Adds .ics endpoints for calendars, topics and posts

app/controllers/discourse_calendar_controller.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+module DiscourseCalendar
+  class DiscourseCalendarController < ::ApplicationController
+    before_action :ensure_discourse_calendar_enabled
+    skip_before_action :check_xhr, only: [ :topic_calendar ], if: :ics_request?
+
+    def topic_calendar
+
+      @topic = Topic.find_by(id: params[:id])
+
+      if @topic && guardian.can_see?(@topic)
+        @events = CalendarEvent.where(topic_id: @topic.id).order(:start_date, :end_date)
+
+        respond_to do |format|
+          format.ics do
+            filename = "topic-#{@topic.id}-calendar"
+            response.headers['Content-Disposition'] = "attachment; filename=\"#{filename}.#{request.format.symbol}\""
+
+            render :topic_calendar
+          end
+        end
+      else
+        raise Discourse::NotFound
+      end
+    end
+
+    def post_dates
+      @post = Post.find_by(id: params[:id])
+
+      if @post && guardian.can_see?(@post)
+        @events = LocalDatesExtractor.new(@post).extract_events
+        respond_to do |format|
+          format.ics do
+            filename = "post-#{@post.id}-dates"
+            response.headers['Content-Disposition'] = "attachment; filename=\"#{filename}.#{request.format.symbol}\""
+
+            render :post_dates
+          end
+        end
+      else
+        raise Discourse::NotFound
+      end
+    end
+
+    def topic_dates
+      @topic = Topic.find_by(id: params[:id])
+
+      if @topic && guardian.can_see?(@topic)
+        @events = @topic.posts.map{|p| LocalDatesExtractor.new(p).extract_events}.flatten
+
+        respond_to do |format|
+          format.ics do
+            filename = "topic-#{@topic.id}-dates"
+            response.headers['Content-Disposition'] = "attachment; filename=\"#{filename}.#{request.format.symbol}\""
+
+            render :post_dates
+          end
+        end
+      else
+        raise Discourse::NotFound
+      end
+    end
+
+    private
+
+    def ensure_discourse_calendar_enabled
+      if !SiteSetting.calendar_enabled
+        raise Discourse::NotFound
+      end
+    end
+
+    def ics_request?
+      request.format.symbol == :ics
+    end
+  end
+end

app/views/discourse_calendar/discourse_calendar/post_dates.ics.erb

@@ -0,0 +1,15 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Discourse//<%= Discourse.current_hostname %>//<%= Discourse.full_version %>//EN
+<% @events.each_with_index do |event, index| %>
+BEGIN:VEVENT
+UID:post_dates_#<%= index %>@<%= Discourse.current_hostname %>
+DTSTAMP:<%= Time.now.utc.strftime("%Y%m%dT%H%M%SZ") %>
+DTSTART:<%= event.start_date.strftime("%Y%m%dT%H%M%SZ") %>
+DTEND:<%= event.end_date.presence ? event.end_date.strftime("%Y%m%dT%H%M%SZ") : (event.start_date + 1.hour).strftime("%Y%m%dT%H%M%SZ") %>
+SUMMARY:<%= event.description %>
+DESCRIPTION:<%= "#{event.description}\\n\\n#{Discourse.base_url}/t/-/#{event.post.topic_id}/#{event.post.post_number}" %>
+URL:<%= Discourse.base_url %>/t/-/<%= event.post.topic_id %>/<%= event.post.post_number %>
+END:VEVENT
+<% end %>
+END:VCALENDAR

app/views/discourse_calendar/discourse_calendar/topic_calendar.ics.erb

@@ -0,0 +1,15 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Discourse//<%= Discourse.current_hostname %>//<%= Discourse.full_version %>//EN
+<% @events.each do |event| %>
+BEGIN:VEVENT
+UID:calendar_post_#<%= event.id %>@<%= Discourse.current_hostname %>
+DTSTAMP:<%= Time.now.utc.strftime("%Y%m%dT%H%M%SZ") %>
+DTSTART:<%= event.start_date.strftime("%Y%m%dT%H%M%SZ") %>
+DTEND:<%= event.end_date.presence ? event.end_date.strftime("%Y%m%dT%H%M%SZ") : (event.start_date + 1.day).strftime("%Y%m%dT%H%M%SZ") %>
+SUMMARY:<%= event.description %>
+DESCRIPTION:<%= "#{PrettyText.format_for_email(event.post.excerpt, event.post).html_safe}\\n\\n#{Discourse.base_url}/t/-/#{event.post.topic_id}/#{event.post.post_number}" %>
+URL:<%= Discourse.base_url %>/t/-/<%= event.post.topic_id %>/<%= event.post.post_number %>
+END:VEVENT
+<% end %>
+END:VCALENDAR

