[feature] Calendar and icalendar meetings

# Calendar and Meetings 
addresses: #1597
This release adds the ability for Violet to handle your calendar. Incoming emails with .ics attachments will automatically be added to your calendar as meetings.

## Calendar UI
![Screenshot from 2023-09-14 00-25-19](https://github.com/restarone/violet_rails/assets/35935196/d6ab2626-85e1-49d3-83d3-f2aadfc34eeb)

## Outgoing Meeting request RSVP controls

![IMG_7264](https://github.com/restarone/violet_rails/assets/35935196/bae81b61-32e4-4970-a9b8-60b787366f11)


todo: 

1. include .vcs file for outlook
2. add validations to meeting model

further reading: 

1. icalendar syncing events: https://joshfrankel.me/blog/lemme-pencil-you-in-using-icalendar-and-rails-to-sync-calendar-events/
2. all the options: https://blog.corsego.com/icalendar-ruby
3. publish? https://stackoverflow.com/questions/55927263/what-does-icalendar-publish-method-do
4. dealing with email client quirkyness when displaying RSVP buttons: https://stackoverflow.com/questions/66102584/when-i-add-method-request-to-icalendar-gmail-stops-recognizing-as-event

Gemfile

@@ -124,4 +124,7 @@ gem 'devise-two-factor', "4.0.2"
 
 gem "slowpoke"
 
-gem "strong_migrations"
+gem "strong_migrations"
+gem "simple_calendar", "~> 3.0"
+
+gem "icalendar", "~> 2.9"

Gemfile.lock

@@ -250,6 +250,9 @@ GEM
       multi_xml (>= 0.5.2)
     i18n (1.10.0)
       concurrent-ruby (~> 1.0)
+    icalendar (2.9.0)
+      ice_cube (~> 0.16)
+    ice_cube (0.16.4)
     image_processing (1.12.2)
       mini_magick (>= 4.9.5, < 5)
       ruby-vips (>= 2.0.17, < 3)
@@ -417,6 +420,8 @@ GEM
       connection_pool (>= 2.2.2)
       rack (~> 2.0)
       redis (>= 4.2.0)
+    simple_calendar (3.0.2)
+      rails (>= 6.1)
     simplecov (0.21.2)
       docile (~> 1.1)
       simplecov-html (~> 0.11)
@@ -535,6 +540,7 @@ DEPENDENCIES
   gravatar_image_tag
   groupdate
   httparty
+  icalendar (~> 2.9)
   image_processing (~> 1.12)
   jbuilder (~> 2.7)
   jsonapi-serializer
@@ -559,6 +565,7 @@ DEPENDENCIES
   ros-apartment-sidekiq
   sass-rails (>= 6)
   selenium-webdriver
+  simple_calendar (~> 3.0)
   simple_discussion!
   simplecov
   sinatra

app/assets/stylesheets/application.scss

@@ -20,6 +20,7 @@
  @import 'select2/dist/css/select2.css';
  @import './direct_upload.scss';
  @import 'daterangepicker/daterangepicker';
+ @import "simple_calendar";
 
  :root {
   --color-primary: #6C5BF5;

app/controllers/comfy/admin/calendars_controller.rb

@@ -0,0 +1,23 @@
+class Comfy::Admin::CalendarsController < Comfy::Admin::Cms::BaseController
+  layout "comfy/admin/cms"
+  before_action :check_email_authorization
+  def new
+
+  end
+
+  def index
+  # Scope your query to the dates being shown:
+  start_date = params.fetch(:start_date, Date.today).to_date
+  @meetings = Meeting.where(start_time: start_date.beginning_of_month.beginning_of_week..start_date.end_of_month.end_of_week)
+  end
+
+
+  private
+
+  def check_email_authorization
+    unless current_user.can_manage_email
+      flash.alert = 'You do not have permission to manage email'
+      redirect_back(fallback_location: root_path)
+    end
+  end
+end

