using Fake;
using Fake.EventBus.RabbitMQ;
using Fake.RabbitMQ;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Oms.Application.Dtos.Orders;
using RabbitMQ.Client;

namespace Oms.Application.Messaging;

public interface IOrderBatchQueueInspector
{
    bool IsEnabled { get; }

    Task<OrderBatchDlxStatsOutput> GetStatsAsync(CancellationToken cancellationToken = default);
}

/// <summary>
/// 巡检 Fake.EventBus.RabbitMQ 的工作队列与死信队列。
/// </summary>
public sealed class OrderBatchQueueInspector(
    IRabbitMqConnectionPool connectionPool,
    IOptions<OrderBatchRabbitMqOptions> options,
    IOptions<RabbitMqEventBusOptions> eventBusOptions,
    IApplicationInfo applicationInfo,
    ILogger<OrderBatchQueueInspector> logger) : IOrderBatchQueueInspector
{
    /// <summary>
    /// DLX 堆积告警默认阈值。
    /// </summary>
    public const uint DefaultDlxAlertThreshold = 100;

    public bool IsEnabled => options.Value.Enabled;

    public Task<OrderBatchDlxStatsOutput> GetStatsAsync(CancellationToken cancellationToken = default)
    {
        if (!options.Value.Enabled)
        {
            return Task.FromResult(new OrderBatchDlxStatsOutput
            {
                Enabled = false,
                DlxAlertThreshold = DefaultDlxAlertThreshold,
            });
        }

        var busOptions = eventBusOptions.Value;
        // 与 RabbitMqEventBus 一致：QueueName 为空时用 ApplicationName
        var queueName = (busOptions.QueueName ?? applicationInfo.ApplicationName).TrimEnd('.') + ".Queue";
        var dlxQueueName = "DLX." + queueName;

        // Connection 由 Fake 连接池托管，禁止 Dispose
        var connection = connectionPool.Get(busOptions.ConnectionName);
        using var channel = connection.CreateModel();

        var queues = new List<OrderBatchQueueStatOutput>
        {
            InspectQueue(channel, queueName),
            InspectQueue(channel, dlxQueueName),
        };

        var dlxCount = queues.First(x => x.QueueName == dlxQueueName).MessageCount;
        logger.LogDebug("Order batch Fake EventBus queue stats, dlxMessages={DeadLetterCount}", dlxCount);

        return Task.FromResult(new OrderBatchDlxStatsOutput
        {
            Enabled = true,
            DeadLetterMessageCount = dlxCount,
            DlxAlertThreshold = DefaultDlxAlertThreshold,
            Alert = dlxCount >= DefaultDlxAlertThreshold,
            Queues = queues,
        });
    }

    private static OrderBatchQueueStatOutput InspectQueue(IModel channel, string queueName)
    {
        try
        {
            var declare = channel.QueueDeclarePassive(queueName);
            return new OrderBatchQueueStatOutput
            {
                QueueName = queueName,
                MessageCount = declare.MessageCount,
                ConsumerCount = declare.ConsumerCount,
            };
        }
        catch (Exception)
        {
            return new OrderBatchQueueStatOutput { QueueName = queueName };
        }
    }
}