using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Threading.Tasks;

namespace GreenTree.Strohrmann.ERP.Services.Notification
{
    public class MailNotificationService : INotificationService
    {
        #region DI fields

        // The global mail notification options object
        private MailNotificationOptions _mailNotificationOptions;

        #endregion

        #region Fields

        // The SMTP client to send the mail notification messages
        private SmtpClient _smtpClient;

        #endregion

        #region Ctor

        /// <summary>
        /// Initializes a new instance of the MailNotificationService class
        /// </summary>
        /// <param name="mailNotificationOptions">The dependant mail notification options.</param>
        public MailNotificationService(
            IOptionsMonitor<MailNotificationOptions> mailNotificationOptions)
        {
            ConfigureService(mailNotificationOptions.CurrentValue);

            mailNotificationOptions.OnChange(config =>
            {
                ConfigureService(mailNotificationOptions.CurrentValue);
            });
        }

        #endregion

        #region Configuration

        /// <summary>
        /// Configure current service
        /// </summary>
        /// <param name="options">The service options.</param>
        private void ConfigureService(MailNotificationOptions options)
        {
            _mailNotificationOptions = options;

            // Create private SMTP client based to mail notification options
            _smtpClient = new SmtpClient(_mailNotificationOptions.SmtpServerAddress);

            // Check if Username is configured
            if (String.IsNullOrEmpty(_mailNotificationOptions.SmtpServerUsername)) return;

            // Use credentials on SMTP client
            _smtpClient.Credentials = new NetworkCredential(_mailNotificationOptions.SmtpServerUsername,
                _mailNotificationOptions.SmtpServerPassword, _mailNotificationOptions.SmtpServerDomain);
        }

        #endregion

        #region Implementation

        /// <summary>
        /// Sends a notification to a specific target
        /// </summary>
        /// <param name="target">The single target.</param>
        /// <param name="subject">The subject.</param>
        /// <param name="message">The message.</param>
        public void SendNotification(string target, string subject, string message)
        {
            // Parameter validation check
            if (String.IsNullOrEmpty(target))
                throw new ArgumentException("Cannot send notification to empty target.", "target");

            // Send message via SMTP client
            _smtpClient.Send(new MailMessage(_mailNotificationOptions.From, target, subject, message));
        }

        /// <summary>
        /// Sends a notification to multiple targets
        /// </summary>
        /// <param name="targets">The targets.</param>
        /// <param name="subject">The subject.</param>
        /// <param name="message">The message.</param>
        public void SendNotification(string[] targets, string subject, string message)
        {
            // Paramter validation check
            if (targets == null)
                throw new ArgumentException("Cannot send notification to empty targets.", "targets");

            // Loop through targets
            foreach (var target in targets)
            {
                // Use single SendNotification method for multiple targets
                SendNotification(target, subject, message);
            }
        }

        #endregion
    }
}