lib/local_dates_extractor.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+class LocalDatesExtractor
+  Event = Struct.new(:start_date, :end_date, :description, :post)
+
+  def initialize(post)
+    @post = post  
+  end
+
+  def extract_events
+
+    events = []
+
+    Loofah.fragment(@post.cooked).css('span.discourse-local-date').map{|d| d.parent}.uniq.map do |paragraph_with_date|
+      next if paragraph_with_date.ancestors("aside").length > 0
+
+      event = Event.new
+      dates = paragraph_with_date.css('span.discourse-local-date')
+
+      # detects date ranges
+      if dates.count == 2 && paragraph_with_date.content.include?(' → ')
+        to, from = dates.each do |cooked_date|
+          date = {}
+          cooked_date.attributes.values.each do |attribute|
+            data_name = attribute.name&.gsub('data-', '')
+            if data_name && %w[date time timezone recurring].include?(data_name)
+              unless attribute.value == 'undefined'
+                date[data_name] = CGI.escapeHTML(attribute.value || '')
+              end
+            end
+          end
+        end
+        event.start_date = LocalDatesExtractor.convert_to_date_time(from)
+        event.end_date = LocalDatesExtractor.convert_to_date_time(to)
+      else #no ranges
+        date = {}
+        paragraph_with_date.css('span.discourse-local-date').attributes.values.each do |attribute|
+          data_name = attribute.name&.gsub('data-', '')
+          if data_name && %w[date time timezone recurring].include?(data_name)
+            unless attribute.value == 'undefined'
+              date[data_name] = CGI.escapeHTML(attribute.value || '')
+            end
+          end
+        end
+
+        event.start_date = LocalDatesExtractor.convert_to_date_time(date)
+      end
+      event.description = paragraph_with_date.children.reject{|c| c&.attributes.dig('class')&.value == 'discourse-local-date'}&.map{|c| c.text}&.join&.gsub(' → ', '')
+      event.post = @post
+      events << event
+    end
+
+    events
+  end
+
+
+  private
+
+  def self.convert_to_date_time(value)
+    return if value.blank?
+
+    attrs = value.attributes
+
+    datetime = attrs['data-date'].value
+    datetime << " #{attrs['data-time'].value}" if attrs['time']
+    timezone = attrs['data-timezone'].value || 'UTC'
+
+    ActiveSupport::TimeZone[timezone].parse(datetime)
+  end
+end

plugin.rb

@@ -291,6 +291,7 @@ def valid_event
   # DISCOURSE CALENDAR
 
   %w[
+    ../app/controllers/discourse_calendar_controller.rb
     ../app/models/calendar_event.rb
     ../app/serializers/user_timezone_serializer.rb
     ../jobs/scheduled/create_holiday_events.rb
@@ -301,9 +302,23 @@ def valid_event
     ../lib/calendar.rb
     ../lib/event_validator.rb
     ../lib/group_timezones.rb
+    ../lib/local_dates_extractor.rb
     ../lib/time_sniffer.rb
   ].each { |path| load File.expand_path(path, __FILE__) }
 
+  Discourse::Application.routes.append do
+    mount ::DiscourseCalendar::Engine, at: '/'
+  end
+
+  DiscourseCalendar::Engine.routes.draw do
+    get '/calendar/topic-calendar/:id' => 'discourse_calendar#topic_calendar',
+        constraints: { format: /ics/ }
+    get '/calendar/topic/:id' => 'discourse_calendar#topic_dates',
+        constraints: { format: /ics/ }
+    get '/calendar/post/:id' => 'discourse_calendar#post_dates',
+        constraints: { format: /ics/ }
+  end
+
   register_post_custom_field_type(
     DiscourseCalendar::CALENDAR_CUSTOM_FIELD,
     :string