using System;
using Svrnty.CQRS.Events.Abstractions.EventStore;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace Svrnty.CQRS.Events.Abstractions.Subscriptions;

/// <summary>
/// Service responsible for delivering events to persistent subscriptions.
/// </summary>
public interface IPersistentSubscriptionDeliveryService
{
    /// <summary>
    /// Deliver an event to all matching subscriptions for a correlation ID.
    /// </summary>
    /// <param name="correlationId">The correlation ID to match subscriptions against.</param>
    /// <param name="event">The event to deliver.</param>
    /// <param name="sequence">The sequence number assigned to this event in the event store.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Number of subscriptions the event was delivered to.</returns>
    Task<int> DeliverEventAsync(
        string correlationId,
        ICorrelatedEvent @event,
        long sequence,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Deliver missed events to a subscription (catch-up).
    /// </summary>
    /// <param name="subscriptionId">The subscription to catch up.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Number of events delivered during catch-up.</returns>
    Task<int> CatchUpSubscriptionAsync(
        string subscriptionId,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Get pending events for a subscription (not yet delivered).
    /// </summary>
    /// <param name="subscriptionId">The subscription ID.</param>
    /// <param name="limit">Maximum number of events to retrieve.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>List of pending events.</returns>
    Task<IReadOnlyList<ICorrelatedEvent>> GetPendingEventsAsync(
        string subscriptionId,
        int limit = 100,
        CancellationToken cancellationToken = default);
}