From 8261e61cb04ad6a24dc239b8d4bb716af7058045 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 08:11:39 +0100
Subject: [PATCH 1/9] Create school_email_domains table

Add a migration to create the school_email_domains table, storing a domain string against a school_id
---
 .../20260420104937_create_school_email_domains.rb  | 14 ++++++++++++++
 db/schema.rb                                       | 12 +++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 db/migrate/20260420104937_create_school_email_domains.rb

diff --git a/db/migrate/20260420104937_create_school_email_domains.rb b/db/migrate/20260420104937_create_school_email_domains.rb
new file mode 100644
index 000000000..0101e995c
--- /dev/null
+++ b/db/migrate/20260420104937_create_school_email_domains.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class CreateSchoolEmailDomains < ActiveRecord::Migration[7.2]
+  def change
+    create_table :school_email_domains, id: :uuid do |t|
+      t.references :school, null: false, foreign_key: true, type: :uuid
+      t.string :domain, null: false
+
+      t.timestamps
+    end
+
+    add_index :school_email_domains, %i[school_id domain], unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 1699e359f..d625a9f69 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2026_03_23_152328) do
+ActiveRecord::Schema[7.2].define(version: 2026_04_20_104937) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -268,6 +268,15 @@
     t.index ["school_id"], name: "index_school_classes_on_school_id"
   end
 
+  create_table "school_email_domains", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
+    t.uuid "school_id", null: false
+    t.string "domain", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["school_id", "domain"], name: "index_school_email_domains_on_school_id_and_domain", unique: true
+    t.index ["school_id"], name: "index_school_email_domains_on_school_id"
+  end
+
   create_table "school_import_results", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
     t.uuid "job_id", null: false
     t.uuid "user_id", null: false
@@ -394,6 +403,7 @@
   add_foreign_key "projects", "schools"
   add_foreign_key "roles", "schools"
   add_foreign_key "school_classes", "schools"
+  add_foreign_key "school_email_domains", "schools"
   add_foreign_key "school_project_transitions", "school_projects"
   add_foreign_key "school_projects", "projects"
   add_foreign_key "school_projects", "schools"

From 49bb35e54a569a48398ef5d4ba1f93640cfa6c91 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 09:09:35 +0100
Subject: [PATCH 2/9] Add SchoolEmailDomain model

Create the model and add initial specs
---
 app/models/school_email_domain.rb       |  3 +++
 spec/models/school_email_domain_spec.rb | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 app/models/school_email_domain.rb
 create mode 100644 spec/models/school_email_domain_spec.rb

diff --git a/app/models/school_email_domain.rb b/app/models/school_email_domain.rb
new file mode 100644
index 000000000..1ecd08d28
--- /dev/null
+++ b/app/models/school_email_domain.rb
@@ -0,0 +1,3 @@
+class SchoolEmailDomain < ApplicationRecord
+    belongs_to :school
+end
\ No newline at end of file
diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
new file mode 100644
index 000000000..e1f0ad1ff
--- /dev/null
+++ b/spec/models/school_email_domain_spec.rb
@@ -0,0 +1,17 @@
+require 'rails_helper'
+
+RSpec.describe SchoolEmailDomain, type: :model do
+    let(:school) { create(:school, creator_id: SecureRandom.uuid) }
+    
+    let(:school_email_domain) do
+        described_class.new(school: school, domain: 'example.edu')
+      end
+    
+    it 'has a school' do
+        expect(school_email_domain.school_id).to eq(school.id)
+    end
+
+    it 'has a domain' do
+        expect(school_email_domain.domain).to eq('example.edu')
+    end
+end
\ No newline at end of file

From 8391fbb08881c99beb0eefa20cfa538798c4c107 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 09:31:51 +0100
Subject: [PATCH 3/9] Format domains

