Refactor

DiscordChatExporter.Domain/Internal/Extensions/BinaryExtensions.cs

@@ -0,0 +1,19 @@
+using System.Text;
+
+namespace DiscordChatExporter.Domain.Internal.Extensions
+{
+    internal static class BinaryExtensions
+    {
+        public static string ToHex(this byte[] data)
+        {
+            var buffer = new StringBuilder();
+
+            foreach (var t in data)
+            {
+                buffer.Append(t.ToString("X2"));
+            }
+
+            return buffer.ToString();
+        }
+    }
+}

DiscordChatExporter.Domain/Internal/Http.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Globalization;
+using System.IO;
+using System.Net;
+using System.Net.Http;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using Polly;
+
+namespace DiscordChatExporter.Domain.Internal
+{
+    internal static class Http
+    {
+        public static HttpClient Client { get; } = new HttpClient();
+
+        public static IAsyncPolicy<HttpResponseMessage> ResponsePolicy { get; } =
+            Policy
+                .Handle<IOException>()
+                .Or<HttpRequestException>()
+                .OrResult<HttpResponseMessage>(m => m.StatusCode == HttpStatusCode.TooManyRequests)
+                .OrResult(m => m.StatusCode == HttpStatusCode.RequestTimeout)
+                .OrResult(m => m.StatusCode >= HttpStatusCode.InternalServerError)
+                .WaitAndRetryAsync(8,
+                    (i, result, ctx) =>
+                    {
+                        // If rate-limited, use retry-after as a guide
+                        if (result.Result.StatusCode == HttpStatusCode.TooManyRequests)
+                        {
+                            // Only start respecting retry-after after a few attempts.
+                            // The reason is that Discord often sends unreasonable (20+ minutes) retry-after
+                            // on the very first request.
+                            if (i > 3)
+                            {
+                                var retryAfterDelay = result.Result.Headers.RetryAfter.Delta;
+                                if (retryAfterDelay != null)
+                                    return retryAfterDelay.Value + TimeSpan.FromSeconds(1); // margin just in case
+                            }
+                        }
+
+                        return TimeSpan.FromSeconds(Math.Pow(2, i) + 1);
+                    },
+                    (response, timespan, retryCount, context) => Task.CompletedTask);
+
+        private static HttpStatusCode? TryGetStatusCodeFromException(HttpRequestException ex)
+        {
+            // This is extremely frail, but there's no other way
+            var statusCodeRaw = Regex.Match(ex.Message, @": (\d+) \(").Groups[1].Value;
+            return !string.IsNullOrWhiteSpace(statusCodeRaw)
+                ? (HttpStatusCode) int.Parse(statusCodeRaw, CultureInfo.InvariantCulture)
+                : (HttpStatusCode?) null;
+        }
+
+        public static IAsyncPolicy ExceptionPolicy { get; } =
+            Policy
+                .Handle<IOException>() // dangerous
+                .Or<HttpRequestException>(ex => TryGetStatusCodeFromException(ex) == HttpStatusCode.TooManyRequests)
+                .Or<HttpRequestException>(ex => TryGetStatusCodeFromException(ex) == HttpStatusCode.RequestTimeout)
+                .Or<HttpRequestException>(ex => TryGetStatusCodeFromException(ex) >= HttpStatusCode.InternalServerError)
+                .WaitAndRetryAsync(4, i => TimeSpan.FromSeconds(Math.Pow(2, i) + 1));
+    }
+}

DiscordChatExporter.Domain/Internal/PathEx.cs

@@ -14,27 +14,5 @@ namespace DiscordChatExporter.Domain.Internal
         }
 
         public static string EscapePath(string path) => EscapePath(new StringBuilder(path)).ToString();
-
-        public static string MakeUniqueFilePath(string baseFilePath, int maxAttempts = int.MaxValue)
-        {
-            if (!File.Exists(baseFilePath))
-                return baseFilePath;
-
-            var baseDirPath = Path.GetDirectoryName(baseFilePath);
-            var baseFileNameWithoutExtension = Path.GetFileNameWithoutExtension(baseFilePath);
-            var baseFileExtension = Path.GetExtension(baseFilePath);
-
-            for (var i = 1; i <= maxAttempts; i++)
-            {
-                var filePath = $"{baseFileNameWithoutExtension} ({i}){baseFileExtension}";
-                if (!string.IsNullOrWhiteSpace(baseDirPath))
-                    filePath = Path.Combine(baseDirPath, filePath);
-
-                if (!File.Exists(filePath))
-                    return filePath;
-            }
-
-            return baseFilePath;
-        }
     }
 }

DiscordChatExporter.Domain/Internal/Singleton.cs

@@ -1,23 +0,0 @@
-using System;
-using System.Net;
-using System.Net.Http;
-
-namespace DiscordChatExporter.Domain.Internal
-{
-    internal static class Singleton
-    {
-        private static readonly Lazy<HttpClient> LazyHttpClient = new Lazy<HttpClient>(() =>
-        {
-            var handler = new HttpClientHandler();
-
-            if (handler.SupportsAutomaticDecompression)
-                handler.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
-
-            handler.UseCookies = false;
-
-            return new HttpClient(handler, true);
-        });
-
-        public static HttpClient HttpClient { get; } = LazyHttpClient.Value;
-    }
-}