2 files changed, 83 insertions, 0 deletions

diff --git a/app/models/concerns/rrule_humanizer.rb b/app/models/concerns/rrule_humanizer.rb
new file mode 100644
index 0000000..6cee711
--- /dev/null
+++ b/app/models/concerns/rrule_humanizer.rb
@@ -0,0 +1,82 @@
+module RruleHumanizer
+  extend ActiveSupport::Concern
+
+  WEEKDAY_NAMES = {
+    de: { "MO"=>"Montag","TU"=>"Dienstag","WE"=>"Mittwoch","TH"=>"Donnerstag","FR"=>"Freitag","SA"=>"Samstag","SU"=>"Sonntag" },
+    en: { "MO"=>"Monday","TU"=>"Tuesday","WE"=>"Wednesday","TH"=>"Thursday","FR"=>"Friday","SA"=>"Saturday","SU"=>"Sunday" }
+  }.freeze
+
+  WEEKDAY_NAMES_ADVERBIAL = {
+    de: { "MO"=>"montags","TU"=>"dienstags","WE"=>"mittwochs","TH"=>"donnerstags","FR"=>"freitags","SA"=>"samstags","SU"=>"sonntags" }
+  }.freeze
+
+  ORDINAL_NAMES = {
+    de: { 1=>"ersten", 2=>"zweiten", 3=>"dritten", 4=>"vierten", -1=>"letzten", -2=>"vorletzten" },
+    en: { 1=>"first", 2=>"second", 3=>"third", 4=>"fourth", -1=>"last", -2=>"second-to-last" }
+  }.freeze
+
+  MONTH_NAMES = {
+    de: %w[Januar Februar März April Mai Juni Juli August September Oktober November Dezember],
+    en: %w[January February March April May June July August September October November December]
+  }.freeze
+
+  def humanize_rrule(locale = I18n.locale)
+    return nil if rrule.blank?
+    parts = Hash[rrule.split(";").map { |p| p.split("=", 2) }]
+    return nil if parts["COUNT"] || parts["UNTIL"] # old one-off data, don't guess
+
+    freq, interval, byday, bymonth = parts["FREQ"], parts["INTERVAL"].to_i, parts["BYDAY"], parts["BYMONTH"]
+    loc = locale.to_sym
+    weekdays = WEEKDAY_NAMES[loc] || WEEKDAY_NAMES[:en]
+    ordinals = ORDINAL_NAMES[loc] || ORDINAL_NAMES[:en]
+    months   = MONTH_NAMES[loc]   || MONTH_NAMES[:en]
+
+    days = byday&.split(",")&.map do |d|
+     if d =~ /^(-?\d+)([A-Z]{2})$/
+        "#{ordinals[$1.to_i]} #{weekdays[$2]}"
+      else
+        weekdays[d]
+      end
+    end
+
+    base =
+      case loc
+      when :de
+        case freq
+        when "WEEKLY"
+          if days
+            if interval == 2
+              adverbial = byday.split(",").map { |d| WEEKDAY_NAMES_ADVERBIAL[:de][d] }
+              "Alle zwei Wochen #{adverbial.join(' und ')}"
+            else
+              "Jeden #{days.join(' und ')}"
+            end
+          else
+            interval == 2 ? "Alle zwei Wochen" : "Wöchentlich"
+          end
+        when "MONTHLY"
+          days ? "Jeden #{days.join(' und ')} im Monat" : "Monatlich"
+        end
+      else
+        case freq
+        when "WEEKLY"
+          days ? "#{interval == 2 ? 'Every other' : 'Every'} #{days.join(' and ')}" : (interval == 2 ? "Every other week" : "Weekly")
+        when "MONTHLY"
+          days ? "Every #{days.join(' and ')} of the month" : "Monthly"
+        end
+      end
+    return nil unless base
+
+    if bymonth
+      included = bymonth.split(",").map(&:to_i)
+      missing = ((1..12).to_a - included)
+      if missing.size == 1
+        excluded_name = months[missing.first - 1]
+        base += (loc == :de ? ", außer im #{excluded_name}" : ", except in #{excluded_name}")
+      end
+      # more than one missing month: bymonth pattern more complex than we handle, leave base as-is silently
+    end
+
+    base
+  end
+end
diff --git a/app/models/event.rb b/app/models/event.rb
index 26c79e4..de82674 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -1,4 +1,5 @@
 class Event < ApplicationRecord
+  include RruleHumanizer
 
   belongs_to :node, optional: true
   has_many   :occurrences