Add fraud check

Adds a mechanisim for admins to upload a csv of know risky trns and
ninos that will cause claims with these attributes to be flagged in the
admin ui.

Flagged values can be removed by uploading a CSV without those values.

According to the govuk guidance we can't show multiple notification
banners on a page and should combine their content. We may want to use a
different method to display fraud prevention warnings to admins.

app/controllers/admin/fraud_risk_csv_downloads_controller.rb

@@ -0,0 +1,25 @@
+module Admin
+  class FraudRiskCsvDownloadsController < BaseAdminController
+    before_action :ensure_service_operator
+
+    def show
+      respond_to do |format|
+        format.csv do
+          send_data(csv, filename: "fraud_risk.csv")
+        end
+      end
+    end
+
+    private
+
+    def csv
+      CSV.generate do |csv|
+        csv << %w[field value]
+
+        RiskIndicator.order(created_at: :asc).pluck(:field, :value).each do |row|
+          csv << row
+        end
+      end
+    end
+  end
+end

app/controllers/admin/fraud_risk_csv_uploads_controller.rb

@@ -0,0 +1,28 @@
+module Admin
+  class FraudRiskCsvUploadsController < BaseAdminController
+    before_action :ensure_service_operator
+
+    def new
+      @form = FraudRiskCsvUploadForm.new
+    end
+
+    def create
+      @form = FraudRiskCsvUploadForm.new(fraud_risk_csv_upload_params)
+
+      if @form.save
+        redirect_to(
+          new_admin_fraud_risk_csv_upload_path,
+          notice: "Fraud prevention list uploaded successfully."
+        )
+      else
+        render :new
+      end
+    end
+
+    private
+
+    def fraud_risk_csv_upload_params
+      params.require(:admin_fraud_risk_csv_upload_form).permit(:file)
+    end
+  end
+end

app/forms/admin/fraud_risk_csv_upload_form.rb

@@ -0,0 +1,45 @@
+module Admin
+  class FraudRiskCsvUploadForm
+    include ActiveModel::Model
+
+    attr_accessor :file
+
+    validates :file, presence: true
+
+    validate :all_records_are_valid, if: -> { file.present? }
+
+    def initialize(params = {})
+      super
+    end
+
+    def save
+      return false unless valid?
+
+      ApplicationRecord.transaction do
+        RiskIndicator.where.not(id: records.map(&:id)).destroy_all
+
+        records.each(&:save!)
+      end
+
+      true
+    end
+
+    private
+
+    def csv
+      @csv ||= CSV.parse(file.read, headers: true, skip_blanks: true)
+    end
+
+    def records
+      @records ||= csv.map do |row|
+        RiskIndicator.find_or_initialize_by(row.to_h)
+      end.uniq { |record| record.attributes.slice("field", "value") }
+    end
+
+    def all_records_are_valid
+      records.select(&:invalid?).each do |record|
+        errors.add(:base, record.errors.map(&:message).join(", "))
+      end
+    end
+  end
+end

app/models/claim.rb

@@ -454,6 +454,10 @@ def awaiting_provider_verification?
     eligibility.awaiting_provider_verification?
   end
 
+  def attributes_flagged_by_risk_indicator
+    @attributes_flagged_by_risk_indicator ||= RiskIndicator.flagged_attributes(self)
+  end
+
   private
 
   def one_login_idv_name_match?

app/models/risk_indicator.rb

@@ -0,0 +1,34 @@
+class RiskIndicator < ApplicationRecord
+  SUPPORTED_FIELDS = %w[
+    teacher_reference_number
+    national_insurance_number
+  ].freeze
+
+  validates :field, presence: {
+    message: "'field' can't be blank"
+  }
+
+  validates :value, presence: {
+    message: "'value' can't be blank"
+  }
+
+  validates :value, uniqueness: {scope: :field}
+
+  validates :field,
+    inclusion: {
+      in: SUPPORTED_FIELDS,
+      message: "'%{value}' is not a valid attribute - must be one of #{SUPPORTED_FIELDS.join(", ")}"
+    }
+
+  def self.flagged_attributes(claim)
+    where(
+      "field = 'national_insurance_number' AND LOWER(value) = :value",
+      value: claim.national_insurance_number.downcase
+    ).or(
+      where(
+        field: "teacher_reference_number",
+        value: claim.eligibility.try(:teacher_reference_number)
+      )
+    ).pluck(:field)
+  end
+end