Removing leading @ symbols and lower case domains
---
 app/models/school_email_domain.rb       | 18 ++++++++++++--
 spec/models/school_email_domain_spec.rb | 33 ++++++++++++++++---------
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/app/models/school_email_domain.rb b/app/models/school_email_domain.rb
index 1ecd08d28..f370e5a95 100644
--- a/app/models/school_email_domain.rb
+++ b/app/models/school_email_domain.rb
@@ -1,3 +1,17 @@
+# frozen_string_literal: true
+
 class SchoolEmailDomain < ApplicationRecord
-    belongs_to :school
-end
\ No newline at end of file
+  belongs_to :school
+
+  validates :domain, presence: true
+
+  before_validation :format_domain
+
+  private
+
+  def format_domain
+    return if domain.nil?
+
+    self.domain = domain.to_s.strip.sub(/\A@+/, '').downcase
+  end
+end
diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index e1f0ad1ff..64ac5faac 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -1,17 +1,26 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
-RSpec.describe SchoolEmailDomain, type: :model do
-    let(:school) { create(:school, creator_id: SecureRandom.uuid) }
-    
-    let(:school_email_domain) do
-        described_class.new(school: school, domain: 'example.edu')
-      end
-    
-    it 'has a school' do
-        expect(school_email_domain.school_id).to eq(school.id)
+RSpec.describe SchoolEmailDomain do
+  let(:school) { create(:school, creator_id: SecureRandom.uuid) }
+
+  it { is_expected.to belong_to(:school) }
+  it { is_expected.to validate_presence_of(:domain) }
+
+  describe 'domain normalisation' do
+    it 'downcases the domain' do
+      record = described_class.new(school:, domain: 'EXAMPLE.EDU')
+      record.valid?
+
+      expect(record.domain).to eq('example.edu')
     end
 
-    it 'has a domain' do
-        expect(school_email_domain.domain).to eq('example.edu')
+    it 'removes a leading @' do
+      record = described_class.new(school:, domain: '@example.edu')
+      record.valid?
+
+      expect(record.domain).to eq('example.edu')
     end
-end
\ No newline at end of file
+  end
+end

From aff003abbfd9dd3d7577ba38408e3d9726d9c0b6 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 11:41:41 +0100
Subject: [PATCH 4/9] Add has_many association on School

---
 app/models/school.rb       |  1 +
 spec/models/school_spec.rb | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/app/models/school.rb b/app/models/school.rb
index fe35f00fa..c256a9379 100644
--- a/app/models/school.rb
+++ b/app/models/school.rb
@@ -6,6 +6,7 @@ class School < ApplicationRecord
   has_many :projects, dependent: :nullify
   has_many :roles, dependent: :nullify
   has_many :school_projects, dependent: :nullify
+  has_many :school_email_domains, dependent: :destroy
 
   VALID_URL_REGEX = %r{\A(?:https?://)?(?:www.)?[a-z0-9]+([-.]{1}[a-z0-9]+)*\.[a-z]{2,63}(\.[a-z]{2,63})*(/.*)?\z}ix
 
diff --git a/spec/models/school_spec.rb b/spec/models/school_spec.rb
index 7aec97db1..2e72cea2c 100644
--- a/spec/models/school_spec.rb
+++ b/spec/models/school_spec.rb
@@ -35,6 +35,12 @@
       expect(school.roles.size).to eq(2)
     end
 
+    it 'has many school email domains' do
+      SchoolEmailDomain.create!(school:, domain: 'example.edu')
+      SchoolEmailDomain.create!(school:, domain: 'other.edu')
+      expect(school.school_email_domains.size).to eq(2)
+    end
+
     context 'when a school is destroyed' do
       let!(:school_class) { create(:school_class, school:, teacher_ids: [teacher.id]) }
       let!(:lesson_1) { create(:lesson, user_id: teacher.id, school_class:) }
@@ -88,6 +94,11 @@
         school.destroy!
         expect(role.reload.school_id).to be_nil
       end
+
+      it 'also destroys school email domains' do
+        SchoolEmailDomain.create!(school:, domain: 'example.edu')
+        expect { school.destroy! }.to change(SchoolEmailDomain, :count).by(-1)
+      end
     end
   end
 