app/controllers/meetings_controller.rb

@@ -0,0 +1,142 @@
+class MeetingsController < Comfy::Admin::Cms::BaseController
+  before_action :set_meeting, only: %i[ show edit update destroy ]
+  before_action :check_email_authorization
+
+  # GET /meetings or /meetings.json
+  def index
+    @meetings = Meeting.all
+  end
+
+  # GET /meetings/1 or /meetings/1.json
+  def show
+  end
+
+  # GET /meetings/new
+  def new
+    @meeting = Meeting.new
+  end
+
+  # GET /meetings/1/edit
+  def edit
+  end
+
+  # POST /meetings or /meetings.json
+  def create
+    @meeting = Meeting.new(meeting_params)
+    @meeting.external_meeting_id = "#{SecureRandom.uuid}.#{Apartment::Tenant.current}@#{ENV['APP_HOST']}"
+    @meeting.status = 'CONFIRMED'
+    @meeting.participant_emails = meeting_params[:participant_emails].filter{ |node| URI::MailTo::EMAIL_REGEXP.match?(node) }
+
+    respond_to do |format|
+      if @meeting.save
+        # send .ics file to participants
+        cal = Icalendar::Calendar.new
+        filename = "Invitation: #{@meeting.name}"
+        from_address = "#{Apartment::Tenant.current}@#{ENV['APP_HOST']}"
+        # to generate outlook
+        if false == 'vcs'
+          cal.prodid = '-//Microsoft Corporation//Outlook MIMEDIR//EN'
+          cal.version = '1.0'
+          filename += '.vcs'
+        else # ical
+          cal.prodid = '-//Restarone Solutions, Inc.//NONSGML ExportToCalendar//EN'
+          cal.version = '2.0'
+          filename += '.ics'
+        end
+        cal.append_custom_property('METHOD', 'REQUEST')
+        cal.event do |e|
+          e.dtstart     = Icalendar::Values::DateTime.new(@meeting.start_time, tzid: @meeting.timezone)
+          e.dtend       = Icalendar::Values::DateTime.new(@meeting.end_time, tzid: @meeting.timezone)
+          e.organizer = Icalendar::Values::CalAddress.new("mailto:#{from_address}", cn: from_address)
+          e.attendee = Icalendar::Values::CalAddress.new("mailto:#{from_address}", partstat: 'ACCEPTED')
+          e.uid = @meeting.external_meeting_id
+          @meeting.participant_emails.each do |email|
+            attendee_params = { 
+              "CUTYPE"   => "INDIVIDUAL",
+              "ROLE"     => "REQ-PARTICIPANT",
+              "PARTSTAT" => "NEEDS-ACTION",
+              "RSVP"     => "TRUE",
+            }
+
+            attendee_value = Icalendar::Values::Text.new("MAILTO:#{email}", attendee_params)
+            cal.append_custom_property("ATTENDEE", attendee_value)
+          end
+          e.description = @meeting.description
+          e.location    = @meeting.location
+          e.sequence = Time.now.to_i
+          e.status = "CONFIRMED"
+          e.summary     = @meeting.name
+
+
+          e.alarm do |a|
+            a.summary = "#{@meeting.name} starts in 30 minutes!"
+            a.trigger = '-PT30M'
+          end
+        end
+        file = cal.to_ical
+        attachment = { filename: filename, mime_type: "text/calendar;method=REQUEST;name=\'#{filename}\'", content: file }
+        blob = ActiveStorage::Blob.create_and_upload!(io: StringIO.new(attachment[:content]), filename: attachment[:filename], content_type: attachment[:mime_type], metadata: nil)
+        email_thread = MessageThread.create!(recipients: @meeting.participant_emails, subject: "Invitation: #{@meeting.name}")
+        email_content = <<-HTML
+        <div>
+          <p>You have been invited to the following meeting, please see details below<br><br>
+          </p>
+
+        </div>
+        HTML
+        email_content += ActionText::Content.new("<action-text-attachment sgid='#{blob.attachable_sgid}'></action-text-attachment>").to_s
+        email_message = email_thread.messages.create!(
+          content: email_content.html_safe,
+          from: from_address
+        )
+        EMailer.with(message: email_message, message_thread: email_thread, attachments: [attachment]).ship.deliver_later
+
+        format.html { redirect_to @meeting, notice: "Meeting was successfully created." }
+        format.json { render :show, status: :created, location: @meeting }
+      else
+        format.html { render :new, status: :unprocessable_entity }
+        format.json { render json: @meeting.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # PATCH/PUT /meetings/1 or /meetings/1.json
+  def update
+    respond_to do |format|
+      if @meeting.update(meeting_params)
+        format.html { redirect_to @meeting, notice: "Meeting was successfully updated." }
+        format.json { render :show, status: :ok, location: @meeting }
+      else
+        format.html { render :edit, status: :unprocessable_entity }
+        format.json { render json: @meeting.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # DELETE /meetings/1 or /meetings/1.json
+  def destroy
+    @meeting.destroy
+    respond_to do |format|
+      format.html { redirect_to meetings_url, notice: "Meeting was successfully destroyed." }
+      format.json { head :no_content }
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_meeting
+      @meeting = Meeting.find(params[:id])
+    end
+
+    # Only allow a list of trusted parameters through.
+    def meeting_params
+      params.require(:meeting).permit(:name, :start_time, :end_time, :description, :timezone, :location, participant_emails: [])
+    end
+
+    def check_email_authorization
+      unless current_user.can_manage_email
+        flash.alert = 'You do not have permission to manage email'
+        redirect_back(fallback_location: root_path)
+      end
+    end
+end

