using System.ComponentModel;
using MimeKit;

namespace Service;

public interface IEmailBackgroundService
{
    /// <summary>
    /// 手动触发邮件同步
    /// </summary>
    Task SyncEmailsAsync();
}

public class EmailBackgroundService(
    IOptions<EmailSettings> emailSettings,
    IServiceProvider serviceProvider,
    IEmailHandleService emailHandleService,
    ILogger<EmailBackgroundService> logger)
    : BackgroundWorker, IEmailBackgroundService
{
    private readonly Dictionary<string, IEmailFetchService> _emailFetchServices = new();
    private bool _isInitialized;

    protected override async void OnDoWork(DoWorkEventArgs e)
    {
        try
        {
            // 启动时建立所有连接
            await InitializeConnectionsAsync();

            while (!CancellationPending)
            {
                try
                {
                    await FetchAndPostCmbTransactionsAsync();
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "后台任务执行出错");
                }

                // 使用 Thread.Sleep 在异步操作中不阻塞
                Thread.Sleep(1000 * 60 * 10); // 每10分钟执行一次任务
            }
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "后台服务工作线程出错");
        }
        finally
        {
            // 停止时断开所有连接
            try
            {
                await DisconnectAllAsync();
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "断开连接时出错");
            }
        }
    }

    /// <summary>
    /// 初始化所有邮箱连接
    /// </summary>
    private async Task InitializeConnectionsAsync()
    {
        if (_isInitialized)
        {
            logger.LogWarning("连接已初始化，跳过重复初始化");
            return;
        }

        try
        {
            if (emailSettings.Value.SmtpList.Length == 0)
            {
                logger.LogWarning("未配置邮箱账户，无法初始化连接");
                return;
            }

            logger.LogInformation("开始初始化 {EmailCount} 个邮箱连接...", emailSettings.Value.SmtpList.Length);

            // 并行初始化所有邮箱连接
            var tasks = emailSettings.Value.SmtpList.Select(async emailConfig =>
            {
                try
                {
                    var emailFetchService = ActivatorUtilities.CreateInstance<EmailFetchService>(serviceProvider);
                    var success = await emailFetchService.ConnectAsync(
                        emailConfig.ImapHost,
                        emailConfig.ImapPort,
                        emailConfig.UseSsl,
                        emailConfig.Email,
                        emailConfig.Password);

                    if (success)
                    {
                        _emailFetchServices[emailConfig.Email] = emailFetchService;
                        logger.LogInformation("邮箱 {Email} 连接建立成功", emailConfig.Email);
                    }
                    else
                    {
                        logger.LogError("邮箱 {Email} 连接建立失败", emailConfig.Email);
                    }
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "初始化邮箱 {Email} 连接时出错", emailConfig.Email);
                }
            });

            await Task.WhenAll(tasks);
            _isInitialized = true;
            logger.LogInformation("所有邮箱连接初始化完成，成功连接 {Count} 个邮箱", _emailFetchServices.Count);
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "初始化邮箱连接失败");
        }
    }

    /// <summary>
    /// 断开所有邮箱连接
    /// </summary>
    private async Task DisconnectAllAsync()
    {
        logger.LogInformation("开始断开所有邮箱连接...");

        var tasks = _emailFetchServices.Select(async kvp =>
        {
            try
            {
                await kvp.Value.DisconnectAsync();
                logger.LogInformation("邮箱 {Email} 已断开连接", kvp.Key);
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "断开邮箱 {Email} 连接时出错", kvp.Key);
            }
        });

        await Task.WhenAll(tasks);
        _emailFetchServices.Clear();
        _isInitialized = false;
        logger.LogInformation("所有邮箱连接已断开");
    }

    /// <summary>
    /// 手动触发邮件同步（公开方法）
    /// </summary>
    public async Task SyncEmailsAsync()
    {
        await FetchAndPostCmbTransactionsAsync();
    }

    /// <summary>
    /// 抓取并处理招商银行邮件交易
    /// </summary>
    private async Task FetchAndPostCmbTransactionsAsync()
    {
        try
        {
            if (_emailFetchServices.Count == 0)
            {
                logger.LogWarning("没有可用的邮箱连接，跳过抓取");
                return;
            }

            logger.LogInformation("开始抓取 {EmailCount} 个邮箱的邮件", _emailFetchServices.Count);

            // 并行处理多个邮箱
            var tasks = _emailFetchServices.Select(async kvp =>
            {
                var email = kvp.Key;
                var emailFetchService = kvp.Value;

                try
                {
                    // 获取未读邮件
                    var unreadMessages = await emailFetchService.FetchUnreadMessagesAsync();
                    logger.LogInformation("邮箱 {Email} 获取到 {MessageCount} 封未读邮件", email, unreadMessages.Count);

                    foreach (var (message, uid) in unreadMessages)
                    {
                        try
                        {
                            logger.LogDebug("邮件信息 - 发送者: {From}, 主题: {Subject}, 接收时间: {Date}",
                                message.From, message.Subject, message.Date);
                            logger.LogDebug("邮件内容预览: {Preview}", GetEmailBodyPreview(message));

                            if (await emailHandleService.HandleEmailAsync(
                                    message.From.ToString(),
                                    message.Subject,
                                    message.Date.DateTime,
                                    message.TextBody ?? message.HtmlBody ?? string.Empty
                                ))
                            {
                                // 标记邮件为已读
                                await emailFetchService.MarkAsReadAsync(uid);    
                            }
                        }
                        catch (Exception ex)
                        {
                            logger.LogError(ex, "处理邮件时出错");
                        }
                    }

                    logger.LogInformation("邮箱 {Email} 邮件抓取完成", email);
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "邮箱 {Email} 邮件抓取失败", email);
                }
            });

            await Task.WhenAll(tasks);
            logger.LogInformation("所有邮箱邮件抓取完成");
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "抓取邮件异常");
        }
    }

    /// <summary>
    /// 获取邮件内容预览
    /// </summary>
    private static string GetEmailBodyPreview(MimeMessage message)
    {
        var body = message.HtmlBody ?? message.TextBody ?? string.Empty;
        var preview = body.Length > 100 ? body.Substring(0, 100) + "..." : body;
        return preview.Replace("\n", " ").Replace("\r", "");
    }
}