Improve error reporting on unexpected HTTP status code

DiscordChatExporter.Core/Discord/DiscordClient.cs

@@ -108,7 +108,7 @@ public class DiscordClient
         if (botResponse.StatusCode != HttpStatusCode.Unauthorized)
             return TokenKind.Bot;
 
-        throw DiscordChatExporterException.Unauthorized();
+        throw new DiscordChatExporterException("Authentication token is invalid.", true);
     }
 
     private async ValueTask<HttpResponseMessage> GetResponseAsync(
@@ -129,10 +129,26 @@ public class DiscordClient
         {
             throw response.StatusCode switch
             {
-                HttpStatusCode.Unauthorized => DiscordChatExporterException.Unauthorized(),
-                HttpStatusCode.Forbidden => DiscordChatExporterException.Forbidden(),
-                HttpStatusCode.NotFound => DiscordChatExporterException.NotFound(url),
-                _ => DiscordChatExporterException.FailedHttpRequest(response)
+                HttpStatusCode.Unauthorized => throw new DiscordChatExporterException(
+                    "Authentication token is invalid.",
+                    true
+                ),
+
+                HttpStatusCode.Forbidden => throw new DiscordChatExporterException(
+                    $"Request to '{url}' failed: forbidden."
+                ),
+
+                HttpStatusCode.NotFound => throw new DiscordChatExporterException(
+                    $"Request to '{url}' failed: not found."
+                ),
+
+                _ => throw new DiscordChatExporterException(
+                    $"""
+                    Request to '{url}' failed: {response.StatusCode.ToString().ToSpaceSeparatedWords().ToLowerInvariant()}.
+                    Response content: {await response.Content.ReadAsStringAsync(cancellationToken)}
+                    """,
+                    true
+                )
             };
         }
 

DiscordChatExporter.Core/Exceptions/DiscordChatExporterException.cs

@@ -1,9 +1,8 @@
 using System;
-using System.Net.Http;
 
 namespace DiscordChatExporter.Core.Exceptions;
 
-public partial class DiscordChatExporterException : Exception
+public class DiscordChatExporterException : Exception
 {
     public bool IsFatal { get; }
 
@@ -12,33 +11,4 @@ public partial class DiscordChatExporterException : Exception
     {
         IsFatal = isFatal;
     }
-}
-
-public partial class DiscordChatExporterException
-{
-    internal static DiscordChatExporterException FailedHttpRequest(HttpResponseMessage response)
-    {
-        var message = $@"
-Failed to perform an HTTP request.
-
-[Request]
-{response.RequestMessage}
-
-[Response]
-{response}";
-
-        return new DiscordChatExporterException(message.Trim(), true);
-    }
-
-    internal static DiscordChatExporterException Unauthorized() =>
-        new("Authentication token is invalid.", true);
-
-    internal static DiscordChatExporterException Forbidden() =>
-        new("Access is forbidden.");
-
-    internal static DiscordChatExporterException NotFound(string resourceId) =>
-        new($"Requested resource ({resourceId}) does not exist.");
-
-    internal static DiscordChatExporterException ChannelIsEmpty() =>
-        new("Channel is empty or contains no messages for the specified period.");
 }

DiscordChatExporter.Core/Exporting/ChannelExporter.cs

@@ -20,11 +20,19 @@ public class ChannelExporter
     {
         // Check if the channel is empty
         if (request.Channel.LastMessageId is null)
-            throw DiscordChatExporterException.ChannelIsEmpty();
+        {
+            throw new DiscordChatExporterException(
+                "Channel does not contain any messages."
+            );
+        }
 
         // Check if the 'after' boundary is valid
         if (request.After is not null && request.Channel.LastMessageId < request.After)
-            throw DiscordChatExporterException.ChannelIsEmpty();
+        {
+            throw new DiscordChatExporterException(
+                "Channel does not contain any messages within the specified period."
+            );
+        }
 
         // Build context
         var context = new ExportContext(_discord, request);
@@ -50,6 +58,10 @@ public class ChannelExporter
 
         // Throw if no messages were exported
         if (messageExporter.MessagesExported <= 0)
-            throw DiscordChatExporterException.ChannelIsEmpty();
+        {
+            throw new DiscordChatExporterException(
+                "Channel does not contain any matching messages within the specified period."
+            );
+        }
     }
 }

DiscordChatExporter.Core/Utils/Extensions/StringExtensions.cs

@@ -16,6 +16,21 @@ public static class StringExtensions
             ? str[..charCount]
             : str;
 
+    public static string ToSpaceSeparatedWords(this string str)
+    {
+        var builder = new StringBuilder(str.Length * 2);
+
+        foreach (var c in str)
+        {
+            if (char.IsUpper(c) && builder.Length > 0)
+                builder.Append(' ');
+
+            builder.Append(c);
+        }
+
+        return builder.ToString();
+    }
+
     public static IEnumerable<Rune> GetRunes(this string str)
     {
         var lastIndex = 0;