app/mailboxes/e_mailbox.rb

@@ -17,15 +17,17 @@ def process
               subject: subject
             )
           end
-
+          uploaded_attachments = attachments
+          multipart_attachments = multipart_attached
           message = Message.create!(
             email_message_id: mail.message_id,
             message_thread: message_thread,
-            content: body,
+            content: body(uploaded_attachments),
             from: mail.from.join(', '),
-            attachments: (attachments + multipart_attached).map{ |a| a[:blob] }
+            attachments: (uploaded_attachments + multipart_attachments).map{ |a| a[:blob] }
           )
           message_thread.update(unread: true)
+          process_attachments(uploaded_attachments) if uploaded_attachments.size > 0
           ApiNamespace::Plugin::V1::SubdomainEventsService.new(message).track_event
         end
       end
@@ -60,10 +62,10 @@ def multipart_attached
     return blobs
   end
 
-  def body
+  def body(uploaded_blobs)
     if mail.multipart? && mail.html_part
       document = Nokogiri::HTML(mail.html_part.body.decoded)
-      attachments.map do |attachment_hash|
+      uploaded_blobs.map do |attachment_hash|
         attachment = attachment_hash[:original]
         blob = attachment_hash[:blob]
         if attachment.content_id.present?
@@ -91,4 +93,35 @@ def sanitize_email_subject_prefixes(subject)
     # examples: 'Re: ', 're: ', 'FWD: ', 'Fwd: ', 'Fw: '
     subject.gsub(/^((re|fw(d)?): )/i, '')
   end
+
+  def process_attachments(blobs)
+    # process .ics files
+    ics_files = blobs.select {|attachment| attachment[:original].content_type.include?('.ics') }
+    ics_files.each do |ics_file|
+      ics_string = ics_file[:blob].download
+      calendars = Icalendar::Calendar.parse(ics_string)
+      calendars.each do |calendar|
+        calendar.events.each do |event|
+          existing_meeting = Meeting.find_by(external_meeting_id: event.uid.to_s)
+          if existing_meeting
+            # handle replies to meeting invites
+            existing_meeting.update(updated_at: Time.now)
+          else
+            meeting = Meeting.create!(
+              name: event.summary,
+              external_meeting_id: event.uid,
+              start_time: event.dtstart,
+              end_time: event.dtend,
+              timezone: Array.wrap(event.dtstart.ical_params['tzid']).join('-'),
+              description: event.description,
+              participant_emails: event.attendee.map{|uri| uri.to },
+              location: event.location,
+              status: 'TENTATIVE',
+              custom_properties: event.custom_properties,
+            )
+          end
+        end
+      end
+    end
+  end
 end

