ersatztv/ErsatzTV/Controllers/SortController.cs

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using ErsatzTV.Application.MediaCollections.Commands;
using MediatR;
using Microsoft.AspNetCore.Mvc;

namespace ErsatzTV.Controllers
{
    [ApiController]
    [ApiExplorerSettings(IgnoreApi = true)]
    public class SortController : ControllerBase
    {
        private readonly IMediator _mediator;

        public SortController(IMediator mediator) => _mediator = mediator;

        [HttpPost("media/collections/{collectionId}/items")]
        public Task SortCollectionItems(
            int collectionId,
            [FromForm]
            SortedMediaItemIds sortedMediaItemIds)
        {
            var ids = sortedMediaItemIds.Item.Map(int.Parse).ToList();

            var request = new UpdateCollectionCustomOrder(
                collectionId,
                ids.Map(i => new MediaItemCustomOrder(i, ids.IndexOf(i))).ToList());

            return _mediator.Send(request);
        }
    }

    public record SortedMediaItemIds(List<string> Item);
}