Enable users to signup to all content by organisation

app/controllers/content_item_signups_controller.rb

@@ -0,0 +1,67 @@
+# This controller takes any content item and makes it possible to subscribe
+# to alerts when documents linked to them are changed (taxons, orgs etc).
+# This is in contrast to EmailAlertSignupsController, which takes a
+# finder_email_signup content item.
+class ContentItemSignupsController < ApplicationController
+  protect_from_forgery except: [:create]
+  before_action :require_content_item_param
+  before_action :validate_document_type
+  helper_method :estimated_email_frequency
+
+  def new
+    @subscription = ContentItemSubscriptionPresenter.new(@content_item)
+  end
+
+  def confirm; end
+
+  def create
+    signup = ContentItemSubscriberList.new(content_item.to_h)
+
+    if signup.has_content_item?
+      redirect_to signup.subscription_management_url
+    else
+      redirect_to confirm_content_item_signup_path(link: content_item_path)
+    end
+  end
+
+private
+
+  PERMITTED_CONTENT_ITEMS = %w(taxon organisation).freeze
+
+  def require_content_item_param
+    unless valid_content_item_param?
+      redirect_to '/'
+      false
+    end
+  end
+
+  def valid_content_item_param?
+    content_item_path.to_s.starts_with?('/') && URI.parse(content_item_path).relative?
+  rescue URI::InvalidURIError
+    false
+  end
+
+  def content_item_path
+    # Topic param left in for backwards compatibility.
+    # Topic is the user-facing terminology for taxons. Expect the taxon base
+    # path to be provided in a param of this name.
+    params[:link] || params[:topic]
+  end
+
+  def content_item
+    @content_item ||= EmailAlertFrontend
+      .services(:content_store)
+      .content_item(content_item_path)
+  end
+
+  def validate_document_type
+    unless PERMITTED_CONTENT_ITEMS.include?(content_item['document_type'])
+      redirect_to '/'
+      false
+    end
+  end
+
+  def estimated_email_frequency
+    EmailVolume::WeeklyEmailVolume.new(content_item).estimate
+  end
+end

app/helpers/application_helper.rb

@@ -9,7 +9,7 @@ def title(text, params = {})
     render 'govuk_publishing_components/components/title', { title: text }.merge(params)
   end
 
-  def live_taxon?(taxon)
-    taxon['phase'] == 'live'
+  def live_content_item?(content_item)
+    content_item['phase'] == 'live'
   end
 end

app/models/content_item_subscriber_list.rb

@@ -0,0 +1,61 @@
+class ContentItemSubscriberList
+  def initialize(content_item)
+    @content_item = content_item
+  end
+
+  def subscription_management_url
+    subscriber_list.dig('subscriber_list', 'subscription_url')
+  end
+
+  def has_content_item?
+    content_item.present?
+  end
+
+private
+
+  attr_accessor :content_item
+
+  class UnsupportedContentItemError < StandardError; end
+
+  def subscriber_list
+    EmailAlertFrontend.services(:email_alert_api)
+      .find_or_create_subscriber_list(subscription_params)
+  end
+
+  def subscription_params
+    {
+      'title' => content_item['title'],
+      'links' => link_hash
+    }
+  end
+
+  def link_hash
+    case content_item_type
+    when 'taxon'
+      taxon_links
+    when 'organisation'
+      organisation_links
+    else
+      message = "No link hash available for content items of type #{content_item_type}!"
+      raise UnsupportedContentItemError, message
+    end
+  end
+
+  def taxon_links
+    {
+      # 'taxon_tree' is the key used in email-alert-service for
+      # notifications, so create a subscriber list with this key.
+      'taxon_tree' => [content_item['content_id']]
+    }
+  end
+
+  def organisation_links
+    {
+      'organisations' => [content_item['content_id']]
+    }
+  end
+
+  def content_item_type
+    content_item.dig('document_type')
+  end
+end

app/models/email_volume/organisation_weekly_email_volume.rb

@@ -0,0 +1,37 @@
+module EmailVolume
+  class OrganisationWeeklyEmailVolume
+    HIGH = '40 - 60'.freeze
+    MEDIUM = '0 - 20'.freeze
+    LOW = '0 - 5'.freeze
+
+    def initialize(organisation)
+      @organisation = organisation
+    end
+
+    def estimate
+      parent_organisation = extract_parent_from(@organisation)
+
+      # It's a top-level organisation like HM Treasury
+      return HIGH if parent_organisation.blank?
+
+      # Is a 2nd level organisation like UK Debt Management Office
+      grandparent_organisation = extract_parent_from(
+        fetch_content_item(parent_organisation.fetch('base_path'))
+      )
+      return MEDIUM if grandparent_organisation.blank?
+
+      # Is a 3rd level organisation
+      LOW
+    end
+
+  private
+
+    def extract_parent_from(content_item)
+      Array(content_item.dig('links', 'ordered_parent_organisations')).first
+    end
+
+    def fetch_content_item(base_path)
+      EmailAlertFrontend.services(:content_store).content_item(base_path)
+    end
+  end
+end

app/models/email_volume/taxon_weekly_email_volume.rb

@@ -0,0 +1,37 @@
+module EmailVolume
+  class TaxonWeeklyEmailVolume
+    HIGH = '40 - 60'.freeze
+    MEDIUM = '0 - 20'.freeze
+    LOW = '0 - 5'.freeze
+
+    def initialize(taxon)
+      @taxon = taxon
+    end
+
+    def estimate
+      parent_taxon = extract_parent_from(@taxon)
+
+      # Is at the top of the taxonomy
+      return HIGH if parent_taxon.blank?
+
+      # Is a 2nd level taxon
+      grandparent_taxon = extract_parent_from(
+        fetch_content_item(parent_taxon.fetch('base_path'))
+      )
+      return MEDIUM if grandparent_taxon.blank?
+
+      # Is a 3rd level taxon or below
+      LOW
+    end
+
+  private
+
+    def extract_parent_from(content_item)
+      Array(content_item.dig('links', 'parent_taxons')).first
+    end
+
+    def fetch_content_item(base_path)
+      EmailAlertFrontend.services(:content_store).content_item(base_path)
+    end
+  end
+end

app/models/email_volume/weekly_email_volume.rb

@@ -0,0 +1,31 @@
+module EmailVolume
+  class WeeklyEmailVolume
+    def initialize(content_item)
+      @content_item = content_item
+    end
+
+    def estimate
+      volume_estimator.estimate
+    end
+
+  private
+
+    class ContentItemNotEstimatableError < StandardError; end
+
+    def volume_estimator
+      case content_item_type
+      when 'taxon'
+        TaxonWeeklyEmailVolume.new(@content_item)
+      when 'organisation'
+        OrganisationWeeklyEmailVolume.new(@content_item)
+      else
+        error_message = "Volume estimate not possible for content items of type #{content_item_type}!"
+        raise ContentItemNotEstimatableError, error_message
+      end
+    end
+
+    def content_item_type
+      @content_item.dig('document_type')
+    end
+  end
+end