app/views/admin/fraud_risk_csv_uploads/new.html.erb

@@ -0,0 +1,31 @@
+<div class="govuk-grid-row">
+  <div class="govuk-grid-column-two-thirds">
+    <h1 class="govuk-heading-xl">
+      Fraud risk CSV upload
+    </h1>
+
+    <%= form_with(
+      url: admin_fraud_risk_csv_uploads_path,
+      model: @form,
+      builder: GOVUKDesignSystemFormBuilder::FormBuilder
+    ) do |f| %>
+      <%= f.govuk_error_summary %>
+
+      <%= f.govuk_file_field(
+        :file,
+        label: { text: "Upload fraud risk CSV file" },
+        hint: {
+          text: "Currently supported attributes are #{RiskIndicator::SUPPORTED_FIELDS.join(", ")}."
+        }
+      ) %>
+
+      <%= f.govuk_submit "Upload CSV" %>
+    <% end %>
+
+    <%= govuk_link_to(
+      "Download CSV",
+      admin_fraud_risk_csv_download_path(format: :csv),
+      class: "govuk-button"
+    ) %>
+  </div>
+</div>

app/views/admin/tasks/index.html.erb

@@ -4,18 +4,33 @@
   <%= govuk_back_link href: claims_backlink_path %>
 <% end %>
 
-<% if @has_matching_claims %>
+<% if @has_matching_claims || @claim.attributes_flagged_by_risk_indicator.any? %>
   <div class="govuk-notification-banner" role="region" aria-labelledby="govuk-notification-banner-title" data-module="govuk-notification-banner">
     <div class="govuk-notification-banner__header">
       <h2 class="govuk-notification-banner__title" id="govuk-notification-banner-title">
         Important
       </h2>
     </div>
     <div class="govuk-notification-banner__content">
-      <p class="govuk-notification-banner__heading">
-        <%= link_to "Multiple claims", admin_claim_task_path(claim_id: @claim.id, name: "matching_details") %>
-        with matching details have been made in this claim window.
-      </p>
+      <div class="govuk-notification-banner__heading">
+        <% if @has_matching_claims %>
+          <p class="govuk-!-margin-0">
+            <%= link_to(
+              "Multiple claims",
+              admin_claim_task_path(claim_id: @claim.id, name: "matching_details")
+            ) %>
+            with matching details have been made in this claim window.
+          </p>
+        <% end %>
+
+        <% if @claim.attributes_flagged_by_risk_indicator.any? %>
+          <p class="<%= class_names("govuk-!-margin-0", "govuk-!-margin-top-4" => @has_matching_claims.present?) %>">
+            This claim has been flagged for fraud prevention as it has a
+            <%= @claim.attributes_flagged_by_risk_indicator.map(&:humanize).to_sentence.downcase %>
+            that is present in the fraud risk CSV.
+          </p>
+        <% end %>
+      </div>
     </div>
   </div>
 <% end %>

config/routes.rb

@@ -146,6 +146,8 @@ def matches?(request)
     resources :school_workforce_census_data_uploads, only: [:new, :create]
     resources :student_loans_data_uploads, only: [:new, :create]
     resources :tps_data_uploads, only: [:new, :create]
+    resources :fraud_risk_csv_uploads, only: [:new, :create]
+    resource :fraud_risk_csv_download, only: :show
 
     resources :payroll_runs, only: [:index, :new, :create, :show, :destroy] do
       resources :payment_confirmation_report_uploads, only: [:new, :create]

db/migrate/20241017160838_create_risk_indicators.rb

@@ -0,0 +1,12 @@
+class CreateRiskIndicators < ActiveRecord::Migration[7.0]
+  def change
+    create_table :risk_indicators, id: :uuid do |t|
+      t.string :field, null: false
+      t.string :value, null: false
+
+      t.index %i[field value], unique: true
+
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2024_10_15_121145) do
+ActiveRecord::Schema[7.0].define(version: 2024_10_17_160838) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "citext"
   enable_extension "pg_trgm"
@@ -420,6 +420,14 @@
     t.string "itt_subject"
   end
 
