SosachContentParser

using System;
using System.IO;
using System.Linq;
using System.Net.Http;
using HtmlAgilityPack;
using System.Threading;

namespace SosachContentParser
{
    public class Program
    {
        const string XPATH_TO_LINK = "//*[contains(@id, post-body)]/div[2]/figure/figcaption/a";

        public static void Main(string[] args)
        {

            var threadUrl = args[0];
            var board = threadUrl.Split('/')[3];
            var contentFilesPath = args[1];

            string rawHtml;
            using (var client = new HttpClient())
            {
                rawHtml = client
                    .GetAsync(threadUrl)
                    .Result
                    .Content
                    .ReadAsStringAsync()
                    .Result;
            }

            var htmlDoc = new HtmlDocument();
            htmlDoc.LoadHtml(rawHtml);

            var links = htmlDoc.DocumentNode
                .SelectNodes(XPATH_TO_LINK)
                .Select(x => x.Attributes)
                .Select(x => x["href"].Value)
                .Select(x => x.Replace("..", "https://2ch.hk/" + board))
                .ToList();

            Console.WriteLine($"Files count: {links.Count}");

            int counter = 0;
            foreach (var link in links.AsParallel())
            {
                byte[] fileByteArray;
                using (var client = new HttpClient())
                {
                    fileByteArray = client
                        .GetAsync(link)
                        .Result
                        .Content
                        .ReadAsByteArrayAsync()
                        .Result;
                }

                File.WriteAllBytes(contentFilesPath + link.Split('/').Last(), fileByteArray);

                Interlocked.Increment(ref counter);
                Console.Clear();
                Console.WriteLine($"Files count: {links.Count}");
                Console.WriteLine($"Files downloaded: {counter}");
            }
        }
    }
}