Add Gitlab::Serverless::FunctionURI class

- Encapsulate functionality for parsing and
  generating function URIs in
  Gitlab::Serverless::FunctionURI
- Update references to Serverless with global
  scope operator
- Delegate Serverless::DomainCluster#domain to
  PagesDomain

Relates to https://gitlab.com/gitlab-org/gitlab/issues/195964

app/models/clusters/applications/knative.rb

@@ -11,7 +11,7 @@ module Clusters
 
       self.table_name = 'clusters_applications_knative'
 
-      has_one :serverless_domain_cluster, class_name: 'Serverless::DomainCluster', foreign_key: 'clusters_applications_knative_id', inverse_of: :knative
+      has_one :serverless_domain_cluster, class_name: '::Serverless::DomainCluster', foreign_key: 'clusters_applications_knative_id', inverse_of: :knative
 
       include ::Clusters::Concerns::ApplicationCore
       include ::Clusters::Concerns::ApplicationStatus

app/models/serverless/domain_cluster.rb

@@ -15,5 +15,7 @@ module Serverless
               format: { with: HEX_REGEXP, message: 'only allows hex characters' }
 
     default_value_for(:uuid, allows_nil: false) { Gitlab::Serverless::Domain.generate_uuid }
+
+    delegate :domain, to: :pages_domain
   end
 end

lib/gitlab/serverless/function_uri.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Serverless
+    class FunctionURI < URI::HTTPS
+      SERVERLESS_DOMAIN_REGEXP = %r{^(?<scheme>https?://)?(?<function>[^.]+)-(?<cluster_left>\h{2})a1(?<cluster_middle>\h{10})f2(?<cluster_right>\h{2})(?<environment_id>\h+)-(?<environment_slug>[^.]+)\.(?<domain>.+)}.freeze
+
+      attr_reader :function, :cluster, :environment
+
+      def initialize(function: nil, cluster: nil, environment: nil)
+        initialize_required_argument(:function, function)
+        initialize_required_argument(:cluster, cluster)
+        initialize_required_argument(:environment, environment)
+
+        @host = "#{function}-#{cluster.uuid[0..1]}a1#{cluster.uuid[2..-3]}f2#{cluster.uuid[-2..-1]}#{"%x" % environment.id}-#{environment.slug}.#{cluster.domain}"
+
+        super('https', nil, host, nil, nil, nil, nil, nil, nil)
+      end
+
+      def self.parse(uri)
+        match = SERVERLESS_DOMAIN_REGEXP.match(uri)
+        return unless match
+
+        cluster = ::Serverless::DomainCluster.find(match[:cluster_left] + match[:cluster_middle] + match[:cluster_right])
+        return unless cluster
+
+        environment = ::Environment.find(match[:environment_id].to_i(16))
+        return unless environment&.slug == match[:environment_slug]
+
+        new(
+          function: match[:function],
+          cluster: cluster,
+          environment: environment
+        )
+      end
+
+      private
+
+      def initialize_required_argument(name, value)
+        raise ArgumentError.new("missing argument: #{name}") unless value
+
+        instance_variable_set("@#{name}".to_sym, value)
+      end
+    end
+  end
+end

spec/factories/pages_domains.rb

@@ -374,5 +374,10 @@ x6zG6WoibsbsJMj70nwseUnPTBQNDP+j61RJjC/r
 -----END EC PRIVATE KEY-----'
       end
     end
+
+    trait :instance_serverless do
+      wildcard { true }
+      domain_type { :instance }
+    end
   end
 end

spec/factories/serverless/domain_cluster.rb

 # frozen_string_literal: true
 
 FactoryBot.define do
-  factory :serverless_domain_cluster, class: 'Serverless::DomainCluster' do
+  factory :serverless_domain_cluster, class: '::Serverless::DomainCluster' do
     pages_domain { create(:pages_domain) }
     knative { create(:clusters_applications_knative) }
     creator { create(:user) }

spec/lib/gitlab/prometheus/queries/knative_invocation_query_spec.rb

@@ -6,7 +6,7 @@ describe Gitlab::Prometheus::Queries::KnativeInvocationQuery do
   include PrometheusHelpers
 
