using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Net.Configuration;
using System.Net.Mail;
using System.Web.Mvc;
using MailKit.Security;
using MimeKit;
using Orchard.ContentManagement;
using Orchard.DisplayManagement;
using Orchard.Email.Models;
using Orchard.Logging;
using SmtpClient = MailKit.Net.Smtp.SmtpClient;

namespace Orchard.Email.Services {
    public class SmtpMessageChannel : Component, ISmtpChannel, IDisposable {
        private readonly SmtpSettingsPart _smtpSettings;
        private readonly IShapeFactory _shapeFactory;
        private readonly IShapeDisplay _shapeDisplay;
        private readonly Lazy<SmtpClient> _smtpClientField;
        public static readonly string MessageType = "Email";

        public SmtpMessageChannel(
            IOrchardServices orchardServices,
            IShapeFactory shapeFactory,
            IShapeDisplay shapeDisplay) {

            _shapeFactory = shapeFactory;
            _shapeDisplay = shapeDisplay;

            _smtpSettings = orchardServices.WorkContext.CurrentSite.As<SmtpSettingsPart>();
            _smtpClientField = new Lazy<SmtpClient>(CreateSmtpClient);
        }

        public void Dispose() {
            if (!_smtpClientField.IsValueCreated) {
                return;
            }

            _smtpClientField.Value.Dispose();
        }

        public void Process(IDictionary<string, object> parameters) {

            if (!_smtpSettings.IsValid()) {
                return;
            }

            var emailMessage = new EmailMessage {
                Body = Read(parameters, "Body"),
                Subject = Read(parameters, "Subject"),
                Recipients = Read(parameters, "Recipients"),
                ReplyTo = Read(parameters, "ReplyTo"),
                From = Read(parameters, "From"),
                Bcc = Read(parameters, "Bcc"),
                Cc = Read(parameters, "CC")
            };

            if (emailMessage.Recipients.Length == 0) {
                Logger.Error("Email message doesn't have any recipient");
                return;
            }

            // Apply default Body alteration for SmtpChannel.
            var template = _shapeFactory.Create("Template_Smtp_Wrapper", Arguments.From(new {
                Content = new MvcHtmlString(emailMessage.Body)
            }));

            var mailMessage = new MimeMessage {
                Subject = emailMessage.Subject,
            };
            var mailBodyBuilder = new BodyBuilder {
                HtmlBody = _shapeDisplay.Display(template),
            };

            if (parameters.TryGetValue("Message", out var possiblyMailMessage) && possiblyMailMessage is MailMessage legacyMessage) {
                // A full message object is provided by the sender.
                if (!String.IsNullOrWhiteSpace(legacyMessage.Subject)) {
                    mailMessage.Subject = legacyMessage.Subject;
                }

                if (!String.IsNullOrWhiteSpace(legacyMessage.Body)) {
                    mailBodyBuilder.TextBody = legacyMessage.IsBodyHtml ? null : legacyMessage.Body;
                    mailBodyBuilder.HtmlBody = legacyMessage.IsBodyHtml ? legacyMessage.Body : null;
                }
            }

            mailMessage.Body = mailBodyBuilder.ToMessageBody();

            try {
                mailMessage.To.AddRange(ParseRecipients(emailMessage.Recipients));

                if (!String.IsNullOrWhiteSpace(emailMessage.Cc)) {
                    mailMessage.Cc.AddRange(ParseRecipients(emailMessage.Cc));
                }

                if (!String.IsNullOrWhiteSpace(emailMessage.Bcc)) {
                    mailMessage.Bcc.AddRange(ParseRecipients(emailMessage.Bcc));
                }

                var fromAddress = default(MailboxAddress);
                if (!String.IsNullOrWhiteSpace(emailMessage.From)) {
                    fromAddress = MailboxAddress.Parse(emailMessage.From);
                }
                else {
                    // Take 'From' address from site settings or web.config.
                    fromAddress = !String.IsNullOrWhiteSpace(_smtpSettings.Address)
                        ? MailboxAddress.Parse(_smtpSettings.Address)
                        : MailboxAddress.Parse(((SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp")).From);
                }

                mailMessage.From.Add(fromAddress);

                if (!String.IsNullOrWhiteSpace(emailMessage.ReplyTo)) {
                    mailMessage.ReplyTo.AddRange(ParseRecipients(emailMessage.ReplyTo));
                }

                _smtpClientField.Value.Send(mailMessage);
            }
            catch (Exception e) {
                Logger.Error(e, "Could not send email");
            }
        }

        private SmtpClient CreateSmtpClient() {
            var smtpConfiguration = new {
                _smtpSettings.Host,
                _smtpSettings.Port,
                _smtpSettings.EncryptionMethod,
                _smtpSettings.AutoSelectEncryption,
                _smtpSettings.RequireCredentials,
                _smtpSettings.UserName,
                _smtpSettings.Password,
            };
            // If no properties are set in the dashboard, use the web.config value.
            if (String.IsNullOrWhiteSpace(_smtpSettings.Host)) {
                var smtpSection = (SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp");
                if (smtpSection.DeliveryMethod != SmtpDeliveryMethod.Network) {
                    throw new NotSupportedException($"Only the {SmtpDeliveryMethod.Network} delivery method is supported, but "
                        + $"{smtpSection.DeliveryMethod} delivery method is configured. Please check your Web.config.");
                }

                smtpConfiguration = new {
                    smtpSection.Network.Host,
                    smtpSection.Network.Port,
                    EncryptionMethod = smtpSection.Network.EnableSsl ? SmtpEncryptionMethod.SslTls : SmtpEncryptionMethod.None,
                    AutoSelectEncryption = !smtpSection.Network.EnableSsl,
                    RequireCredentials = smtpSection.Network.DefaultCredentials || !String.IsNullOrWhiteSpace(smtpSection.Network.UserName),
                    smtpSection.Network.UserName,
                    smtpSection.Network.Password,
                };
            }

            var secureSocketOptions = SecureSocketOptions.Auto;
            if (!smtpConfiguration.AutoSelectEncryption) {
                secureSocketOptions = smtpConfiguration.EncryptionMethod switch {
                    SmtpEncryptionMethod.None => SecureSocketOptions.None,
                    SmtpEncryptionMethod.SslTls => SecureSocketOptions.SslOnConnect,
                    SmtpEncryptionMethod.StartTls => SecureSocketOptions.StartTls,
                    _ => SecureSocketOptions.None,
                };
            }

            var smtpClient = new SmtpClient();
            smtpClient.Connect(smtpConfiguration.Host, smtpConfiguration.Port, secureSocketOptions);

            if (smtpConfiguration.RequireCredentials) {
                smtpClient.Authenticate(smtpConfiguration.UserName, smtpConfiguration.Password);
            }

            return smtpClient;
        }

        private string Read(IDictionary<string, object> dictionary, string key) {
            return dictionary.ContainsKey(key) ? dictionary[key] as string : null;
        }

        private IEnumerable<MailboxAddress> ParseRecipients(string recipients) {
            return recipients.Split(new[] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries)
                .SelectMany(address => {
                    if (MailboxAddress.TryParse(address, out var mailboxAddress)) {
                        return new[] { mailboxAddress };
                    }

                    Logger.Error("Invalid email address: {0}", address);
                    return Enumerable.Empty<MailboxAddress>();
                });
        }
    }
}