Implement RRule::Rule#humanize

.rubocop.yml

@@ -1,5 +1,6 @@
 AllCops:
   TargetRubyVersion: 2.6
+  NewCops: disable
   Exclude:
     - 'gemfiles/**/*'
     - Appraisals

lib/rrule.rb

@@ -6,6 +6,7 @@ module RRule
   autoload :Rule, 'rrule/rule'
   autoload :Context, 'rrule/context'
   autoload :Weekday, 'rrule/weekday'
+  autoload :Humanizer, 'rrule/humanizer'
 
   autoload :Frequency, 'rrule/frequencies/frequency'
   autoload :Daily, 'rrule/frequencies/daily'

lib/rrule/context.rb

@@ -17,15 +17,17 @@ def rebuild(year, month)
 
       if options[:bynweekday] && !options[:bynweekday].empty? && (month != last_month || year != last_year)
         possible_date_ranges = []
-        if options[:freq] == 'YEARLY'
+
+        case options[:freq]
+        when 'YEARLY'
           if options[:bymonth]
             options[:bymonth].each do |mon|
               possible_date_ranges.push(elapsed_days_in_year_by_month[(mon - 1)..mon])
             end
           else
             possible_date_ranges = [[0, year_length_in_days]]
           end
-        elsif options[:freq] == 'MONTHLY'
+        when 'MONTHLY'
           possible_date_ranges = [elapsed_days_in_year_by_month[(month - 1)..month]]
         end
 

lib/rrule/humanizer.rb

@@ -0,0 +1,215 @@
+# frozen_string_literal: true
+
+module RRule
+  # Based off https://github.com/jakubroztocil/rrule/blob/master/src/nlp/totext.ts
+  #
+  class Humanizer
+    attr_reader :rrule, :options
+
+    OPTION_ATTRIBUTE_RE = /_option/.freeze
+
+    DAY_NAMES = %w[
+      Sunday
+      Monday
+      Tuesday
+      Wednesday
+      Thursday
+      Friday
+      Saturday
+    ].freeze
+
+    def initialize(rrule, options)
+      @rrule = rrule
+      @options = options
+
+      # Define instance method for each of the options.
+      options.each { |name, value| define_singleton_method("#{name}_option") { value } }
+    end
+
+    def to_s
+      @buffer = 'every'
+
+      send freq_option.downcase
+
+      if until_option
+        raise 'Implement Until'
+      elsif count_option
+        add 'for'
+        add count_option
+        add plural?(count_option) ? 'times' : 'time'
+      end
+
+      @buffer
+    end
+
+    # Return nil if we're trying to access an option that isn't present.
+    def method_missing(method_name, *args)
+      if method_name.to_s.match?(OPTION_ATTRIBUTE_RE)
+        nil
+      else
+        super
+      end
+    end
+
+    def respond_to_missing?(method_name)
+      super || method_name.to_s.match?(OPTION_ATTRIBUTE_RE)
+    end
+
+    protected
+
+      def list(arr, formatter, final_delimiter = nil, delimiter: ',')
+        *rest, middle, tail = arr.map(&formatter)
+
+        if final_delimiter
+          [*rest, [middle, tail].compact.join(" #{final_delimiter} ")].join("#{delimiter} ")
+        else
+          [*rest, middle, tail].compact.join("#{delimiter} ")
+        end
+      end
+
+      def add(string)
+        @buffer += " #{string}"
+      end
+
+      def plural?(num)
+        num.to_i % 100 != 1
+      end
+
+      def daily
+        add interval_option if interval_option != 1
+
+        if byweekday_option && weekdays?
+          add plural?(interval_option) ? 'weekdays' : 'weekday'
+        else
+          add plural?(interval_option) ? 'days' : 'day'
+        end
+
+        if bymonth_option
+          add 'in'
+          _bymonth
+        end
+
+        if bymonthday_option
+          _bymonthday
+        elsif byweekday_option
+          _byweekday
+        elsif byhour_option
+          _byhour
+        end
+      end
+
+      def weekly
+        if interval_option != 1
+          add interval_option
+          add plural?(interval_option) ? 'weeks' : 'week'
+        end
+
+        if byweekday_option && weekdays?
+          if interval_option == 1
+            add plural?(interval_option) ? 'weekdays' : 'weekday'
+          else
+            add 'on'
+            add 'weekdays'
+          end
+        elsif byweekday_option && every_day?
+          add plural?(interval_option) ? 'days' : 'day'
+        else
+          add 'week' if interval_option == 1
+
+          if bymonth_option
+            add 'in'
+            _bymonth
+          end
+
+          if bymonthday_option
+            _bymonthday
+          elsif byweekday_option
+            _byweekday
+          end
+        end
+      end
+
+      def monthly
+        if bymonth_option
+          if interval_option != 1
+            add interval_option
+            add 'months'
+            add 'in' if plural?(interval_option)
+          end
+
+          _bymonth
+        else
+          add interval_option if interval_option != 1
+
+          add plural?(interval_option) ? 'months' : 'month'
+        end
+
+        if bymonthday_option
+          _bymonthday
+        elsif byweekday_option && weekdays?
+          add 'on'
+          add 'weekdays'
+        elsif byweekday_option || bynweekday_option
+          _byweekday
+        end
+      end
+
+      def weekdaytext(day)
+        [day.ordinal && nth(day.ordinal), DAY_NAMES[day.index]].compact.join(' ')
+      end
+
+      def all_weeks?
+        bynweekday_option.all? { |option| option.ordinal.nil? }
+      end
+
+      def every_day?
+        byweekday_option.sort_by(&:index).map { |day| WEEKDAYS[day.index]} == RRule::WEEKDAYS
+      end
+
+      def weekdays?
+        return false if byweekday_option.none?
+
+        byweekday_option.sort_by(&:index).map { |day| WEEKDAYS[day.index]} == RRule::WEEKDAYS - %w[SA SU]
+      end
+
+      def _bymonth
+        add list(this.options.bymonth, method(:monthtext), 'and')
+      end
+
+      def _byweekday
+        if byweekday_option.any?
+          add 'on'
+          add list(byweekday_option, method(:weekdaytext))
+        end
+
+        return unless bynweekday_option.any?
+
+        add 'and' if all_weeks?
+        add 'on the'
+        add list(bynweekday_option, method(:weekdaytext), 'and')
+      end
+
+      def _byhour
+        add 'at'
+        add list byhour_option, :to_s, 'and'
+      end
+
+      def nth(ordinal)
+        return 'last' if ordinal == -1
+
+        nth =
+          case npos = ordinal.abs
+          when 1, 21, 31
+            "#{npos}st"
+          when 2, 22
+            "#{npos}nd"
+          when 3, 23
+            "#{npos}rd"
+          else
+            "#{npos}th"
+          end
+
+        ordinal < 0 ? "#{nth} last" : nth
+      end
+  end
+end