   let(:project) { create(:project) }
-  let(:serverless_func) { Serverless::Function.new(project, 'test-name', 'test-ns') }
+  let(:serverless_func) { ::Serverless::Function.new(project, 'test-name', 'test-ns') }
   let(:client) { double('prometheus_client') }
 
   subject { described_class.new(client) }

spec/lib/gitlab/serverless/function_uri_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Serverless::FunctionURI do
+  let(:function) { 'test-function' }
+  let(:domain) { 'serverless.gitlab.io' }
+  let(:pages_domain) { create(:pages_domain, :instance_serverless, domain: domain) }
+  let!(:cluster) { create(:serverless_domain_cluster, uuid: 'abcdef12345678', pages_domain: pages_domain) }
+  let(:valid_cluster) { 'aba1cdef123456f278' }
+  let(:invalid_cluster) { 'aba1cdef123456f178' }
+  let!(:environment) { create(:environment, name: 'test') }
+
+  let(:valid_uri) { "https://#{function}-#{valid_cluster}#{"%x" % environment.id}-#{environment.slug}.#{domain}" }
+  let(:valid_fqdn) { "#{function}-#{valid_cluster}#{"%x" % environment.id}-#{environment.slug}.#{domain}" }
+  let(:invalid_uri) { "https://#{function}-#{invalid_cluster}#{"%x" % environment.id}-#{environment.slug}.#{domain}" }
+
+  shared_examples 'a valid FunctionURI class' do
+    describe '#to_s' do
+      it 'matches valid URI' do
+        expect(subject.to_s).to eq valid_uri
+      end
+    end
+
+    describe '#function' do
+      it 'returns function' do
+        expect(subject.function).to eq function
+      end
+    end
+
+    describe '#cluster' do
+      it 'returns cluster' do
+        expect(subject.cluster).to eq cluster
+      end
+    end
+
+    describe '#environment' do
+      it 'returns environment' do
+        expect(subject.environment).to eq environment
+      end
+    end
+  end
+
+  describe '.new' do
+    context 'with valid arguments' do
+      subject { described_class.new(function: function, cluster: cluster, environment: environment) }
+
+      it_behaves_like 'a valid FunctionURI class'
+    end
+
+    context 'with invalid arguments' do
+      subject { described_class.new(function: function, environment: environment) }
+
+      it 'raises an exception' do
+        expect { subject }.to raise_error(ArgumentError)
+      end
+    end
+  end
+
+  describe '.parse' do
+    context 'with valid URI' do
+      subject { described_class.parse(valid_uri) }
+
+      it_behaves_like 'a valid FunctionURI class'
+    end
+
+    context 'with valid FQDN' do
+      subject { described_class.parse(valid_fqdn) }
+
+      it_behaves_like 'a valid FunctionURI class'
+    end
+
+    context 'with invalid URI' do
+      subject { described_class.parse(invalid_uri) }
+
+      it 'returns nil' do
+        expect(subject).to be_nil
+      end
+    end
+  end
+end

spec/models/clusters/applications/knative_spec.rb

@@ -17,7 +17,7 @@ describe Clusters::Applications::Knative do
   end
 
   describe 'associations' do
-    it { is_expected.to have_one(:serverless_domain_cluster).class_name('Serverless::DomainCluster').with_foreign_key('clusters_applications_knative_id').inverse_of(:knative) }
+    it { is_expected.to have_one(:serverless_domain_cluster).class_name('::Serverless::DomainCluster').with_foreign_key('clusters_applications_knative_id').inverse_of(:knative) }
   end
 
   describe 'when cloud run is enabled' do

spec/models/serverless/domain_cluster_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Serverless::DomainCluster do
+describe ::Serverless::DomainCluster do
   subject { create(:serverless_domain_cluster) }
 
   describe 'validations' do
@@ -46,4 +46,8 @@ describe Serverless::DomainCluster do
       end
     end
   end
+
+  describe 'domain' do
+    it { is_expected.to respond_to(:domain) }
+  end
 end

spec/models/serverless/function_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Serverless::Function do
+describe ::Serverless::Function do
   let(:project) { create(:project) }
   let(:func) { described_class.new(project, 'test', 'test-ns') }