Deletion

Facts are immutable, so you cannot really delete them. Instead, you can create a new fact that marks its predecessor as deleted.

[FactType("Construction.Project.Deleted")]
public record ProjectDeleted(Project project, DateTime deletedAt);

var projectADeleted = await j.Fact(new ProjectDeleted(projectA, DateTime.UtcNow));

On its own, this fact does not do anything.

ImmutableList<Project> projects = await j.Query(projectsCreatedByUser, user);

But if you include it in the specification, it will filter out the predecessor from the results.

var projectsCreatedByUser = Given<User>.Match(u =>
    u.Successors().OfType<Project>(p => p.creator)
        .Where(p => !p.Successors().OfType<ProjectDeleted>(d => d.project).Any())
);

ImmutableList<Project> projects = await j.Query(projectsCreatedByUser, user);

Now if you are really concerned about facts never being truly deleted, there is a way to purge unreachable facts. We'll save that for later.

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Restore