From b528185d0615397e45512fbd1fdf25dbd57ff3ef Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 14:53:46 +0100
Subject: [PATCH 5/9] Scope domain uniqueness to school_id

---
 app/models/school_email_domain.rb       |  1 +
 spec/models/school_email_domain_spec.rb | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/app/models/school_email_domain.rb b/app/models/school_email_domain.rb
index f370e5a95..a3535bb8c 100644
--- a/app/models/school_email_domain.rb
+++ b/app/models/school_email_domain.rb
@@ -4,6 +4,7 @@ class SchoolEmailDomain < ApplicationRecord
   belongs_to :school
 
   validates :domain, presence: true
+  validates :domain, uniqueness: { scope: :school_id }
 
   before_validation :format_domain
 
diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index 64ac5faac..55385a340 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -5,6 +5,8 @@
 RSpec.describe SchoolEmailDomain do
   let(:school) { create(:school, creator_id: SecureRandom.uuid) }
 
+  subject { described_class.new(school:, domain: 'example.edu') }
+
   it { is_expected.to belong_to(:school) }
   it { is_expected.to validate_presence_of(:domain) }
 
@@ -22,5 +24,21 @@
 
       expect(record.domain).to eq('example.edu')
     end
+
+    it 'rejects a duplicate domain for the same school after normalisation' do
+      described_class.create!(school:, domain: 'example.edu')
+      duplicate = described_class.new(school:, domain: 'EXAMPLE.EDU')
+      duplicate.valid?
+
+      expect(duplicate.errors[:domain]).to include('has already been taken')
+    end
+
+    it 'allows the same domain for a different school' do
+      described_class.create!(school:, domain: 'example.edu')
+      other_school = create(:school, creator_id: SecureRandom.uuid)
+      other = described_class.new(school: other_school, domain: 'example.edu')
+
+      expect(other).to be_valid
+    end
   end
 end

From cb94318ec88d07d956c0129b0a0f343537b9601d Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 14:59:56 +0100
Subject: [PATCH 6/9] Use type of error instead of string

---
 spec/models/school_email_domain_spec.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index 55385a340..317b89551 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -30,7 +30,7 @@
       duplicate = described_class.new(school:, domain: 'EXAMPLE.EDU')
       duplicate.valid?
 
-      expect(duplicate.errors[:domain]).to include('has already been taken')
+      expect(duplicate.errors.of_kind?(:domain, :taken)).to be(true)
     end
 
     it 'allows the same domain for a different school' do

From ce7c580f5b91660e892761e8f922d01c92c83812 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Tue, 21 Apr 2026 15:39:18 +0100
Subject: [PATCH 7/9] Declare subject above other let statements

---
 spec/models/school_email_domain_spec.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index 317b89551..b9a9f23a1 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -3,10 +3,10 @@
 require 'rails_helper'
 
 RSpec.describe SchoolEmailDomain do
-  let(:school) { create(:school, creator_id: SecureRandom.uuid) }
-
   subject { described_class.new(school:, domain: 'example.edu') }
 
+  let(:school) { create(:school, creator_id: SecureRandom.uuid) }
+
   it { is_expected.to belong_to(:school) }
   it { is_expected.to validate_presence_of(:domain) }
 

From 142142c9dd8041e17866f4d253bb58e8786838d7 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Wed, 22 Apr 2026 10:17:04 +0100
Subject: [PATCH 8/9] Parse and return host when URI provided

---
 app/models/school_email_domain.rb       | 21 +++++++++++++++++++--
 spec/models/school_email_domain_spec.rb | 24 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/app/models/school_email_domain.rb b/app/models/school_email_domain.rb
index a3535bb8c..4b9afc91a 100644
--- a/app/models/school_email_domain.rb
+++ b/app/models/school_email_domain.rb
@@ -1,18 +1,35 @@
 # frozen_string_literal: true
 
+require 'uri'
+
 class SchoolEmailDomain < ApplicationRecord
   belongs_to :school
 
   validates :domain, presence: true
   validates :domain, uniqueness: { scope: :school_id }
 
-  before_validation :format_domain
+  before_validation :validate_domain
 
   private
 
+  def validate_domain
+    self.domain = format_domain
+  end
+
   def format_domain
     return if domain.nil?
 
