using FrameworkBLL.EventSub;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace FrameworkSL.Controllers.EventSub
{
    /// <summary>
    /// Replaces app.MapSubscribeHandler() with a dynamic implementation.
    ///
    /// Dapr calls GET /dapr/subscribe at sidecar startup to discover which
    /// topics this app subscribes to. Instead of returning a static list from
    /// [Topic] attributes, this controller queries MEVENTTYPE in the system DB
    /// and returns one subscription per active EventTypeId — all routed to
    /// /eventsub/handle.
    ///
    /// Adding a new event type in MEVENTTYPE automatically creates the Dapr
    /// subscription on next app restart. No code change required.
    /// </summary>
    [ApiController]
    public class DaprSubscribeController : ControllerBase
    {
        private readonly IDaprSubscriptionBLL _bll;
        private readonly ILogger<DaprSubscribeController> _logger;

        public DaprSubscribeController(
            IDaprSubscriptionBLL bll,
            ILogger<DaprSubscribeController> logger)
        {
            _bll    = bll;
            _logger = logger;
        }

        [HttpGet("/dapr/subscribe")]
        public async Task<IActionResult> GetSubscriptions(CancellationToken ct)
        {
            try
            {
                var subscriptions = await _bll.GetSubscriptionsAsync(ct).ConfigureAwait(false);

                _logger.LogInformation(
                    "Dapr subscribe: returning {Count} dynamic subscription(s)",
                    subscriptions.Count);

                // Log first few topics to aid debugging — visible at startup
                var preview = string.Join(", ", subscriptions
                    .Select(s => s.Topic)
                    .Distinct()
                    .Take(5));
                if (subscriptions.Count > 0)
                    _logger.LogInformation("Dapr subscribe: topics (first 5) = [{Topics}]{More}",
                        preview,
                        subscriptions.Select(s => s.Topic).Distinct().Count() > 5 ? " …" : "");

                return Ok(subscriptions);
            }
            catch (OperationCanceledException) when (ct.IsCancellationRequested)
            {
                return StatusCode(503, "Service unavailable — subscription load cancelled");
            }
            catch (Exception ex)
            {
                // 503 tells Dapr sidecar to retry GET /dapr/subscribe instead of
                // locking in an empty subscription list for the lifetime of the process.
                _logger.LogError(ex,
                    "Dapr subscribe: BLL failed — returning 503 so Dapr retries subscription registration");
                return StatusCode(503, "Service unavailable — subscription data not ready");
            }
        }
    }
}