lib/rrule/rule.rb

@@ -83,6 +83,10 @@ def next
       enumerator.next
     end
 
+    def humanize
+      Humanizer.new(self, options).to_s
+    end
+
     private
 
     attr_reader :options, :max_year, :max_date, :frequency_type

lib/rrule/weekday.rb

@@ -12,7 +12,7 @@ def initialize(index, ordinal = nil)
     def self.parse(weekday)
       match = /([+-]?\d+)?([A-Z]{2})/.match(weekday)
       index = RRule::WEEKDAYS.index(match[2])
-      ordinal = match[1] ? match[1].to_i : nil
+      ordinal = match[1]&.to_i
       new(index, ordinal)
     end
   end

spec/rule_spec.rb

@@ -2598,4 +2598,52 @@
 
     expect(rrule.to_s).to eql rrule_string
   end
+
+  describe '#humanize' do
+    let(:dtstart) { Time.parse('Tue Sep  2 06:00:00 PDT 1997') }
+    let(:timezone) { 'America/New_York' }
+    let(:rrule) { RRule::Rule.new(rule, dtstart: dtstart, tzid: timezone) }
+
+    context 'every day' do
+      let(:rule) { 'RRULE:FREQ=DAILY;INTERVAL=1' }
+
+      it { expect(rrule.humanize).to eq 'every day' }
+    end
+
+    context 'every day at 1' do
+      let(:rule) { 'RRULE:FREQ=DAILY;INTERVAL=1;BYHOUR=1' }
+
+      it { expect(rrule.humanize).to eq 'every day at 1' }
+    end
+
+    context 'every day weekly' do
+      let(:rule) { 'RRULE:FREQ=WEEKLY;INTERVAL=1;BYDAY=MO,TU,WE,TH,FR,SA,SU' }
+
+      it { expect(rrule.humanize).to eq 'every day' }
+    end
+
+    context 'every week on Tuesday, Thursday' do
+      let(:rule) { 'FREQ=WEEKLY;INTERVAL=1;BYDAY=TU,TH' }
+
+      it { expect(rrule.humanize).to eq 'every week on Tuesday, Thursday' }
+    end
+
+    context 'every 2 weeks on Tuesday, Thursday' do
+      let(:rule) { 'FREQ=WEEKLY;INTERVAL=2;BYDAY=TU,TH' }
+
+      it { expect(rrule.humanize).to eq 'every 2 weeks on Tuesday, Thursday' }
+    end
+
+    context 'every month on the last Friday for 7 times' do
+      let(:rule) { 'FREQ=MONTHLY;BYDAY=-1FR;COUNT=7' }
+
+      it { expect(rrule.humanize).to eq 'every month on the last Friday for 7 times' }
+    end
+
+    context 'every month on the first Monday and last Friday for 7 times' do
+      let(:rule) { 'FREQ=MONTHLY;BYDAY=1MO,-1FR;COUNT=7' }
+
+      it { expect(rrule.humanize).to eq 'every month on the 1st Monday and last Friday for 7 times' }
+    end
+  end
 end