Use active period type, local ActivePeriod class

- Update specs, graphql types and docs

doc/api/graphql/reference/index.md

@@ -2096,8 +2096,7 @@ Describes an incident management on-call rotation.
 
 | Field | Type | Description |
 | ----- | ---- | ----------- |
-| `activePeriodEnd` | String | Active period end time for the on-call rotation. |
-| `activePeriodStart` | String | Active period start time for the on-call rotation. |
+| `activePeriod` | OncallRotationActivePeriodType | Active period for the on-call rotation. |
 | `endsAt` | Time | End date and time of the on-call rotation. |
 | `id` | IncidentManagementOncallRotationID! | ID of the on-call rotation. |
 | `length` | Int | Length of the on-call schedule, in the units specified by lengthUnit. |
@@ -2805,6 +2804,15 @@ The rotation participant and color palette.
 | `id` | IncidentManagementOncallParticipantID! | ID of the on-call participant. |
 | `user` | User! | The user who is participating. |
 
+### OncallRotationActivePeriodType
+
+Active period time range for on-call rotation.
+
+| Field | Type | Description |
+| ----- | ---- | ----------- |
+| `from` | String | The start of the rotation interval. |
+| `to` | String | The end of the rotation interval. |
+
 ### OncallRotationCreatePayload
 
 Autogenerated return type of OncallRotationCreate.

ee/app/graphql/types/incident_management/oncall_rotation_active_period_input_type.rb

@@ -4,7 +4,7 @@ module Types
   module IncidentManagement
     # rubocop: disable Graphql/AuthorizeTypes
     class OncallRotationActivePeriodInputType < BaseInputObject
-      graphql_name 'OncallRotationActivePeriodType'
+      graphql_name 'OncallRotationActivePeriodInputType'
       description 'Active period time range for on-call rotation'
 
       argument :from, GraphQL::STRING_TYPE,

ee/app/graphql/types/incident_management/oncall_rotation_active_period_type.rb

+# frozen_string_literal: true
+
+module Types
+  module IncidentManagement
+    # rubocop: disable Graphql/AuthorizeTypes
+    class OncallRotationActivePeriodType < BaseObject
+      graphql_name 'OncallRotationActivePeriodType'
+      description 'Active period time range for on-call rotation'
+
+      field :from, GraphQL::STRING_TYPE,
+                null: true,
+                description: 'The start of the rotation interval.',
+                method: :start_time
+
+      field :to, GraphQL::STRING_TYPE,
+                null: true,
+                description: 'The end of the rotation interval.',
+                method: :end_time
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end

ee/app/graphql/types/incident_management/oncall_rotation_type.rb

@@ -38,15 +38,10 @@ module Types
             null: true,
             description: 'Unit of the on-call rotation length.'
 
-      field :active_period_start,
-            GraphQL::STRING_TYPE,
-            null: true,
-            description: 'Active period start time for the on-call rotation.'
-
-      field :active_period_end,
-            GraphQL::STRING_TYPE,
+      field :active_period,
+            Types::IncidentManagement::OncallRotationActivePeriodType,
             null: true,
-            description: 'Active period end time for the on-call rotation.'
+            description: 'Active period for the on-call rotation.'
 
       field :participants,
             ::Types::IncidentManagement::OncallParticipantType.connection_type,

ee/app/models/incident_management/oncall_rotation.rb

@@ -4,6 +4,23 @@ module IncidentManagement
   class OncallRotation < ApplicationRecord
     include Gitlab::Utils::StrongMemoize
 
+    ActivePeriod = Struct.new(:start_time, :end_time) do
+      def present?
+        start_time && end_time
+      end
+
+      def end_after_start?
+        end_time > start_time if present?
+      end
+
+      def for_date(date)
+        [
+          date.change(hour: start_time.hour, min: start_time.min),
+          date.change(hour: end_time.hour, min: end_time.min)
+        ]
+      end
+    end
+
     self.table_name = 'incident_management_oncall_rotations'
 
     enum length_unit: {
@@ -59,28 +76,12 @@ module IncidentManagement
       weeks? ? (7 * length) : length
     end
 
-    def has_shift_active_period?
-      return false if hours?
-
-      active_period_start.present?
-    end
-
-    def active_period_times
-      return unless has_shift_active_period?
-
-      strong_memoize(:active_period_times) do
-        {
-          start: active_period_start,
-          end: active_period_end
-        }
-      end
+    def active_period
+      ActivePeriod.new(active_period_start, active_period_end)
     end
 
-    def active_period(date)
-      [
-        date.change(hour: active_period_times[:start].hour, min: active_period_times[:start].min),
-        date.change(hour: active_period_times[:end].hour, min: active_period_times[:end].min)
-      ]
+    def has_shift_active_period?
+      !hours? && active_period.present?
     end
 
     private
@@ -90,12 +91,11 @@ module IncidentManagement
     end
 
     def active_period_end_after_start
-      return unless active_period_start && active_period_end
+      return unless active_period.present?
+      return if active_period.end_after_start?
 
-      unless active_period_end > active_period_start
       errors.add(:active_period_end, _('must be later than active period start'))
     end
-    end
 
     def no_active_period_for_hourly_shifts
       if active_period_start || active_period_end

ee/lib/incident_management/oncall_shift_generator.rb

@@ -130,7 +130,7 @@ module IncidentManagement
           #     shift_count = 2                    -> we're calculating the shift for the 3rd day
           # starts_at = Monday 00:00:00 + 8.hours + 2.days => Thursday 08:00:00
 
-          starts_at, ends_at = rotation.active_period(shift_cycle_starts_at + shift_count.days)
+          starts_at, ends_at = rotation.active_period.for_date(shift_cycle_starts_at + shift_count.days)
 
           shift_for(participant, starts_at, limit_end_time(ends_at))
         end

ee/spec/graphql/types/incident_management/oncall_rotation_type_spec.rb

@@ -16,8 +16,7 @@ RSpec.describe GitlabSchema.types['IncidentManagementOncallRotation'] do
       length
       length_unit
       participants
-      active_period_start
-      active_period_end
+      active_period
       shifts
     ]
 

ee/spec/models/incident_management/oncall_rotation_spec.rb

@@ -83,7 +83,7 @@ RSpec.describe IncidentManagement::OncallRotation do
         end
       end
 
-      context 'end time after start time' do
+      context 'end time before start time' do
         it 'raises a validation error if an active period is set' do
           subject.active_period_start = '17:00'
           subject.active_period_end = '08:00'