app/models/meeting.rb

@@ -0,0 +1,6 @@
+class Meeting < ApplicationRecord
+  STATUS_LIST = ['TENTATIVE', 'CONFIRMED', 'CANCELLED']
+  # https://www.kanzaki.com/docs/ical/status.html
+
+  validates :status, inclusion: { in: STATUS_LIST  }
+end

app/views/comfy/admin/calendars/index.html.haml

@@ -0,0 +1,38 @@
+.page-header
+  .h2
+    Calendar
+  %p Early access, feature under active development
+
+
+= month_calendar(events: @meetings, attribute: :start_time) do |date, meetings|
+  = date
+  - meetings.each do |meeting|
+    %div
+      = meeting.name
+
+.h2 Listing meetings
+
+%table.table
+  %thead
+    %tr
+      %th Name
+      %th Start time
+      %th Participant emails
+      %th Status
+      %th
+      %th
+
+  %tbody
+    - @meetings.each do |meeting|
+      %tr
+        %td
+          = link_to meeting.name, meeting
+        %td= meeting.start_time
+        %td= meeting.participant_emails
+        %td= meeting.status
+        %td= link_to 'Edit', edit_meeting_path(meeting)
+        %td= link_to 'Destroy', meeting, method: :delete, data: { confirm: 'Are you sure?' }
+
+%br
+
+= link_to 'New Meeting', new_meeting_path

app/views/comfy/admin/cms/partials/_navigation_inner.haml

@@ -1,6 +1,7 @@
 %li{class: 'nav-item', data: { turbo: 'true'}}
   = active_link_to "Users", admin_users_path, class: 'nav-link'
   = active_link_to "Email", mailbox_path, class: 'nav-link'
+  = active_link_to "Calendar", calendars_path, class: 'nav-link'
   = active_link_to "API", api_namespaces_path, class: 'nav-link'
   = active_link_to "App Settings", edit_web_settings_path, class: 'nav-link'
   = active_link_to "Analytics", dashboard_path, class: 'nav-link'

app/views/meetings/_form.html.haml

@@ -0,0 +1,41 @@
+= form_for @meeting do |f|
+  - if @meeting.errors.any?
+    #error_explanation
+      %h2= "#{pluralize(@meeting.errors.count, "error")} prohibited this meeting from being saved:"
+      %ul
+        - @meeting.errors.full_messages.each do |message|
+          %li= message
+
+  .field
+    = f.label :name
+    = f.text_field :name
+  .field
+    = f.label :start_time
+    = f.datetime_select :start_time
+  .field
+    = f.label :end_time
+    = f.datetime_select :end_time
+  .field
+    = f.label :participant_emails
+    = f.select :participant_emails, options_for_select([]), { include_blank: false }, { multiple: true }
+  .field
+    = f.label :description
+    = f.text_area :description
+  .field
+    = f.label :timezone
+    = f.select :timezone, ActiveSupport::TimeZone::MAPPING
+  .field
+    = f.label :location
+    = f.text_field :location
+  .actions
+    = f.submit 'Save'
+
+:javascript
+  $(document).ready( function() {
+    $("#meeting_participant_emails").select2({
+      multiple: true,
+      required: true,
+      tags: true,
+      tokenSeparators: [',', ' '],
+    })
+  });

app/views/meetings/_meeting.json.jbuilder

@@ -0,0 +1,2 @@
+json.extract! meeting, :id, :name, :start_time, :end_time, :participant_emails, :description, :timezone, :location, :status, :external_meeting_id, :created_at, :updated_at
+json.url meeting_url(meeting, format: :json)

app/views/meetings/edit.html.haml

@@ -0,0 +1,7 @@
+%h1 Editing meeting
+
+= render 'form'
+
+= link_to 'Show', @meeting
+\|
+= link_to 'Back', meetings_path