using System;
using System.Collections.Generic;
using Svrnty.CQRS.Events.Abstractions.Subscriptions;

namespace Svrnty.CQRS.Events.Abstractions.Models;

/// <summary>
/// Represents a client's subscription to events for a specific correlation.
/// </summary>
public sealed class EventSubscription
{
    /// <summary>
    /// Unique identifier for this subscription.
    /// </summary>
    public required string SubscriptionId { get; init; }

    /// <summary>
    /// ID of the user/client that created this subscription.
    /// </summary>
    public required string SubscriberId { get; init; }

    /// <summary>
    /// Correlation ID this subscription is listening to.
    /// </summary>
    public required string CorrelationId { get; init; }

    /// <summary>
    /// Event type names the subscriber wants to receive (e.g., "UserInvitationSentEvent").
    /// Empty set means all event types.
    /// </summary>
    public required HashSet<string> EventTypes { get; init; }

    /// <summary>
    /// Event types that will complete/close this subscription when received.
    /// </summary>
    public HashSet<string> TerminalEventTypes { get; init; } = new();

    /// <summary>
    /// How events should be delivered to the subscriber.
    /// </summary>
    public DeliveryMode DeliveryMode { get; init; } = DeliveryMode.Immediate;

    /// <summary>
    /// When this subscription was created.
    /// </summary>
    public DateTimeOffset CreatedAt { get; init; }

    /// <summary>
    /// Optional expiration time for this subscription.
    /// </summary>
    public DateTimeOffset? ExpiresAt { get; init; }

    /// <summary>
    /// When this subscription was completed (terminal event or cancellation).
    /// </summary>
    public DateTimeOffset? CompletedAt { get; set; }

    /// <summary>
    /// Last successfully delivered event sequence number (for catch-up).
    /// </summary>
    public long LastDeliveredSequence { get; set; }

    /// <summary>
    /// Current status of this subscription.
    /// </summary>
    public SubscriptionStatus Status { get; set; } = SubscriptionStatus.Active;

    /// <summary>
    /// Checks if this subscription is expired.
    /// </summary>
    public bool IsExpired => ExpiresAt.HasValue && DateTimeOffset.UtcNow > ExpiresAt.Value;

    /// <summary>
    /// Checks if this subscription should receive the specified event type.
    /// </summary>
    public bool ShouldReceive(string eventType)
    {
        return EventTypes.Count == 0 || EventTypes.Contains(eventType);
    }

    /// <summary>
    /// Checks if the specified event type is a terminal event for this subscription.
    /// </summary>
    public bool IsTerminalEvent(string eventType)
    {
        return TerminalEventTypes.Contains(eventType);
    }
}