-    self.domain = domain.to_s.strip.sub(/\A@+/, '').downcase
+    str = domain.to_s.strip.sub(/\A@+/, '')
+    str = uri_host_if_http_url(str) || str
+    return str.downcase
+  end
+
+  def uri_host_if_http_url(str)
+    return unless str.match?(/\Ahttps?:\/\//i)
+
+    uri = URI.parse(str)
+    uri.host if uri.is_a?(URI::HTTP) && uri.host.present?
+  rescue URI::InvalidURIError
+    nil
   end
 end
diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index b9a9f23a1..8a982caf7 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -10,7 +10,31 @@
   it { is_expected.to belong_to(:school) }
   it { is_expected.to validate_presence_of(:domain) }
 
+  describe 'public suffix list validation' do
+    it 'rejects domains that are not valid under the public suffix list' do
+      record = described_class.new(school:, domain: 'com')
+      record.valid?
+
+      expect(record).not_to be_valid
+      expect(record.errors.of_kind?(:domain, :invalid)).to be(true)
+    end
+  end
+
   describe 'domain normalisation' do
+    it 'takes the host from an http URL before other normalisation' do
+      record = described_class.new(school:, domain: 'http://mail.school.edu/path?query=1')
+      record.valid?
+
+      expect(record.domain).to eq('mail.school.edu')
+    end
+
+    it 'takes the host from an https URL before other normalisation' do
+      record = described_class.new(school:, domain: 'https://EXAMPLE.EDU/')
+      record.valid?
+
+      expect(record.domain).to eq('example.edu')
+    end
+
     it 'downcases the domain' do
       record = described_class.new(school:, domain: 'EXAMPLE.EDU')
       record.valid?

From 80f2296747c1a644dcdfb23c07073ebbef8ec536 Mon Sep 17 00:00:00 2001
From: Pete Simonovic <69108995+PetarSimonovic@users.noreply.github.com>
Date: Wed, 22 Apr 2026 11:20:03 +0100
Subject: [PATCH 9/9] Validate domains against Public Suffix List

---
 Gemfile                                 |  1 +
 Gemfile.lock                            |  1 +
 app/models/school_email_domain.rb       | 28 +++++++----
 spec/models/school_email_domain_spec.rb | 62 +++++++++++++++++++++----
 4 files changed, 72 insertions(+), 20 deletions(-)

diff --git a/Gemfile b/Gemfile
index 322112698..6382772ab 100644
--- a/Gemfile
+++ b/Gemfile
@@ -38,6 +38,7 @@ gem 'paper_trail'
 gem 'pg', '~> 1.6'
 gem 'postmark-rails'
 gem 'propshaft'
+gem 'public_suffix', '~> 7.0'
 gem 'puma', '~> 7.2'
 gem 'rack_content_type_default', '~> 1.1'
 gem 'rack-cors'
diff --git a/Gemfile.lock b/Gemfile.lock
index 0cc789d5b..e95e70b90 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -614,6 +614,7 @@ DEPENDENCIES
   postmark-rails
   propshaft
   pry-byebug
+  public_suffix (~> 7.0)
   puma (~> 7.2)
   rack-cors
   rack_content_type_default (~> 1.1)
diff --git a/app/models/school_email_domain.rb b/app/models/school_email_domain.rb
index 4b9afc91a..2068557ea 100644
--- a/app/models/school_email_domain.rb
+++ b/app/models/school_email_domain.rb
@@ -1,31 +1,39 @@
 # frozen_string_literal: true
 
-require 'uri'
-
 class SchoolEmailDomain < ApplicationRecord
   belongs_to :school
 
   validates :domain, presence: true
   validates :domain, uniqueness: { scope: :school_id }
 
