Alow to filter epics by different params

Adds support for label, author, title, state,
sort, and description filters in epic fetch query.

ee/app/graphql/resolvers/epic_resolver.rb

@@ -14,6 +14,22 @@ module Resolvers
              required: false,
              description: 'Filter epics by state'
 
+    argument :search, GraphQL::STRING_TYPE,
+             required: false,
+             description: 'Filter epics by title and description'
+
+    argument :sort, Types::EpicSortEnum,
+             required: false,
+             description: 'List epics by sort order'
+
+    argument :author_username, GraphQL::STRING_TYPE,
+             required: false,
+             description: 'List epics for author'
+
+    argument :label_name, [GraphQL::STRING_TYPE],
+             required: false,
+             description: 'List epics that has given label names'
+
     argument :start_date, Types::TimeType,
              required: false,
              description: 'List epics within a time frame where epics.start_date is between start_date and end_date parameters (end_date parameter must be present)'

ee/app/graphql/types/epic_sort_enum.rb

+# frozen_string_literal: true
+
+module Types
+  class EpicSortEnum < BaseEnum
+    graphql_name 'EpicSort'
+    description 'Roadmap sort values'
+
+    value 'start_date_desc', 'Start date at descending order'
+    value 'start_date_asc', 'Start date at ascending order'
+    value 'end_date_desc', 'End date at descending order'
+    value 'end_date_asc', 'End date at ascending order'
+  end
+end

ee/spec/graphql/resolvers/epic_resolver_spec.rb

@@ -102,6 +102,80 @@ describe Resolvers::EpicResolver do
         end
       end
 
+      context 'with search' do
+        let!(:epic1) { create(:epic, group: group, title: 'first created', description: 'description') }
+        let!(:epic2) { create(:epic, group: group, title: 'second created', description: 'text 1') }
+        let!(:epic3) { create(:epic, group: group, title: 'third', description: 'text 2') }
+
+        it 'filters epics by title' do
+          epics = resolve_epics(search: 'created')
+
+          expect(epics).to match_array([epic1, epic2])
+        end
+
+        it 'filters epics by description' do
+          epics = resolve_epics(search: 'text')
+
+          expect(epics).to match_array([epic2, epic3])
+        end
+      end
+
+      context 'with author_username' do
+        it 'filters epics by author' do
+          user = create(:user)
+          epic = create(:epic, group: group, author: user )
+          create(:epic, group: group)
+
+          epics = resolve_epics(author_username: user.username)
+
+          expect(epics).to match_array([epic])
+        end
+      end
+
+      context 'with label_name' do
+        it 'filters epics by labels' do
+          label_1 = create(:group_label, group: group)
+          label_2 = create(:group_label, group: group)
+          epic_1 = create(:labeled_epic, group: group, labels: [label_1, label_2])
+          create(:labeled_epic, group: group, labels: [label_1])
+          create(:labeled_epic, group: group)
+
+          epics = resolve_epics(label_name: [label_1.title, label_2.title])
+
+          expect(epics).to match_array([epic_1])
+        end
+      end
+
+      context 'with sort' do
+        let!(:epic1) { create(:epic, group: group, title: 'first created', description: 'description', start_date: 10.days.ago, end_date: 10.days.from_now) }
+        let!(:epic2) { create(:epic, group: group, title: 'second created', description: 'text 1', start_date: 20.days.ago, end_date: 20.days.from_now) }
+        let!(:epic3) { create(:epic, group: group, title: 'third', description: 'text 2', start_date: 30.days.ago, end_date: 30.days.from_now) }
+
+        it 'orders epics by start date in descending order' do
+          epics = resolve_epics(sort: 'start_date_desc')
+
+          expect(epics).to match_array([epic3, epic2, epic1])
+        end
+
+        it 'orders epics by start date in ascending order' do
+          epics = resolve_epics(sort: 'start_date_asc')
+
+          expect(epics).to match_array([epic1, epic2, epic3])
+        end
+
+        it 'orders epics by end date in descending order' do
+          epics = resolve_epics(sort: 'start_date_asc')
+
+          expect(epics).to match_array([epic1, epic2, epic3])
+        end
+
+        it 'orders epics by end date in ascending order' do
+          epics = resolve_epics(sort: 'start_date_asc')
+
+          expect(epics).to match_array([epic3, epic2, epic1])
+        end
+      end
+
       context 'with subgroups' do
         let(:sub_group) { create(:group, parent: group) }
         let(:iids)      { [epic1, epic2].map(&:iid) }

ee/spec/graphql/types/epic_sort_enum_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe GitlabSchema.types['EpicSort'] do
+  it { expect(described_class.graphql_name).to eq('EpicSort') }
+
+  it 'exposes all the existing epic sort orders' do
+    expect(described_class.values.keys).to include(*%w[start_date_desc start_date_asc end_date_desc end_date_asc])
+  end
+end