UserService/UserService.DatabaseLayer/Repositories/OrganizationUnitsRepository.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using UserService.DatabaseLayer.DataModels;
using UserService.Infrastructure.DataModels;

namespace UserService.DatabaseLayer.Repositories
{
    public class OrganizationUnitsRepository : BaseRepository<OrganizationUnit>, IOrganizationUnitsRepository
    {
        public OrganizationUnitsRepository() : base(x => x.OrganizationUnits)
        {
        }

        /// <inheritdoc cref="GetAllAsync" />
        public override async Task<IReadOnlyList<OrganizationUnit>> GetAllAsync(
            Expression<Func<OrganizationUnit, bool>>? predicate = null, CancellationToken token = default)
        {
            await using var db = new UserServiceDbContext();
            var rootOus = await Context(db)
                .Include(x => x.Parent)
                .WhereOrDefault(predicate)
                .ToListAsync(token).ConfigureAwait(false);

            IEnumerable<OrganizationUnit> Rec(Node node)
            {
                if (!(node is OrganizationUnit organizationUnit)) yield break;
                yield return organizationUnit;
                foreach (var ouChild in rootOus.Where(x => x.ParentId != null && x.ParentId == organizationUnit.Id))
                {
                    foreach (var unit in Rec(ouChild))
                    {
                        yield return unit;
                    }
                }
            }

            var result = new List<OrganizationUnit>();
            foreach (var ou in rootOus.Where(x => x.ParentId is null))
            {
                result.AddRange(Rec(ou));
            }

            return result;
        }
    }
}