using Big.Domain;

namespace Big.Application;

/// <summary>A behandelaar's beoordeling outcome, in domain language.</summary>
public enum BeoordelingsBesluit
{
    /// <summary>Approve — enter the registration in the register.</summary>
    Goedkeuren,

    /// <summary>Reject — turn the registration down.</summary>
    Afwijzen,
}

/// <summary>A behandelaar's decision on a registration.</summary>
public sealed record BeoordeelRegistratieCommand(RegistrationId RegistrationId, BeoordelingsBesluit Besluit);

/// <summary>
/// The beoordeling use case (S-12): apply a behandelaar's decision to a registration.
/// <see cref="BeoordelingsBesluit.Goedkeuren"/> sets the zaak's final status via the ACL (§8.1) and
/// advances the aggregate to INGESCHREVEN; <see cref="BeoordelingsBesluit.Afwijzen"/> advances it to
/// AFGEWEZEN in the domain (propagating a rejection to the zaak, so the openbaar projection reflects
/// it, is a later sub-slice of S-12). After applying the decision it completes the Flowable
/// <c>Beoordelen</c> task (found by registrationId) so the workflow advances (ADR-0013). Both
/// decisions are idempotent — a repeated or redelivered decision that matches the current terminal
/// state is a no-op, so the ACL is not called and the task not completed twice.
/// </summary>
public sealed class BeoordeelRegistratie(IRegistrationStore store, IAclClient acl, IUserTaskClient tasks)
{
    public async Task HandleAsync(BeoordeelRegistratieCommand command, CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(command);

        var registration = await store.GetAsync(command.RegistrationId, ct)
            ?? throw new InvalidOperationException($"No registration {command.RegistrationId} to decide.");

        switch (command.Besluit)
        {
            case BeoordelingsBesluit.Goedkeuren:
                // A repeated approval is a no-op: don't set the zaak status a second time.
                if (registration.Status == RegistrationStatus.Ingeschreven)
                    return;
                if (registration.ZaakUrl is null)
                    throw new InvalidOperationException(
                        $"Registration {command.RegistrationId} has no zaak yet; it cannot be approved.");
                await acl.ApproveZaakAsync(registration.ZaakUrl, ct);
                registration.Approve();
                break;

            case BeoordelingsBesluit.Afwijzen:
                if (registration.Status == RegistrationStatus.Afgewezen)
                    return;
                registration.Reject();
                break;
        }

        await store.SaveAsync(registration, ct);
        await CompleteWorkflowTaskAsync(command.RegistrationId, command.Besluit, ct);
    }

    // Advance the workflow: complete the open Beoordelen task for this registration. If none is open
    // (already completed, or the process hasn't parked yet) the decision still stands — we complete
    // nothing rather than fail.
    private async Task CompleteWorkflowTaskAsync(RegistrationId registrationId, BeoordelingsBesluit besluit, CancellationToken ct)
    {
        var open = await tasks.GetOpenBeoordelingenAsync(ct);
        var task = open.FirstOrDefault(t => t.RegistrationId == registrationId);
        if (task is not null)
            await tasks.CompleteBeoordelingAsync(task.TaskId, besluit, ct);
    }
}