using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using MailKit.Net.Smtp;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Identity.Client;
using MimeKit;
using Oqtane.Models;
using Oqtane.Repository;
using Oqtane.Shared;
using MailKit.Security;

namespace Oqtane.Infrastructure
{
    public class NotificationJob : HostedServiceBase
    {
        // JobType = "Oqtane.Infrastructure.NotificationJob, Oqtane.Server"

        public NotificationJob(IServiceScopeFactory serviceScopeFactory) : base(serviceScopeFactory)
        {
            Name = "Notification Job";
            Frequency = "m"; // minute
            Interval = 1;
            IsEnabled = false;
        }

        // job is executed for each tenant in installation
        public async override Task<string> ExecuteJobAsync(IServiceProvider provider)
        {
            string log = "";

            // get services
            var siteRepository = provider.GetRequiredService<ISiteRepository>();
            var userRepository = provider.GetRequiredService<IUserRepository>();
            var settingRepository = provider.GetRequiredService<ISettingRepository>();
            var notificationRepository = provider.GetRequiredService<INotificationRepository>();

            // iterate through sites for current tenant
            List<Site> sites = siteRepository.GetSites().ToList();
            foreach (Site site in sites)
            {
                log += "Processing Notifications For Site: " + site.Name + "<br />";

                // get site settings
                var settings = settingRepository.GetSettings(EntityNames.Site, site.SiteId, EntityNames.Host, -1);

                if (!site.IsDeleted && settingRepository.GetSettingValue(settings, "SMTPEnabled", "True") == "True")
                {
                    bool valid = true;
                    if (settingRepository.GetSettingValue(settings, "SMTPAuthentication", "Basic") == "Basic")
                    {
                        // basic
                        if (settingRepository.GetSettingValue(settings, "SMTPHost", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPPort", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPSender", "") == "")
                        {
                            log += "SMTP Not Configured Properly In Site Settings - Host, Port, And Sender Are All Required" + "<br />";
                            valid = false;
                        }
                    }
                    else
                    {
                        // oauth
                        if (settingRepository.GetSettingValue(settings, "SMTPHost", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPPort", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPAuthority", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPClientId", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPClientSecret", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPScopes", "") == "" ||
                            settingRepository.GetSettingValue(settings, "SMTPSender", "") == "")
                        {
                            log += "SMTP Not Configured Properly In Site Settings - Host, Port, Authority, Client ID, Client Secret, Scopes, And Sender Are All Required" + "<br />";
                            valid = false;
                        }
                    }


                    if (valid)
                    {
                        // construct SMTP Client
                        using var client = new SmtpClient();

                        var secureSocketOptions = SecureSocketOptions.Auto;
                        switch (settingRepository.GetSettingValue(settings, "SMTPSSL", "Auto"))
                        {
                            case "None":
                                secureSocketOptions = SecureSocketOptions.None;
                                break;
                            case "Auto":
                                secureSocketOptions = SecureSocketOptions.Auto;
                                break;
                            case "StartTls":
                                secureSocketOptions = SecureSocketOptions.StartTls;
                                break;
                            case "SslOnConnect":
                            case "True": // legacy setting value
                                secureSocketOptions = SecureSocketOptions.SslOnConnect;
                                break;
                            case "StartTlsWhenAvailable":
                            case "False": // legacy setting value
                                secureSocketOptions = SecureSocketOptions.StartTlsWhenAvailable;
                                break;
                        }

                        await client.ConnectAsync(settingRepository.GetSettingValue(settings, "SMTPHost", ""),
                                int.Parse(settingRepository.GetSettingValue(settings, "SMTPPort", "")),
                                secureSocketOptions);

                        if (settingRepository.GetSettingValue(settings, "SMTPAuthentication", "Basic") == "Basic")
                        {
                            // it is possible to use basic without any authentication (not recommended)
                            if (settingRepository.GetSettingValue(settings, "SMTPUsername", "") != "" && settingRepository.GetSettingValue(settings, "SMTPPassword", "") != "")
                            {
                                await client.AuthenticateAsync(settingRepository.GetSettingValue(settings, "SMTPUsername", ""),
                                    settingRepository.GetSettingValue(settings, "SMTPPassword", ""));
                            }
                        }
                        else
                        {
                            // oauth authentication
                            var confidentialClientApplication = ConfidentialClientApplicationBuilder.Create(settingRepository.GetSettingValue(settings, "SMTPClientId", ""))
                                .WithAuthority(settingRepository.GetSettingValue(settings, "SMTPAuthority", ""))
                                .WithClientSecret(settingRepository.GetSettingValue(settings, "SMTPClientSecret", ""))
                                .Build();
                            try
                            {
                                var result = await confidentialClientApplication.AcquireTokenForClient(settingRepository.GetSettingValue(settings, "SMTPScopes", "").Split(',')).ExecuteAsync();
                                var oauth2 = new SaslMechanismOAuth2(settingRepository.GetSettingValue(settings, "SMTPSender", ""), result.AccessToken);
                                await client.AuthenticateAsync(oauth2);
                            }
                            catch (Exception ex)
                            {
                                log += "SMTP Not Configured Properly In Site Settings - OAuth Token Could Not Be Retrieved From Authority - " + ex.Message + "<br />";
                                valid = false;
                            }
                        }

