2 files changed, 178 insertions, 0 deletions
diff --git a/lib/gitlab/alerting/alert.rb b/lib/gitlab/alerting/alert.rb
new file mode 100644
index 00000000000..531307b93d4
--- /dev/null
+++ b/lib/gitlab/alerting/alert.rb
@@ -0,0 +1,167 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Alerting
+    class Alert
+      include ActiveModel::Model
+      include Gitlab::Utils::StrongMemoize
+      include Presentable
+
+      attr_accessor :project, :payload
+
+      def gitlab_alert
+        strong_memoize(:gitlab_alert) do
+          parse_gitlab_alert_from_payload
+        end
+      end
+
+      def metric_id
+        strong_memoize(:metric_id) do
+          payload&.dig('labels', 'gitlab_alert_id')
+        end
+      end
+
+      def title
+        strong_memoize(:title) do
+          gitlab_alert&.title || parse_title_from_payload
+        end
+      end
+
+      def description
+        strong_memoize(:description) do
+          parse_description_from_payload
+        end
+      end
+
+      def environment
+        strong_memoize(:environment) do
+          gitlab_alert&.environment || parse_environment_from_payload
+        end
+      end
+
+      def annotations
+        strong_memoize(:annotations) do
+          parse_annotations_from_payload || []
+        end
+      end
+
+      def starts_at
+        strong_memoize(:starts_at) do
+          parse_datetime_from_payload('startsAt')
+        end
+      end
+
+      def starts_at_raw
+        strong_memoize(:starts_at_raw) do
+          payload&.dig('startsAt')
+        end
+      end
+
+      def ends_at
+        strong_memoize(:ends_at) do
+          parse_datetime_from_payload('endsAt')
+        end
+      end
+
+      def full_query
+        strong_memoize(:full_query) do
+          gitlab_alert&.full_query || parse_expr_from_payload
+        end
+      end
+
+      def alert_markdown
+        strong_memoize(:alert_markdown) do
+          parse_alert_markdown_from_payload
+        end
+      end
+
+      def status
+        strong_memoize(:status) do
+          payload&.dig('status')
+        end
+      end
+
+      def firing?
+        status == 'firing'
+      end
+
+      def resolved?
+        status == 'resolved'
+      end
+
+      def gitlab_managed?
+        metric_id.present?
+      end
+
+      def valid?
+        payload.respond_to?(:dig) && project && title && starts_at
+      end
+
+      def present
+        super(presenter_class: Projects::Prometheus::AlertPresenter)
+      end
+
+      private
+
+      def parse_environment_from_payload
+        environment_name = payload&.dig('labels', 'gitlab_environment_name')
+
+        return unless environment_name
+
+        EnvironmentsFinder.new(project, nil, { name: environment_name })
+          .find
+          &.first
+      end
+
+      def parse_gitlab_alert_from_payload
+        return unless metric_id
+
+        Projects::Prometheus::AlertsFinder
+          .new(project: project, metric: metric_id)
+          .execute
+          .first
+      end
+
+      def parse_title_from_payload
+        payload&.dig('annotations', 'title') ||
+          payload&.dig('annotations', 'summary') ||
+          payload&.dig('labels', 'alertname')
+      end
+
+      def parse_description_from_payload
+        payload&.dig('annotations', 'description')
+      end
+
+      def parse_annotations_from_payload
+        payload&.dig('annotations')&.map do |label, value|
+          Alerting::AlertAnnotation.new(label: label, value: value)
+        end
+      end
+
+      def parse_datetime_from_payload(field)
+        value = payload&.dig(field)
+        return unless value
+
+        Time.rfc3339(value)
+      rescue ArgumentError
+      end
+
+      # Parses `g0.expr` from `generatorURL`.
+      #
+      # Example: http://localhost:9090/graph?g0.expr=vector%281%29&g0.tab=1
+      def parse_expr_from_payload
+        url = payload&.dig('generatorURL')
+        return unless url
+
+        uri = URI(url)
+
+        Rack::Utils.parse_query(uri.query).fetch('g0.expr')
+      rescue URI::InvalidURIError, KeyError
+      end
+
+      def parse_alert_markdown_from_payload
+        payload&.dig('annotations', 'gitlab_incident_markdown')
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/alerting/alert_annotation.rb b/lib/gitlab/alerting/alert_annotation.rb
new file mode 100644
index 00000000000..a4b3a97b08c
--- /dev/null
+++ b/lib/gitlab/alerting/alert_annotation.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Alerting
+    class AlertAnnotation
+      include ActiveModel::Model
+
+      attr_accessor :label, :value
+    end
+  end
+end