using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using MoShiro.Protocol;

namespace MoShiro.Backend.Application;

/// <summary>
/// 定时去镜像仓库取各组件（Agent、Backend 自己）最新的签名清单：CI 把清单登记给面板那一步是尽力而为的（网络不通只警告），
/// 面板自己也去仓库取，Backend 的更新通知和节点的更新建议就不依赖那一步。取回来的清单要用发布公钥验过签才登记。
/// </summary>
public sealed partial class ReleasePoller : BackgroundService
{
    private static readonly TimeSpan s_startupDelay = TimeSpan.FromSeconds(20);
    private static readonly TimeSpan s_interval = TimeSpan.FromMinutes(5);
    private static readonly string[] s_components = [ReleaseService.AgentComponent, ReleaseService.BackendComponent];

    private readonly ReleaseService _releases;
    private readonly TimeProvider _time;
    private readonly ILogger<ReleasePoller> _log;

    public ReleasePoller(ReleaseService releases, TimeProvider time, ILogger<ReleasePoller> log)
    {
        _releases = releases;
        _time = time;
        _log = log;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        try
        {
            await Task.Delay(s_startupDelay, _time, stoppingToken);
            using var timer = new PeriodicTimer(s_interval, _time);
            do
            {
                foreach (string component in s_components)
                {
                    try
                    {
                        await _releases.GetOrFetchAsync(component, stoppingToken);
                    }
                    catch (Exception ex) when (ex is not OperationCanceledException)
                    {
                        LogFailed(ex, component);
                    }
                }
            }
            while (await timer.WaitForNextTickAsync(stoppingToken));
        }
        catch (OperationCanceledException)
        {
            // 后端正在停止
        }
    }

    [LoggerMessage(Level = LogLevel.Warning, Message = "could not check the registry for the latest {Component} release")]
    private partial void LogFailed(Exception exception, string component);
}