Extract PrometheusAlertPresenter class

Extract `AlertManagement::PrometheusAlertPresenter`
from `AlertManagement::AlertPresenter`
to present Prometheus specific alerts.

app/models/alert_management/alert.rb

@@ -164,6 +164,12 @@ module AlertManagement
       project.execute_services(hook_data, :alert_hooks)
     end
 
+    def present
+      return super(presenter_class: AlertManagement::PrometheusAlertPresenter) if prometheus?
+
+      super
+    end
+
     private
 
     def hook_data

app/presenters/alert_management/alert_presenter.rb

@@ -47,11 +47,7 @@ module AlertManagement
       end
     end
 
-    def alert_markdown
-      return unless alert.prometheus?
-
-      alerting_alert.alert_markdown
-    end
+    def alert_markdown; end
 
     def metadata_list
       metadata = []
@@ -78,22 +74,14 @@ module AlertManagement
     end
 
     def details_list
-      return alerting_alert.annotation_list if alert.prometheus?
-
       alert.details
         .map { |label, value| list_item(label, value) }
         .join(MARKDOWN_LINE_BREAK)
     end
 
-    def metric_embed_for_alert
-      return unless alert.prometheus?
+    def metric_embed_for_alert; end
 
-      alerting_alert.metric_embed_for_alert
-    end
-
-    def full_query
-      alert.prometheus? ? alerting_alert.full_query : nil
-    end
+    def full_query; end
 
     def list_item(key, value)
       "**#{key}:** #{value}".strip

app/presenters/alert_management/prometheus_alert_presenter.rb

+# frozen_string_literal: true
+
+module AlertManagement
+  class PrometheusAlertPresenter < AlertManagement::AlertPresenter
+    private
+
+    def alert_markdown
+      alerting_alert.alert_markdown
+    end
+
+    def details_list
+      alerting_alert.annotation_list
+    end
+
+    def metric_embed_for_alert
+      alerting_alert.metric_embed_for_alert
+    end
+
+    def full_query
+      alerting_alert.full_query
+    end
+  end
+end

spec/models/alert_management/alert_spec.rb

@@ -337,4 +337,22 @@ describe AlertManagement::Alert do
       expect { subject }.to change { alert.events }.by(1)
     end
   end
+
+  describe '#present' do
+    context 'when alert is generic' do
+      let(:alert) { build(:alert_management_alert) }
+
+      it 'uses generic alert presenter' do
+        expect(alert.present).to be_kind_of(AlertManagement::AlertPresenter)
+      end
+    end
+
+    context 'when alert is Prometheus specific' do
+      let(:alert) { build(:alert_management_alert, :prometheus) }
+
+      it 'uses Prometheus Alert presenter' do
+        expect(alert.present).to be_kind_of(AlertManagement::PrometheusAlertPresenter)
+      end
+    end
+  end
 end

spec/presenters/alert_management/alert_presenter_spec.rb

@@ -11,33 +11,15 @@ RSpec.describe AlertManagement::AlertPresenter do
       'custom' => { 'param' => 73 }
     }
   end
-  let_it_be(:generic_alert) do
+  let_it_be(:alert) do
     create(:alert_management_alert, :with_host, :with_service, :with_monitoring_tool, project: project, payload: generic_payload)
   end
-  let_it_be(:prometheus_payload) do
-    {
-      'annotations' => {
-        'title' => 'Alert title',
-        'gitlab_incident_markdown' => '**`markdown example`**',
-        'custom annotation' => 'custom annotation value'
-      },
-      'startsAt' => '2020-04-27T10:10:22.265949279Z',
-      'generatorURL' => 'http://8d467bd4607a:9090/graph?g0.expr=vector%281%29&g0.tab=1'
-    }
-  end
-  let_it_be(:prometheus_alert) do
-    create(:alert_management_alert, :prometheus, project: project, payload: prometheus_payload)
-  end
-  let(:alert) { generic_alert }
 
   subject(:presenter) { described_class.new(alert) }
 
   describe '#issue_description' do
     let(:markdown_line_break) { '  ' }
 
-    context 'with generic alert' do
-      let(:alert) { generic_alert }
-
     it 'returns an alert issue description' do
       expect(presenter.issue_description).to eq(
         <<~MARKDOWN.chomp
@@ -56,30 +38,4 @@ RSpec.describe AlertManagement::AlertPresenter do
       )
     end
   end
-
-    context 'with prometheus alert' do
-      let(:alert) { prometheus_alert }
-
-      it 'returns an alert issue description' do
-        expect(presenter.issue_description).to eq(
-          <<~MARKDOWN.chomp
-            #### Summary
-
-            **Start time:** #{presenter.start_time}#{markdown_line_break}
-            **Severity:** #{presenter.severity}#{markdown_line_break}
-            **full_query:** `vector(1)`#{markdown_line_break}
-            **Monitoring tool:** Prometheus
-
-            #### Alert Details
-
-            **custom annotation:** custom annotation value
-
-            ---
-
-            **`markdown example`**
-          MARKDOWN
-        )
-      end
-    end
-  end
 end

spec/presenters/alert_management/prometheus_alert_presenter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe AlertManagement::PrometheusAlertPresenter do
+  let_it_be(:project) { create(:project) }
+  let_it_be(:prometheus_payload) do
+    {
+      'annotations' => {
+        'title' => 'Alert title',
+        'gitlab_incident_markdown' => '**`markdown example`**',
+        'custom annotation' => 'custom annotation value'
+      },
+      'startsAt' => '2020-04-27T10:10:22.265949279Z',
+      'generatorURL' => 'http://8d467bd4607a:9090/graph?g0.expr=vector%281%29&g0.tab=1'
+    }
+  end
+  let_it_be(:alert) do
+    create(:alert_management_alert, :prometheus, project: project, payload: prometheus_payload)
+  end
+
+  subject(:presenter) { described_class.new(alert) }
+
+  describe '#issue_description' do
+    let(:markdown_line_break) { '  ' }
+
+    it 'returns an alert issue description' do
+      expect(presenter.issue_description).to eq(
+        <<~MARKDOWN.chomp
+          #### Summary
+
+          **Start time:** #{presenter.start_time}#{markdown_line_break}
+          **Severity:** #{presenter.severity}#{markdown_line_break}
+          **full_query:** `vector(1)`#{markdown_line_break}
+          **Monitoring tool:** Prometheus
+
+          #### Alert Details
+
+          **custom annotation:** custom annotation value
+
+          ---
+
+          **`markdown example`**
+        MARKDOWN
+      )
+    end
+  end
+end