Unfinished: Downloader rework Part I

RuneScapeCacheTools/Cache/Downloader/HttpFileDownloader.cs

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+using System.IO;
+using System.Net;
+using System.Threading.Tasks;
+using Villermen.RuneScapeCacheTools.Cache.Files;
+using Villermen.RuneScapeCacheTools.Cache.RuneTek5;
+using Villermen.RuneScapeCacheTools.Exceptions;
+using Villermen.RuneScapeCacheTools.Extensions;
+
+namespace Villermen.RuneScapeCacheTools.Cache.Downloader
+{
+    public class HttpFileDownloader : IFileDownloader
+    {
+        private readonly string _baseUrl;
+
+        public HttpFileDownloader(string baseUrl = "http://content.runescape.com")
+        {
+            this._baseUrl = baseUrl;
+        }
+
+        public async Task<BinaryFile> DownloadFileAsync(Index index, int fileId, CacheFileInfo fileInfo)
+        {
+            var webRequest = WebRequest.CreateHttp($"{this._baseUrl}/ms?m=0&a={(int)index}&g={fileId}&c={fileInfo.Crc}&v={fileInfo.Version}");
+
+            using (var response = (HttpWebResponse)await webRequest.GetResponseAsync())
+            {
+                if (response.StatusCode != HttpStatusCode.OK)
+                {
+                    throw new DownloaderException($"HTTP interface responded with status code: {response.StatusCode}.");
+                }
+
+                if (response.ContentLength != fileInfo.CompressedSize - 2)
+                {
+                    throw new DownloaderException($"Downloaded file size {response.ContentLength} does not match expected {fileInfo.CompressedSize - 2}.");
+                }
+
+                var dataStream = new MemoryStream();
+                var dataWriter = new BinaryWriter(dataStream);
+
+                var responseReader = new BinaryReader(response.GetResponseStream());
+                dataWriter.Write(responseReader.ReadBytes((int)response.ContentLength));
+
+                // Append version
+                dataWriter.WriteUInt16BigEndian((ushort)fileInfo.Version);
+
+                return RuneTek5FileDecoder.DecodeFile(dataStream.ToArray(), fileInfo);
+            }
+        }
+    }
+}

RuneScapeCacheTools/Cache/Downloader/IFileDownloader.cs

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+using System;
+using System.Collections.Concurrent;
+using System.Threading.Tasks;
+using Villermen.RuneScapeCacheTools.Cache.Files;
+
+namespace Villermen.RuneScapeCacheTools.Cache.Downloader
+{
+    public interface IFileDownloader
+    {
+        Task<BinaryFile> DownloadFileAsync(Index index, int fileId, CacheFileInfo fileInfo);
+    }
+}