimes: []\n")
+        # IceCube::Schedule.new(ActiveSupport::TimeZone['Africa/Cairo'].parse("2022-05-05 00:20:00")).tap do |schedule|
+        #   schedule.add_recurrence_rule IceCube::Rule.weekly.day(:friday)
+        # end
       end
 
       it "has the correct start time" do
         expect(schedule.start_time.iso8601).to eq("2022-05-06T00:20:00+02:00")
       end
 
-      it "calculates the corret occurrences from 2024-04-24" do
-        ref_time = Time.utc(2024, 4, 24, 12, 0, 0)
-        occurrences = schedule.next_occurrences(3, ref_time)
+      it "has the correct start time timezone" do
+        expect(schedule.start_time.zone).to eq("EET")
+      end
+
+      it "calculates the correct occurrences from 2024-04-24" do
+        occurrences = schedule.next_occurrences(3, Time.utc(2024, 4, 24, 12, 0, 0))
         expect(occurrences.map(&:iso8601)).to eq([
           "2024-04-26T00:20:00+03:00",
           "2024-05-03T00:20:00+03:00",
-          "2024-05-10T00:20:00+03:00"
+          "2024-05-10T00:20:00+03:00",
         ])
       end
 
-      it "calculates the corret occurrences from 2024-04-21" do
-        occurrences = schedule.next_occurrences(3, Time.utc(2024, 4, 21, 12, 0, 0))
+      it "calculates the correct occurrences from 2024-04-17" do
+        occurrences = schedule.next_occurrences(3, Time.utc(2024, 4, 17, 12, 0, 0))
         expect(occurrences.map(&:iso8601)).to eq([
+          "2024-04-19T00:20:00+02:00",
           "2024-04-26T01:20:00+03:00",
           "2024-05-03T00:20:00+03:00",
-          "2024-05-10T00:20:00+03:00"
         ])
       end
     end

spec/examples/weekly_rule_spec.rb

@@ -411,19 +411,37 @@ module IceCube
     end
 
     describe :realign do
-      let(:cairo_tz) { ActiveSupport::TimeZone["Africa/Cairo"] }
+      require "active_support/time"
+
+      let(:timezone_name) { "Africa/Cairo" }
+      let(:timezone) { ActiveSupport::TimeZone[timezone_name] }
       let(:utc_tz) { ActiveSupport::TimeZone["UTC"] }
-      let(:start_time) { cairo_tz.parse("2022-05-22 00:20:00") }
+      let(:start_time) { timezone.parse("2022-05-22 00:20:00") }
       let(:time) { utc_tz.parse("2024-04-24 12:00:00") }
-      let(:rule) { Rule.weekly(1, :monday).day(:friday) }
+      let(:recurrence_day) { :friday }
+      let(:rule) { Rule.weekly(1, :monday).day(recurrence_day) }
 
       subject { rule.realign(time, start_time) }
 
-      it { puts cairo_tz.parse("2024-04-26T00:20:00") }
-
       it "realigns the start time to the correct time" do
         expect(subject.iso8601).to eq("2024-04-26T00:20:00+03:00")
       end
+
+      context "Berlin timezone" do
+        let(:recurrence_day) { :sunday }
+        let(:timezone_name) { "Europe/Berlin" }
+        let(:start_time) { timezone.parse("2024-03-24 02:30:00") }
+        let(:time) { timezone.parse("2024-03-27 02:30:00") }
+
+        # the next occurrence is on sunday within the DST shift
+        # where the clock is set forward from 02:00 to 03:00
+        # so the next occurrence is on actually on 03:30 but this
+        # would result in faulty start times for the following
+        # occurrences (03:30 instead of 02:30)
+        it "realigns the start time to the correct time" do
+          expect(subject.iso8601).to eq("2024-03-31T02:30:00+02:00")
+        end
+      end
     end
   end
 end