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 keys = new List<string>();
        await CollectDescendants(uow, command.DocumentId, keys, ct);
        if (!string.IsNullOrEmpty(doc.StorageKey))
        {
            keys.Add(doc.StorageKey);
        }

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

        foreach (var key in keys)
        {
            await contentStore.DeleteAsync(key, ct);
        }
    }

    private static async Task CollectDescendants(
        IUnitOfWork uow, Guid parentId,
        List<string> keys, CancellationToken ct)
    {
        var children = await uow.Documents.GetChildrenAsync(parentId, ct);
        foreach (var child in children)
        {
            if (!string.IsNullOrEmpty(child.StorageKey))
            {
                keys.Add(child.StorageKey);
            }
            await CollectDescendants(uow, child.Id, keys, ct);
        }
    }
}