                        if (valid)
                        {
                            // iterate through undelivered notifications
                            int sent = 0;
                            List<Notification> notifications = notificationRepository.GetNotifications(site.SiteId, -1, -1).ToList();
                            foreach (Notification notification in notifications)
                            {
                                var fromEmail = notification.FromEmail ?? "";
                                var fromName = notification.FromDisplayName ?? "";
                                var toEmail = notification.ToEmail ?? "";
                                var toName = notification.ToDisplayName ?? "";

                                // get sender and receiver information from user information if available
                                if ((string.IsNullOrEmpty(fromEmail) || string.IsNullOrEmpty(fromName)) && notification.FromUserId != null)
                                {
                                    var user = userRepository.GetUser(notification.FromUserId.Value);
                                    if (user != null)
                                    {
                                        fromEmail = string.IsNullOrEmpty(fromEmail) ? user.Email ?? "" : fromEmail;
                                        fromName = string.IsNullOrEmpty(fromName) ? user.DisplayName ?? "" : fromName;
                                    }
                                }
                                if ((string.IsNullOrEmpty(toEmail) || string.IsNullOrEmpty(toName)) && notification.ToUserId != null)
                                {
                                    var user = userRepository.GetUser(notification.ToUserId.Value);
                                    if (user != null)
                                    {
                                        toEmail = string.IsNullOrEmpty(toEmail) ? user.Email ?? "" : toEmail;
                                        toName = string.IsNullOrEmpty(toName) ? user.DisplayName ?? "" : toName;
                                    }
                                }

                                // create mailbox addresses
                                MailboxAddress to = null;
                                MailboxAddress from = null;
                                var mailboxAddressValidationError = "";

                                // sender
                                if (settingRepository.GetSettingValue(settings, "SMTPRelay", "False") != "True")
                                {
                                    fromEmail = settingRepository.GetSettingValue(settings, "SMTPSender", "");
                                    fromName = string.IsNullOrEmpty(fromName) ? site.Name : fromName;
                                }
                                if (MailboxAddress.TryParse(fromEmail, out from))
                                {
                                    from.Name = fromName;
                                }
                                else
                                {

                                    mailboxAddressValidationError += $" Invalid Sender: {fromName} &lt;{fromEmail}&gt;";
                                }

                                // recipient
                                if (MailboxAddress.TryParse(toEmail, out to))
                                {
                                    to.Name = toName;
                                }
                                else
                                {
                                    mailboxAddressValidationError += $" Invalid Recipient: {toName} &lt;{toEmail}&gt;";
                                }

                                // if mailbox addresses are valid
                                if (from != null && to != null)
                                {
                                    // create mail message
                                    MimeMessage mailMessage = new MimeMessage();
                                    mailMessage.From.Add(from);
                                    mailMessage.To.Add(to);

                                    // subject
                                    mailMessage.Subject = notification.Subject;

                                    // body
                                    var bodyText = notification.Body;

                                    if (!bodyText.Contains('<') || !bodyText.Contains('>'))
                                    {
                                        // plain text messages should convert line breaks to HTML tags to preserve formatting
                                        bodyText = bodyText.Replace("\n", "<br />");
                                    }

                                    mailMessage.Body = new TextPart("html", System.Text.Encoding.UTF8)
                                    {
                                        Text = bodyText
                                    };

                                    // send mail
                                    try
                                    {
                                        await client.SendAsync(mailMessage);
                                        sent++;
                                        notification.IsDelivered = true;
                                        notification.DeliveredOn = DateTime.UtcNow;
                                        notificationRepository.UpdateNotification(notification);
                                    }
                                    catch (Exception ex)
                                    {
                                        log += $"Error Sending Notification Id: {notification.NotificationId} - {ex.Message}<br />";
                                    }
                                }
                                else
                                {
                                    // invalid mailbox address
                                    log += $"Notification Id: {notification.NotificationId} Has An {mailboxAddressValidationError} And Has Been Deleted<br />";
                                    notification.IsDeleted = true;
                                    notificationRepository.UpdateNotification(notification);
                                }
                            }

                            log += "Notifications Delivered: " + sent + "<br />";
                        }

                        await client.DisconnectAsync(true);
                    }
                }
                else
                {
                    log += "Site Deleted Or SMTP Disabled In Site Settings" + "<br />";
                }
            }

            return log;
        }
    }
}