+  create_table "risk_indicators", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
+    t.string "field", null: false
+    t.string "value", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["field", "value"], name: "index_risk_indicators_on_field_and_value", unique: true
+  end
+
   create_table "school_workforce_censuses", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
     t.string "teacher_reference_number"
     t.datetime "created_at", null: false

spec/factories/risk_indicators.rb

@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :risk_indicator do
+    field { "MyString" }
+    value { "MyString" }
+  end
+end

spec/features/admin/admin_fraud_prevention_spec.rb

@@ -0,0 +1,77 @@
+require "rails_helper"
+
+RSpec.feature "Admin fraud prevention" do
+  let(:fraud_risk_csv) do
+    File.open(Rails.root.join("spec", "fixtures", "files", "fraud_risk.csv"))
+  end
+
+  before do
+    sign_in_as_service_operator
+  end
+
+  context "when updating the list of flagged attributes" do
+    it "flags any matching claims" do
+      flagged_claim_trn = create(
+        :claim,
+        :submitted,
+        eligibility_attributes: {
+          teacher_reference_number: "1234567"
+        }
+      )
+
+      flagged_claim_nino = create(
+        :claim,
+        :submitted,
+        national_insurance_number: "QQ123456C"
+      )
+
+      flagged_claim_trn_and_nino = create(
+        :claim,
+        :submitted,
+        eligibility_attributes: {
+          teacher_reference_number: "1234567"
+        },
+        national_insurance_number: "QQ123456C"
+      )
+
+      visit new_admin_fraud_risk_csv_upload_path
+      attach_file "Upload fraud risk CSV file", fraud_risk_csv.path
+      click_on "Upload"
+
+      expect(page).to have_content(
+        "Fraud prevention list uploaded successfully."
+      )
+
+      visit admin_claim_tasks_path(flagged_claim_trn)
+
+      expect(page).to have_content(
+        "This claim has been flagged for fraud prevention as it has a " \
+        "teacher reference number that is present in the fraud risk CSV."
+      )
+
+      visit admin_claim_tasks_path(flagged_claim_nino)
+
+      expect(page).to have_content(
+        "This claim has been flagged for fraud prevention as it has a " \
+        "national insurance number that is present in the fraud risk CSV."
+      )
+
+      visit admin_claim_tasks_path(flagged_claim_trn_and_nino)
+
+      expect(page).to have_content(
+        "This claim has been flagged for fraud prevention as it has a " \
+        "national insurance number and teacher reference number that is " \
+        "present in the fraud risk CSV."
+      )
+    end
+  end
+
+  it "allows for downloading the csv" do
+    visit new_admin_fraud_risk_csv_upload_path
+    attach_file "Upload fraud risk CSV file", fraud_risk_csv.path
+    click_on "Upload"
+
+    click_on "Download"
+    expect(page.body).to eq(fraud_risk_csv.read.chomp)
+  end
+end

spec/fixtures/files/fraud_risk.csv

@@ -0,0 +1,4 @@
+field,value
+national_insurance_number,qq123456c
+teacher_reference_number,1234567
+

spec/fixtures/files/fraud_risk_missing_value.csv

@@ -0,0 +1,5 @@
+field,value
+national_insurance_number,qq123456c
+teacher_reference_number,1234567
+teacher_reference_number,
+

spec/fixtures/files/fraud_risk_unknown_attribute.csv

@@ -0,0 +1,5 @@
+field,value
+national_insurance_number,qq123456c
+teacher_reference_number,1234567
+test,1234567
+rest,1234567