using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Mail;
using System.Net;
using System.Configuration;
using System.Threading.Tasks;
using HtmlAgilityPack;

namespace WebscrapeMailer
{
    class Program
    {



        public static void Main()
        {
            // Store configurable values from App.config.

            string mailTo = ConfigurationManager.AppSettings["config.MailTo"];
            string mailFrom = ConfigurationManager.AppSettings["config.MailFrom"];
            string mailSubject = ConfigurationManager.AppSettings["config.MailSubject"];
            string mailServer = ConfigurationManager.AppSettings["config.MailServer"];
            //Create a dictionary which is like a dictionary in the real world.. except that instead of
            //you looking up a word and then its associated definitions, you can store any lookup value, and associate it with anything you want
            //"word" = webURL, "definition" = URLnode.

            Dictionary<string, string> webURLnodePairs = new Dictionary<string, string>();

            webURLnodePairs.Add(ConfigurationManager.AppSettings["config.webURL1"], ConfigurationManager.AppSettings["config.URL1Node"]);
            webURLnodePairs.Add(ConfigurationManager.AppSettings["config.webURL2"], ConfigurationManager.AppSettings["config.URL2Node"]);
            webURLnodePairs.Add(ConfigurationManager.AppSettings["config.webURL3"], ConfigurationManager.AppSettings["config.URL3Node"]);

            //Now imagine being able to spawn 3 separate requests for each screen scrape that execute at roughly the same time
            //It should be 3x as fast!

            var task = GetAllScrapes(webURLnodePairs);  // Im calling an asynchronous method and telling it to wait
            task.Wait();
            List<string> scrapeResults = task.Result; //grab the result from the async call

            SendMail(scrapeResults, mailTo, mailFrom, mailSubject, mailServer);

        }

        static async Task<List<string>> GetAllScrapes(Dictionary<string, string> webURLnodePairs)
        {
            // This is a neat feature.. create a task that waits for all the taks you spawn off using
            //the select method and lambda expression to pick out the url and urlnodes from the dictionary.
            var results = await Task.WhenAll(webURLnodePairs.Select((url, index) => Scrape(url.Key, url.Value)));

            return results.ToList();
        }



        static async Task<string> Scrape(string url, string urlnode)
        {
            //each scrape is on its own thread
            WebClient client = new WebClient();

            //this is relatively unchanged from your code
            string html = client.DownloadString(url);
            HtmlAgilityPack.HtmlDocument doc3 = new HtmlAgilityPack.HtmlDocument();
            doc3.LoadHtml(html);
            HtmlNode node = doc3.DocumentNode.SelectSingleNode(urlnode);

            return node.InnerText;
        }


        static async void SendMail(List<string> scrapeValues, string mailTo, string mailFrom, string mailSubject, string mailServer)
        {
            //sending mail is also on its own thread..

            MailAddress to = new MailAddress(mailTo);
            MailAddress from = new MailAddress(mailFrom);
            MailMessage mail = new MailMessage(from, to);
            mail.Subject = mailSubject;

            mail.Body = "Scrapes: " + Environment.NewLine;
            foreach (string scrape in scrapeValues)
            {
                mail.Body += "Start of new scrape: ";
                mail.Body += scrape;
                mail.Body += Environment.NewLine;
            }

            // Create the smtp object.
            SmtpClient smtp = new SmtpClient();

            // Get relay details, then send.
            smtp.Host = mailServer;
            smtp.Port = 25;

            smtp.Send(mail);
        }
    }


}