using MediatR;
using mws.backend.dotnet.application.Common;
using mws.backend.dotnet.application.Permissions;

namespace mws.backend.dotnet.application.Documents;

public record DeleteDocumentCommand(Guid UserId, Guid DocumentId) : IRequest;

public class DeleteDocumentHandler(IUnitOfWork uow, IDocumentContentStore contentStore)
    : IRequestHandler<DeleteDocumentCommand>
{
    public async Task Handle(DeleteDocumentCommand command, CancellationToken ct)
    {
        var doc = await DocumentAccess.GetDocumentForUserAsync(uow, command.UserId, command.DocumentId, ct);
        await DocumentAccess.EnsureDocumentPermissionAsync(uow, command.UserId, doc.ProjectId, PermissionAction.Delete, ct);

        var allIds = new List<(Guid ProjectId, Guid DocumentId)>();
        await CollectDescendants(uow, command.DocumentId, doc.ProjectId, allIds, ct);
        allIds.Add((doc.ProjectId, doc.Id));

        await DocumentAccess.DeleteDescendantsAsync(uow, command.DocumentId, ct);
        uow.Documents.Remove(doc);
        await uow.SaveChangesAsync(ct);

        foreach (var (projectId, documentId) in allIds)
        {
            await contentStore.DeleteAsync(projectId, documentId, ct);
        }
    }

    private static async Task CollectDescendants(
        IUnitOfWork uow, Guid parentId, Guid projectId,
        List<(Guid ProjectId, Guid DocumentId)> ids, CancellationToken ct)
    {
        var children = await uow.Documents.GetChildrenAsync(parentId, ct);
        foreach (var child in children)
        {
            ids.Add((projectId, child.Id));
            await CollectDescendants(uow, child.Id, projectId, ids, ct);
        }
    }
}