Show teacher names and emails on admin school classes

app/controllers/admin/school_classes_controller.rb

@@ -2,5 +2,12 @@
 
 module Admin
   class SchoolClassesController < Admin::ApplicationController
+    helper_method :class_teacher_users_by_id
+
+    private
+
+    def class_teacher_users_by_id
+      @class_teacher_users_by_id ||= User.from_userinfo(ids: requested_resource.teachers.map(&:user_id).uniq).index_by(&:id)
+    end
   end
 end

app/dashboards/school_class_dashboard.rb

@@ -11,7 +11,7 @@ class SchoolClassDashboard < Administrate::BaseDashboard
   # on pages throughout the dashboard.
   ATTRIBUTE_TYPES = {
     school: Field::BelongsTo,
-    teachers: Field::HasMany,
+    teachers: ClassTeachersField,
     students: Field::HasMany,
     lessons: Field::HasMany,
     id: Field::String,

app/fields/class_teachers_field.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require 'administrate/field/base'
+
+class ClassTeachersField < Administrate::Field::Base
+  def teachers
+    @teachers ||= data.sort_by(&:created_at)
+  end
+
+  def user_display(teacher, users_by_id = {})
+    user = users_by_id[teacher.user_id]
+    user.present? ? user_dashboard.display_resource(user) : teacher.user_id
+  end
+
+  private
+
+  def user_dashboard
+    @user_dashboard ||= UserDashboard.new
+  end
+end

app/views/fields/class_teachers_field/_show.html.erb

@@ -0,0 +1,20 @@
+<% if field.teachers.any? %>
+  <table>
+    <thead>
+      <tr>
+        <th>Teacher</th>
+        <th>Added to class</th>
+      </tr>
+    </thead>
+    <tbody>
+      <% field.teachers.each do |teacher| %>
+        <tr>
+          <td><%= field.user_display(teacher, class_teacher_users_by_id) %></td>
+          <td><%= l(teacher.created_at) %></td>
+        </tr>
+      <% end %>
+    </tbody>
+  </table>
+<% else %>
+  <%= t('administrate.fields.has_many.none', default: '–') %>
+<% end %>

spec/features/admin/school_classes_spec.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Admin school classes', type: :request do
+  let(:admin_user) { create(:admin_user) }
+  let(:school) { create(:school) }
+  let(:teacher) { create(:user, name: 'Tariq Teacher', email: 'teacher@example.com') }
+  let(:other_teacher) { create(:user, name: 'Olivia Teacher', email: 'olivia@example.com') }
+  let(:school_class) { create(:school_class, school:, teacher_ids: [teacher.id, other_teacher.id]) }
+
+  before do
+    allow(User).to receive(:from_omniauth).and_return(admin_user)
+    get '/auth/callback'
+    allow(User).to receive(:from_userinfo).with(ids: contain_exactly(teacher.id, other_teacher.id)).and_return([other_teacher, teacher])
+  end
+
+  it 'displays each teacher name and email using a single batch lookup' do
+    get admin_school_class_path(school_class)
+
+    expect(response).to have_http_status(:success)
+    expect(response.body).to include('Tariq Teacher (teacher@example.com)', 'Olivia Teacher (olivia@example.com)')
+    expect(response.body).to include('<th>Added to class</th>')
+    expect(response.body).not_to include('<th>Updated</th>')
+    expect(response.body).not_to include(teacher.id, other_teacher.id)
+    expect(User).to have_received(:from_userinfo).with(ids: contain_exactly(teacher.id, other_teacher.id)).once
+  end
+
+  it 'falls back to the UUID when a teacher is missing from user info' do
+    allow(User).to receive(:from_userinfo).and_return([teacher])
+
+    get admin_school_class_path(school_class)
+
+    expect(response).to have_http_status(:success)
+    expect(response.body).to include('Tariq Teacher (teacher@example.com)', other_teacher.id)
+  end
+
+  it 'renders an empty teacher list without looking up users' do
+    school_class.teachers.destroy_all
+
+    get admin_school_class_path(school_class)
+
+    expect(response).to have_http_status(:success)
+    expect(User).not_to have_received(:from_userinfo)
+  end
+end