using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace JiShe.CollectBus.Common.WorkService
{
    /// <summary>
    /// 系统后台定时服务
    /// </summary>
    public abstract class SystemBackGroundWorkService : BackgroundService
    {
        /// <summary>
        /// 日志记录
        /// </summary>
        public ILogger<SystemBackGroundWorkService> Logger { get; set; }

        /// <summary>
        /// 创建一个取消标记源
        /// </summary>
        private readonly CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();

        /// <summary>
        /// 任务执行间隔时间
        /// </summary>
        private TimeSpan interval;

        protected SystemBackGroundWorkService(ILogger<SystemBackGroundWorkService> logger)
        {
            Logger = logger;
            interval = GetInterval();
        }

        /// <summary>
        /// 执行时间间隔
        /// </summary>
        /// <returns></returns>
        protected abstract TimeSpan GetInterval();

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            await Task.CompletedTask;// 等待其他任务执行完成，避免阻塞应用程序启动
           // Logger.LogInformation($"任务每隔{interval.TotalSeconds}秒执行一次");
            await InitAsync(cancellationTokenSource.Token);
        }

        protected virtual async Task InitAsync(CancellationToken cancellationToken)
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                try
                {
                    await DoWorkAsync(cancellationToken);
                }
                catch (Exception ex)
                {
                    Logger.LogError(ex, "后台任务执行发生异常");
                }

                await Task.Delay(interval, cancellationToken);
            }
        }

        public override Task StopAsync(CancellationToken cancellationToken)
        {
            Logger.LogInformation("后台服务停止……");
            cancellationTokenSource.Cancel();
            return Task.CompletedTask;
        }

        /// <summary>
        /// 抛出方法入口以便于其服务实现
        /// </summary>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        protected abstract Task DoWorkAsync(CancellationToken cancellationToken);
    }
}