-  before_validation :validate_domain
+  before_validation :normalise_domain
+  validate :validate_public_suffix
 
   private
 
-  def validate_domain
-    self.domain = format_domain
+  def normalise_domain
+    return if domain.nil?
+
+    self.domain = build_normalised_domain_string(domain)
   end
 
-  def format_domain
-    return if domain.nil?
+  # Uses the Public Suffix List via the public_suffix gem: values must be a real
+  # hostname with a registrable name, not a bare suffix like com or co.uk.
+  # https://publicsuffix.org
+  def validate_public_suffix
+    return if domain.blank?
+
+    errors.add(:domain, :invalid) unless PublicSuffix.valid?(domain)
+  end
 
-    str = domain.to_s.strip.sub(/\A@+/, '')
+  def build_normalised_domain_string(raw)
+    str = raw.to_s.strip.sub(/\A@+/, '')
     str = uri_host_if_http_url(str) || str
-    return str.downcase
+    str.downcase
   end
 
   def uri_host_if_http_url(str)
-    return unless str.match?(/\Ahttps?:\/\//i)
+    return unless str.match?(%r{\Ahttps?://}i)
 
     uri = URI.parse(str)
     uri.host if uri.is_a?(URI::HTTP) && uri.host.present?
diff --git a/spec/models/school_email_domain_spec.rb b/spec/models/school_email_domain_spec.rb
index 8a982caf7..dd0c1f6a1 100644
--- a/spec/models/school_email_domain_spec.rb
+++ b/spec/models/school_email_domain_spec.rb
@@ -10,16 +10,6 @@
   it { is_expected.to belong_to(:school) }
   it { is_expected.to validate_presence_of(:domain) }
 
-  describe 'public suffix list validation' do
-    it 'rejects domains that are not valid under the public suffix list' do
-      record = described_class.new(school:, domain: 'com')
-      record.valid?
-
-      expect(record).not_to be_valid
-      expect(record.errors.of_kind?(:domain, :invalid)).to be(true)
-    end
-  end
-
   describe 'domain normalisation' do
     it 'takes the host from an http URL before other normalisation' do
       record = described_class.new(school:, domain: 'http://mail.school.edu/path?query=1')
@@ -48,7 +38,59 @@
 
       expect(record.domain).to eq('example.edu')
     end
+  end
+
+  describe 'public suffix list validation' do
+    context 'when the hostname is only a suffix' do
+      it 'rejects com' do
+        record = described_class.new(school:, domain: 'com')
+        record.valid?
+
+        expect(record).not_to be_valid
+        expect(record.errors.of_kind?(:domain, :invalid)).to be(true)
+      end
+
+      it 'rejects edu' do
+        record = described_class.new(school:, domain: 'edu')
+        record.valid?
+
+        expect(record).not_to be_valid
+        expect(record.errors.of_kind?(:domain, :invalid)).to be(true)
+      end
+
+      it 'rejects co.uk' do
+        record = described_class.new(school:, domain: 'co.uk')
+        record.valid?
+
+        expect(record).not_to be_valid
+        expect(record.errors.of_kind?(:domain, :invalid)).to be(true)
+      end
+    end
+
+    context 'when there is at least one registrable label before the public suffix' do
+      it 'accepts a typical school-style .edu domain' do
+        record = described_class.new(school:, domain: 'example.edu')
+        expect(record).to be_valid
+      end
+
+      it 'accepts a subdomain' do
+        record = described_class.new(school:, domain: 'mail.example.edu')
+        expect(record).to be_valid
+      end
+
+      it 'accepts a hostname under a multi-part public suffix' do
+        record = described_class.new(school:, domain: 'school.example.co.uk')
+        expect(record).to be_valid
+      end
+
+      it 'accepts district-style hosts' do
+        record = described_class.new(school:, domain: 'school.k12.tx.us')
+        expect(record).to be_valid
+      end
+    end
+  end
 
+  describe 'domain uniqueness' do
     it 'rejects a duplicate domain for the same school after normalisation' do
       described_class.create!(school:, domain: 'example.edu')
       duplicate = described_class.new(school:, domain: 'EXAMPLE.EDU')