using QYZH.InteractiveMagazine.Infrastructure.RabbitMQ;

namespace QYZH.InteractiveMagazine.WorkService.Consumers;

/// <summary>
/// RabbitMQ 消费者后台服务，自动发现并启动所有已注册的 IQueueConsumer
/// </summary>
public class RabbitMQHostedService : BackgroundService
{
    private readonly IServiceProvider _serviceProvider;
    private readonly ILogger<RabbitMQHostedService> _logger;

    public RabbitMQHostedService(IServiceProvider serviceProvider, ILogger<RabbitMQHostedService> logger)
    {
        _serviceProvider = serviceProvider;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        using var scope = _serviceProvider.CreateScope();
        var consumers = scope.ServiceProvider.GetServices<IQueueConsumer>().ToList();

        if (consumers.Count == 0)
        {
            _logger.LogWarning("未注册任何队列消费者");
            return;
        }

        _logger.LogInformation("发现 {Count} 个队列消费者，开始启动...", consumers.Count);

        var tasks = consumers.Select(c => StartConsumerAsync(c.QueueName, stoppingToken)).ToList();
        await Task.WhenAll(tasks);
    }

    private async Task StartConsumerAsync(string queueName, CancellationToken stoppingToken)
    {
        _logger.LogInformation("正在启动消费者: {QueueName}", queueName);

        try
        {
            var rabbitMQService = _serviceProvider.GetRequiredService<IRabbitMQService>();

            await rabbitMQService.ReceiveAsync(queueName, async (channel, ea) =>
            {
                // 每条消息创建独立 scope，确保消费者内可注入 Scoped 服务
                using var messageScope = _serviceProvider.CreateScope();
                var consumer = messageScope.ServiceProvider
                    .GetServices<IQueueConsumer>()
                    .First(c => c.QueueName == queueName);

                try
                {
                    await consumer.HandleAsync(ea.Body.ToArray());
                    await channel.BasicAckAsync(ea.DeliveryTag, false, stoppingToken);
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "消费者 {QueueName} 处理消息异常", queueName);
                    await channel.BasicNackAsync(ea.DeliveryTag, false, true, stoppingToken);

                    try
                    {
                        await consumer.OnErrorAsync(ea.Body.ToArray(), ex);
                    }
                    catch (Exception errorEx)
                    {
                        _logger.LogError(errorEx, "消费者 {QueueName} OnErrorAsync 执行异常", queueName);
                    }
                }
            }, stoppingToken);
        }
        catch (OperationCanceledException)
        {
            _logger.LogInformation("消费者 {QueueName} 已停止", queueName);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "消费者 {QueueName} 启动失败", queueName);
        }
    }
}