mws.backend.dotnet/mws.application/Documents/Queries/GetDocumentTree.cs

using AutoMapper;
using MediatR;
using Mws.Application.Common;
using Mws.Application.Permissions;

namespace Mws.Application.Documents;

public record GetDocumentTreeQuery(Guid UserId, Guid ProjectId) : IRequest<List<DocumentNodeDto>>;

public class GetDocumentTreeHandler(IUnitOfWork uow, IMapper mapper) : IRequestHandler<GetDocumentTreeQuery, List<DocumentNodeDto>>
{
    public async Task<List<DocumentNodeDto>> Handle(GetDocumentTreeQuery query, CancellationToken ct)
    {
        await DocumentAccess.EnsureDocumentPermissionAsync(uow, query.UserId, query.ProjectId, PermissionAction.View, ct);

        var docs = await uow.Documents.GetTreeForProjectAsync(query.ProjectId, ct);

        var nodes = docs.ToDictionary(d => d.Id, d => mapper.Map<DocumentNodeDto>(d));

        var roots = new List<DocumentNodeDto>();
        foreach (var node in nodes.Values)
        {
            if (node.ParentId is { } parentId && nodes.TryGetValue(parentId, out var parent))
            {
                parent.Children.Add(node);
            }
            else
            {
                roots.Add(node);
            }
        }

        return roots;
    }
}