Umbraco V12: Extending Content Delivery API

AuthorContentIndexer.cs

using Umbraco.Cms.Core;
using Umbraco.Cms.Core.DeliveryApi;
using Umbraco.Cms.Core.Models;
using Umbraco.Cms.Core.Web;

namespace ExampleProject.ContentDeliveryApi
{
    public class AuthorContentIndexer : IContentIndexHandler
    {
        private readonly IUmbracoContextFactory _umbracoContextFactory;

        public AuthorContentIndexer(IUmbracoContextFactory umbracoContextFactory)
        {
            _umbracoContextFactory = umbracoContextFactory;
        }

        public IEnumerable<IndexField> GetFields()
        {
            return new[]
            {
                new IndexField
                {
                    FieldName = "author",
                    FieldType = FieldType.StringSortable,
                    VariesByCulture = false
                }
            };
        }

        public IEnumerable<IndexFieldValue> GetFieldValues(IContent content, string? culture)
        {
            var authorId = content.GetValue<GuidUdi>("author");

            if (authorId == null)
            {
                return Enumerable.Empty<IndexFieldValue>();
            }

            var ctxRef = _umbracoContextFactory.EnsureUmbracoContext();

            if (ctxRef != null)
            {
                var pickedAuthorNode = ctxRef?.UmbracoContext?.Content?.GetById(authorId);

                if (pickedAuthorNode != null)
                {
                    return new[]
                    {
                        new IndexFieldValue
                        {
                            FieldName = "author",
                            Values = new object[] { pickedAuthorNode.Name }
                        }
                    };
                }
            }

            return Enumerable.Empty<IndexFieldValue>();
        }
    }
}

AuthorFilter.cs

using Umbraco.Cms.Core.DeliveryApi;

namespace ExampleProject.ContentDeliveryApi
{
    public class AuthorFilter : IFilterHandler
    {
        private const string FilterType = "author:";

        public FilterOption BuildFilterOption(string filter)
        {
            var authorFilterValue = filter.Substring(FilterType.Length);

            return new FilterOption
            {
                FieldName = "author",
                Operator = FilterOperation.Is,
                Values = new[] { authorFilterValue }
            };
        }

        public bool CanHandle(string query)
        {
            return string.IsNullOrWhiteSpace(query) ? false : query.StartsWith(FilterType, StringComparison.OrdinalIgnoreCase);
        }
    }
}

AuthorSort.cs

using Umbraco.Cms.Core;
using Umbraco.Cms.Core.DeliveryApi;

namespace ExampleProject.ContentDeliveryApi
{
    public class AuthorSort : ISortHandler
    {
        private const string SortType = "author:";

        public SortOption BuildSortOption(string sort)
        {
            var sortDirection = sort.Substring(SortType.Length);

            return new SortOption
            {
                Direction = sortDirection.StartsWith("asc", StringComparison.OrdinalIgnoreCase) ? Direction.Ascending : Direction.Descending,
                FieldName = "author"
            };
        }

        public bool CanHandle(string query)
        {
            return string.IsNullOrWhiteSpace(query) ? false : query.StartsWith(SortType, StringComparison.OrdinalIgnoreCase);
        }
    }
}