using System;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;

namespace Svrnty.CQRS.Events.SignalR;

/// <summary>
/// Extension methods for registering SignalR event streaming services.
/// </summary>
public static class ServiceCollectionExtensions
{
    /// <summary>
    /// Adds SignalR-based real-time event streaming to the service collection.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <returns>The service collection for method chaining.</returns>
    /// <remarks>
    /// <para>
    /// This registers the EventStreamHub and enables real-time event push to browser clients.
    /// Clients can connect via SignalR and subscribe to event streams.
    /// </para>
    /// <para>
    /// <strong>Prerequisites:</strong>
    /// - Call <c>services.AddSignalR()</c> first to register SignalR core services
    /// - Event streaming must be configured via <c>AddSvrntyEvents()</c>
    /// </para>
    /// </remarks>
    /// <example>
    /// <code>
    /// var builder = WebApplication.CreateBuilder(args);
    ///
    /// // Register SignalR and event streaming
    /// builder.Services.AddSignalR();
    /// builder.Services.AddSvrntyEvents();
    /// builder.Services.AddEventStreamHub();  // Enable SignalR event streaming
    ///
    /// var app = builder.Build();
    ///
    /// // Map the hub endpoint
    /// app.MapHub&lt;EventStreamHub&gt;("/hubs/events");
    ///
    /// app.Run();
    /// </code>
    /// </example>
    public static IServiceCollection AddEventStreamHub(this IServiceCollection services)
    {
        if (services == null)
            throw new ArgumentNullException(nameof(services));

        // EventStreamHub is automatically registered by SignalR when mapped
        // No explicit registration needed here

        return services;
    }

    /// <summary>
    /// Maps the EventStreamHub to the specified endpoint.
    /// </summary>
    /// <param name="app">The web application.</param>
    /// <param name="pattern">The URL pattern for the hub endpoint (default: "/hubs/events").</param>
    /// <returns>The web application for method chaining.</returns>
    /// <example>
    /// <code>
    /// app.MapEventStreamHub();  // Maps to /hubs/events
    /// app.MapEventStreamHub("/api/events");  // Custom endpoint
    /// </code>
    /// </example>
    public static WebApplication MapEventStreamHub(
        this WebApplication app,
        string pattern = "/hubs/events")
    {
        if (app == null)
            throw new ArgumentNullException(nameof(app));

        if (string.IsNullOrWhiteSpace(pattern))
            throw new ArgumentException("Pattern cannot be null or empty", nameof(pattern));

        app.MapHub<EventStreamHub>(pattern);

        return app;
    }

    /// <summary>
    /// Adds persistent subscription support via SignalR to the service collection.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <returns>The service collection for method chaining.</returns>
    /// <remarks>
    /// <para>
    /// This registers the PersistentSubscriptionHub for correlation-based event subscriptions
    /// that persist across disconnections and support selective event filtering.
    /// </para>
    /// <para>
    /// <strong>Prerequisites:</strong>
    /// - Call <c>services.AddSignalR()</c> first to register SignalR core services
    /// - Call <c>services.AddPersistentSubscriptions()</c> to register subscription infrastructure
    /// - Event streaming must be configured via <c>AddSvrntyEvents()</c>
    /// </para>
    /// </remarks>
    /// <example>
    /// <code>
    /// var builder = WebApplication.CreateBuilder(args);
    ///
    /// // Register services
    /// builder.Services.AddSignalR();
    /// builder.Services.AddSvrntyEvents();
    /// builder.Services.AddPersistentSubscriptions();
    /// builder.Services.AddPersistentSubscriptionHub();
    ///
    /// var app = builder.Build();
    ///
    /// // Map the hub endpoint
    /// app.MapPersistentSubscriptionHub("/hubs/subscriptions");
    ///
    /// app.Run();
    /// </code>
    /// </example>
    public static IServiceCollection AddPersistentSubscriptionHub(this IServiceCollection services)
    {
        if (services == null)
            throw new ArgumentNullException(nameof(services));

        // PersistentSubscriptionHub is automatically registered by SignalR when mapped
        // No explicit registration needed here

        return services;
    }

    /// <summary>
    /// Maps the PersistentSubscriptionHub to the specified endpoint.
    /// </summary>
    /// <param name="app">The web application.</param>
    /// <param name="pattern">The URL pattern for the hub endpoint (default: "/hubs/subscriptions").</param>
    /// <returns>The web application for method chaining.</returns>
    /// <example>
    /// <code>
    /// app.MapPersistentSubscriptionHub();  // Maps to /hubs/subscriptions
    /// app.MapPersistentSubscriptionHub("/api/subscriptions");  // Custom endpoint
    /// </code>
    /// </example>
    public static WebApplication MapPersistentSubscriptionHub(
        this WebApplication app,
        string pattern = "/hubs/subscriptions")
    {
        if (app == null)
            throw new ArgumentNullException(nameof(app));

        if (string.IsNullOrWhiteSpace(pattern))
            throw new ArgumentException("Pattern cannot be null or empty", nameof(pattern));

        app.MapHub<PersistentSubscriptionHub>(pattern);

        return app;
    }
}