Add optional read-only CDN cache

Author: Marlamin

TACTSharp/CDN.cs

@@ -184,6 +184,21 @@ public async Task<string> GetPatchServiceFile(string product, string file = "ver
                         return File.ReadAllBytes(cachePath);
             }
 
+            if (!string.IsNullOrEmpty(Settings.CDNDir))
+            {
+                var cdnPath = Path.Combine(Settings.CDNDir, ProductDirectory, type, $"{hash[0]}{hash[1]}", $"{hash[2]}{hash[3]}", hash);
+                FileLocks.TryAdd(cdnPath, new Lock());
+
+                if (File.Exists(cdnPath))
+                {
+                    if (size > 0 && (ulong)new FileInfo(cdnPath).Length != size)
+                        Console.WriteLine("Warning! Found " + hash + " in CDN dir but size does not match! " + size + " != " + new FileInfo(cachePath).Length + ", continuing to download.");
+                    else
+                        lock (FileLocks[cdnPath])
+                            return File.ReadAllBytes(cdnPath);
+                }
+            }
+
             for (var i = 0; i < CDNServers.Count; i++)
             {
                 var url = $"http://{CDNServers[i]}/{ProductDirectory}/{type}/{hash[0]}{hash[1]}/{hash[2]}{hash[3]}/{hash}";
@@ -301,6 +316,31 @@ public unsafe bool TryGetLocalFile(string eKey, out ReadOnlySpan<byte> data)
                     File.Delete(cachePath);
             }
 
+            if (!string.IsNullOrEmpty(Settings.CDNDir))
+            {
+                var cdnPath = Path.Combine(Settings.CDNDir, ProductDirectory, "data", $"{archive[0]}{archive[1]}", $"{archive[2]}{archive[3]}", archive);
+                if (File.Exists(cdnPath))
+                {
+                    if (new FileInfo(cdnPath).Length != (offset + size))
+                        Console.WriteLine("Warning! Found " + archive + " in CDN dir but size is lower than offset+size " + offset + size + " != " + new FileInfo(cachePath).Length + ", continuing to download.");
+                    else
+                    {
+                        lock (FileLocks[cdnPath])
+                        {
+                            using (var ms = new MemoryStream())
+                            {
+                                using (var fs = new FileStream(cdnPath, FileMode.Open, FileAccess.Read))
+                                {
+                                    var buffer = new byte[size];
+                                    fs.ReadExactly(buffer, offset, size);
+                                    return buffer;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+
             lock (cdnLock)
             {
                 if (CDNServers.Count == 0)

TACTSharp/GroupIndex.cs

@@ -29,10 +29,15 @@ public string Generate(CDN CDN, Settings Settings, string? hash, string[] archiv
 
             Parallel.For(0, archives.Length, archiveIndex =>
             {
+                var archiveName = archives[archiveIndex];
                 string indexPath = "";
-                if (!string.IsNullOrEmpty(Settings.BaseDir) && File.Exists(Path.Combine(Settings.BaseDir, "Data", "indices", archives[archiveIndex] + ".index")))
+                if (!string.IsNullOrEmpty(Settings.BaseDir) && File.Exists(Path.Combine(Settings.BaseDir, "Data", "indices", archiveName + ".index")))
                 {
-                    indexPath = Path.Combine(Settings.BaseDir, "Data", "indices", archives[archiveIndex] + ".index");
+                    indexPath = Path.Combine(Settings.BaseDir, "Data", "indices", archiveName + ".index");
+                }
+                else if(!string.IsNullOrEmpty(Settings.CDNDir) && File.Exists(Path.Combine(Settings.CDNDir, CDN.ProductDirectory, "data", $"{archiveName[0]}{archiveName[1]}", $"{archiveName[2]}{archiveName[3]}", archiveName + ".index")))
+                {
+                    indexPath = Path.Combine(Settings.CDNDir, CDN.ProductDirectory, "data", $"{archiveName[0]}{archiveName[1]}", $"{archiveName[2]}{archiveName[3]}", archiveName + ".index");
                 }
                 else
                 {
@@ -166,6 +171,9 @@ public string Generate(CDN CDN, Settings Settings, string? hash, string[] archiv
                     if (fullFooterMD5Hash != hash)
                         throw new Exception("Footer MD5 of group index does not match group index filename");
 
+                    if (!Directory.Exists(Path.Combine(Settings.CacheDir, CDN.ProductDirectory, "data")))
+                        Directory.CreateDirectory(Path.Combine(Settings.CacheDir, CDN.ProductDirectory, "data"));
+
                     File.WriteAllBytes(Path.Combine(Settings.CacheDir, CDN.ProductDirectory, "data", hash + ".index"), ms.ToArray());
                 }
                 else

TACTSharp/Settings.cs

@@ -10,6 +10,7 @@ public class Settings
         public string? BuildConfig;
         public string? CDNConfig;
         public string CacheDir = "cache";
+        public string CDNDir = "";
         public bool ListfileFallback = true;
         public string ListfileURL = "https://github.com/wowdev/wow-listfile/releases/latest/download/community-listfile.csv";
     }

TACTTool/Program.cs

@@ -65,6 +65,10 @@ static async Task Main(string[] args)
             baseDirOption.AddAlias("-d");
             rootCommand.AddOption(baseDirOption);
 
+            var cdnDirOption = new Option<string?>(name: "--cdndir", description: "CDN folder to use as read-only file cache (if available)");
+            cdnDirOption.AddAlias("-cdn");
+            rootCommand.AddOption(cdnDirOption);
+
             rootCommand.SetHandler(CommandLineArgHandler);
 
             build = new BuildInstance();
@@ -234,7 +238,9 @@ private static async Task CommandLineArgHandler(InvocationContext context)
                             _ => throw new Exception("Invalid input mode. Available modes: list, ekey/ehash, ckey/chash, fdid/id, filename/name"),
                         };
                         break;
-
+                    case "cdndir":
+                        build.Settings.CDNDir = (string)optionValue;
+                        break;
                     case "version":
                     case "help":
                         break;