using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MailKit.Net.Smtp;
using System.Configuration;
using Bowin.Common.Utility;
using System.IO;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;
using MimeKit;
using MailKit.Net.Pop3;

namespace Bowin.Common.Mail
{
    public static class MailHelper
    {
        private const int _DEFAULT_SMTP_PORT = 25;
        private const int _DEFAULT_POP3_PORT = 110;

        private static MailSettings Settings { get; set; }

        static MailHelper()
        {
            var configuration = new ConfigurationBuilder()
                  .SetBasePath(Directory.GetCurrentDirectory())
                  .AddJsonFile("appsettings.json")
                  .Build();

            Settings = configuration.GetSection("BowinMail").Get<MailSettings>();
        }

        private static string GetSenderEmail()
        {
            string hostName = Settings.SMTPServer.Substring(Settings.SMTPServer.IndexOf('.') + 1);
            return Settings.UserName + "@" + hostName;
        }

        public static void SendMail(string receiver, string title, string content)
        {
            if (string.IsNullOrEmpty(Settings.SMTPServer))
            {
                throw new SendMailException("请指定发送邮件的STMP服务器地址。");
            }
            if (!Settings.SMTPPort.HasValue)
            {
                Settings.SMTPPort = _DEFAULT_SMTP_PORT;
            }
            if (!Settings.SMTPIsSSL.HasValue)
            {
                Settings.SMTPIsSSL = false;
            }
            if (string.IsNullOrEmpty(Settings.UserName) || string.IsNullOrEmpty(Settings.Password))
            {
                throw new SendMailException("请指定发送邮件的账号和密码。");
            }

            MimeMessage message = new MimeMessage();
            message.From.Add(new MailboxAddress(GetSenderEmail()));
            message.To.Add(new MailboxAddress(receiver));
            message.Subject = title;
            message.Body = new BodyBuilder()
            {
                HtmlBody = content
            }.ToMessageBody();

            using (var client = new SmtpClient())
            {
                try
                {
                    client.ServerCertificateValidationCallback = (s, c, h, e) => true;

                    client.Connect(Settings.SMTPServer, Settings.SMTPPort.Value, Settings.SMTPIsSSL.Value);

                    client.AuthenticationMechanisms.Remove("XOAUTH2");

                    client.Authenticate(Settings.UserName, Settings.Password);

                    client.Send(message);
                    client.Disconnect(true);
                }
                catch (Exception ex)
                {
                    throw new SendMailException("邮件发送失败，详情请参考InnerException", ex);
                }
            }
        }

        public static List<MimeMessage> ReceiveMail(string mailAddress)
        {
            if (string.IsNullOrEmpty(Settings.Pop3Server))
            {
                throw new ReceiveMailException("请指定发送邮件的POP3服务器地址。");
            }
            if (!Settings.Pop3Port.HasValue)
            {
                Settings.Pop3Port = _DEFAULT_POP3_PORT;
            }
            if (!Settings.Pop3IsSSL.HasValue)
            {
                Settings.Pop3IsSSL = false;
            }
            if (string.IsNullOrEmpty(Settings.UserName) || string.IsNullOrEmpty(Settings.Password))
            {
                throw new ReceiveMailException("请指定接收邮件的账号和密码。");
            }
            List<MimeMessage> mailList = new List<MimeMessage>();
            using (var client = new Pop3Client())
            {
                client.ServerCertificateValidationCallback = (s, c, h, e) => true;

                client.Connect(Settings.Pop3Server, Settings.Pop3Port.Value, Settings.Pop3IsSSL.Value);

                client.AuthenticationMechanisms.Remove("XOAUTH2");

                client.Authenticate(Settings.UserName, Settings.Password);

                for (int i = 0; i < client.Count; i++)
                {
                    var message = client.GetMessage(i);
                    mailList.Add(message);
                }

                client.Disconnect(true);
            }
            return mailList; 
        }
    }
}