using Jaina;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using System;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Channels;
using System.Threading.Tasks;

namespace WaterCloud.Service.Event
{
	public sealed class RabbitMQEventSourceStorer : IEventSourceStorer, IDisposable
	{
		/// <summary>
		/// 内存通道事件源存储器
		/// </summary>
		private readonly Channel<IEventSource> _channel;
		/// <summary>
		/// 通道对象
		/// </summary>
		private readonly IModel _model;
		/// <summary>
		/// 连接对象
		/// </summary>
		private readonly IConnection _connection;
		/// <summary>
		/// 路由键
		/// </summary>
		private readonly string _routeKey;
		/// <summary>
		/// 构造函数
		/// </summary>
		/// <param name="factory">连接工厂</param>
		/// <param name="routeKey">路由键</param>
		/// <param name="capacity">存储器最多能够处理多少消息，超过该容量进入等待写入</param>
		public RabbitMQEventSourceStorer(ConnectionFactory factory, string routeKey, int capacity)
		{
			// 配置通道，设置超出默认容量后进入等待
			var boundedChannelOptions = new BoundedChannelOptions(capacity)
			{
				FullMode = BoundedChannelFullMode.Wait
			};
			// 创建有限容量通道
			_channel = Channel.CreateBounded<IEventSource>(boundedChannelOptions);
			// 创建连接
			_connection = factory.CreateConnection();
			_routeKey = routeKey;
			// 创建通道
			_model = _connection.CreateModel();
			// 声明路由队列
			_model.QueueDeclare(routeKey, false, false, false, null);
			// 创建消息订阅者
			var consumer = new EventingBasicConsumer(_model);
			// 订阅消息并写入内存 Channel
			consumer.Received += (ch, ea) =>
			{
				// 读取原始消息
				var stringEventSource = Encoding.UTF8.GetString(ea.Body.ToArray());
				// 转换为 IEventSource，这里可以选择自己喜欢的序列化工具，如果自定义了 EventSource，注意属性是可读可写
				var eventSource = JsonSerializer.Deserialize<BaseEventSource>(stringEventSource);
				// 写入内存管道存储器
				_channel.Writer.WriteAsync(eventSource);
				// 确认该消息已被消费
				_model.BasicAck(ea.DeliveryTag, false);
			};
			// 启动消费者 设置为手动应答消息
			_model.BasicConsume(routeKey, false, consumer);
		}
		/// <summary>
		/// 将事件源写入存储器
		/// </summary>
		/// <param name="eventSource">事件源对象</param>
		/// <param name="cancellationToken">取消任务 Token</param>
		/// <returns><see cref="ValueTask"/></returns>
		public async ValueTask WriteAsync(IEventSource eventSource, CancellationToken cancellationToken)
		{
			// 空检查
			if (eventSource == default)
			{
				throw new ArgumentNullException(nameof(eventSource));
			}
			// 这里判断是否是 ChannelEventSource 或者 自定义的 EventSource
			if (eventSource is ChannelEventSource source)
			{
				// 序列化，这里可以选择自己喜欢的序列化工具
				var data = Encoding.UTF8.GetBytes(JsonSerializer.Serialize(source));
				// 发布
				_model.BasicPublish("", _routeKey, null, data);
			}
			else
			{
				// 这里处理动态订阅问题
				await _channel.Writer.WriteAsync(eventSource, cancellationToken);
			}
		}
		/// <summary>
		/// 从存储器中读取一条事件源
		/// </summary>
		/// <param name="cancellationToken">取消任务 Token</param>
		/// <returns>事件源对象</returns>
		public async ValueTask<IEventSource> ReadAsync(CancellationToken cancellationToken)
		{
			// 读取一条事件源
			var eventSource = await _channel.Reader.ReadAsync(cancellationToken);
			return eventSource;
		}
		/// <summary>
		/// 释放非托管资源
		/// </summary>
		public void Dispose()
		{
			_model.Dispose();
			_connection.Dispose();
		}
	}
}
